package middlewares

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	configs "goFiber/config"
	database "goFiber/database/config"
	"goFiber/database/models"
	"log"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/gofiber/fiber/v3"
	"github.com/redis/go-redis/v9"
	"gorm.io/gorm"
)

type rateLimitRuntime struct {
	Name          string `json:"name"`
	MaxRequests   int64  `json:"max_requests"`
	WindowSeconds int    `json:"window_seconds"`
	IsActive      bool   `json:"is_active"`
}

// RequireRateLimit applies Redis-backed per-IP rate limiting by setting name.
func RequireRateLimit(name string, fallbackMax int64, fallbackWindowSeconds int) fiber.Handler {
	return func(c fiber.Ctx) error {
		if database.DB == nil {
			return c.Next()
		}

		setting, err := loadRateLimitRuntime(name, fallbackMax, fallbackWindowSeconds)
		if err != nil {
			return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "rate limit configuration error"})
		}
		if !setting.IsActive {
			return c.Next()
		}
		if database.RedisClient == nil {
			rateLimitLogf("[rate-limit][warn] redis unavailable, skipping enforcement name=%s", setting.Name)
			return c.Next()
		}

		ip := strings.TrimSpace(c.IP())
		if ip == "" {
			ip = "unknown"
		}

		counterKey := fmt.Sprintf("ratelimit:%s:%s", setting.Name, ip)
		count, err := database.RedisClient.Incr(context.Background(), counterKey).Result()
		if err != nil {
			return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "rate limit check failed"})
		}
		if count == 1 {
			_ = database.RedisClient.Expire(context.Background(), counterKey, time.Duration(setting.WindowSeconds)*time.Second).Err()
		}

		if count > setting.MaxRequests {
			ttl, _ := database.RedisClient.TTL(context.Background(), counterKey).Result()
			retryAfter := int(ttl.Seconds())
			if retryAfter < 1 {
				retryAfter = setting.WindowSeconds
			}
			c.Set("Retry-After", strconv.Itoa(retryAfter))
			log.Printf("[rate-limit][blocked] name=%s ip=%s count=%d max=%d window=%ds", setting.Name, ip, count, setting.MaxRequests, setting.WindowSeconds)
			return c.Status(http.StatusTooManyRequests).JSON(fiber.Map{
				"error":       "too many requests",
				"retry_after": retryAfter,
			})
		}

		rateLimitLogf("[rate-limit][allow] name=%s ip=%s count=%d max=%d window=%ds", setting.Name, ip, count, setting.MaxRequests, setting.WindowSeconds)
		return c.Next()
	}
}

func loadRateLimitRuntime(name string, fallbackMax int64, fallbackWindowSeconds int) (*rateLimitRuntime, error) {
	cacheKey := "ratelimit:setting:" + name
	if cached, err := database.Get(cacheKey); err == nil {
		var s rateLimitRuntime
		if jsonErr := json.Unmarshal([]byte(cached), &s); jsonErr == nil {
			return &s, nil
		}
	} else if !errors.Is(err, redis.Nil) {
		return nil, err
	}

	setting := &rateLimitRuntime{
		Name:          name,
		MaxRequests:   fallbackMax,
		WindowSeconds: fallbackWindowSeconds,
		IsActive:      true,
	}

	var dbSetting models.RateLimitSetting
	if err := database.DB.Where("name = ?", name).First(&dbSetting).Error; err != nil {
		if !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
		rateLimitLogf("[rate-limit][config] setting=%s not found, using fallback max=%d window=%ds", name, fallbackMax, fallbackWindowSeconds)
	} else {
		setting.MaxRequests = dbSetting.MaxRequests
		setting.WindowSeconds = dbSetting.WindowSeconds
		setting.IsActive = dbSetting.IsActive
		rateLimitLogf("[rate-limit][config] loaded from db name=%s active=%t max=%d window=%ds", name, setting.IsActive, setting.MaxRequests, setting.WindowSeconds)
	}

	cacheJSON, _ := json.Marshal(setting)
	_ = database.SetEx(cacheKey, string(cacheJSON), 60)

	return setting, nil
}

func rateLimitLogf(format string, args ...interface{}) {
	if configs.AppConfig != nil && configs.AppConfig.CorsDebug {
		log.Printf(format, args...)
	}
}