package dto

import (
	"encoding/json"
	"github.com/mithral/vellum/internal/library"
	"slices"
	"testing"

	"github.com/mithral/vellum/internal/catalog"
)

// These tests pin the WIRE contract. Real Jellyfin apps parse this JSON and
// there is no client in this repository that would fail if a field name
// changed, so every test here compares against a literal, not against a value
// recomputed by the same helpers the production code uses.

// jsonKeys returns the sorted top-level object keys of v, so a test can assert
// both the exact set and (with the golden tests) the exact rendering.
func jsonKeys(t *testing.T, v any) []string {
	t.Helper()
	b, err := json.Marshal(v)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	var m map[string]any
	if err := json.Unmarshal(b, &m); err != nil {
		t.Fatalf("unmarshal %s: %v", b, err)
	}
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	slices.Sort(out)
	return out
}

// sampleView is a fully populated ItemView: every optional field populated, so
// the golden JSON below contains every key BaseItemDto can emit.
func sampleView() ItemView {
	return ItemView{
		Item: catalog.Item{
			ID:        42,
			LibraryID: 7,
			Kind:      "video",
			Path:      "The Movie (2001).mp4",
			Title:     "The Movie (2001)",
			Year:      2001,
		},
		File: catalog.File{
			ID:         100,
			Path:       "The Movie (2001).mp4",
			Size:       1000,
			Container:  "mp4",
			DurationMS: 5000,
			VCodec:     "h264",
			ACodec:     "aac",
			Width:      640,
			Height:     360,
		},
		SortTitle: "the movie (2001)",
		ParentID:  7,
		HasCover:  true,

		PositionMS: 2500,
		Percent:    0.5,
		PlayCount:  3,
		Favorite:   true,
	}
}

// TestToBaseItemDtoGoldenJSON pins every JSON field name and value of the
// browse DTO. RunTimeTicks is the load-bearing one: Jellyfin counts 100ns
// ticks and Vellum stores milliseconds, so 5000ms must be 50,000,000 ticks.
// Getting this wrong makes every client seek to the wrong offset.
func TestToBaseItemDtoGoldenJSON(t *testing.T) {
	got, err := json.Marshal(ToBaseItemDto(sampleView(), false, ""))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := `{"Id":"0000000000000000000000000000002a",` +
		`"Name":"The Movie (2001)","Type":"Movie","MediaType":"Video",` +
		`"Container":"mp4","RunTimeTicks":50000000,"ProductionYear":2001,` +
		`"ParentId":"00000000000000000000000000000007","IsFolder":false,` +
		`"SortName":"the movie (2001)","Path":"The Movie (2001).mp4",` +
		`"ImageTags":{"Primary":"0000000000000000000000000000002a"},` +
		`"UserData":{"PlaybackPositionTicks":25000000,"PlayedPercentage":50,` +
		`"PlayCount":3,"IsFavorite":true,"Played":false}}`
	if string(got) != want {
		t.Errorf("BaseItemDto JSON changed.\n got: %s\nwant: %s", got, want)
	}
}

// TestToBaseItemDtoExactKeys asserts the key set, so adding or dropping a field
// fails even if the golden above is regenerated.
func TestToBaseItemDtoExactKeys(t *testing.T) {
	want := []string{
		"Container", "Id", "ImageTags", "IsFolder", "MediaType", "Name",
		"ParentId", "Path", "ProductionYear",
		"RunTimeTicks", "SortName", "Type", "UserData",
	}
	got := jsonKeys(t, ToBaseItemDto(sampleView(), false, ""))
	if !slices.Equal(got, want) {
		t.Errorf("BaseItemDto keys = %v\nwant %v", got, want)
	}
}

// TestToBaseItemDtoOmitsEmptyOptionals pins which keys are absent rather than
// zero-valued. A client that switches on the presence of MediaSources must not
// see an empty array where "not requested" is meant.
func TestToBaseItemDtoOmitsEmptyOptionals(t *testing.T) {
	v := ItemView{Item: catalog.Item{ID: 1, Kind: "video", Title: "T"}}
	got := jsonKeys(t, ToBaseItemDto(v, false, ""))
	// MediaType is present because the kind is known; the omitted keys are the
	// ones that are genuinely empty (Container, Path, ProductionYear,
	// RunTimeTicks, ImageTags, ParentId).
	want := []string{"Id", "IsFolder", "MediaType", "Name", "Type", "UserData"}
	if !slices.Equal(got, want) {
		t.Errorf("minimal keys = %v\nwant %v", got, want)
	}

	if keys := jsonKeys(t, ToBaseItemDto(v, true, "k")); !slices.Contains(keys, "MediaSources") {
		t.Errorf("includeMediaSources=true must emit MediaSources; keys = %v", keys)
	}
}

// TestToBaseItemDtoUserDataTicks pins the tick conversion on the per-user
// overlay: Vellum stores a resume position in ms, Jellyfin clients send and
// expect 100ns ticks.
func TestToBaseItemDtoUserDataTicks(t *testing.T) {
	v := sampleView()
	v.PositionMS = 1 // 1ms must be 10000 ticks, not 1
	d := ToBaseItemDto(v, false, "")
	if d.UserData.PlaybackPositionTicks != 10_000 {
		t.Errorf("PlaybackPositionTicks = %d, want 10000", d.UserData.PlaybackPositionTicks)
	}
	if got := TicksToMS(d.UserData.PlaybackPositionTicks); got != 1 {
		t.Errorf("TicksToMS round-trip = %d, want 1", got)
	}
	if d.RunTimeTicks != 50_000_000 {
		t.Errorf("RunTimeTicks = %d, want 50000000", d.RunTimeTicks)
	}
	if MsToTicks(0) != 0 || MsToTicks(1) != 10_000 {
		t.Errorf("MsToTicks broken: %d %d", MsToTicks(0), MsToTicks(1))
	}
}

// TestToBaseItemDtoParentIDZero pins that ParentId is omitted, not sent as the
// zero id, when an item has no parent.
func TestToBaseItemDtoParentIDZero(t *testing.T) {
	v := sampleView()
	v.ParentID = 0
	d := ToBaseItemDto(v, false, "")
	if d.ParentId != "" {
		t.Errorf("ParentId = %q, want empty for ParentID 0", d.ParentId)
	}
	if slices.Contains(jsonKeys(t, d), "ParentId") {
		t.Error("ParentId key must be omitted when there is no parent")
	}
}

// TestImageTagsOnlyWithCover: ImageTags is what makes a client fetch
// /Images/Primary. Emitting it for an item with no artwork produces a request
// that 404s on every browse.
func TestImageTagsOnlyWithCover(t *testing.T) {
	v := sampleView()
	v.HasCover = true
	d := ToBaseItemDto(v, false, "")
	want := map[string]string{"Primary": ItemID(42)}
	if !jsonEq(want, d.ImageTags) {
		t.Errorf("ImageTags = %v, want %v", d.ImageTags, want)
	}

	v.HasCover = false
	d = ToBaseItemDto(v, false, "")
	if d.ImageTags != nil {
		t.Errorf("ImageTags = %v, want nil without a cover", d.ImageTags)
	}
	if slices.Contains(jsonKeys(t, d), "ImageTags") {
		t.Error("ImageTags key must be absent without a cover")
	}
}

// TestMediaSourceNeverTranscodes is the contract that matters most on a
// headless, GPU-less host: Vellum cannot transcode, and a client told
// transcoding is available will wait forever for a stream that never starts.
// The refusal happens in the handler (ErrorCode), but the source it is built
// from must never advertise transcoding.
func TestMediaSourceNeverTranscodes(t *testing.T) {
	ms := BuildMediaSource(sampleView().Item, sampleView().File, "tok123")
	if ms.SupportsTranscoding {
		t.Error("SupportsTranscoding = true: Vellum never transcodes")
	}
	if !ms.SupportsDirectPlay {
		t.Error("SupportsDirectPlay = false, want true")
	}
	if !ms.SupportsDirectStream {
		t.Error("SupportsDirectStream = false, want true")
	}
	if ms.Protocol != "File" || ms.Type != "Default" || ms.IsRemote {
		t.Errorf("protocol/type/remote = %q/%q/%v, want File/Default/false",
			ms.Protocol, ms.Type, ms.IsRemote)
	}
}

// TestDirectStreamURLCarriesAPIKey: media elements cannot set request headers,
// so the token has to be in the URL or playback fails with a 401 mid-stream.
// This is the single most common Jellyfin integration break.
func TestDirectStreamURLCarriesAPIKey(t *testing.T) {
	item := catalog.Item{ID: 42, Kind: "video", Title: "T"}

	if got, want := BuildMediaSource(item, catalog.File{}, "abc123").DirectStreamUrl,
		"/Videos/"+ItemID(42)+"/stream?api_key=abc123"; got != want {
		t.Errorf("video DirectStreamUrl = %q, want %q", got, want)
	}
	item.Kind = "audiobooks"
	if got, want := BuildMediaSource(item, catalog.File{}, "abc123").DirectStreamUrl,
		"/Audio/"+ItemID(42)+"/stream?api_key=abc123"; got != want {
		t.Errorf("non-video DirectStreamUrl = %q, want %q", got, want)
	}
	item.Kind = "video"
	if got, want := BuildMediaSource(item, catalog.File{}, "").DirectStreamUrl,
		"/Videos/"+ItemID(42)+"/stream"; got != want {
		t.Errorf("no-key DirectStreamUrl = %q, want %q", got, want)
	}
}

// TestMediaStreamsFromProbeFacts: the codec facts are what let a CLIENT decide
// whether it can direct-play, which matters precisely because Vellum will not
// help it otherwise.
func TestMediaStreamsFromProbeFacts(t *testing.T) {
	ms := BuildMediaSource(sampleView().Item, sampleView().File, "")
	if len(ms.MediaStreams) != 2 {
		t.Fatalf("MediaStreams = %d, want 2", len(ms.MediaStreams))
	}
	if ms.MediaStreams[0] != (MediaStream{Type: "Video", Codec: "h264", Index: 0, IsDefault: true, Width: 640, Height: 360}) {
		t.Errorf("video stream = %+v", ms.MediaStreams[0])
	}
	if ms.MediaStreams[1] != (MediaStream{Type: "Audio", Codec: "aac", Index: 1, IsDefault: true}) {
		t.Errorf("audio stream = %+v", ms.MediaStreams[1])
	}

	// A file with no probed codecs yields no streams rather than empty entries.
	ms = BuildMediaSource(catalog.Item{ID: 1}, catalog.File{Container: "mp3"}, "")
	if ms.MediaStreams != nil {
		t.Errorf("MediaStreams = %v, want nil without probe facts", ms.MediaStreams)
	}
	if ms.Size != 0 || ms.RunTimeTicks != 0 {
		t.Errorf("zero File must not invent facts: %+v", ms)
	}
}

// TestMediaSourceGoldenJSON pins the source shape clients parse.
func TestMediaSourceGoldenJSON(t *testing.T) {
	v := sampleView()
	got, err := json.Marshal(BuildMediaSource(v.Item, v.File, "abc123"))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := `{"Id":"0000000000000000000000000000002a","Name":"The Movie (2001)",` +
		`"Path":"The Movie (2001).mp4","Container":"mp4","RunTimeTicks":50000000,` +
		`"Size":1000,"SupportsDirectPlay":true,"SupportsDirectStream":true,` +
		`"SupportsTranscoding":false,` +
		`"DirectStreamUrl":"/Videos/0000000000000000000000000000002a/stream?api_key=abc123",` +
		`"Protocol":"File","Type":"Default","IsRemote":false,` +
		`"MediaStreams":[` +
		`{"Type":"Video","Codec":"h264","Index":0,"IsDefault":true,"Width":640,"Height":360},` +
		`{"Type":"Audio","Codec":"aac","Index":1,"IsDefault":true}]}`
	if string(got) != want {
		t.Errorf("MediaSourceInfo JSON changed.\n got: %s\nwant: %s", got, want)
	}
}

// TestKindMappings pins the kind-to-type table. A mis-mapped kind does not
// crash: the client just renders an empty library view.
func TestKindMappings(t *testing.T) {
	cases := []struct{ kind, item, media, collection string }{
		{"video", "Movie", "Video", "movies"},
		{"audiobooks", "Audio", "Audio", "music"},
		{"music", "Audio", "Audio", "music"},
		{"photos", "Photo", "Photo", "homevideos"},
		{"ebooks", "Book", "Book", "books"},
		{"comics", "Book", "Book", "books"},
		{"games", "Folder", "", ""},
		{"", "Folder", "", ""},
	}
	for _, c := range cases {
		if got := ItemType(c.kind); got != c.item {
			t.Errorf("ItemType(%q) = %q, want %q", c.kind, got, c.item)
		}
		if got := MediaType(c.kind); got != c.media {
			t.Errorf("MediaType(%q) = %q, want %q", c.kind, got, c.media)
		}
		if got := CollectionType(c.kind); got != c.collection {
			t.Errorf("CollectionType(%q) = %q, want %q", c.kind, got, c.collection)
		}
	}
}

// TestKindsForTypes pins the inverse map, including that an unknown Jellyfin
// type maps to NOTHING rather than to everything: "show me everything I did not
// ask for" is a data leak, not a convenience.
func TestKindsForTypes(t *testing.T) {
	if got := KindsForTypes(nil); got != nil {
		t.Errorf("KindsForTypes(nil) = %v, want nil", got)
	}
	if got := KindsForTypes([]string{"Episode", "Nonsense"}); got != nil {
		t.Errorf("unknown types = %v, want nil", got)
	}
	if got, want := KindsForTypes([]string{"Movie"}), []string{"video"}; !slices.Equal(got, want) {
		t.Errorf("Movie = %v, want %v", got, want)
	}
	if got, want := KindsForTypes([]string{"Audio"}), []string{"audiobooks", "music"}; !slices.Equal(got, want) {
		t.Errorf("Audio = %v, want %v", got, want)
	}
}

// TestLibraryDto: a library is a folder, and its CollectionType is what tells a
// client which view to render. A library rendered without CollectionType shows
// up as an empty generic folder.
func TestLibraryDto(t *testing.T) {
	d := LibraryDto(libraryFixture())
	if d.Id != LibraryID(7) {
		t.Errorf("Id = %q, want %q", d.Id, LibraryID(7))
	}
	if d.Type != "CollectionFolder" || !d.IsFolder {
		t.Errorf("Type/IsFolder = %q/%v, want CollectionFolder/true", d.Type, d.IsFolder)
	}
	if d.CollectionType != "movies" || d.Name != "Movies" || d.SortName != "Movies" {
		t.Errorf("library dto = %+v", d)
	}
	// A folder carries no media facts.
	keys := jsonKeys(t, d)
	for _, k := range []string{"Container", "RunTimeTicks", "MediaSources", "Path"} {
		if slices.Contains(keys, k) {
			t.Errorf("folder DTO must not carry %q; keys = %v", k, keys)
		}
	}
}

// jsonEq compares two string maps without depending on map iteration order.
// libraryFixture is the library the LibraryDto test maps. CollectionType comes
// from the library's kind, so "video" must render as a movies collection.
func libraryFixture() library.Library {
	return library.Library{
		ID:       7,
		Name:     "Movies",
		Kind:     "video",
		RootPath: "/media/movies",
	}
}

func jsonEq(want, got map[string]string) bool {
	if len(want) != len(got) {
		return false
	}
	for k, v := range want {
		if got[k] != v {
			return false
		}
	}
	return true
}