package httpx

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"net/http"
	"strings"
)

type reqIDKey struct{}

func RequestID() func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			rid := incomingRID(r)
			if rid == "" {
				rid = genRID()
			}
			w.Header().Set("X-Request-ID", rid)
			ctx := context.WithValue(r.Context(), reqIDKey{}, rid)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

func RequestIDFromContext(r *http.Request) string {
	v := r.Context().Value(reqIDKey{})
	if s, ok := v.(string); ok {
		return s
	}
	return ""
}

func incomingRID(r *http.Request) string {
	h := r.Header.Get("X-Request-ID")
	if h == "" {
		h = r.Header.Get("X-Request-Id")
	}
	return strings.TrimSpace(h)
}

func genRID() string {
	var b [16]byte
	_, _ = rand.Read(b[:])
	return hex.EncodeToString(b[:])
}