package middleware

import (
	"net/http"
	"time"

	"github.com/go-chi/httprate"
)

const (
	// loginRateLimit is the maximum number of login attempts
	// per interval.
	loginRateLimit = 5

	// loginRateInterval is the time window for the rate limit.
	loginRateInterval = 1 * time.Minute

	// passwordChangeRateLimit is the maximum number of password
	// change attempts per interval. Each attempt verifies the
	// current password, so the endpoint must be rate-limited
	// like any other password-based authentication endpoint.
	passwordChangeRateLimit = 5

	// passwordChangeRateInterval is the time window for the
	// password change rate limit.
	passwordChangeRateInterval = 1 * time.Minute
)

// LoginRateLimit returns middleware that enforces per-IP rate
// limiting on login attempts using go-chi/httprate. Only POST
// requests are rate-limited; GET requests (rendering the login
// form) pass through unaffected. When the rate limit is exceeded,
// a 429 Too Many Requests response is returned. IP extraction
// honours X-Forwarded-For, X-Real-IP, and True-Client-IP headers
// for reverse-proxy setups.
func (m *Middleware) LoginRateLimit() func(http.Handler) http.Handler {
	return m.postRateLimit(
		loginRateLimit,
		loginRateInterval,
		"login rate limit exceeded",
		"Too many login attempts. Please try again later.",
	)
}

// PasswordChangeRateLimit returns middleware that enforces
// per-IP rate limiting on password change attempts. The change
// endpoint verifies the current password, so without a limit a
// stolen session could be used to brute-force it; the limit
// matches the login endpoint's.
func (m *Middleware) PasswordChangeRateLimit() func(http.Handler) http.Handler {
	return m.postRateLimit(
		passwordChangeRateLimit,
		passwordChangeRateInterval,
		"password change rate limit exceeded",
		"Too many password change attempts. "+
			"Please try again later.",
	)
}

// postRateLimit builds middleware that enforces a per-IP rate
// limit on POST requests only; all other methods pass through
// unaffected. Requests over the limit receive a 429 with the
// given response message, and each rejection is logged with the
// given log message. IP extraction honours X-Forwarded-For,
// X-Real-IP, and True-Client-IP headers for reverse-proxy
// setups.
func (m *Middleware) postRateLimit(
	limit int,
	interval time.Duration,
	logMessage, responseMessage string,
) func(http.Handler) http.Handler {
	limiter := httprate.Limit(
		limit,
		interval,
		httprate.WithKeyFuncs(httprate.KeyByRealIP),
		httprate.WithLimitHandler(http.HandlerFunc(
			func(w http.ResponseWriter, r *http.Request) {
				m.log.Warn(logMessage,
					"path", r.URL.Path,
				)
				http.Error(
					w,
					responseMessage,
					http.StatusTooManyRequests,
				)
			},
		)),
	)

	return func(next http.Handler) http.Handler {
		limited := limiter(next)

		return http.HandlerFunc(func(
			w http.ResponseWriter,
			r *http.Request,
		) {
			// Only rate-limit POST requests.
			if r.Method != http.MethodPost {
				next.ServeHTTP(w, r)

				return
			}

			limited.ServeHTTP(w, r)
		})
	}
}