package transcode

import (
	"reflect"
	"testing"
)

// TestDetectNoFFmpeg is the first gate: without ffmpeg there is no capability,
// full stop, and the candidates/probe are never consulted.
func TestDetectNoFFmpeg(t *testing.T) {
	got := detect(checks{
		ffmpeg: func() bool { return false },
		candidates: func() []Encoder {
			t.Fatal("candidates consulted without ffmpeg")
			return nil
		},
		probe: func(Encoder) bool {
			t.Fatal("probe run without ffmpeg")
			return false
		},
	})
	if got.Available() {
		t.Errorf("no ffmpeg: got %+v, want no capability", got)
	}
}

// TestDetectNoCandidates covers a host with ffmpeg but no device nodes at all.
func TestDetectNoCandidates(t *testing.T) {
	got := detect(checks{
		ffmpeg:     func() bool { return true },
		candidates: func() []Encoder { return nil },
		probe: func(Encoder) bool {
			t.Fatal("probe run with no candidates")
			return false
		},
	})
	if got.Available() {
		t.Errorf("no candidates: got %+v, want no capability", got)
	}
}

// TestDetectProbeFails is the branch ADR-008 exists for: a device node exists
// but the encode does not actually work. Reporting it would produce a transcode
// that starts and then cannot keep up.
func TestDetectProbeFails(t *testing.T) {
	got := detect(checks{
		ffmpeg: func() bool { return true },
		candidates: func() []Encoder {
			return []Encoder{{Name: EncoderVAAPI, Args: []string{"-c:v", "h264_vaapi"}}}
		},
		probe: func(Encoder) bool { return false },
	})
	if got.Available() {
		t.Errorf("probe failed: got %+v, want no capability", got)
	}
}

// TestDetectFirstWorkingWins checks the candidate order and that a later
// candidate is used when an earlier one fails.
func TestDetectFirstWorkingWins(t *testing.T) {
	vaapi := Encoder{
		Name: EncoderVAAPI,
		Args: []string{"-vaapi_device", "/dev/dri/renderD128", "-vf", "format=nv12,hwupload", "-c:v", "h264_vaapi"},
	}
	nvenc := Encoder{Name: EncoderNVENC, Args: []string{"-c:v", "h264_nvenc"}}
	qsv := Encoder{Name: EncoderQSV, Args: []string{"-c:v", "h264_qsv"}}

	tests := []struct {
		name  string
		ok    map[string]bool
		want  Encoder
		tried []string
	}{
		{
			name:  "vaapi works",
			ok:    map[string]bool{EncoderVAAPI: true},
			want:  vaapi,
			tried: []string{EncoderVAAPI},
		},
		{
			name:  "vaapi fails, nvenc works",
			ok:    map[string]bool{EncoderNVENC: true},
			want:  nvenc,
			tried: []string{EncoderVAAPI, EncoderNVENC},
		},
		{
			name:  "vaapi and nvenc fail, qsv works",
			ok:    map[string]bool{EncoderQSV: true},
			want:  qsv,
			tried: []string{EncoderVAAPI, EncoderNVENC, EncoderQSV},
		},
		{
			name:  "none work",
			ok:    map[string]bool{},
			want:  Encoder{},
			tried: []string{EncoderVAAPI, EncoderNVENC, EncoderQSV},
		},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			var tried []string
			got := detect(checks{
				ffmpeg:     func() bool { return true },
				candidates: func() []Encoder { return []Encoder{vaapi, nvenc, qsv} },
				probe: func(e Encoder) bool {
					tried = append(tried, e.Name)
					return tc.ok[e.Name]
				},
			})
			if tc.want.Name == "" {
				if got.Available() {
					t.Fatalf("got %+v, want no capability", got)
				}
			} else {
				if got.Encoder != tc.want.Name {
					t.Errorf("Encoder = %q, want %q", got.Encoder, tc.want.Name)
				}
				if !reflect.DeepEqual(got.Args, tc.want.Args) {
					t.Errorf("Args = %q, want %q", got.Args, tc.want.Args)
				}
			}
			if !reflect.DeepEqual(tried, tc.tried) {
				t.Errorf("probed %q, want %q", tried, tc.tried)
			}
		})
	}
}

// TestHostCandidatesOrder pins the candidate order the task requires:
// VAAPI, then NVENC, then QSV. It reads this host, so it only asserts on
// ordering, not on which nodes happen to exist.
func TestHostCandidatesOrder(t *testing.T) {
	order := map[string]int{EncoderVAAPI: 0, EncoderNVENC: 1, EncoderQSV: 2}
	prev := -1
	for _, enc := range hostCandidates() {
		i, ok := order[enc.Name]
		if !ok {
			t.Fatalf("hostCandidates returned unknown encoder %q", enc.Name)
		}
		if i <= prev {
			t.Errorf("candidate %q out of order", enc.Name)
		}
		prev = i
		if len(enc.Args) == 0 {
			t.Errorf("candidate %q has no args", enc.Name)
		}
	}
}

// TestDetectReal runs the real detection once. It must not panic and must be
// consistent; on a host with no usable hardware it reports none. Cached, so
// calling it twice must return the same thing.
func TestDetectReal(t *testing.T) {
	first := Detect()
	t.Logf("real detection on this host: %+v", first)
	if second := Detect(); !reflect.DeepEqual(first, second) {
		t.Errorf("Detect not cached: %+v then %+v", first, second)
	}
	if first.Available() && first.Args == nil {
		t.Error("Detect reported an encoder with nil args")
	}
}

// TestProbeEncodeRejectsBogusEncoder proves the probe checks a real ffmpeg
// result rather than trusting the candidate's name. Skips without ffmpeg.
func TestProbeEncodeRejectsBogusEncoder(t *testing.T) {
	if !ffmpegOnPath() {
		t.Skip("ffmpeg not on PATH")
	}
	if probeEncode(Encoder{Name: "nope", Args: []string{"-c:v", "definitely_not_a_codec"}}) {
		t.Error("probeEncode accepted a nonexistent encoder")
	}
}