package config

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"maps"
	"os"
	"path/filepath"
	"slices"
	"strings"
	"sync"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/gruntwork-io/terragrunt/internal/awshelper"
	"github.com/gruntwork-io/terragrunt/internal/cache"
	"github.com/gruntwork-io/terragrunt/internal/experiment"
	"github.com/gruntwork-io/terragrunt/internal/iacargs"
	"github.com/gruntwork-io/terragrunt/internal/remotestate"
	"github.com/gruntwork-io/terragrunt/pkg/log"

	s3backend "github.com/gruntwork-io/terragrunt/internal/remotestate/backend/s3"

	"github.com/gruntwork-io/terragrunt/internal/getter"
	"github.com/zclconf/go-cty/cty"
	"github.com/zclconf/go-cty/cty/gocty"
	ctyjson "github.com/zclconf/go-cty/cty/json"
	"golang.org/x/sync/errgroup"

	"github.com/gruntwork-io/terragrunt/internal/codegen"
	"github.com/gruntwork-io/terragrunt/internal/iam"
	"github.com/gruntwork-io/terragrunt/internal/report"
	"github.com/gruntwork-io/terragrunt/internal/runner/run"
	"github.com/gruntwork-io/terragrunt/internal/runner/run/creds"
	"github.com/gruntwork-io/terragrunt/internal/runner/run/creds/providers/amazonsts"
	"github.com/gruntwork-io/terragrunt/internal/runner/run/creds/providers/externalcmd"
	"github.com/gruntwork-io/terragrunt/internal/shell"
	"github.com/gruntwork-io/terragrunt/internal/telemetry"
	"github.com/gruntwork-io/terragrunt/internal/tf"
	"github.com/gruntwork-io/terragrunt/internal/util"
	"github.com/gruntwork-io/terragrunt/pkg/config/hclparse"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
)

const (
	renderJSONCommand = "render-json"
	renderCommand     = "render"
)

type Dependencies []Dependency

// Struct to hold the decoded dependency blocks.
type dependencyOutputCache struct {
	Enabled *bool
	Inputs  cty.Value
}

type Dependency struct {
	ConfigPath                          cty.Value  `hcl:"config_path,attr" cty:"config_path"`
	Enabled                             *bool      `hcl:"enabled,attr" cty:"enabled"`
	SkipOutputs                         *bool      `hcl:"skip_outputs,attr" cty:"skip"`
	MockOutputs                         *cty.Value `hcl:"mock_outputs,attr" cty:"mock_outputs"`
	MockOutputsAllowedTerraformCommands *[]string  `hcl:"mock_outputs_allowed_terraform_commands,attr" cty:"mock_outputs_allowed_terraform_commands"`

	// MockOutputsMergeWithState is deprecated. Use MockOutputsMergeStrategyWithState
	MockOutputsMergeWithState *bool `hcl:"mock_outputs_merge_with_state,attr" cty:"mock_outputs_merge_with_state"`

	MockOutputsMergeStrategyWithState *MergeStrategyType `hcl:"mock_outputs_merge_strategy_with_state" cty:"mock_outputs_merge_strategy_with_state"`

	// Used to store the rendered outputs for use when the config is imported or read with `read_terragrunt_config`
	RenderedOutputs *cty.Value `cty:"outputs"`

	Inputs *cty.Value `cty:"inputs"`
	Name   string     `hcl:",label" cty:"name"`
}

// DeepMerge will deep merge two Dependency configs, updating the target. Deep merge for Dependency configs is defined
// as follows:
//   - For simple attributes (bools and strings), the source will override the target.
//   - For MockOutputs, the two maps will be deeply merged together. This means that maps are recursively merged, while
//     lists are concatenated together.
//   - For MockOutputsAllowedTerraformCommands, the source will be concatenated to the target.
//
// Note that RenderedOutputs is ignored in the deep merge operation.
func (dep *Dependency) DeepMerge(sourceDepConfig *Dependency) error {
	if sourceDepConfig.ConfigPath.AsString() != "" {
		dep.ConfigPath = sourceDepConfig.ConfigPath
	}

	if sourceDepConfig.Enabled != nil {
		dep.Enabled = sourceDepConfig.Enabled
	}

	if sourceDepConfig.SkipOutputs != nil {
		dep.SkipOutputs = sourceDepConfig.SkipOutputs
	}

	if err := dep.mergeMockOutputs(sourceDepConfig); err != nil {
		return err
	}

	dep.mergeMockOutputsAllowedTerraformCommands(sourceDepConfig)

	return nil
}

// mergeMockOutputs deep-merges sourceDepConfig.MockOutputs into dep.MockOutputs, adopting the source pointer when dep is unset and skipping when both sides point at the same value.
func (dep *Dependency) mergeMockOutputs(sourceDepConfig *Dependency) error {
	if sourceDepConfig.MockOutputs == nil {
		return nil
	}

	if dep.MockOutputs == nil {
		dep.MockOutputs = sourceDepConfig.MockOutputs
		return nil
	}

	if dep.MockOutputs == sourceDepConfig.MockOutputs {
		return nil
	}

	merged, err := deepMergeCtyMaps(*dep.MockOutputs, *sourceDepConfig.MockOutputs)
	if err != nil {
		return err
	}

	dep.MockOutputs = merged

	return nil
}

// mergeMockOutputsAllowedTerraformCommands concatenates source commands onto dep's, adopting the source pointer when dep is unset and skipping when both sides point at the same slice.
func (dep *Dependency) mergeMockOutputsAllowedTerraformCommands(sourceDepConfig *Dependency) {
	if sourceDepConfig.MockOutputsAllowedTerraformCommands == nil {
		return
	}

	if dep.MockOutputsAllowedTerraformCommands == nil {
		dep.MockOutputsAllowedTerraformCommands = sourceDepConfig.MockOutputsAllowedTerraformCommands
		return
	}

	if dep.MockOutputsAllowedTerraformCommands == sourceDepConfig.MockOutputsAllowedTerraformCommands {
		return
	}

	merged := append(*dep.MockOutputsAllowedTerraformCommands, *sourceDepConfig.MockOutputsAllowedTerraformCommands...)
	dep.MockOutputsAllowedTerraformCommands = &merged
}

// getMockOutputsMergeStrategy returns the merge strategy for mock outputs, prioritizing mock_outputs_merge_strategy_with_state over the deprecated mock_outputs_merge_with_state boolean and defaulting to NoMerge.
func (dep *Dependency) getMockOutputsMergeStrategy() MergeStrategyType {
	if dep.MockOutputsMergeStrategyWithState != nil {
		return *dep.MockOutputsMergeStrategyWithState
	}

	if dep.MockOutputsMergeWithState != nil && (*dep.MockOutputsMergeWithState) {
		return ShallowMerge
	}

	return NoMerge
}

// Given a dependency config, we should only attempt to get the outputs if SkipOutputs is nil or false
func (dep *Dependency) shouldGetOutputs(ctx *ParsingContext) bool {
	return !ctx.SkipOutput && dep.isEnabled() && (dep.SkipOutputs == nil || !*dep.SkipOutputs)
}

// isEnabled returns true if the dependency is enabled
func (dep *Dependency) isEnabled() bool {
	if dep.Enabled == nil {
		return true
	}

	return *dep.Enabled
}

// isDisabled returns true if the dependency is disabled
func (dep *Dependency) isDisabled() bool {
	return !dep.isEnabled()
}

// Given a dependency config, we should only attempt to merge mocks outputs with the outputs if MockOutputsMergeWithState is not nil or true
func (dep *Dependency) shouldMergeMockOutputsWithState(ctx *ParsingContext) bool {
	allowedCommand :=
		dep.MockOutputsAllowedTerraformCommands == nil ||
			len(*dep.MockOutputsAllowedTerraformCommands) == 0 ||
			slices.Contains(*dep.MockOutputsAllowedTerraformCommands, ctx.OriginalTerraformCommand)

	return allowedCommand && dep.getMockOutputsMergeStrategy() != NoMerge
}

func (dep *Dependency) setRenderedOutputs(ctx context.Context, pctx *ParsingContext, l log.Logger) error {
	if dep == nil {
		return nil
	}

	if dep.shouldGetOutputs(pctx) || dep.shouldReturnMockOutputs(pctx) {
		outputVal, err := getTerragruntOutputIfAppliedElseConfiguredDefault(ctx, pctx, l, dep)
		if err != nil {
			return err
		}

		dep.RenderedOutputs = outputVal
	}

	return nil
}

// outputLocksFromContext retrieves the KeyLocks from the context for synchronizing output retrieval.
// If not present in context, returns a new KeyLocks instance.
func outputLocksFromContext(ctx context.Context) *util.KeyLocks {
	if val, ok := ctx.Value(OutputLocksContextKey).(*util.KeyLocks); ok && val != nil {
		return val
	}

	return util.NewKeyLocks()
}

// Decode the dependency blocks from the file, and then retrieve all the outputs from the remote state. Then encode the
// resulting map as a cty.Value object.
// TODO: In the future, consider allowing importing dependency blocks from included config
// NOTE FOR MAINTAINER: When implementing importation of other config blocks (e.g referencing inputs), carefully
//
//	consider whether or not the implementation of the cyclic dependency detection still makes sense.
func decodeAndRetrieveOutputs(ctx context.Context, pctx *ParsingContext, l log.Logger, file *hclparse.File) (*cty.Value, error) {
	evalParsingContext, err := createTerragruntEvalContext(ctx, pctx, l, file.ConfigPath)
	if err != nil {
		return nil, err
	}

	decodedDependency := TerragruntDependency{}
	if err := file.Decode(&decodedDependency, evalParsingContext); err != nil {
		return nil, err
	}

	// In normal operation, if a dependency block does not have a `config_path` attribute, decoding returns an error since this attribute is required, but the `hclvalidate` command suppresses decoding errors and this causes a cycle between modules, so we need to filter out dependencies without a defined `config_path`.
	decodedDependency.Dependencies = decodedDependency.Dependencies.FilteredWithoutConfigPath()

	// Fold sibling autoinclude dependency blocks in before output retrieval so the unit body can reference them, like a regular include.
	decodedDependency.Dependencies, err = foldSiblingAutoIncludeDeps(ctx, pctx, l, decodedDependency.Dependencies)
	if err != nil {
		return nil, err
	}

	// Validate that dependency config_path is not an empty string.
	// Skip null/unknown values and non-strings (which can appear during partial decode or hclvalidate).
	for _, dep := range decodedDependency.Dependencies {
		if dep.isDisabled() {
			continue
		}

		if !IsValidConfigPath(dep.ConfigPath) {
			// During hcl validate, config_path may be unresolvable (e.g., references an
			// unavailable local). Skip the invalid dependency instead of aborting — it will
			// get a cty.DynamicVal placeholder in dependencyBlocksToCtyValue.
			if pctx.SkipOutput {
				continue
			}

			return nil, DependencyInvalidConfigPathError{DependencyName: dep.Name}
		}
	}

	if err := checkForDependencyBlockCycles(ctx, pctx, l, pctx.TerragruntConfigPath, decodedDependency); err != nil {
		return nil, err
	}

	updatedDependencies, err := decodeDependencies(ctx, pctx, l, decodedDependency)
	if err != nil {
		return nil, err
	}

	decodedDependency = *updatedDependencies

	// Merge in included dependencies
	if pctx.TrackInclude != nil {
		mergedDecodedDependency, err := handleIncludeForDependency(ctx, pctx, l, decodedDependency)
		if err != nil {
			return nil, err
		}

		decodedDependency = *mergedDecodedDependency
	}

	// Extract dependency names for tracing
	dependencyNames := make([]string, 0, len(decodedDependency.Dependencies))
	for _, dep := range decodedDependency.Dependencies {
		dependencyNames = append(dependencyNames, dep.Name)
	}

	var result *cty.Value

	err = TraceParseDependencies(ctx, file.ConfigPath, pctx.SkipOutputsResolution, len(decodedDependency.Dependencies), dependencyNames, func(ctx context.Context) error {
		var depErr error

		result, depErr = dependencyBlocksToCtyValue(ctx, pctx, l, decodedDependency.Dependencies)

		return depErr
	})

	return result, err
}

// decodeDependencies decode dependencies and fetch inputs
func decodeDependencies(ctx context.Context, pctx *ParsingContext, l log.Logger, decodedDependency TerragruntDependency) (*TerragruntDependency, error) {
	updatedDependencies := TerragruntDependency{}
	depCache := cache.ContextCache[*dependencyOutputCache](ctx, DependencyOutputCacheContextKey)

	for _, dep := range decodedDependency.Dependencies {
		if !dep.isEnabled() {
			updatedDependencies.Dependencies = append(updatedDependencies.Dependencies, dep)
			continue
		}

		if !IsValidConfigPath(dep.ConfigPath) {
			if pctx.SkipOutput {
				updatedDependencies.Dependencies = append(updatedDependencies.Dependencies, dep)
				continue
			}

			return &updatedDependencies, DependencyInvalidConfigPathError{DependencyName: dep.Name}
		}

		depPath := getCleanedTargetConfigPath(dep.ConfigPath.AsString(), pctx.TerragruntConfigPath)

		if !util.FileExists(depPath) {
			updatedDependencies.Dependencies = append(updatedDependencies.Dependencies, dep)

			continue
		}

		cacheKey := filepath.Join(pctx.WorkingDir, depPath)

		// Cache hit - reuse cached values
		if cachedDependency, found := depCache.Get(ctx, cacheKey); found {
			dep.Enabled = cachedDependency.Enabled
			dep.Inputs = &cachedDependency.Inputs
			updatedDependencies.Dependencies = append(updatedDependencies.Dependencies, dep)

			continue
		}

		// Cache miss - parse and cache

		if !pctx.SkipOutputsResolution {
			l.Debugf("Reading Terragrunt config file at %s", util.RelPathForLog(pctx.RootWorkingDir, depPath, pctx.LogShowAbsPaths))
		}

		_, depCtx, err := pctx.WithDependencyConfigPath(l, depPath)
		if err != nil {
			return nil, err
		}

		if depCtx.IAMRoleOptions != depCtx.OriginalIAMRoleOptions {
			depCtx.IAMRoleOptions = iam.RoleOptions{}
		}

		depCtx = depCtx.WithDecodeList(TerragruntFlags).WithDiagnosticsSuppressed(l)

		depConfig, err := PartialParseConfigFile(ctx, depCtx, l, depPath, nil)
		if err != nil {
			l.Warnf("Error reading partial config for dependency %s at %s: %v", dep.Name, depPath, err)
			updatedDependencies.Dependencies = append(updatedDependencies.Dependencies, dep)

			continue
		}

		inputsCty, err := convertToCtyWithJSON(depConfig.Inputs)
		if err != nil {
			return nil, fmt.Errorf("failed to convert inputs for dependency %q: %w", dep.Name, err)
		}

		cachedValue := dependencyOutputCache{
			Enabled: dep.Enabled,
			Inputs:  inputsCty,
		}
		depCache.Put(ctx, cacheKey, &cachedValue)

		dep.Inputs = &inputsCty

		updatedDependencies.Dependencies = append(updatedDependencies.Dependencies, dep)
	}

	return &updatedDependencies, nil
}

// Convert the list of parsed Dependency blocks into a list of module dependencies. Each output block should
// become a dependency of the current config, since that module has to be applied before we can read the output.
func dependencyBlocksToModuleDependencies(l log.Logger, decodedDependencyBlocks []Dependency) *ModuleDependencies {
	if len(decodedDependencyBlocks) == 0 {
		return nil
	}

	paths := []string{}

	for _, decodedDependencyBlock := range decodedDependencyBlocks {
		// skip dependency if is not enabled
		if !decodedDependencyBlock.isEnabled() {
			continue
		}

		// Skip if ConfigPath is not a known string value (can happen during discovery phase)
		if decodedDependencyBlock.ConfigPath.IsNull() ||
			!decodedDependencyBlock.ConfigPath.IsWhollyKnown() ||
			!decodedDependencyBlock.ConfigPath.Type().Equals(cty.String) {
			l.Debugf("Skipping dependency %q: ConfigPath is not a valid known string value", decodedDependencyBlock.Name)
			continue
		}

		paths = append(paths, decodedDependencyBlock.ConfigPath.AsString())
	}

	return &ModuleDependencies{Paths: paths}
}

// Check for cyclic dependency blocks to avoid infinite `terragrunt output` loops. To avoid reparsing the config, we
// kickstart the initial loop using what we already decoded.
func checkForDependencyBlockCycles(ctx context.Context, pctx *ParsingContext, l log.Logger, configPath string, decodedDependency TerragruntDependency) error {
	visitedPaths := []string{}
	currentTraversalPaths := []string{configPath}

	for _, dependency := range decodedDependency.Dependencies {
		if dependency.isDisabled() {
			continue
		}

		if !IsValidConfigPath(dependency.ConfigPath) {
			if pctx.SkipOutput {
				continue
			}

			return DependencyInvalidConfigPathError{DependencyName: dependency.Name}
		}

		dependencyPath := getCleanedTargetConfigPath(dependency.ConfigPath.AsString(), configPath)

		// Skip cycle checking for nonexistent dependency targets — there is nothing to traverse.
		if !util.FileExists(dependencyPath) {
			continue
		}

		l, dependencyContext, err := pctx.WithDependencyConfigPath(l, dependencyPath)
		if err != nil {
			return err
		}

		if err := checkForDependencyBlockCyclesUsingDFS(ctx, dependencyContext, l, dependencyPath, &visitedPaths, &currentTraversalPaths); err != nil {
			return err
		}
	}

	return nil
}

// Helper function for checkForDependencyBlockCycles.
//
// Same implementation as configstack/graph.go:checkForCyclesUsingDepthFirstSearch, except walks the graph of
// dependencies by `dependency` blocks (which make explicit `terragrunt output` calls) instead of explicit dependencies.
func checkForDependencyBlockCyclesUsingDFS(
	ctx context.Context,
	pctx *ParsingContext,
	l log.Logger,
	dependencyPath string,
	visitedPaths *[]string,
	currentTraversalPaths *[]string,
) error {
	if slices.Contains(*visitedPaths, dependencyPath) {
		return nil
	}

	if slices.Contains(*currentTraversalPaths, dependencyPath) {
		return DependencyCycleError(append(*currentTraversalPaths, dependencyPath))
	}

	*currentTraversalPaths = append(*currentTraversalPaths, dependencyPath)

	dependencyPaths, err := getDependencyBlockConfigPathsByFilepath(ctx, pctx, l, dependencyPath)
	if err != nil {
		return err
	}

	for _, dependency := range dependencyPaths {
		dependencyPath := getCleanedTargetConfigPath(dependency, dependencyPath)

		// Skip cycle checking for nonexistent dependency targets such as stack directories.
		if !util.FileExists(dependencyPath) {
			continue
		}

		l, dependencyContext, err := pctx.WithDependencyConfigPath(l, dependencyPath)
		if err != nil {
			return err
		}

		if err := checkForDependencyBlockCyclesUsingDFS(ctx, dependencyContext, l, dependencyPath, visitedPaths, currentTraversalPaths); err != nil {
			return err
		}
	}

	*visitedPaths = append(*visitedPaths, dependencyPath)
	*currentTraversalPaths = slices.DeleteFunc(*currentTraversalPaths, func(path string) bool { return path == dependencyPath })

	return nil
}

// Given the config path, return the list of config paths that are specified as dependency blocks in the config
func getDependencyBlockConfigPathsByFilepath(ctx context.Context, pctx *ParsingContext, l log.Logger, configPath string) ([]string, error) {
	// This will automatically parse everything needed to parse the dependency block configs, and load them as
	// TerragruntConfig.Dependencies. Note that since we aren't passing in `DependenciesBlock` to the
	// PartialDecodeSectionType list, the Dependencies attribute will not include any dependencies specified via the
	// dependencies block.
	tgConfig, err := PartialParseConfigFile(ctx, pctx.WithDecodeList(DependencyBlock).WithDiagnosticsSuppressed(l), l, configPath, nil)
	if err != nil {
		return nil, err
	}

	if tgConfig.Dependencies == nil {
		return []string{}, nil
	}

	return tgConfig.Dependencies.Paths, nil
}

// Encode the list of dependency blocks into a single cty.Value object that maps the dependency block name to the
// encoded dependency mapping. The encoded dependency mapping should have the attributes:
//   - outputs: The map of outputs of the corresponding terraform module that lives at the target config of the
//     dependency.
//
// This routine will go through the process of obtaining the outputs using `terragrunt output` from the target config.
// The traceCtx parameter is the trace context from the parent span (parse_dependencies) to establish parent-child
// relationship for individual dependency traces.
func dependencyBlocksToCtyValue(traceCtx context.Context, pctx *ParsingContext, l log.Logger, dependencyConfigs []Dependency) (*cty.Value, error) {
	paths := []string{}

	// dependencyMap is the top level map that maps dependency block names to the encoded version, which includes
	// various attributes for accessing information about the target config (including the module outputs).
	dependencyMap := map[string]cty.Value{}
	lock := sync.Mutex{}
	dependencyErrGroup, _ := errgroup.WithContext(traceCtx)

	for _, dependencyConfig := range dependencyConfigs {
		dependencyErrGroup.Go(func() error {
			// Tag the context with the dependency block name so dependency_output_fetch can attach it.
			ctx := contextWithDependencyName(traceCtx, dependencyConfig.Name)

			// Loose struct to hold the attributes of the dependency. This includes:
			// - outputs: The module outputs of the target config
			dependencyEncodingMap := map[string]cty.Value{}

			// Encode the outputs and nest under `outputs` attribute if we should get the outputs or the `mock_outputs`
			if err := dependencyConfig.setRenderedOutputs(ctx, pctx, l); err != nil {
				return fmt.Errorf("resolving dependency %q outputs: %w", dependencyConfig.Name, err)
			}

			if dependencyConfig.RenderedOutputs != nil {
				lock.Lock()

				paths = append(paths, dependencyConfig.ConfigPath.AsString())

				lock.Unlock()

				dependencyEncodingMap["outputs"] = *dependencyConfig.RenderedOutputs
			} else if pctx.SkipOutput {
				// During hcl validate, output resolution is skipped. Use cty.DynamicVal so that
				// attribute access on dependency outputs (e.g. dependency.x.outputs.y) evaluates
				// to unknown rather than producing an "Unsupported attribute" error.
				l.Debugf("Setting outputs for dependency %s to DynamicVal (output resolution skipped)", dependencyConfig.Name)

				dependencyEncodingMap["outputs"] = cty.DynamicVal
			}

			if dependencyConfig.Inputs != nil {
				dependencyEncodingMap["inputs"] = *dependencyConfig.Inputs
			} else if pctx.SkipOutput {
				l.Debugf("Setting inputs for dependency %s to DynamicVal (output resolution skipped)", dependencyConfig.Name)

				dependencyEncodingMap["inputs"] = cty.DynamicVal
			}

			// Once the dependency is encoded into a map, we need to convert to a cty.Value again so that it can be fed to
			// the higher order dependency map.
			dependencyEncodingMapEncoded, err := gocty.ToCtyValue(dependencyEncodingMap, generateTypeFromValuesMap(dependencyEncodingMap))
			if err != nil {
				lock.Lock()
				err = TerragruntOutputListEncodingError{Paths: slices.Clone(paths), Err: err}
				lock.Unlock()

				return err
			}

			// Lock the map as only one goroutine should be writing to the map at a time
			lock.Lock()
			defer lock.Unlock()

			// Finally, feed the encoded dependency into the higher order map under the block name
			dependencyMap[dependencyConfig.Name] = dependencyEncodingMapEncoded

			return nil
		})
	}

	if err := dependencyErrGroup.Wait(); err != nil {
		return nil, err
	}

	// We need to convert the value map to a single cty.Value at the end so that it can be used in the execution ctx
	convertedOutput, err := gocty.ToCtyValue(dependencyMap, generateTypeFromValuesMap(dependencyMap))
	if err != nil {
		err = TerragruntOutputListEncodingError{Paths: paths, Err: err}
	}

	return &convertedOutput, err
}

// This will attempt to get the outputs from the target terragrunt config if it is applied. If it is not applied, the
// behavior is different depending on the configuration of the dependency:
//   - If the dependency block indicates a mock_outputs attribute, this will return that.
//     If the dependency block indicates a mock_outputs_merge_strategy_with_state attribute, mock_outputs and state outputs will be merged following the merge strategy
//   - If the dependency block does NOT indicate a mock_outputs attribute, this will return an error.
func getTerragruntOutputIfAppliedElseConfiguredDefault(
	ctx context.Context,
	pctx *ParsingContext,
	l log.Logger,
	dependencyConfig *Dependency,
) (*cty.Value, error) {
	if dependencyConfig.isDisabled() {
		l.Debugf("Skipping outputs reading for disabled dependency %s", dependencyConfig.Name)
		return dependencyConfig.MockOutputs, nil
	}

	if dependencyConfig.shouldGetOutputs(pctx) {
		outputVal, isEmpty, err := getTerragruntOutput(ctx, pctx, l, dependencyConfig)
		if err != nil {
			return nil, err
		}

		if !isEmpty && dependencyConfig.shouldMergeMockOutputsWithState(pctx) && dependencyConfig.MockOutputs != nil {
			mockMergeStrategy := dependencyConfig.getMockOutputsMergeStrategy()

			switch mockMergeStrategy { // nolint:exhaustive
			case NoMerge:
				return outputVal, nil
			case ShallowMerge:
				return shallowMergeCtyMaps(*outputVal, *dependencyConfig.MockOutputs)
			case DeepMergeMapOnly:
				return deepMergeCtyMapsMapOnly(*dependencyConfig.MockOutputs, *outputVal)
			default:
				return nil, InvalidMergeStrategyTypeError(mockMergeStrategy)
			}
		} else if !isEmpty {
			return outputVal, err
		}
	}

	// When we get no output, it can be an indication that either the module has no outputs or the module is not
	// applied. In either case, check if there are default output values to return. If yes, return that. Else,
	// return error.
	targetConfig := getCleanedTargetConfigPath(dependencyConfig.ConfigPath.AsString(), pctx.TerragruntConfigPath)

	if dependencyConfig.shouldReturnMockOutputs(pctx) {
		l.Warnf("Config %s is a dependency of %s that has no outputs, but mock outputs provided and returning those in dependency output.",
			targetConfig,
			pctx.TerragruntConfigPath,
		)

		return dependencyConfig.MockOutputs, nil
	}

	// At this point, we expect outputs to exist because there is a `dependency` block without skip_outputs = true, and
	// returning mocks is not allowed. So return a useful error message indicating that we expected outputs, but they
	// did not exist.
	err := TerragruntOutputTargetNoOutputs{
		targetName:    dependencyConfig.Name,
		targetPath:    dependencyConfig.ConfigPath.AsString(),
		targetConfig:  targetConfig,
		currentConfig: pctx.TerragruntConfigPath,
	}

	return nil, err
}

// We should only return default outputs if the mock_outputs attribute is set, and if we are running one of the
// allowed commands when `mock_outputs_allowed_terraform_commands` is set as well.
func (dep *Dependency) shouldReturnMockOutputs(pctx *ParsingContext) bool {
	if dep.isDisabled() {
		return true
	}

	defaultOutputsSet := dep.MockOutputs != nil

	allowedCommand :=
		dep.MockOutputsAllowedTerraformCommands == nil ||
			len(*dep.MockOutputsAllowedTerraformCommands) == 0 ||
			slices.Contains(*dep.MockOutputsAllowedTerraformCommands, pctx.OriginalTerraformCommand)

	return defaultOutputsSet && allowedCommand || isRenderJSONCommand(pctx) || isRenderCommand(pctx)
}

// Return the output from the state of another module, managed by terragrunt. This function will parse the provided
// terragrunt config and extract the desired output from the remote state. Note that this will error if the targeted
// module hasn't been applied yet.
func getTerragruntOutput(
	ctx context.Context,
	pctx *ParsingContext,
	l log.Logger,
	dependencyConfig *Dependency,
) (*cty.Value, bool, error) {
	// target config check: make sure the target config exists
	targetConfigPath := getCleanedTargetConfigPath(
		dependencyConfig.ConfigPath.AsString(),
		pctx.TerragruntConfigPath,
	)

	// Check if config_path points to a directory containing a stack file. If so,
	// resolve outputs from all units in the stack as a nested map.
	stackOutput, handled, err := tryGetStackOutput(ctx, pctx, l, targetConfigPath, dependencyConfig)
	if handled {
		return stackOutput, stackOutput == nil, err
	}

	if !util.FileExists(targetConfigPath) {
		return nil, true, DependencyConfigNotFound{Path: targetConfigPath}
	}

	jsonBytes, err := getOutputJSONWithCaching(ctx, pctx, l, targetConfigPath)
	if err != nil {
		if !isRenderJSONCommand(pctx) && !isRenderCommand(pctx) && !isAwsS3NoSuchKey(err) {
			return nil, true, err
		}

		l.Warnf(
			"Failed to read outputs from %s referenced in %s as %s, fallback to mock outputs. Error: %v",
			targetConfigPath,
			pctx.TerragruntConfigPath,
			dependencyConfig.Name,
			err,
		)

		jsonBytes, err = json.Marshal(dependencyConfig.MockOutputs)
		if err != nil {
			return nil, true, err
		}
	}

	isEmpty := string(jsonBytes) == "{}"

	outputMap, err := TerraformOutputJSONToCtyValueMap(targetConfigPath, jsonBytes)
	if err != nil {
		return nil, isEmpty, err
	}

	// We need to convert the value map to a single cty.Value at the end for use in the terragrunt config.
	convertedOutput, err := gocty.ToCtyValue(outputMap, generateTypeFromValuesMap(outputMap))
	if err != nil {
		err = TerragruntOutputEncodingError{Path: targetConfigPath, Err: err}
	}

	return &convertedOutput, isEmpty, err
}

// collectStackUnitOutputs aggregates per-unit outputs keyed by unit name for dependency.<stack>.outputs.<unit>.<key> resolution.
func collectStackUnitOutputs(ctx context.Context, pctx *ParsingContext, l log.Logger, stackDir string, units []*Unit) (map[string]cty.Value, error) {
	unitOutputs := make(map[string]cty.Value)

	for _, unit := range units {
		unitDir := unit.GeneratedPath(stackDir)
		unitConfigPath := filepath.Join(unitDir, DefaultTerragruntConfigPath)

		if !util.FileExists(unitConfigPath) {
			l.Warnf("Stack unit %s config not found at %s, skipping", unit.Name, unitConfigPath)

			continue
		}

		jsonBytes, err := getOutputJSONWithCaching(ctx, pctx, l, unitConfigPath)
		if err != nil {
			return nil, fmt.Errorf("stack unit %s output fetch failed: %w", unit.Name, err)
		}

		outputMap, err := TerraformOutputJSONToCtyValueMap(unitConfigPath, jsonBytes)
		if err != nil {
			return nil, fmt.Errorf("stack unit %s output parse failed: %w", unit.Name, err)
		}

		if len(outputMap) > 0 {
			convertedOutput, err := gocty.ToCtyValue(outputMap, generateTypeFromValuesMap(outputMap))
			if err != nil {
				return nil, fmt.Errorf("stack unit %s output convert failed: %w", unit.Name, err)
			}

			unitOutputs[unit.Name] = convertedOutput
		}
	}

	return unitOutputs, nil
}

// tryGetStackOutput checks if targetConfigPath points to a stack directory
// (contains terragrunt.stack.hcl) and resolves aggregated outputs from all
// units in the stack. Returns (output, handled, error) where handled=true
// means the path was a stack and was processed (even if there was an error).
func tryGetStackOutput(
	ctx context.Context,
	pctx *ParsingContext,
	l log.Logger,
	targetConfigPath string,
	dependencyConfig *Dependency,
) (*cty.Value, bool, error) {
	stackFilePath, isStackCandidate := resolveStackFilePath(dependencyConfig.ConfigPath.AsString(), targetConfigPath)
	if !isStackCandidate {
		return nil, false, nil
	}

	if !util.FileExists(stackFilePath) {
		return nil, false, nil
	}

	l.Debugf("Dependency %s points to stack %s, resolving stack outputs", dependencyConfig.Name, stackFilePath)

	stackDir := filepath.Dir(stackFilePath)

	// Load values from the target stack's directory before parsing,
	// mirroring the GenerateStackFile flow so stacks using values.* work.
	stackValues, err := ReadValues(ctx, pctx, l, stackDir)
	if err != nil {
		return nil, true, fmt.Errorf("failed to read values for stack %s: %w", stackFilePath, err)
	}

	// Parse the stack config to discover units
	stackConfig, err := ReadStackConfigFile(ctx, l, pctx, stackFilePath, stackValues)
	if err != nil {
		return nil, true, fmt.Errorf("failed to parse stack config %s: %w", stackFilePath, err)
	}

	unitOutputs, err := collectStackUnitOutputs(ctx, pctx, l, stackDir, stackConfig.Units)
	if err != nil {
		return nil, true, fmt.Errorf("failed to collect stack unit outputs for %s: %w", stackFilePath, err)
	}

	if len(unitOutputs) == 0 {
		return nil, true, nil
	}

	result := cty.ObjectVal(unitOutputs)

	return &result, true, nil
}

// resolveStackFilePath returns the candidate terragrunt.stack.hcl path for a dependency target; ok=false when the dep points at a unit config.
func resolveStackFilePath(rawConfigPath, targetConfigPath string) (string, bool) {
	switch filepath.Base(filepath.Clean(rawConfigPath)) {
	case DefaultStackFile:
		// Honor the contract even when target is malformed: anchor on target's directory.
		return filepath.Join(filepath.Dir(targetConfigPath), DefaultStackFile), true
	case DefaultTerragruntConfigPath, DefaultTerragruntJSONConfigPath:
		return "", false
	}

	switch filepath.Base(targetConfigPath) {
	case DefaultStackFile:
		return targetConfigPath, true
	case DefaultTerragruntConfigPath, DefaultTerragruntJSONConfigPath:
		return filepath.Join(filepath.Dir(targetConfigPath), DefaultStackFile), true
	default:
		return filepath.Join(targetConfigPath, DefaultStackFile), true
	}
}

func isAwsS3NoSuchKey(err error) bool {
	if err != nil {
		errStr := err.Error()
		return strings.Contains(errStr, "NoSuchKey") || strings.Contains(errStr, "NotFound")
	}

	return false
}

// isRenderJSONCommand This function will true if terragrunt was invoked with render-json
func isRenderJSONCommand(pctx *ParsingContext) bool {
	if pctx.TerraformCliArgs == nil {
		return false
	}

	return pctx.TerraformCliArgs.Contains(renderJSONCommand)
}

// isRenderCommand will return true if terragrunt was invoked with render
func isRenderCommand(pctx *ParsingContext) bool {
	if pctx.TerraformCliArgs == nil {
		return false
	}

	return pctx.TerraformCliArgs.Contains(renderCommand)
}

type dependencyNameKey struct{}

// contextWithDependencyName tags ctx with the HCL `dependency "<name>"` block label so
// dependency_output_fetch can include it as a span attribute.
func contextWithDependencyName(ctx context.Context, name string) context.Context {
	return context.WithValue(ctx, dependencyNameKey{}, name)
}

// dependencyNameFromContext returns the dependency block name attached to ctx, or "".
func dependencyNameFromContext(ctx context.Context) string {
	if v, ok := ctx.Value(dependencyNameKey{}).(string); ok {
		return v
	}

	return ""
}

// getOutputJSONWithCaching will run terragrunt output on the target config if it is not already cached.
func getOutputJSONWithCaching(ctx context.Context, pctx *ParsingContext, l log.Logger, targetConfig string) ([]byte, error) {
	locks := outputLocksFromContext(ctx)

	locks.Lock(targetConfig)
	defer locks.Unlock(targetConfig)

	l.Debugf("Getting output of dependency %s for config %s", util.RelPathForLog(pctx.RootWorkingDir, targetConfig, pctx.LogShowAbsPaths), util.RelPathForLog(pctx.RootWorkingDir, pctx.TerragruntConfigPath, pctx.LogShowAbsPaths))

	var newJSONBytes []byte

	fetchAttrs := map[string]any{
		"target": targetConfig,
		"caller": pctx.TerragruntConfigPath,
	}
	if name := dependencyNameFromContext(ctx); name != "" {
		fetchAttrs["dependency_name"] = name
	}

	err := telemetry.TelemeterFromContext(ctx).Collect(ctx, "dependency_output_fetch", fetchAttrs, func(fetchCtx context.Context) error {
		jsonCache := cache.ContextCache[[]byte](fetchCtx, JSONOutputCacheContextKey)
		if cached, found := jsonCache.Get(fetchCtx, targetConfig); found {
			l.Debugf("%s was run before. Using cached output.", targetConfig)

			if span := trace.SpanFromContext(fetchCtx); span.IsRecording() {
				span.SetAttributes(attribute.Bool("cache_hit", true))
			}

			newJSONBytes = cached

			return nil
		}

		fetched, strategy, fetchErr := resolveOutputJSON(fetchCtx, pctx, l, targetConfig)

		if span := trace.SpanFromContext(fetchCtx); span.IsRecording() {
			span.SetAttributes(attribute.Bool("cache_hit", false))

			if strategy != "" {
				span.SetAttributes(attribute.String("strategy", strategy))
			}
		}

		if fetchErr != nil {
			return fetchErr
		}

		// `tofu/terraform output -json` stdout can be polluted with non-JSON text on either side of the JSON object:
		//   - Leading: AWS Client Side Monitoring (CSM) logs (e.g., "2023/05/04 20:22:43 Enabling CSM"),
		//     ANSI color escape sequences from warning blocks.
		//     Refs: https://github.com/aws/aws-sdk-go/blob/81d1cbbc6a2028023aff7bcab0fe1be320cd39f7/aws/session/session.go#L444
		//           https://github.com/gruntwork-io/terragrunt/issues/2233
		//   - Trailing: Terraform 1.15+ emits backend deprecation warnings (e.g., for the S3
		//     `dynamodb_table` parameter) on stdout after the JSON has already been printed.
		//     Refs: https://github.com/gruntwork-io/terragrunt/issues/6001
		//
		// To make parsing robust to either, isolate the first JSON object in the buffer.
		trimmed, trimErr := extractFirstJSONObject(fetched)
		if trimErr != nil {
			return TerragruntOutputParsingError{Path: targetConfig, Err: trimErr}
		}

		newJSONBytes = trimmed
		jsonCache.Put(fetchCtx, targetConfig, newJSONBytes)

		return nil
	})
	if err != nil {
		return nil, err
	}

	return newJSONBytes, nil
}

// extractFirstJSONObject returns the first complete JSON object found in data, ignoring any
// non-JSON content that precedes or follows it. This is needed because `tofu/terraform output -json`
// can intermix log lines, ANSI escape codes, or deprecation warnings with the JSON output, depending
// on the version and backend in use.
//
// If data contains no `{`, the original bytes are returned so downstream JSON parsing surfaces the
// usual "unexpected end of JSON input" error rather than a cryptic message from this helper.
func extractFirstJSONObject(data []byte) ([]byte, error) {
	start := bytes.IndexByte(data, '{')
	if start < 0 {
		return data, nil
	}

	dec := json.NewDecoder(bytes.NewReader(data[start:]))

	var raw json.RawMessage
	if err := dec.Decode(&raw); err != nil {
		return nil, err
	}

	return raw, nil
}

// adjustSourceForTargetModule rewrites a `--source` CLI override so it points at targetConfig's own module subdir
// rather than the original unit's. The override carries only the module root ("everything before //"); the subdir
// comes from the target's terraform source. A no-op when `--source` was not set or the target has no source.
func adjustSourceForTargetModule(pctx *ParsingContext, targetConfig string, targetCfg *TerragruntConfig) error {
	if pctx.Source == "" {
		return nil
	}

	moduleURL, _ := getter.SourceDirSubdir(pctx.Source)

	targetSource, err := GetTerragruntSourceForModule(moduleURL, filepath.Dir(targetConfig), targetCfg)
	if err != nil {
		return err
	}

	pctx.Source = targetSource

	return nil
}

// resolveOutputJSON retrieves the outputs from the terraform state in the target configuration. It
// attempts to optimize retrieval if the following conditions are true:
//   - State backends are managed with a `remote_state` block.
//   - The `remote_state` block does not depend on any `dependency` outputs.
//
// If these conditions are met, terragrunt can avoid recursively retrieving dependency outputs by
// pulling the state file directly. Otherwise it falls back to running `terragrunt output`.
//
// The returned strategy string ("run", "state", or "init_folder") is purely for telemetry
// annotation on the caller's span; callers should not branch on it.
func resolveOutputJSON(ctx context.Context, pctx *ParsingContext, l log.Logger, targetConfig string) ([]byte, string, error) {
	l, pctx, err := pctx.WithDependencyConfigPath(l, targetConfig)
	if err != nil {
		return nil, "", err
	}

	// Set dependency-specific fields
	pctx.ForwardTFStdout = false
	pctx.CheckDependentUnits = false
	pctx.TerraformCommand = "output"
	pctx.TerraformCliArgs = iacargs.New().SetCommand("output").AppendFlag("-json")

	// Clear IAM if changed from original
	if pctx.IAMRoleOptions != pctx.OriginalIAMRoleOptions {
		pctx.IAMRoleOptions = iam.RoleOptions{}
	}

	// Decode dependency blocks plus terraform source and extra_arguments, skipping hooks that may reference the dependency namespace.
	partialTerragruntConfig, err := PartialParseConfigFile(
		ctx,
		pctx.WithDecodeList(DependencyBlock, TerraformExtraArgs).WithDiagnosticsSuppressed(l),
		l,
		targetConfig,
		nil,
	)
	if err != nil {
		// The config being parsed may reference dependency outputs that this lightweight parse can't resolve; the
		// full output run can, so fall back instead of failing the dependent unit. That parse error is often the
		// misleading "no variable named dependency" diagnostic, so it is logged for debugging but not returned; the
		// full run is authoritative and reproduces any genuine error. runTerragruntOutputJSON retargets any `--source`
		// override to the target module from its fully resolved source, so a stale subdir from the calling unit — even
		// one whose source itself consumes a dependency output — is not carried into the run.
		l.Debugf("Could not partially parse terraform block from target config %s: %v", pctx.TerragruntConfigPath, err)
		l.Debugf("Falling back to terragrunt output.")

		out, runErr := runTerragruntOutputJSON(ctx, pctx, l, targetConfig)

		return out, "run", runErr
	}

	// Only override TFPath if it was not explicitly set by the user via CLI or environment variable
	if !pctx.TFPathExplicitlySet && partialTerragruntConfig.TerraformBinary != "" {
		pctx.TFPath = partialTerragruntConfig.TerraformBinary
	}

	// Apply extra_arguments env_vars for the output command so env dependent backends can be read.
	applyExtraArgsEnvVarsForOutput(pctx, partialTerragruntConfig.Terraform)

	// If the Source is set, then we need to recompute it in the ctx of the target config.
	if err := adjustSourceForTargetModule(pctx, targetConfig, partialTerragruntConfig); err != nil {
		return nil, "", err
	}

	// First attempt to parse the `remote_state` blocks without parsing/getting dependency outputs. If this is possible,
	// proceed to routine that fetches remote state directly. Otherwise, fallback to calling `terragrunt output`
	// directly.

	// we need to suspend logging diagnostic errors on this attempt
	parseOptions := slices.Concat(pctx.ParserOptions, []hclparse.Option{hclparse.WithDiagnosticsWriter(io.Discard, true)})

	remoteStateTGConfig, err := PartialParseConfigFile(
		ctx,
		pctx.WithParseOption(parseOptions).WithDecodeList(
			RemoteStateBlock,
			TerragruntFlags,
			EngineBlock,
		),
		l,
		targetConfig,
		nil,
	)
	// Check err before dereferencing the config: a remote_state block that references the dependency namespace makes
	// this parse fail and return a nil config, so the short-circuit avoids a nil pointer panic.
	if err != nil || !canGetRemoteState(remoteStateTGConfig.RemoteState) {
		l.Debugf("Could not parse remote_state block from target config %s", pctx.TerragruntConfigPath)
		l.Debugf("Falling back to terragrunt output.")

		out, runErr := runTerragruntOutputJSON(ctx, pctx, l, targetConfig)

		return out, "run", runErr
	}

	// In optimization mode, see if there is already an init-ed folder that terragrunt can use, and if so, run
	// `terraform output` in the working directory.
	isInit, workingDir, err := terragruntAlreadyInit(ctx, l, pctx, targetConfig)
	if err != nil {
		return nil, "", err
	}

	// Fetch engine options so they can be passed to the dependency functions
	engineOpts, err := remoteStateTGConfig.EngineOptions()
	if err != nil {
		return nil, "", err
	}

	pctx.EngineConfig = engineOpts

	shouldFetchFromState := pctx.Experiments.Evaluate(experiment.DependencyFetchOutputFromState) &&
		!pctx.NoDependencyFetchOutputFromState &&
		remoteStateTGConfig.RemoteState.BackendName == s3backend.BackendName

	if shouldFetchFromState {
		out, fetchErr := getTerragruntOutputJSONFromRemoteState(
			ctx,
			pctx,
			l,
			targetConfig,
			remoteStateTGConfig.RemoteState,
			remoteStateTGConfig.GetIAMRoleOptions(),
		)

		return out, "state", fetchErr
	}

	if isInit {
		mergedIAM := iam.MergeRoleOptions(remoteStateTGConfig.GetIAMRoleOptions(), pctx.OriginalIAMRoleOptions)
		if err = creds.NewGetter().ObtainAndUpdateEnvIfNecessary(
			ctx,
			l,
			pctx.Venv,
			externalcmd.NewProvider(l, pctx.AuthProviderCmd, shellRunOptsFromPctx(pctx)),
			amazonsts.NewProvider(l, mergedIAM, pctx.Venv.Env),
		); err != nil {
			return nil, "", err
		}

		out, fetchErr := getTerragruntOutputJSONFromInitFolder(
			ctx,
			pctx,
			l,
			workingDir,
		)

		return out, "init_folder", fetchErr
	}

	out, fetchErr := getTerragruntOutputJSONFromRemoteState(
		ctx,
		pctx,
		l,
		targetConfig,
		remoteStateTGConfig.RemoteState,
		remoteStateTGConfig.GetIAMRoleOptions(),
	)

	return out, "state", fetchErr
}

// canGetRemoteState returns true if the remote state block is not nil and dependency optimization is not disabled
func canGetRemoteState(remoteState *remotestate.RemoteState) bool {
	return remoteState != nil && !remoteState.DisableDependencyOptimization
}

// applyExtraArgsEnvVarsForOutput merges extra_arguments env_vars whose commands include output into pctx.Venv.Env
func applyExtraArgsEnvVarsForOutput(pctx *ParsingContext, terraformConfig *TerraformConfig) {
	if terraformConfig == nil {
		return
	}

	for i := range terraformConfig.ExtraArgs {
		arg := &terraformConfig.ExtraArgs[i]
		if arg.EnvVars == nil || !slices.Contains(arg.Commands, tf.CommandNameOutput) {
			continue
		}

		maps.Copy(pctx.Venv.Env, *arg.EnvVars)
	}
}

// terragruntAlreadyInit returns true if it detects that the module specified by the given terragrunt configuration is
// already initialized with the terraform source. This will also return the working directory where you can run
// terraform.
func terragruntAlreadyInit(ctx context.Context, l log.Logger, pctx *ParsingContext, configPath string) (bool, string, error) {
	// We need to first determine the working directory where the terraform source should be located. This is dependent
	// on the source field of the terraform block in the config.
	terraformBlockTGConfig, err := PartialParseConfigFile(ctx, pctx.WithDecodeList(TerraformSource), l, configPath, nil)
	if err != nil {
		return false, "", err
	}

	sourceURL, err := GetTerraformSourceURL(pctx.Source, pctx.SourceMap, pctx.OriginalTerragruntConfigPath, terraformBlockTGConfig)
	if err != nil {
		return false, "", err
	}

	// sourceURL will always be at least "." (current directory) to ensure cache is always used.
	// Always compute the cache working directory using NewSource.
	walkWithSymlinks := pctx.Experiments.Evaluate(experiment.Symlinks)
	// Apply the rewrite so the .terraform existence check below targets the
	// same working dir the downloader writes to. Without it, plain
	// https://www.googleapis.com/storage/... sources force a redundant init
	// on every run.
	sourceURL = tf.RewriteLegacyGCSPublicSource(ctx, l, sourceURL, pctx.StrictControls)

	terraformSource, err := tf.NewSource(l, sourceURL, pctx.DownloadDir, pctx.WorkingDir, walkWithSymlinks)
	if err != nil {
		return false, "", err
	}
	// We're only interested in the computed working dir.
	workingDir := terraformSource.WorkingDir
	// Terragrunt is already init-ed if the terraform state dir (.terraform) exists in the working dir.
	// NOTE: if the ref changes, the workingDir would be different as the download dir includes a base64 encoded hash of
	// the source URL with ref. This would ensure that this routine would not return true if the new ref is not already
	// init-ed.
	return util.FileExists(filepath.Join(workingDir, ".terraform")), workingDir, nil
}

// getTerragruntOutputJSONFromInitFolder will retrieve the outputs directly from the module's working directory without
// running init. Callers must populate pctx.Venv.Env with auth-provider-cmd credentials and any
// TG_IAM_ROLE assumption beforehand.
func getTerragruntOutputJSONFromInitFolder(
	ctx context.Context,
	pctx *ParsingContext,
	l log.Logger,
	terraformWorkingDir string,
) ([]byte, error) {
	targetConfigPath := pctx.TerragruntConfigPath

	tfRunOpts := setupTFRunOptsForBareTerraform(pctx, terraformWorkingDir)

	l.Debugf(
		"Unit '%s' is already init-ed. "+
			"Retrieving outputs directly from working directory.",
		util.RelPathForLog(
			pctx.RootWorkingDir,
			filepath.Dir(targetConfigPath),
			pctx.LogShowAbsPaths,
		),
	)

	bareCtx := tf.ContextWithTerraformCommandHook(ctx, nil)

	// Discard streamed stdout; the JSON is read from the returned CmdOutput.
	discardV := pctx.Venv.WithWriter(io.Discard)

	out, err := tf.RunCommandWithOutput(bareCtx, l, discardV, tfRunOpts, tf.CommandNameOutput, "-json")
	if err != nil {
		return nil, err
	}

	jsonString := strings.TrimSpace(out.Stdout.String())
	jsonBytes := []byte(jsonString)

	l.Debugf(
		"Retrieved output from %s as json: %s",
		util.RelPathForLog(
			pctx.RootWorkingDir,
			targetConfigPath,
			pctx.LogShowAbsPaths,
		),
		jsonString,
	)

	return jsonBytes, nil
}

// getTerragruntOutputJSONFromRemoteState will retrieve the outputs directly by using just the remote state block. This
// uses terraform's feature where `output` and `init` can work without the real source, as long as you have the
// `backend` configured.
// To do this, this function will:
// - Create a temporary folder
// - Generate the backend.tf file with the backend configuration from the remote_state block
// - Copy the provider lock file, if there is one in the dependency's working directory
// - Run terraform init and terraform output
// - Clean up folder once json file is generated
// NOTE: terragruntOptions should be in the ctx of the targetConfig already.
func getTerragruntOutputJSONFromRemoteState(
	ctx context.Context,
	pctx *ParsingContext,
	l log.Logger,
	targetConfigPath string,
	remoteState *remotestate.RemoteState,
	iamRoleOpts iam.RoleOptions,
) ([]byte, error) {
	l.Debugf("Detected remote state block with generate config. Resolving dependency by pulling remote state.")
	// Create working directory where we will run terraform in. We will create the temporary directory in the download
	// directory for consistency with other file generation capabilities of terragrunt. Make sure it is cleaned up
	// before the function returns.
	if err := util.EnsureDirectory(pctx.DownloadDir); err != nil {
		return nil, err
	}

	tempWorkDir, err := os.MkdirTemp(pctx.DownloadDir, "")
	if err != nil {
		return nil, err
	}

	defer func(path string) {
		err := os.RemoveAll(path)
		if err != nil {
			l.Warnf("Failed to remove %s: %v", path, err)
		}
	}(tempWorkDir)

	l.Debugf("Setting dependency working directory to %s", tempWorkDir)

	mergedIAM := iam.MergeRoleOptions(iamRoleOpts, pctx.OriginalIAMRoleOptions)
	if err = creds.NewGetter().ObtainAndUpdateEnvIfNecessary(
		ctx,
		l,
		pctx.Venv,
		externalcmd.NewProvider(l, pctx.AuthProviderCmd, shellRunOptsFromPctx(pctx)),
		amazonsts.NewProvider(l, mergedIAM, pctx.Venv.Env),
	); err != nil {
		return nil, err
	}

	tfRunOpts := setupTFRunOptsForBareTerraform(pctx, tempWorkDir)

	// To speed up dependencies processing it is possible to retrieve its output directly from the backend without init dependencies
	if pctx.Experiments.Evaluate(experiment.DependencyFetchOutputFromState) && !pctx.NoDependencyFetchOutputFromState {
		switch backend := remoteState.BackendName; backend {
		case s3backend.BackendName:
			jsonBytes, s3GetErr := getTerragruntOutputJSONFromRemoteStateS3(
				ctx,
				l,
				pctx,
				remoteState,
			)
			if s3GetErr != nil {
				return nil, s3GetErr
			}

			l.Debugf("Retrieved output from %s as json: %s using s3 bucket", pctx.TerragruntConfigPath, jsonBytes)

			return jsonBytes, nil
		default:
			l.Debugf("dependency-fetch-output-from-state experiment is not supported for backend %s, falling back to default output retrieval", backend)
		}
	}

	// Generate the backend configuration in the working dir. If no generate config is set on the remote state block,
	// set a temporary generate config so we can generate the backend code.
	if remoteState.Generate == nil {
		remoteState.Generate = &remotestate.ConfigGenerate{
			Path:     "backend.tf",
			IfExists: codegen.ExistsOverwriteTerragruntStr,
		}
	}

	if err := remoteState.GenerateOpenTofuCode(l, tempWorkDir); err != nil {
		return nil, err
	}

	l.Debugf("Generated remote state configuration in working dir %s", tempWorkDir)

	// Check for a provider lock file and copy it to the working dir if it exists.
	terragruntDir := filepath.Dir(pctx.TerragruntConfigPath)
	if err := CopyLockFile(l, pctx.RootWorkingDir, pctx.LogShowAbsPaths, terragruntDir, tempWorkDir); err != nil {
		return nil, err
	}

	// The working directory is now set up to interact with the state, so pull it down to get the json output.

	// Clone pctx and discard init stdout so it doesn't leak into the caller's output buffer.
	initPctx := pctx.Clone()
	initPctx.Venv = initPctx.Venv.WithWriter(io.Discard)

	// First run init to setup the backend configuration so that we can run output.
	runTerraformInitForDependencyOutput(ctx, initPctx, l, tempWorkDir)

	// Now that the backend is initialized, run terraform output to get the data and return it.
	bareCtx := tf.ContextWithTerraformCommandHook(ctx, nil)

	// Discard streamed stdout; the JSON is read from the returned CmdOutput.
	discardV := pctx.Venv.WithWriter(io.Discard)

	out, err := tf.RunCommandWithOutput(bareCtx, l, discardV, tfRunOpts, tf.CommandNameOutput, "-json")
	if err != nil {
		return nil, err
	}

	jsonString := strings.TrimSpace(out.Stdout.String())
	jsonBytes := []byte(jsonString)
	l.Debugf("Retrieved output from %s as json: %s", targetConfigPath, jsonString)

	return jsonBytes, nil
}

// getTerragruntOutputJSONFromRemoteStateS3 pulls the output directly from an S3 bucket without calling Terraform
func getTerragruntOutputJSONFromRemoteStateS3(ctx context.Context, l log.Logger, pctx *ParsingContext, remoteState *remotestate.RemoteState) ([]byte, error) {
	bucket := fmt.Sprintf("%s", remoteState.BackendConfig["bucket"])
	key := fmt.Sprintf("%s", remoteState.BackendConfig["key"])

	l.Debugf("Fetching outputs directly from s3://%s/%s", bucket, key)

	var jsonOutputs []byte

	err := telemetry.TelemeterFromContext(ctx).Collect(ctx, "dependency_output_state_s3", map[string]any{
		"bucket": bucket,
		"key":    key,
	}, func(ctx context.Context) error {
		s3ConfigExtended, err := s3backend.Config(remoteState.BackendConfig).ParseExtendedS3Config()
		if err != nil {
			return fmt.Errorf("parsing s3 backend config for s3://%s/%s: %w", bucket, key, err)
		}

		sessionConfig := s3ConfigExtended.GetAwsSessionConfig()

		s3Client, err := awshelper.NewAWSConfigBuilder().
			WithSessionConfig(sessionConfig).
			WithEnv(pctx.Venv.Env).
			WithIAMRoleOptions(pctx.IAMRoleOptions).
			BuildS3Client(ctx, l)
		if err != nil {
			return fmt.Errorf("building s3 client for s3://%s/%s: %w", bucket, key, err)
		}

		result, err := s3Client.GetObject(ctx, &s3.GetObjectInput{
			Bucket: aws.String(bucket),
			Key:    aws.String(key),
		})
		if err != nil {
			return fmt.Errorf("fetching dependency state from s3://%s/%s: %w", bucket, key, err)
		}

		defer func(Body io.ReadCloser) {
			err := Body.Close()
			if err != nil {
				l.Warnf("Failed to close remote state response %v", err)
			}
		}(result.Body)

		steateBody, err := io.ReadAll(result.Body)
		if err != nil {
			return fmt.Errorf("reading dependency state body from s3://%s/%s: %w", bucket, key, err)
		}

		jsonMap := make(map[string]any)
		if err := json.Unmarshal(steateBody, &jsonMap); err != nil {
			return fmt.Errorf("parsing dependency state JSON from s3://%s/%s: %w", bucket, key, err)
		}

		jsonOutputs, err = json.Marshal(jsonMap["outputs"])
		if err != nil {
			return fmt.Errorf("encoding outputs from dependency state at s3://%s/%s: %w", bucket, key, err)
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	return jsonOutputs, nil
}

// setupTFRunOptsForBareTerraform builds a *tf.TFOptions for running terraform without
// going through the full RunTerragrunt operation. Callers must obtain credentials
// (auth-provider-cmd and any TG_IAM_ROLE assumption) before invoking, so those steps
// run from the unit's directory rather than the bare-terraform working directory.
func setupTFRunOptsForBareTerraform(pctx *ParsingContext, workingDir string) *tf.TFOptions {
	shellOpts := shellRunOptsFromPctx(pctx)
	shellOpts.WorkingDir = workingDir

	return &tf.TFOptions{
		JSONLogFormat:                pctx.JSONLogFormat,
		OriginalTerragruntConfigPath: pctx.OriginalTerragruntConfigPath,
		ShellOptions:                 shellOpts,
	}
}

// runTerragruntOutputJSON uses terragrunt running functions to extract the json output from the target config.
func runTerragruntOutputJSON(ctx context.Context, pctx *ParsingContext, l log.Logger, targetConfig string) ([]byte, error) {
	// Update the stdout buffer so we can capture the output
	var stdoutBuffer bytes.Buffer

	stdoutBufferWriter := bufio.NewWriter(&stdoutBuffer)

	// Override pctx for this specific operation
	pctx = pctx.Clone()
	pctx.ForwardTFStdout = false
	pctx.JSONLogFormat = false
	pctx.Venv = pctx.Venv.WithWriter(stdoutBufferWriter)

	cfg, err := ParseConfigFile(ctx, pctx, l, pctx.TerragruntConfigPath, nil)
	if err != nil {
		return nil, err
	}

	// A `--source` override carries the module subdir of whichever unit the run started from, not the dependency being
	// resolved here, so retarget it to this module's own subdir before running. The full parse above resolves the
	// target's real source even when it references a dependency output (which the lightweight parse in resolveOutputJSON
	// cannot), making it the authoritative input. Without this, a dependency whose source consumes a dependency output
	// would run against the caller's stale subdir and read the wrong module's outputs.
	if err := adjustSourceForTargetModule(pctx, targetConfig, cfg); err != nil {
		return nil, err
	}

	runCfg := cfg.ToRunConfig(l)

	credsGetter := creds.NewGetter()
	if err = credsGetter.ObtainAndUpdateEnvIfNecessary(
		ctx,
		l,
		pctx.Venv,
		externalcmd.NewProvider(l, pctx.AuthProviderCmd, shellRunOptsFromPctx(pctx)),
	); err != nil {
		return nil, err
	}

	// Build run.Options directly from ParsingContext fields.
	runOpts := run.NewOptions()
	runOpts.LogShowAbsPaths = pctx.LogShowAbsPaths
	runOpts.LogDisableErrorSummary = pctx.LogDisableErrorSummary
	runOpts.TerragruntConfigPath = pctx.TerragruntConfigPath
	runOpts.OriginalTerragruntConfigPath = pctx.OriginalTerragruntConfigPath
	runOpts.UnitDir = pctx.WorkingDir
	runOpts.CacheDir = pctx.WorkingDir
	runOpts.RootWorkingDir = pctx.RootWorkingDir
	runOpts.DownloadDir = pctx.DownloadDir
	runOpts.Source = pctx.Source
	runOpts.SourceMap = pctx.SourceMap
	runOpts.TerraformCommand = pctx.TerraformCommand
	runOpts.OriginalTerraformCommand = pctx.OriginalTerraformCommand
	runOpts.TerraformCliArgs = pctx.TerraformCliArgs
	runOpts.IAMRoleOptions = pctx.IAMRoleOptions
	runOpts.OriginalIAMRoleOptions = pctx.OriginalIAMRoleOptions
	runOpts.Experiments = pctx.Experiments
	runOpts.StrictControls = pctx.StrictControls
	runOpts.FeatureFlags = pctx.FeatureFlags
	runOpts.EngineConfig = pctx.EngineConfig
	runOpts.EngineOptions = pctx.EngineOptions
	runOpts.TFPath = pctx.TFPath
	runOpts.TofuImplementation = pctx.TofuImplementation
	runOpts.Headless = pctx.Headless
	runOpts.Debug = pctx.Debug
	runOpts.AutoInit = pctx.AutoInit
	runOpts.BackendBootstrap = pctx.BackendBootstrap
	runOpts.Telemetry = pctx.Telemetry
	runOpts.AuthProviderCmd = pctx.AuthProviderCmd
	runOpts.CASCloneDepth = pctx.CASCloneDepth

	err = run.Run(ctx, l, pctx.Venv, runOpts, report.NewReport(), runCfg, credsGetter)
	if err != nil {
		return nil, err
	}

	err = stdoutBufferWriter.Flush()
	if err != nil {
		return nil, err
	}

	jsonString := strings.TrimSpace(stdoutBuffer.String())
	jsonBytes := []byte(jsonString)

	l.Debugf("Retrieved output from %s as json: %s", targetConfig, jsonString)

	return jsonBytes, nil
}

// shellRunOptsFromPctx builds a *shell.ShellOptions from ParsingContext flat fields.
func shellRunOptsFromPctx(pctx *ParsingContext) *shell.ShellOptions {
	s := shell.NewShellOptions().
		WithWorkingDir(pctx.WorkingDir).
		WithTelemetry(pctx.Telemetry).
		WithEngine(pctx.EngineConfig, pctx.EngineOptions).
		WithTFPath(pctx.TFPath).
		WithRootWorkingDir(pctx.RootWorkingDir).
		WithExperiments(pctx.Experiments).
		WithHeadless(pctx.Headless).
		WithForwardTFStdout(pctx.ForwardTFStdout)
	s.LogShowAbsPaths = pctx.LogShowAbsPaths
	s.LogDisableErrorSummary = pctx.LogDisableErrorSummary

	return s
}

// tfRunOptsFromPctx builds a *tf.RunOptions from ParsingContext flat fields.
func tfRunOptsFromPctx(pctx *ParsingContext) *tf.TFOptions {
	return &tf.TFOptions{
		JSONLogFormat:                pctx.JSONLogFormat,
		OriginalTerragruntConfigPath: pctx.OriginalTerragruntConfigPath,
		ShellOptions:                 shellRunOptsFromPctx(pctx),
	}
}

// TerraformOutputJSONToCtyValueMap takes the terraform output json and converts to a mapping between output keys to the
// parsed cty.Value encoding of the json objects.
func TerraformOutputJSONToCtyValueMap(targetConfigPath string, jsonBytes []byte) (map[string]cty.Value, error) {
	// When getting all outputs, terraform returns a json with the data containing metadata about the types, so we
	// can't quite return the data directly. Instead, we will need further processing to get the output we want.
	// To do so, we first Unmarshal the json into a simple go map to a OutputMeta struct.
	type OutputMeta struct {
		Type      json.RawMessage `json:"type"`
		Value     json.RawMessage `json:"value"`
		Sensitive bool            `json:"sensitive"`
	}

	var outputs map[string]OutputMeta

	err := json.Unmarshal(jsonBytes, &outputs)
	if err != nil {
		return nil, TerragruntOutputParsingError{Path: targetConfigPath, Err: err}
	}

	flattenedOutput := map[string]cty.Value{}

	for k, v := range outputs {
		outputType, err := ctyjson.UnmarshalType(v.Type)
		if err != nil {
			return nil, TerragruntOutputParsingError{Path: targetConfigPath, Err: err}
		}

		outputVal, err := ctyjson.Unmarshal(v.Value, outputType)
		if err != nil {
			return nil, TerragruntOutputParsingError{Path: targetConfigPath, Err: err}
		}

		flattenedOutput[k] = outputVal
	}

	return flattenedOutput, nil
}

// runTerraformInitForDependencyOutput will run terraform init in a mode that doesn't pull down plugins or modules. Note
// that this will cause the command to fail for most modules as terraform init does a validation check to make sure the
// plugins are available, even though we don't need it for our purposes (terraform output does not depend on any of the
// plugins being available). As such this command will ignore errors in the init command.
// To help with debuggability, the errors will be printed to the console when TG_LOG=debug is set.
func runTerraformInitForDependencyOutput(ctx context.Context, pctx *ParsingContext, l log.Logger, workingDir string) {
	stderr := bytes.Buffer{}

	initRunOpts := tfRunOptsFromPctx(pctx)
	initRunOpts.ShellOptions.WorkingDir = workingDir

	initV := pctx.Venv.WithErrWriter(&stderr)

	bareCtx := tf.ContextWithTerraformCommandHook(ctx, nil)

	if err := tf.RunCommand(bareCtx, l, initV, initRunOpts, tf.CommandNameInit, "-get=false"); err != nil {
		l.Debugf("Ignoring expected error from dependency init call")
		l.Debugf("Init call stderr:")
		l.Debugf("%s", stderr.String())
	}
}

func (deps Dependencies) FilteredWithoutConfigPath() Dependencies {
	var filteredDeps Dependencies

	for _, dep := range deps {
		if !dep.ConfigPath.IsNull() {
			filteredDeps = append(filteredDeps, dep)
		}
	}

	return filteredDeps
}

// foldSiblingAutoIncludeDeps merges the registered sibling autoinclude dependency blocks over the unit's own same-name blocks (shallow, by name, with the autoinclude winning), mirroring a regular include's default merge strategy.
func foldSiblingAutoIncludeDeps(ctx context.Context, pctx *ParsingContext, l log.Logger, deps []Dependency) ([]Dependency, error) {
	if pctx.TrackInclude == nil || pctx.TrackInclude.AutoIncludeOverride == nil {
		return deps, nil
	}

	autoIncludePath := pctx.TrackInclude.AutoIncludeOverride.Path

	autoFile, err := parseAutoIncludeFileCached(ctx, pctx, autoIncludePath)
	if err != nil {
		return nil, err
	}

	// Rescope to the autoinclude's own locals so the unit's locals do not leak into the autoinclude decode.
	autoPctx := pctx.Clone()
	// Files the autoinclude pulls in through its own includes must not re-merge a sibling autoinclude.
	autoPctx.skipAutoIncludeMerge = true

	baseBlocks, err := DecodeBaseBlocks(ctx, autoPctx, l, autoFile, nil)
	if err != nil {
		return nil, err
	}

	if baseBlocks != nil {
		autoPctx = autoPctx.WithTrackInclude(baseBlocks.TrackInclude)
		autoPctx = autoPctx.WithFeatures(baseBlocks.FeatureFlags)
		autoPctx = autoPctx.WithLocals(baseBlocks.Locals)
	}

	evalCtx, err := createTerragruntEvalContext(ctx, autoPctx, l, autoIncludePath)
	if err != nil {
		return nil, err
	}

	decoded := TerragruntDependency{}
	if err := autoFile.Decode(&decoded, evalCtx); err != nil {
		return nil, err
	}

	// Fold in dependency blocks the autoinclude inherits through its own include blocks, mirroring the unit decode path so inherited deps resolve before the unit body is evaluated.
	if autoPctx.TrackInclude != nil && len(autoPctx.TrackInclude.CurrentList) > 0 {
		merged, err := handleIncludeForDependency(ctx, autoPctx, l, decoded)
		if err != nil {
			return nil, err
		}

		decoded = *merged
	}

	autoDeps := decoded.Dependencies.FilteredWithoutConfigPath()
	if len(autoDeps) == 0 {
		return deps, nil
	}

	return mergeDependencyBlocks(deps, autoDeps), nil
}

// parseAutoIncludeFileCached parses the sibling autoinclude through the run-scoped HCL file cache so repeated dependency-output decodes reuse one parse, rebinding the shared AST to a fresh parser per call.
func parseAutoIncludeFileCached(ctx context.Context, pctx *ParsingContext, autoIncludePath string) (*hclparse.File, error) {
	fileInfo, err := os.Stat(autoIncludePath)
	if err != nil {
		return nil, err
	}

	hclCache := cache.ContextCache[*hclparse.File](ctx, HclCacheContextKey)
	// Prefix the key so it cannot collide with the unit-config keys ParseConfigFile stores.
	cacheKey := fmt.Sprintf("autoinclude-%v-%v", autoIncludePath, fileInfo.ModTime().UnixMicro())

	if cached, found := hclCache.Get(ctx, cacheKey); found {
		return cached.Rebind(hclparse.NewParser(pctx.ParserOptions...)), nil
	}

	file, err := hclparse.NewParser(pctx.ParserOptions...).ParseFromFile(autoIncludePath)
	if err != nil {
		return nil, err
	}

	hclCache.Put(ctx, cacheKey, file)

	return file, nil
}

// IsValidConfigPath checks if a cty.Value is a valid, usable config path.
func IsValidConfigPath(v cty.Value) bool {
	if v.IsNull() || !v.IsWhollyKnown() || !v.Type().Equals(cty.String) {
		return false
	}

	// Empty string is not a valid config path
	if v.AsString() == "" {
		return false
	}

	return true
}
