package server

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

	"ddc/internal/diskspace"
	"ddc/internal/files"
	"ddc/internal/jobs"
	"ddc/internal/preferences"
)

type errorResponse struct {
	Error     string `json:"error"`
	RequestID string `json:"requestId,omitempty"`
}

func writeJSON(writer http.ResponseWriter, status int, payload any) {
	writer.Header().Set("Content-Type", "application/json; charset=utf-8")
	writer.WriteHeader(status)
	if err := json.NewEncoder(writer).Encode(payload); err != nil {
		slog.Debug("could not write response", "error", err)
	}
}

func writeError(writer http.ResponseWriter, status int, message string) {
	writeJSON(writer, status, errorResponse{Error: message, RequestID: writer.Header().Get("X-Request-ID")})
}

func writeFailure(writer http.ResponseWriter, request *http.Request, err error) {
	status := statusFor(err)
	if status != http.StatusInternalServerError {
		writeError(writer, status, err.Error())
		return
	}

	requestID := requestIDFrom(request)
	slog.Error("request failed",
		"request_id", requestID,
		"method", request.Method,
		"path", request.URL.Path,
		"error", err,
	)
	writeError(writer, status, internalErrorMessage(requestID))
}

func decodeBody(writer http.ResponseWriter, request *http.Request, target any) bool {
	decoder := json.NewDecoder(request.Body)
	decoder.DisallowUnknownFields()
	err := decoder.Decode(target)
	if err == nil {
		return true
	}

	var tooLarge *http.MaxBytesError
	if errors.As(err, &tooLarge) {
		writeError(writer, http.StatusRequestEntityTooLarge, "request body is too large")
		return false
	}
	writeError(writer, http.StatusBadRequest, "invalid request body: "+err.Error())
	return false
}

func statusFor(err error) int {
	switch {
	case errors.Is(err, jobs.ErrJobNotFound):
		return http.StatusNotFound
	case errors.Is(err, jobs.ErrJobBusy), errors.Is(err, files.ErrDestinationExists):
		return http.StatusConflict
	case errors.Is(err, jobs.ErrInvalidRequest), errors.Is(err, preferences.ErrInvalid):
		return http.StatusBadRequest
	case errors.Is(err, diskspace.ErrInsufficientSpace):
		return http.StatusInsufficientStorage
	default:
		return http.StatusInternalServerError
	}
}