package validator

import (
	"encoding/json"
	"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 Severity string

const (
	SeverityError   Severity = "error"
	SeverityWarning Severity = "warning"
)

type Diagnostic struct {
	Path     string
	Message  string
	Severity Severity
}

type Report struct {
	Diagnostics []Diagnostic
	SourceCount int
}

type loadedDocument struct {
	Path      string
	ResRef    string
	Extension string
	Document  gff.Document
}

type assetOccurrence struct {
	Path  string
	Group string
}

type assetGroupResolver struct {
	configs      []project.HAKConfig
	defaultGroup string
}

var requiredFields = map[string][]string{
	"ifo": {"Mod_Name"},
}

var builtinScriptPrefixes = []string{
	"nw_",
	"x0_",
	"x1_",
	"x2_",
	"x3_",
	"ga_",
	"gc_",
	"gen_",
	"gui_",
	"nwg_",
	"ta_",
}

func ValidateProject(p *project.Project) Report {
	report := Report{}
	resourceIndex := map[string]string{}
	scriptIndex := map[string]string{}
	assetIndex := map[string]string{}
	assetOccurrences := map[string][]assetOccurrence{}
	documents := make([]loadedDocument, 0, len(p.Inventory.SourceFiles))
	resolver := newAssetGroupResolver(p)

	for _, rel := range p.Inventory.SourceFiles {
		if hasUppercaseResourceName(rel) {
			report.add(rel, "resource filenames should be lowercase", SeverityWarning)
		}
		abs := filepath.Join(p.SourceDir(), filepath.FromSlash(rel))
		document, resref, extension, err := loadDocument(abs)
		if err != nil {
			report.add(rel, err.Error(), SeverityError)
			continue
		}
		report.SourceCount++
		documents = append(documents, loadedDocument{
			Path:      rel,
			ResRef:    resref,
			Extension: extension,
			Document:  document,
		})

		key := strings.ToLower(resref) + "." + extension
		if previous, exists := resourceIndex[key]; exists {
			report.add(rel, fmt.Sprintf("duplicate resource %s also defined by %s", key, previous), SeverityError)
		} else {
			resourceIndex[key] = rel
		}

		validateDocumentStructure(&report, rel, extension, document)
	}

	for _, rel := range p.Inventory.ScriptFiles {
		if hasUppercaseResourceName(rel) {
			report.add(rel, "resource filenames should be lowercase", SeverityWarning)
		}
		base := strings.ToLower(strings.TrimSuffix(filepath.Base(rel), filepath.Ext(rel)))
		if previous, exists := scriptIndex[base]; exists {
			report.add(rel, fmt.Sprintf("duplicate script resource %s also defined by %s", base, previous), SeverityError)
		} else {
			scriptIndex[base] = rel
		}
	}

	for _, rel := range p.Inventory.AssetFiles {
		if hasUppercaseResourceName(rel) {
			report.add(rel, "resource filenames should be lowercase", SeverityWarning)
		}
		base := strings.ToLower(strings.TrimSuffix(filepath.Base(rel), filepath.Ext(rel)))
		extension := strings.TrimPrefix(strings.ToLower(filepath.Ext(rel)), ".")
		key := strings.ToLower(base) + "." + extension
		if _, exists := assetIndex[key]; !exists {
			assetIndex[key] = rel
		}

		group, err := resolver.groupFor(rel)
		if err != nil {
			report.add(rel, err.Error(), SeverityError)
			continue
		}

		assetOccurrences[key] = append(assetOccurrences[key], assetOccurrence{
			Path:  rel,
			Group: group,
		})
	}

	classifyAssetDuplicates(&report, assetOccurrences)

	for _, document := range documents {
		validateReferences(&report, document, resourceIndex, scriptIndex, assetIndex)
	}

	slices.SortFunc(report.Diagnostics, func(a, b Diagnostic) int {
		if cmp := strings.Compare(a.Path, b.Path); cmp != 0 {
			return cmp
		}
		if cmp := strings.Compare(string(a.Severity), string(b.Severity)); cmp != 0 {
			return cmp
		}
		return strings.Compare(a.Message, b.Message)
	})

	return report
}

func (r *Report) add(path, message string, severity Severity) {
	r.Diagnostics = append(r.Diagnostics, Diagnostic{Path: path, Message: message, Severity: severity})
}

func (r Report) HasErrors() bool {
	return r.ErrorCount() > 0
}

func (r Report) ErrorCount() int {
	count := 0
	for _, diagnostic := range r.Diagnostics {
		if diagnostic.Severity == SeverityError {
			count++
		}
	}
	return count
}

func (r Report) WarningCount() int {
	count := 0
	for _, diagnostic := range r.Diagnostics {
		if diagnostic.Severity == SeverityWarning {
			count++
		}
	}
	return count
}

func loadDocument(path string) (gff.Document, string, string, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return gff.Document{}, "", "", fmt.Errorf("read file: %w", err)
	}

	stem := strings.TrimSuffix(filepath.Base(path), ".json")
	extension := strings.TrimPrefix(strings.ToLower(filepath.Ext(stem)), ".")
	if extension == "" {
		return gff.Document{}, "", "", fmt.Errorf("missing resource extension before .json")
	}
	resref := strings.ToLower(strings.TrimSuffix(stem, "."+extension))

	var document gff.Document
	if err := json.Unmarshal(raw, &document); err != nil {
		return gff.Document{}, "", "", fmt.Errorf("parse json: %w", err)
	}
	return document, resref, extension, nil
}

func validateDocumentStructure(report *Report, path, extension string, document gff.Document) {
	expectedType := strings.ToUpper(extension)
	if strings.TrimSpace(document.FileType) != "" && strings.TrimSpace(document.FileType) != expectedType {
		report.add(path, fmt.Sprintf("file_type %q does not match expected %q", document.FileType, expectedType), SeverityError)
	}

	required := requiredFields[extension]
	if len(required) > 0 {
		fields := map[string]struct{}{}
		for _, field := range document.Root.Fields {
			fields[field.Label] = struct{}{}
		}
		for _, label := range required {
			if _, ok := fields[label]; !ok {
				report.add(path, fmt.Sprintf("missing required field %q", label), SeverityError)
			}
		}
	}

	validateUniqueLabels(report, path, "root", document.Root)
}

func validateUniqueLabels(report *Report, path, scope string, s gff.Struct) {
	seen := map[string]struct{}{}
	for _, field := range s.Fields {
		if _, exists := seen[field.Label]; exists {
			report.add(path, fmt.Sprintf("duplicate field label %q in %s", field.Label, scope), SeverityError)
		} else {
			seen[field.Label] = struct{}{}
		}

		switch value := field.Value.(type) {
		case gff.Struct:
			validateUniqueLabels(report, path, scope+"."+field.Label, value)
		case gff.ListValue:
			for index, item := range value {
				validateUniqueLabels(report, path, fmt.Sprintf("%s.%s[%d]", scope, field.Label, index), item)
			}
		}
	}
}

func validateReferences(report *Report, document loadedDocument, resources, scripts, assets map[string]string) {
	walkFields(document.Document.Root, func(field gff.Field) {
		value, ok := fieldStringValue(field.Value)
		if !ok || value == "" {
			return
		}

		switch {
		case isScriptField(field.Label):
			if isBuiltinScript(value) {
				return
			}
			if _, exists := scripts[strings.ToLower(value)]; !exists {
				report.add(document.Path, fmt.Sprintf("missing script reference %q from field %q", value, field.Label), SeverityError)
			}
		case field.Label == "Conversation":
			key := strings.ToLower(value) + ".dlg"
			if _, exists := resources[key]; !exists {
				report.add(document.Path, fmt.Sprintf("missing dialog reference %q", key), SeverityError)
			}
		case field.Label == "Mod_Entry_Area":
			key := strings.ToLower(value) + ".are"
			if _, exists := resources[key]; !exists {
				report.add(document.Path, fmt.Sprintf("missing area reference %q", key), SeverityError)
			}
		case field.Label == "Model":
			if !hasAsset(strings.ToLower(value), []string{"mdl"}, assets) {
				report.add(document.Path, fmt.Sprintf("missing model asset for %q", value), SeverityError)
			}
		case field.Label == "Sound":
			if !hasAsset(strings.ToLower(value), []string{"wav"}, assets) {
				report.add(document.Path, fmt.Sprintf("missing sound asset for %q", value), SeverityError)
			}
		}
	})
}

func classifyAssetDuplicates(report *Report, occurrences map[string][]assetOccurrence) {
	keys := make([]string, 0, len(occurrences))
	for key := range occurrences {
		keys = append(keys, key)
	}
	slices.Sort(keys)

	for _, key := range keys {
		entries := occurrences[key]
		if len(entries) < 2 {
			continue
		}

		groups := make([]string, 0, len(entries))
		groupSet := map[string]struct{}{}
		paths := make([]string, 0, len(entries))
		for _, entry := range entries {
			paths = append(paths, entry.Path)
			if _, exists := groupSet[entry.Group]; exists {
				continue
			}
			groupSet[entry.Group] = struct{}{}
			groups = append(groups, entry.Group)
		}
		slices.Sort(groups)
		slices.Sort(paths)

		if len(groups) == 1 {
			report.add(entries[0].Path, fmt.Sprintf("duplicate asset resource %s appears multiple times in hak group %q (%s); build will fail if duplicates land in the same generated hak", key, groups[0], strings.Join(paths, ", ")), SeverityWarning)
			continue
		}

		report.add(entries[0].Path, fmt.Sprintf("duplicate asset resource %s is split across hak groups %s (%s); later hak order overrides earlier at runtime", key, strings.Join(groups, ", "), strings.Join(paths, ", ")), SeverityWarning)
	}
}

func newAssetGroupResolver(p *project.Project) assetGroupResolver {
	configs := make([]project.HAKConfig, len(p.Config.HAKs))
	copy(configs, p.Config.HAKs)
	slices.SortFunc(configs, func(a, b project.HAKConfig) int {
		if a.Priority != b.Priority {
			if a.Priority < b.Priority {
				return -1
			}
			return 1
		}
		return strings.Compare(a.Name, b.Name)
	})
	return assetGroupResolver{configs: configs, defaultGroup: p.Config.Module.ResRef}
}

func (r assetGroupResolver) groupFor(rel string) (string, error) {
	if len(r.configs) == 0 {
		return r.defaultGroup, nil
	}
	for _, cfg := range r.configs {
		if matchesAnyPattern(rel, cfg.Include) {
			return cfg.Name, nil
		}
	}
	return "", fmt.Errorf("asset does not match any hak include pattern")
}

func matchesAnyPattern(path string, patterns []string) bool {
	for _, pattern := range patterns {
		if matchPathPattern(filepath.ToSlash(path), filepath.ToSlash(pattern)) {
			return true
		}
	}
	return false
}

func matchPathPattern(path, pattern string) bool {
	pathSegs := strings.Split(strings.Trim(path, "/"), "/")
	patternSegs := strings.Split(strings.Trim(pattern, "/"), "/")
	return matchSegments(pathSegs, patternSegs)
}

func matchSegments(pathSegs, patternSegs []string) bool {
	if len(patternSegs) == 0 {
		return len(pathSegs) == 0
	}
	if patternSegs[0] == "**" {
		if matchSegments(pathSegs, patternSegs[1:]) {
			return true
		}
		if len(pathSegs) > 0 {
			return matchSegments(pathSegs[1:], patternSegs)
		}
		return false
	}
	if len(pathSegs) == 0 {
		return false
	}
	ok, err := filepath.Match(patternSegs[0], pathSegs[0])
	if err != nil || !ok {
		return false
	}
	return matchSegments(pathSegs[1:], patternSegs[1:])
}

func walkFields(s gff.Struct, visit func(gff.Field)) {
	for _, field := range s.Fields {
		visit(field)
		switch value := field.Value.(type) {
		case gff.Struct:
			walkFields(value, visit)
		case gff.ListValue:
			for _, item := range value {
				walkFields(item, visit)
			}
		}
	}
}

func hasUppercaseResourceName(rel string) bool {
	base := filepath.Base(rel)
	return base != strings.ToLower(base)
}

func fieldStringValue(value gff.Value) (string, bool) {
	switch typed := value.(type) {
	case gff.StringValue:
		return string(typed), true
	case gff.ResRefValue:
		return string(typed), true
	default:
		return "", false
	}
}

func isScriptField(label string) bool {
	return strings.HasPrefix(label, "On") || strings.HasSuffix(label, "Script") || strings.Contains(label, "Script")
}

func hasAsset(name string, extensions []string, assets map[string]string) bool {
	for _, extension := range extensions {
		if _, exists := assets[name+"."+extension]; exists {
			return true
		}
	}
	return false
}

func isBuiltinScript(name string) bool {
	lower := strings.ToLower(name)
	for _, prefix := range builtinScriptPrefixes {
		if strings.HasPrefix(lower, prefix) {
			return true
		}
	}
	return false
}

func ResourceTypeForSourceExtension(extension string) (uint16, bool) {
	return erf.ResourceTypeForExtension(extension)
}