package middleware

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"time"

	"a301_server/pkg/database"
	"github.com/gofiber/fiber/v2"
)

const idempotencyTTL = 10 * time.Minute
const redisTimeout = 5 * time.Second

type cachedResponse struct {
	StatusCode int             `json:"s"`
	Body       json.RawMessage `json:"b"`
}

// Idempotency checks the Idempotency-Key header to prevent duplicate transactions.
// If the same key is seen again within the TTL, the cached response is returned.
func Idempotency(c *fiber.Ctx) error {
	key := c.Get("Idempotency-Key")
	if key == "" {
		return c.Next()
	}

	// userID가 있으면 키에 포함하여 사용자 간 캐시 충돌 방지
	redisKey := "idempotency:"
	if uid, ok := c.Locals("userID").(uint); ok {
		redisKey += fmt.Sprintf("u%d:", uid)
	}
	redisKey += key

	ctx, cancel := context.WithTimeout(context.Background(), redisTimeout)
	defer cancel()

	// Check if this key was already processed
	cached, err := database.RDB.Get(ctx, redisKey).Bytes()
	if err == nil && len(cached) > 0 {
		var cr cachedResponse
		if json.Unmarshal(cached, &cr) == nil {
			c.Set("Content-Type", "application/json")
			c.Set("X-Idempotent-Replay", "true")
			return c.Status(cr.StatusCode).Send(cr.Body)
		}
	}

	// Process the request
	if err := c.Next(); err != nil {
		return err
	}

	// Cache successful responses (2xx)
	status := c.Response().StatusCode()
	if status >= 200 && status < 300 {
		cr := cachedResponse{StatusCode: status, Body: c.Response().Body()}
		if data, err := json.Marshal(cr); err == nil {
			if err := database.RDB.Set(ctx, redisKey, data, idempotencyTTL).Err(); err != nil {
				log.Printf("WARNING: idempotency cache write failed (key=%s): %v", key, err)
			}
		}
	}

	return nil
}