package middleware

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

// statusRecorder wraps http.ResponseWriter to capture the response status
// code so the Logger middleware can include it in the structured log line.
//
// The default status is initialised to http.StatusOK because net/http
// implicitly emits a 200 when a handler writes a body without calling
// WriteHeader explicitly; mirroring that behaviour keeps logs accurate.
type statusRecorder struct {
	http.ResponseWriter
	status int
}

// WriteHeader records the status code before delegating to the wrapped
// ResponseWriter so the original response semantics are preserved.
func (s *statusRecorder) WriteHeader(code int) {
	s.status = code
	s.ResponseWriter.WriteHeader(code)
}

// Logger returns HTTP middleware that emits a single structured log line
// per request once the downstream handler has finished. The line includes
// method, path, response status, elapsed duration in milliseconds, and the
// request ID (if RequestID middleware is mounted upstream).
//
// The middleware is intentionally placed *inside* RequestID so the
// generated identifier is available via context; placing it outside would
// log an empty request_id.
func Logger(log *slog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			start := time.Now()
			rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
			next.ServeHTTP(rec, r)
			ctx := r.Context()
			log.LogAttrs(ctx, slog.LevelInfo, "http",
				slog.String("method", r.Method),
				slog.String("path", r.URL.Path),
				slog.Int("status", rec.status),
				slog.Int64("duration_ms", time.Since(start).Milliseconds()),
				slog.String("request_id", RequestIDFromContext(ctx)),
			)
		})
	}
}