package service

import (
	"bufio"
	"database/sql"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/gabriel-vasile/mimetype"

	"vidarchive/internal/config"
	"vidarchive/internal/models"
	"vidarchive/internal/repository"
)

type DownloadService struct {
	repo        *repository.DownloadRepository
	mediaRepo   *repository.MediaRepository
	presetSvc   *PresetService
	settingsSvc *SettingsService
	cfg         *config.Config
	cache       *ProgressCache
	processMu   sync.Mutex
	processes   map[int64]*os.Process
}

func NewDownloadService(repo *repository.DownloadRepository, mediaRepo *repository.MediaRepository, presetSvc *PresetService, settingsSvc *SettingsService, cfg *config.Config) *DownloadService {
	return &DownloadService{
		repo:        repo,
		mediaRepo:   mediaRepo,
		presetSvc:   presetSvc,
		settingsSvc: settingsSvc,
		cfg:         cfg,
		cache:       NewProgressCache(),
		processes:   make(map[int64]*os.Process),
	}
}

func (s *DownloadService) Create(url string, presetID *int64, formatOverride, customFlags, outputDir string) (*models.Download, error) {
	d := &models.Download{
		URL:            url,
		Status:         "queued",
		FormatOverride: formatOverride,
		CustomFlags:    customFlags,
		OutputDir:      sql.NullString{String: outputDir, Valid: outputDir != ""},
	}

	if presetID != nil {
		d.PresetID = sqlNullInt64(*presetID)
	}

	if err := s.repo.Create(d); err != nil {
		return nil, err
	}
	return d, nil
}

func (s *DownloadService) GetByID(id int64) (*models.Download, error) {
	// Check cache first for live logs
	if live, ok := s.cache.Get(id); ok {
		d, err := s.repo.GetByID(id)
		if err != nil {
			return nil, err
		}
		logs := live.Logs.String()
		if logs != "" {
			d.Logs = sql.NullString{String: logs, Valid: true}
		}
		return d, nil
	}
	return s.repo.GetByID(id)
}

func (s *DownloadService) GetAll(status, sortBy string) ([]*models.Download, error) {
	downloads, err := s.repo.GetAll(status, sortBy)
	if err != nil {
		return nil, err
	}

	// Overlay live logs from cache
	for _, d := range downloads {
		if live, ok := s.cache.Get(d.ID); ok {
			logs := live.Logs.String()
			if logs != "" {
				d.Logs = sql.NullString{String: logs, Valid: true}
			}
		}
	}

	return downloads, nil
}

func (s *DownloadService) GetQueued(limit int) ([]*models.Download, error) {
	return s.repo.GetQueued(limit)
}

func (s *DownloadService) Delete(id int64) error {
	s.killProcess(id)
	s.cache.Delete(id)
	return s.repo.Delete(id)
}

func (s *DownloadService) killProcess(id int64) {
	s.processMu.Lock()
	proc, ok := s.processes[id]
	delete(s.processes, id)
	s.processMu.Unlock()

	if !ok || proc == nil {
		return
	}

	// Kill the process group (negative PID kills the group on Linux)
	// The process group was created by Setpgid in ExecuteDownload
	_ = syscall.Kill(-proc.Pid, syscall.SIGKILL)
}

func (s *DownloadService) DeleteAll() error {
	return s.repo.DeleteAll()
}

func (s *DownloadService) ResetStalledDownloads() error {
	return s.repo.UpdateStatusWhere("downloading", "queued")
}

func (s *DownloadService) ListFormats(url string) ([]*models.FormatInfo, error) {
	cmd := exec.Command(s.cfg.YTDLPPath, "-F", "--no-warnings", url)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return nil, fmt.Errorf("yt-dlp -F failed: %w\nOutput: %s", err, string(output))
	}

	return parseFormatList(string(output)), nil
}

func (s *DownloadService) ExecuteDownload(d *models.Download) error {
	if err := s.repo.MarkStarted(d.ID); err != nil {
		return err
	}

	// Initialize in-memory cache for logs
	s.cache.Set(d.ID, &LiveDownload{
		LastUpdate: time.Now(),
	})
	defer s.cache.Delete(d.ID)

	var preset *models.Preset
	var err error

	if d.PresetID.Valid {
		preset, err = s.presetSvc.GetByID(d.PresetID.Int64)
		if err != nil {
			preset, _ = s.presetSvc.GetDefault()
		}
	} else {
		preset, _ = s.presetSvc.GetDefault()
	}

	if preset == nil {
		preset = &models.Preset{
			OutputTemplate: "%(title)s.%(ext)s",
		}
	}

	// Build output path with optional subdirectory
	downloadDir := s.cfg.DownloadDir
	if d.OutputDir.Valid && d.OutputDir.String != "" {
		// Sanitize and validate output directory
		cleanDir := filepath.Clean(d.OutputDir.String)
		// Prevent path traversal: ensure the cleaned path doesn't escape the download dir
		fullPath := filepath.Join(downloadDir, cleanDir)
		resolvedPath, err := filepath.Abs(fullPath)
		if err != nil {
			return fmt.Errorf("invalid output directory: %w", err)
		}
		resolvedDownloadDir, _ := filepath.Abs(downloadDir)
		if !strings.HasPrefix(resolvedPath, resolvedDownloadDir+string(filepath.Separator)) && resolvedPath != resolvedDownloadDir {
			return fmt.Errorf("invalid output directory: path traversal attempt detected")
		}
		downloadDir = fullPath
		// Ensure directory exists
		if err := os.MkdirAll(downloadDir, 0755); err != nil {
			return fmt.Errorf("create output directory: %w", err)
		}
	}

	args := s.presetSvc.BuildArgs(preset, d.FormatOverride, d.CustomFlags)

	// Write cookies to temp file if configured
	cookies, err := s.settingsSvc.GetCookies()
	if err == nil && strings.TrimSpace(cookies) != "" {
		tmpFile, err := os.CreateTemp("", "cookies-*.txt")
		if err == nil {
			tmpFile.WriteString(cookies)
			tmpFile.Close()
			args = append(args, "--cookies", tmpFile.Name())
			defer os.Remove(tmpFile.Name())
		}
	}

	args = append(args, "-P", downloadDir)
	args = append(args, d.URL)

	cmd := exec.Command(s.cfg.YTDLPPath, args...)
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		s.finalizeError(d.ID, err)
		return err
	}
	cmd.Stderr = cmd.Stdout

	if err := cmd.Start(); err != nil {
		s.finalizeError(d.ID, err)
		return err
	}

	// Track the process so it can be killed on delete
	s.processMu.Lock()
	s.processes[d.ID] = cmd.Process
	s.processMu.Unlock()
	defer func() {
		s.processMu.Lock()
		delete(s.processes, d.ID)
		s.processMu.Unlock()
	}()

	scanner := bufio.NewScanner(stdout)
	
	ticker := time.NewTicker(10 * time.Second)
	defer ticker.Stop()
	done := make(chan struct{})
	go func() {
		for {
			select {
			case <-ticker.C:
				logs := s.cache.FlushLogs(d.ID)
				if logs != "" {
					s.repo.UpdateLogs(d.ID, logs)
				}
			case <-done:
				return
			}
		}
	}()

	for scanner.Scan() {
		line := scanner.Text()
		s.cache.AppendLog(d.ID, line)
	}

	close(done)

	// Final log flush
	logs := s.cache.FlushLogs(d.ID)
	if logs != "" {
		s.repo.UpdateLogs(d.ID, logs)
	}

	if err := cmd.Wait(); err != nil {
		s.finalizeError(d.ID, err)
		return err
	}

	// Mark as completed
	if err := s.repo.MarkCompleted(d.ID, "completed"); err != nil {
		return err
	}

	// Scan for new media files
	s.scanForNewMedia(d.URL, downloadDir)

	return nil
}

func (s *DownloadService) finalizeError(id int64, err error) {
	logs := s.cache.FlushLogs(id)
	if logs != "" {
		s.repo.UpdateLogs(id, logs)
	}
	s.repo.MarkError(id, err.Error())
}

func (s *DownloadService) scanForNewMedia(url string, downloadDir string) {
	// Give filesystem a moment
	time.Sleep(100 * time.Millisecond)
	
	// Walk download dir and add any new files
	filepath.Walk(downloadDir, func(path string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() {
			return nil
		}

		relPath, _ := filepath.Rel(s.cfg.DownloadDir, path)
		relPath = filepath.ToSlash(relPath)

		_, err = s.mediaRepo.GetByRelativePath(relPath)
		if err == nil {
			return nil // already exists
		}

		// Use content-based MIME detection
		mtype, err := mimetype.DetectFile(path)
		if err != nil {
			return nil
		}

		isAudio := mtype != nil && strings.HasPrefix(mtype.String(), "audio/")
		isVideo := mtype != nil && strings.HasPrefix(mtype.String(), "video/")

		if !isAudio && !isVideo {
			return nil
		}

		ext := strings.ToLower(filepath.Ext(path))
		basePath := strings.TrimSuffix(path, ext)
		infoJSONPath := basePath + ".info.json"
		if _, err := os.Stat(infoJSONPath); err != nil {
			infoJSONPath = ""
		}

		media := &models.Media{
			URL:            url,
			Filepath:       path,
			RelativePath:   relPath,
			IsAudio:        isAudio,
			HasEmbeddedThumbnail: true,
			InfoJSONPath:   infoJSONPath,
			Title:          strings.TrimSuffix(filepath.Base(path), ext),
			Duration:       extractDuration(infoJSONPath, path),
		}

		s.mediaRepo.Create(media)
		return nil
	})
}

func parseFormatList(output string) []*models.FormatInfo {
	lines := strings.Split(output, "\n")
	var formats []*models.FormatInfo
	
	inFormats := false
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		
		if strings.Contains(line, "ID") && strings.Contains(line, "EXT") {
			inFormats = true
			continue
		}
		
		if !inFormats {
			continue
		}
		
		parts := strings.Fields(line)
		if len(parts) >= 4 {
			format := &models.FormatInfo{
				ID:   parts[0],
				Ext:  parts[1],
			}
			
			for i, part := range parts {
				if strings.Contains(part, "x") && !strings.Contains(part, "http") {
					format.Resolution = part
					if i+1 < len(parts) {
						format.FPS = parts[i+1]
					}
					break
				}
			}
			
			if len(parts) > 3 {
				format.Note = strings.Join(parts[3:], " ")
			}
			
			formats = append(formats, format)
		}
	}
	
	return formats
}

func sqlNullInt64(v int64) sql.NullInt64 {
	return sql.NullInt64{Int64: v, Valid: true}
}