package transcode_test

import (
	"context"
	"net/http"
	"net/http/httptest"
	"testing"

	flatbuffers "github.com/google/flatbuffers/go"

	"scrabble/gateway/internal/backendclient"
	"scrabble/gateway/internal/transcode"
	fb "scrabble/pkg/fbs/scrabblefb"
)

// fakeBackend serves the subset of backend endpoints the slice handlers call.
func fakeBackend(t *testing.T, h http.HandlerFunc) (*backendclient.Client, func()) {
	t.Helper()
	srv := httptest.NewServer(h)
	c, err := backendclient.New(srv.URL, "localhost:9090", 2_000_000_000)
	if err != nil {
		t.Fatalf("backendclient: %v", err)
	}
	return c, func() {
		_ = c.Close()
		srv.Close()
	}
}

func TestGuestAuthRoundTrip(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/api/v1/internal/sessions/guest" {
			t.Errorf("unexpected path %q", r.URL.Path)
		}
		_, _ = w.Write([]byte(`{"token":"tok-1","user_id":"u-1","is_guest":true,"display_name":"Guest"}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, ok := reg.Lookup(transcode.MsgAuthGuest)
	if !ok {
		t.Fatal("auth.guest not registered")
	}
	payload, err := op.Handler(context.Background(), transcode.Request{})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	sess := fb.GetRootAsSession(payload, 0)
	if string(sess.Token()) != "tok-1" || string(sess.UserId()) != "u-1" || !sess.IsGuest() {
		t.Fatalf("session decoded wrong: token=%q user=%q guest=%v", sess.Token(), sess.UserId(), sess.IsGuest())
	}
}

func TestGameStateRoundTripForwardsUserID(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		if got := r.Header.Get("X-User-ID"); got != "u-7" {
			t.Errorf("X-User-ID = %q, want u-7", got)
		}
		if r.URL.Path != "/api/v1/user/games/g-1/state" {
			t.Errorf("unexpected path %q", r.URL.Path)
		}
		_, _ = w.Write([]byte(`{"game":{"id":"g-1","variant":"scrabble_en","status":"active","players":2,"to_move":1,"seats":[{"seat":0,"account_id":"u-7","score":5}]},"seat":0,"rack":[0,1],"bag_len":80,"hints_remaining":1}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, _ := reg.Lookup(transcode.MsgGameState)

	b := flatbuffers.NewBuilder(32)
	gid := b.CreateString("g-1")
	fb.StateRequestStart(b)
	fb.StateRequestAddGameId(b, gid)
	b.Finish(fb.StateRequestEnd(b))

	payload, err := op.Handler(context.Background(), transcode.Request{Payload: b.FinishedBytes(), UserID: "u-7"})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	st := fb.GetRootAsStateView(payload, 0)
	if st.BagLen() != 80 || st.RackLength() != 2 || st.HintsRemaining() != 1 {
		t.Fatalf("state decoded wrong: bag=%d rack=%d hints=%d", st.BagLen(), st.RackLength(), st.HintsRemaining())
	}
	game := st.Game(nil)
	if game == nil || string(game.Id()) != "g-1" || string(game.Variant()) != "scrabble_en" || game.ToMove() != 1 {
		t.Fatalf("nested game decoded wrong: %+v", game)
	}
}

func TestEnqueueRoundTripEncodesMatch(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte(`{"matched":true,"game":{"id":"g-9","variant":"scrabble_en","status":"active","players":2,"to_move":0,"seats":[]}}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, _ := reg.Lookup(transcode.MsgLobbyEnqueue)

	b := flatbuffers.NewBuilder(32)
	v := b.CreateString("scrabble_en")
	fb.EnqueueRequestStart(b)
	fb.EnqueueRequestAddVariant(b, v)
	b.Finish(fb.EnqueueRequestEnd(b))

	payload, err := op.Handler(context.Background(), transcode.Request{Payload: b.FinishedBytes(), UserID: "u-1"})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	m := fb.GetRootAsMatchResult(payload, 0)
	if !m.Matched() {
		t.Fatal("match result should be matched")
	}
	if g := m.Game(nil); g == nil || string(g.Id()) != "g-9" {
		t.Fatalf("match game decoded wrong: %+v", g)
	}
}

func TestDomainErrorSurfacesBackendCode(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusConflict)
		_, _ = w.Write([]byte(`{"error":{"code":"not_your_turn","message":"nope"}}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, _ := reg.Lookup(transcode.MsgGameState)

	b := flatbuffers.NewBuilder(32)
	gid := b.CreateString("g-1")
	fb.StateRequestStart(b)
	fb.StateRequestAddGameId(b, gid)
	b.Finish(fb.StateRequestEnd(b))

	_, err := op.Handler(context.Background(), transcode.Request{Payload: b.FinishedBytes(), UserID: "u-1"})
	if err == nil {
		t.Fatal("expected backend error")
	}
	code, ok := transcode.DomainCode(err)
	if !ok || code != "not_your_turn" {
		t.Fatalf("DomainCode = (%q, %v), want (not_your_turn, true)", code, ok)
	}
}

// gameActionPayload builds a GameActionRequest payload (pass / resign / hint / etc.).
func gameActionPayload(gameID string) []byte {
	b := flatbuffers.NewBuilder(32)
	gid := b.CreateString(gameID)
	fb.GameActionRequestStart(b)
	fb.GameActionRequestAddGameId(b, gid)
	b.Finish(fb.GameActionRequestEnd(b))
	return b.FinishedBytes()
}

// TestHideGameForwardsToBackend checks game.hide reuses GameActionRequest, POSTs to the
// game's /hide endpoint with the caller's id, and echoes an Ack (Stage 17).
func TestHideGameForwardsToBackend(t *testing.T) {
	var hit bool
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		hit = true
		if r.Method != http.MethodPost || r.URL.Path != "/api/v1/user/games/g-1/hide" {
			t.Errorf("unexpected %s %q", r.Method, r.URL.Path)
		}
		if got := r.Header.Get("X-User-ID"); got != "u-1" {
			t.Errorf("X-User-ID = %q, want u-1", got)
		}
		_, _ = w.Write([]byte(`{"ok":true}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, ok := reg.Lookup(transcode.MsgGameHide)
	if !ok {
		t.Fatal("game.hide not registered")
	}
	payload, err := op.Handler(context.Background(), transcode.Request{UserID: "u-1", Payload: gameActionPayload("g-1")})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	if !hit {
		t.Error("backend not called")
	}
	if ack := fb.GetRootAsAck(payload, 0); !ack.Ok() {
		t.Error("ack not ok")
	}
}

func TestGamesListRoundTripDecodesSeatNames(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		if got := r.Header.Get("X-User-ID"); got != "u-9" {
			t.Errorf("X-User-ID = %q, want u-9", got)
		}
		if r.URL.Path != "/api/v1/user/games" {
			t.Errorf("unexpected path %q", r.URL.Path)
		}
		_, _ = w.Write([]byte(`{"games":[{"id":"g-1","variant":"scrabble_en","status":"active","players":2,"to_move":0,"last_activity_unix":1717000000,"seats":[{"seat":0,"account_id":"u-9","display_name":"You","score":10},{"seat":1,"account_id":"a-1","display_name":"Ann","score":7}]}]}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, _ := reg.Lookup(transcode.MsgGamesList)
	payload, err := op.Handler(context.Background(), transcode.Request{UserID: "u-9"})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	gl := fb.GetRootAsGameList(payload, 0)
	if gl.GamesLength() != 1 {
		t.Fatalf("games length = %d, want 1", gl.GamesLength())
	}
	var g fb.GameView
	gl.Games(&g, 0)
	if string(g.Id()) != "g-1" {
		t.Errorf("game id = %q, want g-1", g.Id())
	}
	if g.LastActivityUnix() != 1717000000 {
		t.Errorf("last activity = %d, want 1717000000", g.LastActivityUnix())
	}
	var seat fb.SeatView
	g.Seats(&seat, 1)
	if string(seat.DisplayName()) != "Ann" {
		t.Errorf("seat display name = %q, want Ann", seat.DisplayName())
	}
}

func TestPassRoundTrip(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/api/v1/user/games/g-2/pass" {
			t.Errorf("unexpected path %q", r.URL.Path)
		}
		_, _ = w.Write([]byte(`{"move":{"player":0,"action":"pass"},"game":{"id":"g-2","status":"active","seats":[{"seat":0,"account_id":"u-1","display_name":"You"}]}}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, _ := reg.Lookup(transcode.MsgGamePass)
	payload, err := op.Handler(context.Background(), transcode.Request{UserID: "u-1", Payload: gameActionPayload("g-2")})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	mr := fb.GetRootAsMoveResult(payload, 0)
	var move fb.MoveRecord
	mr.Move(&move)
	if string(move.Action()) != "pass" {
		t.Errorf("action = %q, want pass", move.Action())
	}
}

func TestHintRoundTrip(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/api/v1/user/games/g-3/hint" {
			t.Errorf("unexpected path %q", r.URL.Path)
		}
		_, _ = w.Write([]byte(`{"move":{"player":0,"action":"play","words":["CAT"],"score":9},"hints_remaining":2}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil)
	op, _ := reg.Lookup(transcode.MsgGameHint)
	payload, err := op.Handler(context.Background(), transcode.Request{UserID: "u-1", Payload: gameActionPayload("g-3")})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	hr := fb.GetRootAsHintResult(payload, 0)
	if hr.HintsRemaining() != 2 {
		t.Errorf("hints remaining = %d, want 2", hr.HintsRemaining())
	}
	var move fb.MoveRecord
	hr.Move(&move)
	if move.Score() != 9 {
		t.Errorf("hint move score = %d, want 9", move.Score())
	}
}