package skills

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"log"
	"mime"
	"mime/multipart"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strings"
	"time"
	"unicode/utf8"

	"gorm.io/gorm"
	"yingce/backend/internal/kernel"
	"yingce/backend/internal/model"
)

const (
	maxSkillPackageBytes       = 20 << 20
	maxSkillFileBytes          = 8 << 20
	maxSkillPackageFiles       = 512
	maxSkillPreviewBytes       = 512 << 10
	SkillPackageUploadMaxBytes = maxSkillPackageBytes + (1 << 20)
)

type SkillInstallRequest struct {
	Name        string
	Description string
	Tag         string
	IsPrivate   bool
}

type SkillGitHubInstallRequest struct {
	URL        string `json:"url"`
	Ref        string `json:"ref"`
	Subdir     string `json:"subdir"`
	Tag        string `json:"tag"`
	IsPrivate  bool   `json:"isPrivate"`
	AutoUpdate bool   `json:"autoUpdate"`
}

type SkillPackageFileItem struct {
	Path     string `json:"path"`
	Kind     string `json:"kind"`
	MimeType string `json:"mimeType"`
	Size     int64  `json:"size"`
	SHA256   string `json:"sha256"`
}

type SkillPackageFileContent struct {
	File    SkillPackageFileItem `json:"file"`
	Content string               `json:"content"`
	Binary  bool                 `json:"binary"`
}

type SkillPackageBundleFile struct {
	Path          string `json:"path"`
	MimeType      string `json:"mimeType"`
	ContentBase64 string `json:"contentBase64"`
}

type SkillPackageBundle struct {
	SkillID     string                   `json:"skillId"`
	Name        string                   `json:"name"`
	Description string                   `json:"description"`
	VersionID   string                   `json:"versionId"`
	Version     string                   `json:"version"`
	ContentHash string                   `json:"contentHash"`
	Files       []SkillPackageBundleFile `json:"files"`
}

type SkillFileSearchResult struct {
	Path    string `json:"path"`
	Line    int    `json:"line"`
	Snippet string `json:"snippet"`
}

type skillPackageMetadata struct {
	Name        string
	Description string
	Version     string
}

type skillPackageArchive struct {
	Files       map[string][]byte
	Metadata    skillPackageMetadata
	ContentHash string
	TotalBytes  int64
}

type skillPackageSnapshot struct {
	skill    *model.Skill
	version  *model.SkillVersion
	files    []model.SkillFile
	legacy   bool
	contents map[string][]byte
}

type githubSkillSpec struct {
	Owner  string
	Repo   string
	Ref    string
	Subdir string
}

func (s *Service) EnsureSkillPackages() error {
	skills, err := s.repo.SkillsForPackageEnsure()
	if err != nil {
		return err
	}
	for index := range skills {
		skill := &skills[index]
		version, files, healthErr := s.skillPackageHealth(skill)
		if healthErr == nil {
			if err := s.syncSkillPackageMetadata(skill, version, files); err != nil {
				return fmt.Errorf("同步技能 %s 文件包元数据失败: %w", skill.ID, err)
			}
			// User-installed ZIP/GitHub skills are authoritative in skill_files and
			// must never be replaced by the legacy instruction column at startup.
			if skill.Source == skillSourceUser || skill.SourceType == "builtin" {
				continue
			}
			if strings.TrimSpace(skill.Instruction) == "" {
				continue
			}
			archive, archiveErr := archiveFromMarkdown([]byte(skill.Instruction), truncateSkillMetadata(skill.Name, 80), truncateSkillMetadata(skill.Description, 500))
			if archiveErr != nil {
				log.Printf("技能 %s 的内置正文无法刷新文件包：%v", skill.ID, archiveErr)
				continue
			}
			if version.ContentHash == archive.ContentHash {
				continue
			}
			if err := s.addSkillArchiveVersion(skill, archive, skillSourceTypeForRepair(skill), skill.SourceURL, skill.SourceRef, skill.SourceSubdir, skill.SourceCommit, skill.AutoUpdate); err != nil {
				return fmt.Errorf("刷新技能 %s 文件包失败: %w", skill.ID, err)
			}
			continue
		}

		// A legacy row may contain only skills.instruction. Rebuild that single
		// entry when package metadata, files, or the archive is missing. If no
		// source body exists, keep the service available and leave a diagnostic
		// instead of failing every user request during boot.
		if strings.TrimSpace(skill.Instruction) == "" {
			log.Printf("技能 %s 文件包不完整且没有 legacy instruction，跳过自动修复：%v", skill.ID, healthErr)
			continue
		}
		archive, archiveErr := archiveFromMarkdown([]byte(skill.Instruction), truncateSkillMetadata(skill.Name, 80), truncateSkillMetadata(skill.Description, 500))
		if archiveErr != nil {
			log.Printf("技能 %s 文件包损坏且 legacy instruction 无法重建：%v", skill.ID, archiveErr)
			continue
		}
		if err := s.addSkillArchiveVersion(skill, archive, skillSourceTypeForRepair(skill), skill.SourceURL, skill.SourceRef, skill.SourceSubdir, skill.SourceCommit, skill.AutoUpdate); err != nil {
			return fmt.Errorf("修复技能 %s 文件包失败: %w", skill.ID, err)
		}
	}
	return nil
}

func (s *Service) InstallSkillUpload(userID string, sourceType string, header *multipart.FileHeader, req SkillInstallRequest) (*SkillItem, error) {
	sourceType = strings.ToLower(strings.TrimSpace(sourceType))
	if sourceType == "" && header != nil {
		switch strings.ToLower(path.Ext(header.Filename)) {
		case ".md", ".markdown":
			sourceType = "markdown"
		case ".zip":
			sourceType = "zip"
		}
	}
	if sourceType != "markdown" && sourceType != "zip" {
		return nil, kernel.BadAuthRequest("技能文件仅支持 Markdown 或 ZIP")
	}
	if header == nil || header.Size <= 0 || header.Size > maxSkillPackageBytes {
		return nil, kernel.BadAuthRequest("技能文件大小必须在 1B-20MB 之间")
	}
	file, err := header.Open()
	if err != nil {
		return nil, err
	}
	defer file.Close()
	data, err := io.ReadAll(io.LimitReader(file, maxSkillPackageBytes+1))
	if err != nil {
		return nil, err
	}
	if len(data) > maxSkillPackageBytes {
		return nil, kernel.BadAuthRequest("技能文件不能超过 20MB")
	}
	var archive skillPackageArchive
	if sourceType == "markdown" {
		archive, err = archiveFromMarkdown(data, req.Name, req.Description)
	} else {
		archive, err = archiveFromZip(data, "")
	}
	if err != nil {
		return nil, err
	}
	return s.createSkillFromArchive(userID, archive, req, sourceType, "", "", "", "", false)
}

func (s *Service) InstallGitHubSkill(userID string, req SkillGitHubInstallRequest) (*SkillItem, error) {
	spec, err := parseGitHubSkillURL(req.URL, req.Ref, req.Subdir)
	if err != nil {
		return nil, err
	}
	archive, commit, canonicalURL, resolvedRef, err := fetchGitHubSkillArchive(context.Background(), spec)
	if err != nil {
		var appErr *kernel.AppError
		if errors.As(err, &appErr) {
			return nil, err
		}
		return nil, kernel.WrapAppError(http.StatusBadGateway, "GitHub 技能读取失败，请检查仓库地址和网络", err)
	}
	return s.createSkillFromArchive(userID, archive, SkillInstallRequest{Tag: req.Tag, IsPrivate: req.IsPrivate}, "github", canonicalURL, resolvedRef, spec.Subdir, commit, req.AutoUpdate)
}

func (s *Service) SyncGitHubSkill(userID string, skillID string) (*SkillItem, error) {
	skill, err := s.ownedSkill(userID, skillID)
	if err != nil {
		return nil, err
	}
	if skill.SourceType != "github" {
		return nil, kernel.BadAuthRequest("只有 GitHub 技能可以同步")
	}
	if err := s.syncGitHubSkill(skill); err != nil {
		var appErr *kernel.AppError
		if errors.As(err, &appErr) {
			return nil, err
		}
		return nil, kernel.WrapAppError(http.StatusBadGateway, "GitHub 技能同步失败，请稍后重试", err)
	}
	return s.SkillDetail(userID, skill.ID)
}

func (s *Service) StartSyncWorker(ctx context.Context) {
	s.runWorkerLoop(func(ctx context.Context) {
		ticker := time.NewTicker(6 * time.Hour)
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				skills, err := s.repo.AutoUpdatingGitHubSkills()
				if err != nil {
					continue
				}
				for index := range skills {
					_ = s.syncGitHubSkillWithContext(ctx, &skills[index])
				}
			}
		}
	})
}

func (s *Service) syncGitHubSkill(skill *model.Skill) error {
	return s.syncGitHubSkillWithContext(context.Background(), skill)
}

func (s *Service) syncGitHubSkillWithContext(ctx context.Context, skill *model.Skill) error {
	now := time.Now()
	spec, err := parseGitHubSkillURL(skill.SourceURL, skill.SourceRef, skill.SourceSubdir)
	if err != nil {
		skill.SyncStatus = "failed"
		skill.SyncError = err.Error()
		skill.LastCheckedAt = &now
		_ = s.repo.SaveSkill(skill)
		return err
	}
	archive, commit, canonicalURL, resolvedRef, err := fetchGitHubSkillArchive(ctx, spec)
	skill.LastCheckedAt = &now
	if err != nil {
		skill.SyncStatus = "failed"
		skill.SyncError = err.Error()
		_ = s.repo.SaveSkill(skill)
		return err
	}
	if commit == skill.SourceCommit {
		skill.SyncStatus = "synced"
		skill.SyncError = ""
		return s.repo.SaveSkill(skill)
	}
	skill.Name = archive.Metadata.Name
	skill.Description = archive.Metadata.Description
	skill.Instruction = string(archive.Files["SKILL.md"])
	if err := s.addSkillArchiveVersion(skill, archive, "github", canonicalURL, resolvedRef, spec.Subdir, commit, skill.AutoUpdate); err != nil {
		skill.SyncStatus = "failed"
		skill.SyncError = err.Error()
		_ = s.repo.SaveSkill(skill)
		return err
	}
	return nil
}

func (s *Service) createSingleMarkdownSkill(userID string, req SkillMutationRequest) (*SkillItem, error) {
	archive, err := archiveFromMarkdown([]byte(req.Instruction), req.SkillName, req.Description)
	if err != nil {
		return nil, err
	}
	return s.createSkillFromArchive(userID, archive, SkillInstallRequest{Name: req.SkillName, Description: req.Description, Tag: req.Tag, IsPrivate: req.IsPrivate}, "markdown", req.MarkdownURL, "", "", "", false)
}

func (s *Service) updateSingleMarkdownSkill(skill *model.Skill, req SkillMutationRequest) error {
	if strings.TrimSpace(req.Instruction) == "" {
		return s.repo.SaveSkill(skill)
	}
	archive, err := archiveFromMarkdown([]byte(req.Instruction), req.SkillName, req.Description)
	if err != nil {
		return err
	}
	skill.Instruction = req.Instruction
	return s.addSkillArchiveVersion(skill, archive, "markdown", req.MarkdownURL, "", "", "", false)
}

func (s *Service) createSkillFromArchive(userID string, archive skillPackageArchive, req SkillInstallRequest, sourceType string, sourceURL string, sourceRef string, sourceSubdir string, sourceCommit string, autoUpdate bool) (*SkillItem, error) {
	name := strings.TrimSpace(req.Name)
	if name == "" {
		name = archive.Metadata.Name
	}
	description := strings.TrimSpace(req.Description)
	if description == "" {
		description = archive.Metadata.Description
	}
	if utf8.RuneCountInString(name) == 0 || utf8.RuneCountInString(name) > 80 {
		return nil, kernel.BadAuthRequest("技能名称必须为 1-80 个字符")
	}
	if utf8.RuneCountInString(description) == 0 || utf8.RuneCountInString(description) > 500 {
		return nil, kernel.BadAuthRequest("技能简介必须为 1-500 个字符")
	}
	tag := strings.TrimSpace(req.Tag)
	if _, ok := skillCategoryLabels[tag]; !ok {
		tag = "others"
	}
	skillID := kernel.NewID()
	versionID := kernel.NewID()
	packageKey, version, files, err := s.persistSkillArchive(skillID, versionID, archive, sourceCommit)
	if err != nil {
		return nil, err
	}
	now := time.Now()
	versionLabel := archive.Metadata.Version
	if versionLabel == "" {
		versionLabel = "1"
		if sourceCommit != "" {
			versionLabel = shortCommit(sourceCommit)
		}
	}
	version.VersionLabel = versionLabel
	skill := &model.Skill{
		ID: skillID, OwnerID: userID, Name: name, Description: description, Instruction: string(archive.Files["SKILL.md"]),
		CurrentVersionID: versionID, VersionLabel: versionLabel, ContentHash: archive.ContentHash, FileCount: len(archive.Files), TotalBytes: archive.TotalBytes,
		SourceType: sourceType, SourceURL: sourceURL, SourceRef: sourceRef, SourceSubdir: sourceSubdir, SourceCommit: sourceCommit,
		SyncStatus: "synced", AutoUpdate: autoUpdate, LastCheckedAt: &now, LastSyncedAt: &now,
		Status: skillStatusEnabled, Source: skillSourceUser, Tag: tag, IsPrivate: req.IsPrivate, MarkdownURL: sourceURL, ShowcaseMediaJSON: "[]",
	}
	state := &model.UserSkillState{ID: kernel.NewID(), UserID: userID, SkillID: skillID, Added: true, InstalledVersionID: versionID, AutoUpdate: autoUpdate}
	if err := s.repo.CreateSkillWithPackage(skill, version, files, state); err != nil {
		_ = os.Remove(filepath.Join(s.dataDir, "skill-packages", filepath.FromSlash(packageKey)))
		return nil, err
	}
	return s.SkillDetail(userID, skillID)
}

func (s *Service) addSkillArchiveVersion(skill *model.Skill, archive skillPackageArchive, sourceType string, sourceURL string, sourceRef string, sourceSubdir string, sourceCommit string, autoUpdate bool) error {
	versionID := kernel.NewID()
	packageKey, version, files, err := s.persistSkillArchive(skill.ID, versionID, archive, sourceCommit)
	if err != nil {
		return err
	}
	versionLabel := archive.Metadata.Version
	if versionLabel == "" {
		versionLabel = "1"
		if sourceCommit != "" {
			versionLabel = shortCommit(sourceCommit)
		} else if skill.CurrentVersionID != "" {
			versionLabel = time.Now().UTC().Format("20060102-150405")
		}
	}
	version.VersionLabel = versionLabel
	now := time.Now()
	skill.CurrentVersionID = versionID
	skill.VersionLabel = versionLabel
	skill.ContentHash = archive.ContentHash
	skill.FileCount = len(archive.Files)
	skill.TotalBytes = archive.TotalBytes
	skill.SourceType = sourceType
	skill.SourceURL = sourceURL
	skill.SourceRef = sourceRef
	skill.SourceSubdir = sourceSubdir
	skill.SourceCommit = sourceCommit
	skill.SyncStatus = "synced"
	skill.SyncError = ""
	skill.AutoUpdate = autoUpdate
	skill.LastCheckedAt = &now
	skill.LastSyncedAt = &now
	if err := s.repo.AddSkillVersion(skill, version, files); err != nil {
		_ = os.Remove(filepath.Join(s.dataDir, "skill-packages", filepath.FromSlash(packageKey)))
		return err
	}
	return nil
}

func (s *Service) persistSkillArchive(skillID string, versionID string, archive skillPackageArchive, sourceCommit string) (string, *model.SkillVersion, []model.SkillFile, error) {
	packageKey := path.Join(skillID, versionID+".zip")
	absolute := filepath.Join(s.dataDir, "skill-packages", filepath.FromSlash(packageKey))
	if err := os.MkdirAll(filepath.Dir(absolute), 0o750); err != nil {
		return "", nil, nil, err
	}
	data, err := encodeSkillArchive(archive.Files)
	if err != nil {
		return "", nil, nil, err
	}
	temporary, err := os.CreateTemp(filepath.Dir(absolute), ".skill-*.zip")
	if err != nil {
		return "", nil, nil, err
	}
	temporaryPath := temporary.Name()
	defer os.Remove(temporaryPath)
	if err := temporary.Chmod(0o600); err != nil {
		temporary.Close()
		return "", nil, nil, err
	}
	if _, err := temporary.Write(data); err != nil {
		temporary.Close()
		return "", nil, nil, err
	}
	if err := temporary.Close(); err != nil {
		return "", nil, nil, err
	}
	if err := os.Rename(temporaryPath, absolute); err != nil {
		return "", nil, nil, err
	}
	version := &model.SkillVersion{ID: versionID, SkillID: skillID, ContentHash: archive.ContentHash, EntryPath: "SKILL.md", PackageKey: packageKey, FileCount: len(archive.Files), TotalBytes: archive.TotalBytes, SourceCommit: sourceCommit}
	paths := sortedSkillPaths(archive.Files)
	files := make([]model.SkillFile, 0, len(paths))
	for _, filePath := range paths {
		content := archive.Files[filePath]
		digest := sha256.Sum256(content)
		files = append(files, model.SkillFile{ID: kernel.NewID(), SkillVersionID: versionID, Path: filePath, Kind: skillFileKind(filePath), MimeType: skillFileMime(filePath, content), Size: int64(len(content)), SHA256: hex.EncodeToString(digest[:])})
	}
	return packageKey, version, files, nil
}

func normalizeSkillPath(value string) (string, error) {
	value = strings.ReplaceAll(strings.TrimSpace(value), "\\", "/")
	if value == "" || strings.ContainsRune(value, 0) || strings.HasPrefix(value, "/") {
		return "", kernel.BadAuthRequest("技能文件路径无效")
	}
	clean := path.Clean(value)
	if clean == "." || clean == ".." || strings.HasPrefix(clean, "../") || strings.Contains(clean, "/../") || strings.HasPrefix(clean, ".git/") || clean == ".git" {
		return "", kernel.BadAuthRequest("技能文件路径越界或包含禁止目录")
	}
	if utf8.RuneCountInString(clean) > 1000 {
		return "", kernel.BadAuthRequest("技能文件路径过长")
	}
	return clean, nil
}

func skillFileMime(filePath string, content []byte) string {
	if filePath == "SKILL.md" || strings.HasSuffix(strings.ToLower(filePath), ".md") {
		return "text/markdown; charset=utf-8"
	}
	if detected := mime.TypeByExtension(strings.ToLower(path.Ext(filePath))); detected != "" {
		return detected
	}
	return http.DetectContentType(content)
}

func skillFileKind(filePath string) string {
	extension := strings.ToLower(path.Ext(filePath))
	switch extension {
	case ".md", ".mdx":
		return "markdown"
	case ".png", ".jpg", ".jpeg", ".gif", ".webp", ".svg":
		return "image"
	case ".mp4", ".webm", ".mov":
		return "video"
	case ".mp3", ".wav", ".m4a", ".ogg":
		return "audio"
	case ".py", ".js", ".ts", ".tsx", ".jsx", ".go", ".sh", ".json", ".yaml", ".yml", ".toml", ".html", ".css":
		return "code"
	case ".txt", ".csv":
		return "text"
	default:
		return "binary"
	}
}

func isPreviewText(mimeType string, filePath string) bool {
	return strings.HasPrefix(mimeType, "text/") || strings.Contains(mimeType, "json") || strings.Contains(mimeType, "yaml") || strings.Contains(mimeType, "toml") || skillFileKind(filePath) == "code"
}

func skillFileItem(file model.SkillFile) SkillPackageFileItem {
	return SkillPackageFileItem{Path: file.Path, Kind: file.Kind, MimeType: file.MimeType, Size: file.Size, SHA256: file.SHA256}
}

func sortedSkillPaths(files map[string][]byte) []string {
	paths := make([]string, 0, len(files))
	for filePath := range files {
		paths = append(paths, filePath)
	}
	sort.Strings(paths)
	return paths
}

func shortCommit(value string) string {
	if len(value) <= 12 {
		return value
	}
	return value[:12]
}

func isSkillPackageNotFound(err error) bool {
	return errors.Is(err, gorm.ErrRecordNotFound) || errors.Is(err, os.ErrNotExist)
}