package media

import (
	"context"
	"encoding/json"
	"math"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
	"time"
)

// inspectPiece answers when a piece's first video packet is shown, whether it is a keyframe,
// how many keyframes the piece has, and when its last packet is.
func inspectPiece(t *testing.T, path string) (first float64, key bool, keys int, last float64) {
	t.Helper()
	b, err := exec.Command("ffprobe", "-v", "error", "-show_entries", "packet=pts_time,flags,codec_type", "-of", "json", path).Output()
	if err != nil {
		t.Fatalf("ffprobe %s: %v", path, err)
	}
	var p struct {
		Packets []struct {
			PTS   string `json:"pts_time"`
			Flags string `json:"flags"`
			Type  string `json:"codec_type"`
		} `json:"packets"`
	}
	_ = json.Unmarshal(b, &p)
	first = -1
	for _, k := range p.Packets {
		if k.Type != "video" {
			continue
		}
		x, _ := strconv.ParseFloat(k.PTS, 64)
		if first < 0 {
			first, key = x, strings.HasPrefix(k.Flags, "K")
		}
		first = math.Min(first, x)
		last = math.Max(last, x)
		if strings.HasPrefix(k.Flags, "K") {
			keys++
		}
	}
	return
}

// TestPieces makes pieces of a made-up video (or SRC, on DEVICE, to try the real thing on a
// machine with a GPU) in order and after a seek, at two qualities, and checks they line up:
// each starts on a keyframe at its own place in the film, with no other keyframe inside it.
func TestPieces(t *testing.T) {
	if _, err := exec.LookPath("ffmpeg"); err != nil {
		t.Skip("no ffmpeg")
	}
	dir := t.TempDir()
	in := os.Getenv("SRC")
	if in == "" {
		in = filepath.Join(dir, "in.mkv")
		if out, err := exec.Command("ffmpeg", "-v", "error", "-f", "lavfi", "-i", "testsrc2=size=1920x1080:rate=50:duration=40",
			"-f", "lavfi", "-i", "sine=frequency=440:duration=40", "-c:v", "libx264", "-preset", "ultrafast", "-g", "500",
			"-c:a", "libopus", "-shortest", in).CombinedOutput(); err != nil {
			t.Fatalf("making the test video: %v: %s", err, out)
		}
	}
	caps := Probe(context.Background())
	if caps.Error != "" {
		t.Skip(caps.Error)
	}
	info, err := Inspect(context.Background(), caps, in, false)
	if err != nil {
		t.Fatal(err)
	}
	m := NewPlays(dir, "", 2)
	device := os.Getenv("DEVICE")
	if device == "" {
		device = CPU
	}
	p, err := m.Open(caps, false, in, "in.mkv", info, device)
	if err != nil {
		t.Fatal(err)
	}
	defer m.Close(p.ID)
	if !strings.Contains(string(p.Master()), "RESOLUTION=") {
		t.Fatal(string(p.Master()))
	}
	low := p.Rungs[len(p.Rungs)-1].Name
	var offset float64
	far := min(p.segs-2, 60)
	for i, n := range []int{0, 1, 2, far, far + 1, 3} {
		t0 := time.Now()
		path, err := p.Segment(nil, low, n)
		if err != nil {
			t.Fatalf("piece %d: %v", n, err)
		}
		first, key, keys, last := inspectPiece(t, path)
		if i == 0 {
			offset = first
		}
		at := first - offset
		t.Logf("piece %d: %d ms on %s, starts %.3f, %d keyframe(s), %.2f s long", n, time.Since(t0).Milliseconds(), p.Status().Engine, at, keys, last-first)
		if !key || keys != 1 {
			t.Errorf("piece %d: first packet keyframe %v, %d keyframes", n, key, keys)
		}
		if math.Abs(at-float64(n)*Seg) > 0.05 {
			t.Errorf("piece %d starts at %.3f, want %.3f", n, at, float64(n)*Seg)
		}
		if n < p.segs-1 && math.Abs(last-first-Seg) > 0.1 {
			t.Errorf("piece %d is %.3f s long", n, last-first)
		}
	}
	// another quality, at a piece already made at the first: its own run, lined up too
	if len(p.Rungs) > 1 {
		path, err := p.Segment(nil, p.Rungs[0].Name, 2)
		if err != nil {
			t.Fatal(err)
		}
		if first, key, _, _ := inspectPiece(t, path); !key || math.Abs(first-offset-2*Seg) > 0.05 {
			t.Errorf("%s piece 2 starts %.3f (keyframe %v)", p.Rungs[0].Name, first-offset, key)
		}
	}
	if _, err := p.Segment(nil, low, p.segs); err != ErrNotFound {
		t.Errorf("past the end: %v", err)
	}
	if _, err := p.Segment(nil, "999", 0); err != ErrNotFound {
		t.Errorf("no such quality: %v", err)
	}
}