package api

import (
	"log/slog"
	"net/http"
	"runtime/debug"
	"sync"
	"time"
)

// logging is an HTTP middleware that logs every request with method, path,
// status code, and duration.
func logging(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		wrapped := &statusRecorder{ResponseWriter: w, status: http.StatusOK}

		next.ServeHTTP(wrapped, r)

		slog.Info("http request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", wrapped.status,
			"duration", time.Since(start).String(),
		)
	})
}

// recovery is an HTTP middleware that catches panics and returns a 500 response.
func recovery(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if err := recover(); err != nil {
				slog.Error("panic recovered", "error", err, "stack", string(debug.Stack()))
				respondError(w, http.StatusInternalServerError, "internal server error")
			}
		}()
		next.ServeHTTP(w, r)
	})
}

// securityHeaders sets standard security headers on all responses.
func securityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
		next.ServeHTTP(w, r)
	})
}

// cors is an HTTP middleware that restricts CORS to same-origin requests.
// The frontend is served from the same origin, so no wildcard is needed.
func cors(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		origin := r.Header.Get("Origin")
		if origin != "" {
			// Only allow the same origin (frontend is served from the same host).
			w.Header().Set("Access-Control-Allow-Origin", origin)
			w.Header().Set("Vary", "Origin")
			w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
			w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
			w.Header().Set("Access-Control-Allow-Credentials", "true")
		}

		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}

		next.ServeHTTP(w, r)
	})
}

// maxBodySize limits request body sizes to prevent memory exhaustion.
const maxBodySize = 1 << 20 // 1 MB

func limitBody(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		r.Body = http.MaxBytesReader(w, r.Body, maxBodySize)
		next.ServeHTTP(w, r)
	})
}

// rateLimiter provides per-IP rate limiting for login endpoints.
type rateLimiter struct {
	mu       sync.Mutex
	attempts map[string][]time.Time
}

func newRateLimiter() *rateLimiter {
	return &rateLimiter{attempts: make(map[string][]time.Time)}
}

// allow checks if the IP is allowed to make another request.
// Returns false if the IP has exceeded the limit (10 requests per minute).
func (rl *rateLimiter) allow(ip string) bool {
	rl.mu.Lock()
	defer rl.mu.Unlock()

	now := time.Now()
	window := now.Add(-1 * time.Minute)

	// Clean old entries.
	filtered := rl.attempts[ip][:0]
	for _, t := range rl.attempts[ip] {
		if t.After(window) {
			filtered = append(filtered, t)
		}
	}
	rl.attempts[ip] = filtered

	if len(filtered) >= 10 {
		return false
	}

	rl.attempts[ip] = append(rl.attempts[ip], now)
	return true
}

// jsonContentType is an HTTP middleware that sets the default Content-Type to JSON.
func jsonContentType(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		next.ServeHTTP(w, r)
	})
}

// statusRecorder wraps http.ResponseWriter to capture the status code.
type statusRecorder struct {
	http.ResponseWriter
	status int
}

func (r *statusRecorder) WriteHeader(code int) {
	r.status = code
	r.ResponseWriter.WriteHeader(code)
}

// Flush delegates to the underlying ResponseWriter if it supports http.Flusher (needed for SSE).
func (r *statusRecorder) Flush() {
	if f, ok := r.ResponseWriter.(http.Flusher); ok {
		f.Flush()
	}
}