package pipeline

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"slices"
	"strings"

	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/erf"
	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/gff"
	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/project"
)

type ExtractResult struct {
	ModulePath          string
	HAKPaths            []string
	DeletedArchivePaths []string
	Written             int
	Overwritten         int
	Removed             int
	Skipped             int
}

type extractionArchive struct {
	Path      string
	Rel       string
	Extension string
}

type extractionScope struct {
	Source bool
	Assets bool
}

func Extract(p *project.Project, files ...string) (ExtractResult, error) {
	var result ExtractResult
	var failures []error
	desired := map[string]struct{}{}
	scope := extractionScope{}

	archives, err := resolveExtractionArchives(p, files)
	if err != nil {
		return result, err
	}
	for _, archivePath := range archives {
		input, err := os.Open(archivePath.Path)
		if err != nil {
			failures = append(failures, fmt.Errorf("open archive %s: %w", archivePath.Path, err))
			continue
		}
		archive, err := erf.Read(input)
		input.Close()
		if err != nil {
			failures = append(failures, fmt.Errorf("read archive %s: %w", archivePath.Path, err))
			continue
		}

		switch archivePath.Extension {
		case ".mod":
			if result.ModulePath == "" {
				result.ModulePath = archivePath.Path
			}
		case ".hak":
			result.HAKPaths = append(result.HAKPaths, archivePath.Path)
		}

		written, overwritten, skipped, extractedScope, errs := extractArchiveResources(p, archive, desired)
		result.Written += written
		result.Overwritten += overwritten
		result.Skipped += skipped
		scope.Source = scope.Source || extractedScope.Source
		scope.Assets = scope.Assets || extractedScope.Assets
		failures = append(failures, errs...)
	}

	if p.EffectiveConfig().Extract.CleanupStale == nil || *p.EffectiveConfig().Extract.CleanupStale {
		removed, errs := cleanupStaleFiles(p, desired, scope)
		result.Removed = removed
		failures = append(failures, errs...)
	}

	if len(failures) > 0 {
		return result, errors.Join(failures...)
	}
	consumeAll, consumeModules := extractionConsumePolicy(p)
	if consumeAll || consumeModules {
		for _, archivePath := range archives {
			if !consumeAll && archivePath.Extension != ".mod" {
				continue
			}
			if err := os.Remove(archivePath.Path); err != nil {
				return result, fmt.Errorf("delete consumed archive %s: %w", archivePath.Path, err)
			}
			result.DeletedArchivePaths = append(result.DeletedArchivePaths, archivePath.Path)
		}
	}
	return result, nil
}

func extractArchiveResources(p *project.Project, archive erf.Archive, desired map[string]struct{}) (int, int, int, extractionScope, []error) {
	var failures []error
	writtenCount := 0
	overwrittenCount := 0
	skippedCount := 0
	scope := extractionScope{}

	ignored := make(map[string]bool)
	for _, ext := range p.Config.Extract.IgnoreExtensions {
		ext := strings.TrimPrefix(ext, ".")
		ignored[ext] = true
	}

	for _, resource := range archive.Resources {
		ext, ok := erf.ExtensionForResourceType(resource.Type)
		if !ok {
			failures = append(failures, fmt.Errorf("unsupported resource type 0x%04X for %s", resource.Type, resource.Name))
			continue
		}
		if ignored[ext] {
			skippedCount++
			continue
		}

		target, data, err := extractedFile(p, resource, ext)
		if err != nil {
			failures = append(failures, err)
			continue
		}
		desired[target] = struct{}{}
		scope.Source = scope.Source || pathWithinRoot(target, p.SourceDir())
		scope.Assets = scope.Assets || pathWithinRoot(target, p.AssetsDir())

		state, err := writeManagedFile(target, data)
		if err != nil {
			failures = append(failures, err)
			continue
		}
		switch state {
		case writeNew:
			writtenCount++
		case writeOverwritten:
			overwrittenCount++
		case writeSkipped:
			skippedCount++
		}
	}

	return writtenCount, overwrittenCount, skippedCount, scope, failures
}

func resolveExtractionArchives(p *project.Project, overrides []string) ([]extractionArchive, error) {
	patterns := p.EffectiveConfig().Extract.Archives
	if len(overrides) > 0 {
		patterns = overrides
	}
	if len(patterns) == 0 {
		return nil, fmt.Errorf("extract.archives must contain at least one build-relative archive pattern")
	}

	buildRoot := filepath.Clean(p.BuildDir())
	byPath := map[string]extractionArchive{}
	for _, rawPattern := range patterns {
		pattern, err := normalizeExtractionArchivePattern(p, rawPattern)
		if err != nil {
			return nil, err
		}
		matched, err := matchExtractionArchives(buildRoot, pattern)
		if err != nil {
			return nil, err
		}
		if len(matched) == 0 {
			return nil, fmt.Errorf("extract archive pattern %q matched no files under %s", rawPattern, buildRoot)
		}
		for _, archive := range matched {
			byPath[archive.Path] = archive
		}
	}

	archives := make([]extractionArchive, 0, len(byPath))
	for _, archive := range byPath {
		archives = append(archives, archive)
	}
	slices.SortFunc(archives, func(a, b extractionArchive) int {
		return strings.Compare(a.Rel, b.Rel)
	})
	return archives, nil
}

func normalizeExtractionArchivePattern(p *project.Project, raw string) (string, error) {
	pattern := strings.TrimSpace(raw)
	if pattern == "" {
		return "", fmt.Errorf("extract archive pattern must not be empty")
	}
	pattern = strings.NewReplacer(
		"{module.resref}", strings.TrimSpace(p.Config.Module.ResRef),
	).Replace(pattern)
	if strings.Contains(pattern, "\x00") {
		return "", fmt.Errorf("extract archive pattern %q must not contain NUL bytes", raw)
	}
	if filepath.IsAbs(pattern) {
		return "", fmt.Errorf("extract archive pattern %q must be relative to paths.build", raw)
	}
	clean := filepath.Clean(filepath.FromSlash(pattern))
	if clean == "." || clean == ".." || strings.HasPrefix(clean, ".."+string(filepath.Separator)) {
		return "", fmt.Errorf("extract archive pattern %q must not escape paths.build", raw)
	}
	return filepath.ToSlash(clean), nil
}

func matchExtractionArchives(buildRoot, pattern string) ([]extractionArchive, error) {
	var archives []extractionArchive
	err := filepath.WalkDir(buildRoot, func(path string, entry os.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if entry.IsDir() {
			return nil
		}
		rel, err := filepath.Rel(buildRoot, path)
		if err != nil {
			return err
		}
		rel = filepath.ToSlash(rel)
		if !matchPathPattern(rel, pattern) {
			return nil
		}
		archive, err := validateExtractionArchive(buildRoot, rel)
		if err != nil {
			return err
		}
		archives = append(archives, archive)
		return nil
	})
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil, fmt.Errorf("scan build directory %s: %w", buildRoot, err)
		}
		return nil, err
	}
	return archives, nil
}

func validateExtractionArchive(buildRoot, rel string) (extractionArchive, error) {
	cleanRel := filepath.Clean(filepath.FromSlash(rel))
	if cleanRel == "." || cleanRel == ".." || strings.HasPrefix(cleanRel, ".."+string(filepath.Separator)) {
		return extractionArchive{}, fmt.Errorf("extract archive %q must not escape paths.build", rel)
	}
	path := filepath.Join(buildRoot, cleanRel)
	if !pathWithinRoot(path, buildRoot) {
		return extractionArchive{}, fmt.Errorf("extract archive %q resolves outside paths.build", rel)
	}
	extension := strings.ToLower(filepath.Ext(cleanRel))
	switch extension {
	case ".mod", ".hak":
		return extractionArchive{Path: path, Rel: filepath.ToSlash(cleanRel), Extension: extension}, nil
	case ".erf":
		return extractionArchive{}, fmt.Errorf("extract archive %q is an .erf; ERF extraction is unsafe because ERFs lack module.ifo context", rel)
	default:
		return extractionArchive{}, fmt.Errorf("extract archive %q uses unsupported extension %q", rel, extension)
	}
}

func extractionConsumePolicy(p *project.Project) (consumeAll bool, consumeModules bool) {
	if configured := p.Config.Extract.ConsumeArchives; configured != nil {
		return *configured, false
	}
	return false, p.Config.Extract.DeleteModuleArchiveAfterSuccess
}

func pathWithinRoot(path, root string) bool {
	root = filepath.Clean(root)
	if root == "" || root == "." {
		return false
	}
	rel, err := filepath.Rel(root, path)
	if err != nil {
		return false
	}
	return rel != ".." && !strings.HasPrefix(rel, ".."+string(filepath.Separator)) && !filepath.IsAbs(rel)
}

func extractedFile(p *project.Project, resource erf.Resource, extension string) (string, []byte, error) {
	resref := strings.ToLower(resource.Name)
	effective := p.EffectiveConfig()

	switch extension {
	case "nss":
		target, err := extractionTarget(p, "paths.source", effective.Paths.Source, p.SourceDir(), filepath.FromSlash(effective.Scripts.SourceDir), resref+".nss")
		if err != nil {
			return "", nil, err
		}
		return target, resource.Data, nil
	case "utc", "utd", "ute", "uti", "utm", "utp", "uts", "utt", "utw",
		"are", "dlg", "fac", "gic", "git", "ifo", "itp", "jrl":
		document, err := gff.Read(bytes.NewReader(resource.Data))
		if err != nil {
			return "", nil, fmt.Errorf("decode gff %s.%s: %w", resource.Name, extension, err)
		}
		target, err := extractionTarget(p, "paths.source", effective.Paths.Source, p.SourceDir(), sourceSubdir(extension), resref+"."+extension+".json")
		if err != nil {
			return "", nil, err
		}
		if err := mergeExtractedGFFJSON(p, target, &document); err != nil {
			return "", nil, fmt.Errorf("merge extracted gff json %s.%s: %w", resource.Name, extension, err)
		}
		formatted, err := json.MarshalIndent(document, "", "  ")
		if err != nil {
			return "", nil, fmt.Errorf("marshal json %s.%s: %w", resource.Name, extension, err)
		}
		formatted = append(formatted, '\n')
		return target, formatted, nil
	default:
		target, err := extractionTarget(p, "paths.assets", effective.Paths.Assets, p.AssetsDir(), extension, resref+"."+extension)
		if err != nil {
			return "", nil, err
		}
		return target, resource.Data, nil
	}
}

func extractionTarget(p *project.Project, field, configured, root string, parts ...string) (string, error) {
	if strings.TrimSpace(configured) == "" {
		return "", fmt.Errorf("cannot extract resource: %s is not configured", field)
	}

	cleanRoot := filepath.Clean(root)
	if cleanRoot == "." || cleanRoot == string(filepath.Separator) || cleanRoot == filepath.Clean(p.Root) {
		return "", fmt.Errorf("cannot extract resource: %s resolves to unsafe extraction root %s", field, cleanRoot)
	}

	target := filepath.Join(append([]string{cleanRoot}, parts...)...)
	rel, err := filepath.Rel(cleanRoot, target)
	if err != nil {
		return "", fmt.Errorf("resolve extraction target %s: %w", target, err)
	}
	if rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) || filepath.IsAbs(rel) {
		return "", fmt.Errorf("refusing to extract resource outside %s: %s", cleanRoot, target)
	}
	return target, nil
}

func mergeExtractedGFFJSON(p *project.Project, target string, extracted *gff.Document) error {
	rule, ok, err := extractGFFJSONMergeRule(p, target)
	if err != nil || !ok {
		return err
	}

	raw, err := os.ReadFile(target)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil
		}
		return fmt.Errorf("read existing source %s: %w", target, err)
	}
	var existing gff.Document
	if err := json.Unmarshal(raw, &existing); err != nil {
		return fmt.Errorf("parse existing source %s: %w", target, err)
	}

	for _, label := range rule.PreserveFields {
		if field, ok := gffField(existing.Root, label); ok {
			setGFFField(&extracted.Root, field)
		}
	}
	for _, listRule := range rule.MergeLists {
		if err := mergeGFFListByKey(&extracted.Root, existing.Root, listRule); err != nil {
			return err
		}
	}
	return nil
}

func extractGFFJSONMergeRule(p *project.Project, target string) (project.ExtractGFFJSONMergeRule, bool, error) {
	rel, err := filepath.Rel(filepath.Clean(p.SourceDir()), filepath.Clean(target))
	if err != nil {
		return project.ExtractGFFJSONMergeRule{}, false, fmt.Errorf("resolve source-relative target %s: %w", target, err)
	}
	rel = filepath.ToSlash(rel)
	if rel == ".." || strings.HasPrefix(rel, "../") {
		return project.ExtractGFFJSONMergeRule{}, false, nil
	}
	for _, rule := range p.EffectiveConfig().Extract.Merge.GFFJSON {
		if rule.Target == rel {
			return rule, true, nil
		}
	}
	return project.ExtractGFFJSONMergeRule{}, false, nil
}

func gffField(s gff.Struct, label string) (gff.Field, bool) {
	for _, field := range s.Fields {
		if field.Label == label {
			return field, true
		}
	}
	return gff.Field{}, false
}

func setGFFField(s *gff.Struct, replacement gff.Field) {
	for index, field := range s.Fields {
		if field.Label == replacement.Label {
			s.Fields[index] = replacement
			return
		}
	}
	s.Fields = append(s.Fields, replacement)
}

func mergeGFFListByKey(extracted *gff.Struct, existing gff.Struct, rule project.ExtractListMergeRule) error {
	extractedField, ok := gffField(*extracted, rule.Field)
	if !ok {
		return fmt.Errorf("extracted field %q not found", rule.Field)
	}
	extractedList, ok := extractedField.Value.(gff.ListValue)
	if !ok {
		return fmt.Errorf("extracted field %q is %s, not List", rule.Field, extractedField.Type)
	}
	existingField, ok := gffField(existing, rule.Field)
	if !ok {
		return nil
	}
	existingList, ok := existingField.Value.(gff.ListValue)
	if !ok {
		return fmt.Errorf("existing field %q is %s, not List", rule.Field, existingField.Type)
	}

	extractedByKey := map[string]gff.Struct{}
	extractedOrder := make([]string, 0, len(extractedList))
	for _, item := range extractedList {
		key, err := gffStructKey(item, rule.KeyField)
		if err != nil {
			return fmt.Errorf("extracted field %q: %w", rule.Field, err)
		}
		if _, exists := extractedByKey[key]; exists {
			return fmt.Errorf("extracted field %q has duplicate %s key %q", rule.Field, rule.KeyField, key)
		}
		extractedByKey[key] = item
		extractedOrder = append(extractedOrder, key)
	}

	merged := make(gff.ListValue, 0, len(extractedList))
	seen := map[string]struct{}{}
	for _, item := range existingList {
		key, err := gffStructKey(item, rule.KeyField)
		if err != nil {
			return fmt.Errorf("existing field %q: %w", rule.Field, err)
		}
		if _, duplicate := seen[key]; duplicate {
			return fmt.Errorf("existing field %q has duplicate %s key %q", rule.Field, rule.KeyField, key)
		}
		if extractedItem, exists := extractedByKey[key]; exists {
			merged = append(merged, extractedItem)
			seen[key] = struct{}{}
		}
	}
	for _, key := range extractedOrder {
		if _, exists := seen[key]; exists {
			continue
		}
		merged = append(merged, extractedByKey[key])
	}

	setGFFField(extracted, gff.NewField(rule.Field, merged))
	return nil
}

func gffStructKey(s gff.Struct, keyField string) (string, error) {
	field, ok := gffField(s, keyField)
	if !ok {
		return "", fmt.Errorf("key field %q not found", keyField)
	}
	switch value := field.Value.(type) {
	case gff.ResRefValue:
		return string(value), nil
	case gff.StringValue:
		return string(value), nil
	default:
		return "", fmt.Errorf("key field %q is %s, not ResRef or CExoString", keyField, field.Type)
	}
}

type writeState int

const (
	writeSkipped writeState = iota
	writeNew
	writeOverwritten
)

func writeManagedFile(path string, data []byte) (writeState, error) {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return writeSkipped, fmt.Errorf("create parent directory for %s: %w", path, err)
	}

	existing, err := os.ReadFile(path)
	if err == nil {
		if bytes.Equal(existing, data) {
			return writeSkipped, nil
		}
		if err := os.WriteFile(path, data, 0o644); err != nil {
			return writeSkipped, fmt.Errorf("overwrite %s: %w", path, err)
		}
		return writeOverwritten, nil
	}
	if !errors.Is(err, os.ErrNotExist) {
		return writeSkipped, fmt.Errorf("check existing file %s: %w", path, err)
	}

	if err := os.WriteFile(path, data, 0o644); err != nil {
		return writeSkipped, fmt.Errorf("write %s: %w", path, err)
	}
	return writeNew, nil
}

func cleanupStaleFiles(p *project.Project, desired map[string]struct{}, scope extractionScope) (int, []error) {
	candidates := make([]string, 0, len(p.Inventory.SourceFiles)+len(p.Inventory.ScriptFiles)+len(p.Inventory.AssetFiles))
	if scope.Source && safeCleanupRoot(p.SourceDir(), p.Root) {
		for _, rel := range p.Inventory.SourceFiles {
			candidates = append(candidates, filepath.Join(p.SourceDir(), filepath.FromSlash(rel)))
		}
		for _, rel := range p.Inventory.ScriptFiles {
			candidates = append(candidates, filepath.Join(p.SourceDir(), filepath.FromSlash(rel)))
		}
	}
	if scope.Assets && safeCleanupRoot(p.AssetsDir(), p.Root) {
		for _, rel := range p.Inventory.AssetFiles {
			candidates = append(candidates, filepath.Join(p.AssetsDir(), filepath.FromSlash(rel)))
		}
	}

	removed := 0
	var failures []error
	for _, path := range candidates {
		if _, keep := desired[path]; keep {
			continue
		}
		if err := os.Remove(path); err != nil {
			if errors.Is(err, os.ErrNotExist) {
				continue
			}
			failures = append(failures, fmt.Errorf("remove stale file %s: %w", path, err))
			continue
		}
		removed++
		cleanupEmptyParents(filepath.Dir(path), p.SourceDir(), p.AssetsDir())
	}

	return removed, failures
}

func safeCleanupRoot(root, projectRoot string) bool {
	cleanRoot := filepath.Clean(root)
	return cleanRoot != "." && cleanRoot != string(filepath.Separator) && cleanRoot != filepath.Clean(projectRoot)
}

func cleanupEmptyParents(dir string, roots ...string) {
	for {
		if dir == "." || dir == string(filepath.Separator) {
			return
		}
		stop := false
		for _, root := range roots {
			if dir == root {
				stop = true
				break
			}
		}
		if stop {
			return
		}
		if err := os.Remove(dir); err != nil {
			return
		}
		dir = filepath.Dir(dir)
	}
}

func sourceSubdir(extension string) string {
	switch strings.ToLower(extension) {
	case "are":
		return "areas"
	case "dlg":
		return "dialogs"
	case "fac":
		return "factions"
	case "gic":
		return "instance"
	case "git":
		return "instance"
	case "ifo":
		return "module"
	case "itp":
		return "palettes"
	case "jrl":
		return "journal"
	case "utc":
		return filepath.Join("blueprints", "creatures")
	case "utd":
		return filepath.Join("blueprints", "doors")
	case "ute":
		return filepath.Join("blueprints", "encounters")
	case "uti":
		return filepath.Join("blueprints", "items")
	case "utm":
		return filepath.Join("blueprints", "merchants")
	case "utp":
		return filepath.Join("blueprints", "placeables")
	case "uts":
		return filepath.Join("blueprints", "sounds")
	case "utt":
		return filepath.Join("blueprints", "triggers")
	case "utw":
		return filepath.Join("blueprints", "waypoints")
	default:
		return extension
	}
}