package main

import (
	"bytes"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

func prunePreviewCacheDir(previewDir string, maxFrames int, maxAge time.Duration) {
	entries, err := os.ReadDir(previewDir)
	if err != nil {
		return
	}

	type frame struct {
		path string
		mt   time.Time
	}

	now := time.Now()

	var frames []frame

	for _, e := range entries {
		name := e.Name()
		path := filepath.Join(previewDir, name)

		// .part Dateien immer weg
		if strings.HasSuffix(name, ".part") {
			_ = os.Remove(path)
			continue
		}

		// optional: preview.jpg neu erzeugen lassen, wenn uralt
		if name == "preview.jpg" {
			if info, err := e.Info(); err == nil {
				if maxAge > 0 && now.Sub(info.ModTime()) > maxAge {
					_ = os.Remove(path)
				}
			}
			continue
		}

		// Nur t_*.jpg verwalten
		if strings.HasPrefix(name, "t_") && strings.HasSuffix(name, ".jpg") {
			info, err := e.Info()
			if err != nil {
				continue
			}

			// alte Frames löschen
			if maxAge > 0 && now.Sub(info.ModTime()) > maxAge {
				_ = os.Remove(path)
				continue
			}

			frames = append(frames, frame{path: path, mt: info.ModTime()})
		}
	}

	// Anzahl begrenzen: älteste zuerst löschen
	if maxFrames > 0 && len(frames) > maxFrames {
		sort.Slice(frames, func(i, j int) bool { return frames[i].mt.Before(frames[j].mt) })
		toDelete := len(frames) - maxFrames
		for i := 0; i < toDelete; i++ {
			_ = os.Remove(frames[i].path)
		}
	}
}

func servePreviewJPEGBytes(w http.ResponseWriter, img []byte) {
	w.Header().Set("Content-Type", "image/jpeg")
	w.Header().Set("Cache-Control", "public, max-age=31536000")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(img)
}

func servePreviewJPEGBytesNoStore(w http.ResponseWriter, img []byte) {
	w.Header().Set("Content-Type", "image/jpeg")
	w.Header().Set("Cache-Control", "no-store, max-age=0")
	w.Header().Set("Pragma", "no-cache")
	w.Header().Set("Expires", "0")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(img)
}

func serveLivePreviewJPEGBytes(w http.ResponseWriter, img []byte) {
	w.Header().Set("Content-Type", "image/jpeg")
	w.Header().Set("Cache-Control", "no-store, max-age=0, must-revalidate")
	w.Header().Set("Pragma", "no-cache")
	w.Header().Set("Expires", "0")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(img)
}

func servePreviewJPEGFile(w http.ResponseWriter, r *http.Request, path string) {
	w.Header().Set("Content-Type", "image/jpeg")
	w.Header().Set("Cache-Control", "public, max-age=31536000")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	http.ServeFile(w, r, path)
}

func extractFirstFrameJPEG(path string) ([]byte, error) {
	cmd := exec.Command(
		ffmpegPath,
		"-hide_banner",
		"-loglevel", "error",
		"-i", path,
		"-frames:v", "1",
		"-vf", "scale=720:-2",
		"-q:v", "10",
		"-f", "image2pipe",
		"-vcodec", "mjpeg",
		"pipe:1",
	)

	var out bytes.Buffer
	var stderr bytes.Buffer
	cmd.Stdout = &out
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		return nil, fmt.Errorf("ffmpeg first-frame: %w (%s)", err, strings.TrimSpace(stderr.String()))
	}
	return out.Bytes(), nil
}