package handler

import (
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"

	"github.com/google/uuid"

	"learning-service/internal/repository"
)

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, map[string]any{"error": msg})
}

// writeRepoError — маппит repository.Err* на HTTP-коды. Для остальных
// логируем и отдаём 500 без деталей (наружу не светим внутренние ошибки).
func writeRepoError(w http.ResponseWriter, r *http.Request, err error, action string) {
	switch {
	case errors.Is(err, repository.ErrNotFound):
		writeError(w, http.StatusNotFound, "not found")
	case errors.Is(err, repository.ErrForbidden):
		writeError(w, http.StatusForbidden, "forbidden")
	default:
		slog.Error("repo error", "action", action, "error", err, "path", r.URL.Path)
		writeError(w, http.StatusInternalServerError, "internal error")
	}
}

func decodeJSON(r *http.Request, v any) error {
	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()
	return dec.Decode(v)
}

func parseUUID(s string) (uuid.UUID, error) {
	if s == "" {
		return uuid.Nil, errors.New("empty uuid")
	}
	return uuid.Parse(s)
}

// userIDFromHeader — portal-gateway проставляет X-User-Id после валидации JWT.
// Все НЕ-internal handler'ы читают отсюда; пустой = unauthorized.
func userIDFromHeader(r *http.Request) (uuid.UUID, bool) {
	v := r.Header.Get("X-User-Id")
	if v == "" {
		return uuid.Nil, false
	}
	id, err := uuid.Parse(v)
	if err != nil {
		return uuid.Nil, false
	}
	return id, true
}