package draw

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/DATA-DOG/go-sqlmock"
	"github.com/perfect-panel/server/internal/model/lottery"
	"github.com/perfect-panel/server/pkg/xerr"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
)

// ---- test fakes ------------------------------------------------------------

type fakeRateLimiter struct {
	mu    sync.Mutex
	err   error
	calls int
}

func (f *fakeRateLimiter) Allow(_ context.Context, _ int64) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	f.calls++
	return f.err
}

type fakeChance struct {
	mu               sync.Mutex
	consumeRemaining int64
	consumeErr       error
	consumeCalls     int
	queryRemaining   int64
}

func (f *fakeChance) Grant(context.Context, int64, int64, string, string, int) error {
	return nil
}
func (f *fakeChance) Consume(_ context.Context, _ *gorm.DB, _, _ int64) (int64, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	f.consumeCalls++
	if f.consumeErr != nil {
		return 0, f.consumeErr
	}
	return f.consumeRemaining, nil
}
func (f *fakeChance) Query(_ context.Context, _, _ int64) (int64, error) {
	return f.queryRemaining, nil
}

type fakeEvaluator struct {
	passed bool
	unmet  []lottery.UnmetReason
	err    error
}

func (f *fakeEvaluator) Evaluate(context.Context, *lottery.EligibilityRule, lottery.RuleContext) (bool, []lottery.UnmetReason, error) {
	return f.passed, f.unmet, f.err
}

type fakePicker struct {
	idx int
	err error
}

func (f *fakePicker) Pick([]lottery.Prize) (int, error) { return f.idx, f.err }

type fakeContextBuilder struct{}

func (fakeContextBuilder) Build(_ context.Context, uid int64) (lottery.RuleContext, error) {
	return lottery.RuleContext{UserId: uid}, nil
}

type recordingHandler struct {
	handlerType string
	auto        bool
	result      lottery.DispatchResult
	err         error
	calls       int
}

func (h *recordingHandler) Type() string { return h.handlerType }
func (h *recordingHandler) IsAuto() bool { return h.auto }
func (h *recordingHandler) Dispatch(_ context.Context, _ *gorm.DB, _ lottery.DispatchRequest) (lottery.DispatchResult, error) {
	h.calls++
	return h.result, h.err
}
func (h *recordingHandler) ValidateClaim([]byte) error { return nil }

// stubRegistry only knows what we register.
type stubRegistry struct {
	handlers map[string]lottery.PrizeHandler
}

func (r *stubRegistry) Get(t string) (lottery.PrizeHandler, bool) {
	h, ok := r.handlers[t]
	return h, ok
}
func (r *stubRegistry) MustGet(t string) (lottery.PrizeHandler, error) {
	if h, ok := r.handlers[t]; ok {
		return h, nil
	}
	return nil, lottery.ErrHandlerNotRegistered
}

// ---- shared harness --------------------------------------------------------

func newTestDB(t *testing.T) (*gorm.DB, sqlmock.Sqlmock, func()) {
	t.Helper()
	sqlDB, mock, err := sqlmock.New(sqlmock.QueryMatcherOption(sqlmock.QueryMatcherFunc(func(expected, actual string) error {
		if strings.Contains(actual, expected) {
			return nil
		}
		return fmt.Errorf("actual sql %q does not contain %q", actual, expected)
	})))
	if err != nil {
		t.Fatalf("sqlmock: %v", err)
	}
	db, err := gorm.Open(mysql.New(mysql.Config{Conn: sqlDB, SkipInitializeWithVersion: true}), &gorm.Config{})
	if err != nil {
		_ = sqlDB.Close()
		t.Fatalf("gorm: %v", err)
	}
	return db, mock, func() { _ = sqlDB.Close() }
}

// expectRunningActivity sets up the pre-tx activity load.
func expectRunningActivity(mock sqlmock.Sqlmock, activityId int64) {
	now := time.Now()
	mock.ExpectQuery("FROM `lottery_activity`").
		WillReturnRows(sqlmock.NewRows([]string{
			"id", "title", "start_at", "end_at", "status", "grid_size", "eligibility", "chance_sources", "unmet_action",
		}).AddRow(activityId, "test", now.Add(-1*time.Hour), now.Add(24*time.Hour), lottery.ActivityStatusRunning, 9, "{}", "[]", "block"))
}

// expectPrizePool sets up the pre-tx prize load.
func expectPrizePool(mock sqlmock.Sqlmock, activityId int64, prizes ...lottery.Prize) {
	rows := sqlmock.NewRows([]string{"id", "activity_id", "slot", "type", "name", "icon_url", "config", "weight", "total_stock", "remaining_stock", "is_fallback", "version"})
	for _, p := range prizes {
		rows.AddRow(p.Id, p.ActivityId, p.Slot, p.Type, p.Name, p.IconURL, p.Config, p.Weight, p.TotalStock, p.RemainingStock, p.IsFallback, p.Version)
	}
	mock.ExpectQuery("FROM `lottery_prize`").WillReturnRows(rows)
}

// expectExistingDrawEmpty sets up the tx-inner nonce lookup returning no rows.
func expectExistingDrawEmpty(mock sqlmock.Sqlmock) {
	mock.ExpectQuery("FROM `lottery_draw`").WillReturnError(gorm.ErrRecordNotFound)
}

// ---- Test cases ------------------------------------------------------------

func TestDraw_RejectsWhenFeatureFlagDisabled(t *testing.T) {
	db, _, cleanup := newTestDB(t)
	defer cleanup()

	svc := NewService(Deps{
		DB:      db,
		Enabled: false,
	})
	_, err := svc.Draw(context.Background(), Request{UserId: 42, ActivityId: 100, ClientNonce: "n1"})
	code, ok := errAsCode(err)
	if !ok || code != xerr.LotteryActivityEnded {
		t.Fatalf("expected LotteryActivityEnded when disabled, got %v", err)
	}
}

func TestDraw_ValidatesRequest(t *testing.T) {
	db, _, cleanup := newTestDB(t)
	defer cleanup()

	svc := NewService(Deps{DB: db, Enabled: true})
	cases := []Request{
		{UserId: 0, ActivityId: 1, ClientNonce: "n"},
		{UserId: 1, ActivityId: 0, ClientNonce: "n"},
		{UserId: 1, ActivityId: 1, ClientNonce: ""},
		{UserId: 1, ActivityId: 1, ClientNonce: strings.Repeat("x", 65)},
	}
	for i, c := range cases {
		if _, err := svc.Draw(context.Background(), c); err == nil {
			t.Fatalf("case %d expected error, got nil", i)
		}
	}
}

func TestDraw_RateLimited(t *testing.T) {
	db, _, cleanup := newTestDB(t)
	defer cleanup()

	limiter := &fakeRateLimiter{err: ErrRateLimited}
	svc := NewService(Deps{DB: db, Enabled: true, RateLimiter: limiter})
	_, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 1, ClientNonce: "n"})
	code, ok := errAsCode(err)
	if !ok || code != xerr.LotteryRateLimited {
		t.Fatalf("expected LotteryRateLimited, got %v", err)
	}
}

func TestDraw_NonceIdempotency_ReturnsExisting(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)
	expectPrizePool(mock, 100, lottery.Prize{Id: 1, ActivityId: 100, Slot: 0, Type: lottery.PrizeTypeNone, Name: "谢谢参与", Config: "{}", Weight: 1})

	mock.ExpectBegin()
	// nonce hit — the flow short-circuits
	mock.ExpectQuery("FROM `lottery_draw`").
		WillReturnRows(sqlmock.NewRows([]string{"id", "user_id", "activity_id", "client_nonce", "prize_id", "is_win", "dispatch_state", "drawn_at"}).
			AddRow(int64(999), int64(42), int64(100), "same-nonce", nil, false, lottery.DispatchStateAutoClaimed, time.Now()))
	// snapshot lookup
	mock.ExpectQuery("FROM `lottery_prize_snapshot`").
		WillReturnRows(sqlmock.NewRows([]string{"id", "draw_id", "prize_id", "slot", "type", "name", "config"}).
			AddRow(int64(1), int64(999), int64(0), 0, lottery.PrizeTypeNone, "谢谢参与", "{}"))
	mock.ExpectCommit()

	chance := &fakeChance{queryRemaining: 3}
	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         chance,
		Evaluator:      &fakeEvaluator{passed: true},
		Picker:         &fakePicker{idx: 0},
		Registry:       &stubRegistry{handlers: map[string]lottery.PrizeHandler{}},
		ContextBuilder: fakeContextBuilder{},
	})
	res, err := svc.Draw(context.Background(), Request{UserId: 42, ActivityId: 100, ClientNonce: "same-nonce"})
	if err != nil {
		t.Fatalf("Draw: %v", err)
	}
	if res.DrawId != 999 {
		t.Fatalf("expected reuse existing draw id=999, got %d", res.DrawId)
	}
	if chance.consumeCalls != 0 {
		t.Fatalf("must NOT Consume a chance on nonce replay")
	}
}

func TestDraw_NoChancesReturnsCode(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)
	expectPrizePool(mock, 100, lottery.Prize{Id: 1, ActivityId: 100, Slot: 0, Type: lottery.PrizeTypeNone, Name: "谢谢参与", Config: "{}", Weight: 1})

	mock.ExpectBegin()
	expectExistingDrawEmpty(mock)
	mock.ExpectRollback()

	chance := &fakeChance{consumeErr: lottery.ErrNoChances}
	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         chance,
		Evaluator:      &fakeEvaluator{passed: true},
		Picker:         &fakePicker{idx: 0},
		Registry:       &stubRegistry{handlers: map[string]lottery.PrizeHandler{}},
		ContextBuilder: fakeContextBuilder{},
	})
	_, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 100, ClientNonce: "n"})
	code, ok := errAsCode(err)
	if !ok || code != xerr.LotteryNoChances {
		t.Fatalf("expected LotteryNoChances, got %v", err)
	}
}

func TestDraw_NotEligibleRejectsBeforeConsume(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)

	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         &fakeChance{},
		Evaluator:      &fakeEvaluator{passed: false, unmet: []lottery.UnmetReason{{Rule: "invite_count", Hint: "need 3"}}},
		Picker:         &fakePicker{},
		Registry:       &stubRegistry{},
		ContextBuilder: fakeContextBuilder{},
	})
	_, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 100, ClientNonce: "n"})
	code, ok := errAsCode(err)
	if !ok || code != xerr.LotteryNotEligible {
		t.Fatalf("expected LotteryNotEligible, got %v", err)
	}
	// Ensure no mock expectations remain (we didn't set up prize load).
	if err := mock.ExpectationsWereMet(); err != nil {
		t.Fatalf("expectations: %v", err)
	}
}

func TestDraw_SuccessAutoClaimedNoneReturnsDrawWithoutDispatch(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)
	// Two prizes: one none (weight 100) — picker returns idx 0 always
	expectPrizePool(mock, 100,
		lottery.Prize{Id: 1, ActivityId: 100, Slot: 0, Type: lottery.PrizeTypeNone, Name: "谢谢参与", Config: "{}", Weight: 100},
	)

	mock.ExpectBegin()
	expectExistingDrawEmpty(mock)
	// insert draw
	mock.ExpectExec("INSERT INTO `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(555, 1))
	// insert prize_snapshot
	mock.ExpectExec("INSERT INTO `lottery_prize_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	// insert eligibility_snapshot
	mock.ExpectExec("INSERT INTO `lottery_eligibility_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	// finalize draw state
	mock.ExpectExec("UPDATE `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(0, 1))
	mock.ExpectCommit()

	chance := &fakeChance{consumeRemaining: 2}
	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         chance,
		Evaluator:      &fakeEvaluator{passed: true},
		Picker:         &fakePicker{idx: 0},
		Registry:       &stubRegistry{handlers: map[string]lottery.PrizeHandler{}},
		ContextBuilder: fakeContextBuilder{},
	})
	res, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 100, ClientNonce: "unique-1"})
	if err != nil {
		t.Fatalf("Draw: %v", err)
	}
	if res.IsWin {
		t.Fatalf("none prize should not count as win")
	}
	if res.DrawId == 0 {
		t.Fatalf("expected draw id from LastInsertId")
	}
	if res.ChancesRemaining != 2 {
		t.Fatalf("expected remaining=2 from Consume, got %d", res.ChancesRemaining)
	}
}

func TestDraw_LimitedStockFallback(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)
	// prize 0 = limited (remaining=0 → sold out); prize 1 = fallback
	expectPrizePool(mock, 100,
		lottery.Prize{Id: 10, ActivityId: 100, Slot: 0, Type: "vpn_duration", Name: "3天", Config: `{"duration_days":3}`, Weight: 100, TotalStock: sql.NullInt64{Int64: 1, Valid: true}, RemainingStock: sql.NullInt64{Int64: 1, Valid: true}},
		lottery.Prize{Id: 20, ActivityId: 100, Slot: 1, Type: lottery.PrizeTypeNone, Name: "谢谢参与", Config: "{}", Weight: 0, IsFallback: true},
	)

	mock.ExpectBegin()
	expectExistingDrawEmpty(mock)
	// stock decrement returns 0 rows affected → sold out
	mock.ExpectExec("UPDATE `lottery_prize`").
		WillReturnResult(sqlmock.NewResult(0, 0))
	mock.ExpectExec("INSERT INTO `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(778, 1))
	mock.ExpectExec("INSERT INTO `lottery_prize_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("INSERT INTO `lottery_eligibility_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("UPDATE `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(0, 1))
	mock.ExpectCommit()

	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         &fakeChance{consumeRemaining: 1},
		Evaluator:      &fakeEvaluator{passed: true},
		Picker:         &fakePicker{idx: 0},
		Registry:       &stubRegistry{handlers: map[string]lottery.PrizeHandler{}},
		ContextBuilder: fakeContextBuilder{},
	})
	res, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 100, ClientNonce: "n"})
	if err != nil {
		t.Fatalf("Draw: %v", err)
	}
	if res.IsWin {
		t.Fatalf("fallback none should not win")
	}
	if res.DrawId != 778 {
		t.Fatalf("expected draw id 778, got %d", res.DrawId)
	}
}

func TestDraw_WinCallsAutoHandlerDispatch(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)
	expectPrizePool(mock, 100,
		lottery.Prize{Id: 30, ActivityId: 100, Slot: 5, Type: lottery.PrizeTypeVPNDuration, Name: "3 天", Config: `{"duration_days":3}`, Weight: 100},
	)

	handler := &recordingHandler{
		handlerType: lottery.PrizeTypeVPNDuration,
		auto:        true,
		result:      lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: "已加 3 天"},
	}

	mock.ExpectBegin()
	expectExistingDrawEmpty(mock)
	mock.ExpectExec("INSERT INTO `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(1234, 1))
	mock.ExpectExec("INSERT INTO `lottery_prize_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("INSERT INTO `lottery_eligibility_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("UPDATE `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(0, 1))
	mock.ExpectCommit()

	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         &fakeChance{consumeRemaining: 0},
		Evaluator:      &fakeEvaluator{passed: true},
		Picker:         &fakePicker{idx: 0},
		Registry:       &stubRegistry{handlers: map[string]lottery.PrizeHandler{lottery.PrizeTypeVPNDuration: handler}},
		ContextBuilder: fakeContextBuilder{},
	})
	res, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 100, ClientNonce: "w"})
	if err != nil {
		t.Fatalf("Draw: %v", err)
	}
	if !res.IsWin {
		t.Fatalf("expected IsWin=true for vpn_duration")
	}
	if handler.calls != 1 {
		t.Fatalf("expected handler.Dispatch called once, got %d", handler.calls)
	}
	if res.Claim.AutoClaimed != true {
		t.Fatalf("expected AutoClaimed=true, got %+v", res.Claim)
	}
	if res.Message != "已加 3 天" {
		t.Fatalf("expected message from Dispatch, got %q", res.Message)
	}
	if res.Prize == nil || res.Prize.Type != lottery.PrizeTypeVPNDuration {
		t.Fatalf("expected prize summary, got %+v", res.Prize)
	}
	// Prize.Config should be embedded json.RawMessage — verify decodes
	var cfg map[string]any
	if err := json.Unmarshal(res.Prize.Config, &cfg); err != nil {
		t.Fatalf("Prize.Config invalid: %v", err)
	}
	if cfg["duration_days"].(float64) != 3 {
		t.Fatalf("expected duration_days=3, got %v", cfg["duration_days"])
	}
}

func TestDraw_UnregisteredAutoHandlerFallsBackToPendingClaim(t *testing.T) {
	db, mock, cleanup := newTestDB(t)
	defer cleanup()

	expectRunningActivity(mock, 100)
	expectPrizePool(mock, 100,
		lottery.Prize{Id: 40, ActivityId: 100, Slot: 0, Type: "encrypted", Name: "Encrypted", Config: "{}", Weight: 100},
	)

	mock.ExpectBegin()
	expectExistingDrawEmpty(mock)
	mock.ExpectExec("INSERT INTO `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("INSERT INTO `lottery_prize_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("INSERT INTO `lottery_eligibility_snapshot`").
		WillReturnResult(sqlmock.NewResult(1, 1))
	mock.ExpectExec("UPDATE `lottery_draw`").
		WillReturnResult(sqlmock.NewResult(0, 1))
	mock.ExpectCommit()

	svc := NewService(Deps{
		DB:             db,
		Enabled:        true,
		Chance:         &fakeChance{consumeRemaining: 0},
		Evaluator:      &fakeEvaluator{passed: true},
		Picker:         &fakePicker{idx: 0},
		Registry:       &stubRegistry{handlers: map[string]lottery.PrizeHandler{}},
		ContextBuilder: fakeContextBuilder{},
	})
	res, err := svc.Draw(context.Background(), Request{UserId: 1, ActivityId: 100, ClientNonce: "w2"})
	if err != nil {
		t.Fatalf("Draw: %v", err)
	}
	if res.Claim.Required != true {
		t.Fatalf("expected Claim.Required=true when handler unregistered, got %+v", res.Claim)
	}
}

// errAsCode helps assert xerr.CodeError codes.
func errAsCode(err error) (uint32, bool) {
	if err == nil {
		return 0, false
	}
	var ce *xerr.CodeError
	if errors.As(err, &ce) {
		return ce.GetErrCode(), true
	}
	return 0, false
}