package server

import (
	"strconv"
	"time"

	"a301_server/pkg/apperror"
	"a301_server/pkg/config"
	"a301_server/pkg/metrics"
	"a301_server/pkg/middleware"

	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/cors"
	"github.com/gofiber/fiber/v2/middleware/limiter"
	"github.com/gofiber/fiber/v2/middleware/logger"
	"github.com/gofiber/fiber/v2/middleware/recover"
	"github.com/redis/go-redis/v9"
	"gorm.io/gorm"
)

// New creates a configured Fiber app with all global middleware applied.
func New() *fiber.App {
	app := fiber.New(fiber.Config{
		StreamRequestBody: true,
		BodyLimit:         4 * 1024 * 1024 * 1024, // 4GB
		ErrorHandler:      middleware.ErrorHandler,
	})
	app.Use(recover.New(recover.Config{
		EnableStackTrace: true,
	}))
	app.Use(middleware.RequestID)
	app.Use(middleware.Metrics)
	app.Get("/metrics", metrics.Handler)
	app.Use(logger.New(logger.Config{
		Format:     `{"time":"${time}","status":${status},"latency":"${latency}","method":"${method}","path":"${path}","ip":"${ip}","reqId":"${locals:requestID}"}` + "\n",
		TimeFormat: "2006-01-02T15:04:05Z07:00",
	}))
	app.Use(middleware.SecurityHeaders)
	app.Use(cors.New(cors.Config{
		AllowOrigins:     config.C.CORSAllowOrigins,
		AllowHeaders:     "Origin, Content-Type, Authorization, Idempotency-Key, X-API-Key, X-Requested-With",
		AllowMethods:     "GET, POST, PUT, PATCH, DELETE",
		ExposeHeaders:    "X-Request-ID, X-Idempotent-Replay",
		AllowCredentials: true,
	}))
	return app
}

// AuthLimiter returns a rate limiter for auth endpoints (10 req/min per IP).
func AuthLimiter() fiber.Handler {
	return limiter.New(limiter.Config{
		Max:        10,
		Expiration: 1 * time.Minute,
		KeyGenerator: func(c *fiber.Ctx) string {
			return c.IP()
		},
		LimitReached: func(c *fiber.Ctx) error {
			return apperror.ErrRateLimited
		},
	})
}

// APILimiter returns a rate limiter for general API endpoints (120 req/min per IP).
func APILimiter() fiber.Handler {
	return limiter.New(limiter.Config{
		Max:        120,
		Expiration: 1 * time.Minute,
		KeyGenerator: func(c *fiber.Ctx) string {
			return c.IP()
		},
		LimitReached: func(c *fiber.Ctx) error {
			return apperror.ErrRateLimited
		},
	})
}

// RefreshLimiter returns a rate limiter for refresh token endpoint (5 req/min per IP).
// Separate from AuthLimiter to avoid NAT collisions while still preventing abuse.
func RefreshLimiter() fiber.Handler {
	return limiter.New(limiter.Config{
		Max:        5,
		Expiration: 1 * time.Minute,
		KeyGenerator: func(c *fiber.Ctx) string {
			return "refresh:" + c.IP()
		},
		LimitReached: func(c *fiber.Ctx) error {
			return apperror.ErrRateLimited
		},
	})
}

// ChainUserLimiter returns a rate limiter for chain transactions (20 req/min per user).
func ChainUserLimiter() fiber.Handler {
	return limiter.New(limiter.Config{
		Max:        20,
		Expiration: 1 * time.Minute,
		KeyGenerator: func(c *fiber.Ctx) string {
			if uid, ok := c.Locals("userID").(uint); ok {
				return "chain_user:" + strconv.FormatUint(uint64(uid), 10)
			}
			return "chain_ip:" + c.IP()
		},
		LimitReached: func(c *fiber.Ctx) error {
			return apperror.ErrRateLimited
		},
	})
}

// HealthCheck returns a handler that reports server liveness.
func HealthCheck() fiber.Handler {
	return func(c *fiber.Ctx) error {
		return c.JSON(fiber.Map{"status": "ok"})
	}
}

// ReadyCheck returns a handler that verifies DB and Redis connectivity.
func ReadyCheck(db *gorm.DB, rdb *redis.Client) fiber.Handler {
	return func(c *fiber.Ctx) error {
		sqlDB, err := db.DB()
		if err != nil {
			return c.Status(fiber.StatusServiceUnavailable).JSON(fiber.Map{"status": "error", "detail": "db pool"})
		}
		if err := sqlDB.Ping(); err != nil {
			return c.Status(fiber.StatusServiceUnavailable).JSON(fiber.Map{"status": "error", "detail": "db"})
		}
		if err := rdb.Ping(c.Context()).Err(); err != nil {
			return c.Status(fiber.StatusServiceUnavailable).JSON(fiber.Map{"status": "error", "detail": "redis"})
		}
		return c.JSON(fiber.Map{"status": "ok"})
	}
}