package httpapi

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"log/slog"
	"net/http"
	"runtime/debug"
	"strings"
	"time"
)

type contextKey string

const traceIDKey contextKey = "trace_id"

func TraceID(ctx context.Context) string {
	value, _ := ctx.Value(traceIDKey).(string)
	return value
}

func RequestContext(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		traceID := strings.TrimSpace(r.Header.Get("X-Request-ID"))
		if !validRequestID(traceID) {
			traceID = randomID()
		}
		ctx := context.WithValue(r.Context(), traceIDKey, traceID)
		w.Header().Set("X-Request-ID", traceID)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func validRequestID(value string) bool {
	if len(value) < 8 || len(value) > 128 {
		return false
	}
	for _, character := range value {
		if (character >= 'a' && character <= 'z') || (character >= 'A' && character <= 'Z') || (character >= '0' && character <= '9') || character == '-' || character == '_' || character == '.' {
			continue
		}
		return false
	}
	return true
}

func Recover(logger *slog.Logger, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if recovered := recover(); recovered != nil {
				logger.Error("request panic", "trace_id", TraceID(r.Context()), "panic", recovered, "stack", string(debug.Stack()))
				writeError(w, r, http.StatusInternalServerError, "INTERNAL_ERROR", "Beklenmeyen bir sunucu hatası oluştu.")
			}
		}()
		next.ServeHTTP(w, r)
	})
}

func AccessLog(logger *slog.Logger, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		started := time.Now()
		wrapped := &statusWriter{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(wrapped, r)
		logger.Info("http request", "method", r.Method, "path", r.URL.Path, "status", wrapped.status, "duration_ms", time.Since(started).Milliseconds(), "trace_id", TraceID(r.Context()))
	})
}

type statusWriter struct {
	http.ResponseWriter
	status int
}

func (w *statusWriter) WriteHeader(status int) {
	w.status = status
	w.ResponseWriter.WriteHeader(status)
}

func randomID() string {
	var bytes [16]byte
	if _, err := rand.Read(bytes[:]); err != nil {
		return "trace-unavailable"
	}
	return hex.EncodeToString(bytes[:])
}