// Package middleware provides HTTP middleware.
package middleware

import (
	"log/slog"
	"net"
	"net/http"
	"sync"
	"time"

	"github.com/99designs/basicauth-go"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/cors"
	"github.com/gorilla/csrf"
	"go.uber.org/fx"
	"golang.org/x/time/rate"

	"git.eeqj.de/sneak/upaas/internal/config"
	"git.eeqj.de/sneak/upaas/internal/globals"
	"git.eeqj.de/sneak/upaas/internal/logger"
	"git.eeqj.de/sneak/upaas/internal/service/auth"
)

// corsMaxAge is the maximum age for CORS preflight responses in seconds.
const corsMaxAge = 300

// Params contains dependencies for Middleware.
type Params struct {
	fx.In

	Logger  *logger.Logger
	Globals *globals.Globals
	Config  *config.Config
	Auth    *auth.Service
}

// Middleware provides HTTP middleware.
type Middleware struct {
	log    *slog.Logger
	params *Params
}

// New creates a new Middleware instance.
func New(_ fx.Lifecycle, params Params) (*Middleware, error) {
	return &Middleware{
		log:    params.Logger.Get(),
		params: &params,
	}, nil
}

// loggingResponseWriter wraps http.ResponseWriter to capture status code.
type loggingResponseWriter struct {
	http.ResponseWriter

	statusCode int
}

func newLoggingResponseWriter(
	writer http.ResponseWriter,
) *loggingResponseWriter {
	return &loggingResponseWriter{writer, http.StatusOK}
}

func (lrw *loggingResponseWriter) WriteHeader(code int) {
	lrw.statusCode = code
	lrw.ResponseWriter.WriteHeader(code)
}

// Logging returns a request logging middleware.
func (m *Middleware) Logging() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(
			writer http.ResponseWriter,
			request *http.Request,
		) {
			start := time.Now()
			lrw := newLoggingResponseWriter(writer)
			ctx := request.Context()

			defer func() {
				latency := time.Since(start)
				reqID := middleware.GetReqID(ctx)
				m.log.InfoContext(ctx, "request",
					"request_start", start,
					"method", request.Method,
					"url", request.URL.String(),
					"useragent", request.UserAgent(),
					"request_id", reqID,
					"referer", request.Referer(),
					"proto", request.Proto,
					"remoteIP", ipFromHostPort(request.RemoteAddr),
					"status", lrw.statusCode,
					"latency_ms", latency.Milliseconds(),
				)
			}()

			next.ServeHTTP(lrw, request)
		})
	}
}

func ipFromHostPort(hostPort string) string {
	host, _, err := net.SplitHostPort(hostPort)
	if err != nil {
		return hostPort
	}

	return host
}

// CORS returns CORS middleware.
func (m *Middleware) CORS() func(http.Handler) http.Handler {
	return cors.Handler(cors.Options{
		AllowedOrigins:   []string{"*"},
		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
		AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-CSRF-Token"},
		ExposedHeaders:   []string{"Link"},
		AllowCredentials: false,
		MaxAge:           corsMaxAge,
	})
}

// MetricsAuth returns basic auth middleware for metrics endpoint.
func (m *Middleware) MetricsAuth() func(http.Handler) http.Handler {
	if m.params.Config.MetricsUsername == "" {
		return func(next http.Handler) http.Handler {
			return next
		}
	}

	return basicauth.New(
		"metrics",
		map[string][]string{
			m.params.Config.MetricsUsername: {m.params.Config.MetricsPassword},
		},
	)
}

// SessionAuth returns middleware that requires authentication.
func (m *Middleware) SessionAuth() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(
			writer http.ResponseWriter,
			request *http.Request,
		) {
			user, err := m.params.Auth.GetCurrentUser(request.Context(), request)
			if err != nil || user == nil {
				http.Redirect(writer, request, "/login", http.StatusSeeOther)

				return
			}

			next.ServeHTTP(writer, request)
		})
	}
}

// CSRF returns CSRF protection middleware using gorilla/csrf.
func (m *Middleware) CSRF() func(http.Handler) http.Handler {
	return csrf.Protect(
		[]byte(m.params.Config.SessionSecret),
		csrf.Secure(false), // Allow HTTP for development; reverse proxy handles TLS
		csrf.Path("/"),
	)
}

// loginRateLimit configures the login rate limiter.
const (
	loginRateLimit = rate.Limit(5.0 / 60.0) // 5 requests per 60 seconds
	loginBurst     = 5                       // allow burst of 5
)

// ipLimiter tracks per-IP rate limiters for login attempts.
type ipLimiter struct {
	mu       sync.Mutex
	limiters map[string]*rate.Limiter
}

func newIPLimiter() *ipLimiter {
	return &ipLimiter{
		limiters: make(map[string]*rate.Limiter),
	}
}

func (i *ipLimiter) getLimiter(ip string) *rate.Limiter {
	i.mu.Lock()
	defer i.mu.Unlock()

	limiter, exists := i.limiters[ip]
	if !exists {
		limiter = rate.NewLimiter(loginRateLimit, loginBurst)
		i.limiters[ip] = limiter
	}

	return limiter
}

// loginLimiter is the singleton IP rate limiter for login attempts.
//
//nolint:gochecknoglobals // intentional singleton for rate limiting state
var loginLimiter = newIPLimiter()

// LoginRateLimit returns middleware that rate-limits login attempts per IP.
// It allows 5 attempts per minute and returns 429 Too Many Requests when exceeded.
func (m *Middleware) LoginRateLimit() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(
			writer http.ResponseWriter,
			request *http.Request,
		) {
			ip := ipFromHostPort(request.RemoteAddr)
			limiter := loginLimiter.getLimiter(ip)

			if !limiter.Allow() {
				m.log.WarnContext(request.Context(), "login rate limit exceeded",
					"remoteIP", ip,
				)
				http.Error(
					writer,
					"Too Many Requests",
					http.StatusTooManyRequests,
				)

				return
			}

			next.ServeHTTP(writer, request)
		})
	}
}

// SetupRequired returns middleware that redirects to setup if no user exists.
func (m *Middleware) SetupRequired() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(
			writer http.ResponseWriter,
			request *http.Request,
		) {
			setupRequired, err := m.params.Auth.IsSetupRequired(request.Context())
			if err != nil {
				m.log.Error("failed to check setup status", "error", err)
				http.Error(
					writer,
					"Internal Server Error",
					http.StatusInternalServerError,
				)

				return
			}

			if setupRequired {
				// Allow access to setup page
				if request.URL.Path == "/setup" {
					next.ServeHTTP(writer, request)

					return
				}

				http.Redirect(writer, request, "/setup", http.StatusSeeOther)

				return
			}

			// Block setup page if already set up
			if request.URL.Path == "/setup" {
				http.Redirect(writer, request, "/", http.StatusSeeOther)

				return
			}

			next.ServeHTTP(writer, request)
		})
	}
}