package media

import (
	"bytes"
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	pkgmedia "spark-server/internal/pkg/media"
)

// VideoResult is compressed video output (H.264 MP4).
type VideoResult struct {
	Data   []byte
	Width  int
	Height int
	MIME   string
}

// CompressVideoBytes writes src to a temp file, runs ffmpeg scale+libx264, returns MP4 bytes.
// Requires ffmpeg on PATH (or Options.FFmpegPath). Returns error if ffmpeg is missing.
func CompressVideoBytes(ctx context.Context, src []byte, opt Options) (*VideoResult, error) {
	opt = opt.normalize()
	if len(src) == 0 {
		return nil, fmt.Errorf("media: empty video")
	}
	if int64(len(src)) > opt.Limits.VideoMaxBytes*2 {
		// refuse absurd remote downloads before temp write
		return nil, fmt.Errorf("media: video source too large")
	}
	dir, err := os.MkdirTemp("", "spark-media-*")
	if err != nil {
		return nil, err
	}
	defer func() { _ = os.RemoveAll(dir) }()
	inPath := filepath.Join(dir, "in.bin")
	outPath := filepath.Join(dir, "out.mp4")
	if err := os.WriteFile(inPath, src, 0o600); err != nil {
		return nil, err
	}
	w, h, err := probeVideoSize(ctx, opt.FFmpegPath, inPath)
	if err != nil {
		// ffprobe may be absent; fall through to always re-encode
		w, h = 0, 0
	}
	if w > 0 && h > 0 && !pkgmedia.NeedsResize(w, h, opt.Limits.VideoMaxEdge) && int64(len(src)) <= opt.Limits.VideoMaxBytes {
		return &VideoResult{Data: src, Width: w, Height: h, MIME: "video/mp4"}, nil
	}
	if err := runFFmpegCompress(ctx, opt, inPath, outPath); err != nil {
		return nil, err
	}
	out, err := os.ReadFile(outPath)
	if err != nil {
		return nil, err
	}
	if int64(len(out)) > opt.Limits.VideoMaxBytes {
		return nil, fmt.Errorf("media: compressed video still too large (%d > %d)", len(out), opt.Limits.VideoMaxBytes)
	}
	ow, oh, _ := probeVideoSize(ctx, opt.FFmpegPath, outPath)
	if ow <= 0 {
		ow, oh = w, h
	}
	return &VideoResult{Data: out, Width: ow, Height: oh, MIME: "video/mp4"}, nil
}

func runFFmpegCompress(ctx context.Context, opt Options, inPath, outPath string) error {
	if ctx == nil {
		ctx = context.Background()
	}
	if _, ok := ctx.Deadline(); !ok {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, 3*time.Minute)
		defer cancel()
	}
	maxEdge := opt.Limits.VideoMaxEdge
	// Longest side ≤ maxEdge; force_original_aspect_ratio keeps aspect, even dims for H.264.
	vf := fmt.Sprintf("scale=%d:%d:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2", maxEdge, maxEdge)
	args := []string{
		"-y", "-hide_banner", "-loglevel", "error",
		"-i", inPath,
		"-vf", vf,
		"-c:v", "libx264", "-crf", strconv.Itoa(opt.VideoCRF), "-preset", "veryfast",
		"-c:a", "aac", "-b:a", "128k",
		"-movflags", "+faststart",
		outPath,
	}
	cmd := exec.CommandContext(ctx, opt.FFmpegPath, args...)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		msg := strings.TrimSpace(stderr.String())
		if msg == "" {
			msg = err.Error()
		}
		if isExecNotFound(err) {
			return fmt.Errorf("media: ffmpeg not found (install ffmpeg for bot video compress): %w", err)
		}
		return fmt.Errorf("media: ffmpeg: %s", msg)
	}
	return nil
}

func probeVideoSize(ctx context.Context, ffmpegPath, path string) (w, h int, err error) {
	// Prefer ffprobe beside ffmpeg; fall back to ffmpeg -i parse.
	probe := strings.Replace(ffmpegPath, "ffmpeg", "ffprobe", 1)
	if probe == ffmpegPath {
		probe = "ffprobe"
	}
	cmd := exec.CommandContext(ctx, probe,
		"-v", "error", "-select_streams", "v:0",
		"-show_entries", "stream=width,height", "-of", "csv=p=0:s=x", path,
	)
	out, err := cmd.Output()
	if err != nil {
		return 0, 0, err
	}
	parts := strings.Split(strings.TrimSpace(string(out)), "x")
	if len(parts) != 2 {
		return 0, 0, fmt.Errorf("media: bad ffprobe output")
	}
	w, _ = strconv.Atoi(parts[0])
	h, _ = strconv.Atoi(parts[1])
	if w <= 0 || h <= 0 {
		return 0, 0, fmt.Errorf("media: invalid video size")
	}
	return w, h, nil
}

func isExecNotFound(err error) bool {
	if err == nil {
		return false
	}
	return strings.Contains(err.Error(), "executable file not found") ||
		strings.Contains(err.Error(), "no such file") ||
		os.IsNotExist(err)
}

// FFmpegAvailable reports whether the configured ffmpeg binary can be executed.
func FFmpegAvailable(opt Options) bool {
	opt = opt.normalize()
	path, err := exec.LookPath(opt.FFmpegPath)
	return err == nil && path != ""
}