package store

import (
	"context"
	"errors"
	"os"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/easyai/easyai-ai-gateway/apps/api/internal/auth"
)

func TestReserveTaskBillingSerializesConcurrentWalletReservations(t *testing.T) {
	databaseURL := strings.TrimSpace(os.Getenv("AI_GATEWAY_TEST_DATABASE_URL"))
	if databaseURL == "" {
		t.Skip("set AI_GATEWAY_TEST_DATABASE_URL to run the wallet reservation integration test")
	}

	ctx := context.Background()
	db, err := Connect(ctx, databaseURL)
	if err != nil {
		t.Fatalf("connect store: %v", err)
	}
	defer db.Close()

	tenantID, userID := seedWalletReservationUser(t, ctx, db)
	if _, err := db.SetUserWalletBalance(ctx, WalletBalanceAdjustmentInput{
		GatewayUserID: userID,
		Currency:      "resource",
		Balance:       10,
		Reason:        "seed wallet reservation test",
	}); err != nil {
		t.Fatalf("seed wallet balance: %v", err)
	}

	firstTaskID := newWalletReservationTestUUID(t, ctx, db)
	secondTaskID := newWalletReservationTestUUID(t, ctx, db)
	billings := []any{map[string]any{"currency": "resource", "amount": float64(10)}}
	user := &auth.User{GatewayUserID: userID, GatewayTenantID: tenantID}
	tasks := []GatewayTask{
		{ID: firstTaskID, GatewayUserID: userID, GatewayTenantID: tenantID, Kind: "images.generations", Model: "mock-image"},
		{ID: secondTaskID, GatewayUserID: userID, GatewayTenantID: tenantID, Kind: "videos.generations", Model: "mock-video"},
	}

	type reserveResult struct {
		reservations []WalletBillingReservation
		err          error
	}
	results := make(chan reserveResult, len(tasks))
	var wg sync.WaitGroup
	for _, task := range tasks {
		task := task
		wg.Add(1)
		go func() {
			defer wg.Done()
			reservations, err := db.ReserveTaskBilling(ctx, task, user, billings)
			results <- reserveResult{reservations: reservations, err: err}
		}()
	}
	wg.Wait()
	close(results)

	var successReservations []WalletBillingReservation
	successCount := 0
	insufficientCount := 0
	for result := range results {
		if result.err == nil {
			successCount++
			successReservations = result.reservations
			continue
		}
		if errors.Is(result.err, ErrInsufficientWalletBalance) {
			insufficientCount++
			continue
		}
		t.Fatalf("unexpected reservation error: %v", result.err)
	}
	if successCount != 1 || insufficientCount != 1 {
		t.Fatalf("expected one successful reservation and one insufficient balance rejection, got success=%d insufficient=%d", successCount, insufficientCount)
	}
	if len(successReservations) != 1 || !walletFloatNear(successReservations[0].Amount, 10) {
		t.Fatalf("unexpected successful reservations: %+v", successReservations)
	}

	balance, frozen, spent := readWalletReservationAccount(t, ctx, db, userID)
	if !walletFloatNear(balance, 10) || !walletFloatNear(frozen, 10) || !walletFloatNear(spent, 0) {
		t.Fatalf("reservation should freeze balance without spending it, balance=%f frozen=%f spent=%f", balance, frozen, spent)
	}

	settleTask := GatewayTask{
		ID:                successReservations[0].TaskID,
		GatewayUserID:     userID,
		GatewayTenantID:   tenantID,
		Kind:              "images.generations",
		Model:             "mock-image",
		ResolvedModel:     "mock-image",
		Billings:          billings,
		BillingSummary:    map[string]any{"currency": "resource", "totalAmount": float64(10)},
		FinalChargeAmount: 10,
	}
	if err := db.SettleTaskBilling(ctx, settleTask); err != nil {
		t.Fatalf("settle reserved task billing: %v", err)
	}
	if err := db.SettleTaskBilling(ctx, settleTask); err != nil {
		t.Fatalf("settle reserved task billing should be idempotent: %v", err)
	}
	balance, frozen, spent = readWalletReservationAccount(t, ctx, db, userID)
	if !walletFloatNear(balance, 0) || !walletFloatNear(frozen, 0) || !walletFloatNear(spent, 10) {
		t.Fatalf("settlement should release reservation and debit once, balance=%f frozen=%f spent=%f", balance, frozen, spent)
	}
}

func seedWalletReservationUser(t *testing.T, ctx context.Context, db *Store) (string, string) {
	t.Helper()
	suffix := strconv.FormatInt(time.Now().UnixNano(), 10)
	var tenantID string
	if err := db.pool.QueryRow(ctx, `
INSERT INTO gateway_tenants (tenant_key, name)
VALUES ($1, $2)
RETURNING id::text`, "wallet-reservation-"+suffix, "Wallet Reservation Test "+suffix).Scan(&tenantID); err != nil {
		t.Fatalf("insert test tenant: %v", err)
	}
	var userID string
	if err := db.pool.QueryRow(ctx, `
INSERT INTO gateway_users (user_key, username, gateway_tenant_id, tenant_key, roles)
VALUES ($1, $2, $3::uuid, $4, '["basic"]'::jsonb)
RETURNING id::text`, "wallet-reservation-user-"+suffix, "wallet_reservation_"+suffix, tenantID, "wallet-reservation-"+suffix).Scan(&userID); err != nil {
		t.Fatalf("insert test user: %v", err)
	}
	t.Cleanup(func() {
		cleanupCtx := context.Background()
		_, _ = db.pool.Exec(cleanupCtx, `DELETE FROM gateway_users WHERE id = $1::uuid`, userID)
		_, _ = db.pool.Exec(cleanupCtx, `DELETE FROM gateway_tenants WHERE id = $1::uuid`, tenantID)
	})
	return tenantID, userID
}

func newWalletReservationTestUUID(t *testing.T, ctx context.Context, db *Store) string {
	t.Helper()
	var id string
	if err := db.pool.QueryRow(ctx, `SELECT gen_random_uuid()::text`).Scan(&id); err != nil {
		t.Fatalf("generate uuid: %v", err)
	}
	return id
}

func readWalletReservationAccount(t *testing.T, ctx context.Context, db *Store, userID string) (float64, float64, float64) {
	t.Helper()
	var balance float64
	var frozen float64
	var spent float64
	if err := db.pool.QueryRow(ctx, `
SELECT balance::float8, frozen_balance::float8, total_spent::float8
FROM gateway_wallet_accounts
WHERE gateway_user_id = $1::uuid
  AND currency = 'resource'`, userID).Scan(&balance, &frozen, &spent); err != nil {
		t.Fatalf("read wallet account: %v", err)
	}
	return balance, frozen, spent
}

func walletFloatNear(a float64, b float64) bool {
	delta := a - b
	if delta < 0 {
		delta = -delta
	}
	return delta < 0.000001
}