// Package handler holds HTTP handlers. Handlers parse the request, call into
// service, and translate the result (or error) into an HTTP response.
package handler

import (
	"encoding/json"
	"net/http"

	"github.com/dbiz/cdp/data-layer/api/internal/apperr"
)

type errorResponse struct {
	Error string `json:"error"`
	Field string `json:"field,omitempty"`
}

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

func writeError(w http.ResponseWriter, err error) {
	if ae, ok := apperr.As(err); ok {
		if ae.RetryAfter > 0 {
			w.Header().Set("Retry-After", itoa(ae.RetryAfter))
		}
		writeJSON(w, ae.Code, errorResponse{Error: ae.Message, Field: ae.Field})
		return
	}
	writeJSON(w, http.StatusInternalServerError, errorResponse{Error: "internal server error"})
}

func itoa(i int) string {
	const digits = "0123456789"
	if i == 0 {
		return "0"
	}
	var buf [20]byte
	pos := len(buf)
	for i > 0 {
		pos--
		buf[pos] = digits[i%10]
		i /= 10
	}
	return string(buf[pos:])
}