app: parse SRS from request

maps/request.go

@@ -63,20 +63,25 @@ func ParseMapRequest(r *http.Request) (*Request, error) {
	}

	req := &Request{
		HTTP:     r,
		Query:    query,
		EPSGCode: 3857,
		HTTP:  r,
		Query: query,
	}

	req.Width, req.Height, err = parseSize(req.Query)
	if err != nil {
		return nil, err
	}

	req.BBOX, err = parseBBOX(req.Query)
	if err != nil {
		return nil, err
	}

	req.EPSGCode, err = parseEPSGCode(req.Query)
	if err != nil {
		return nil, err
	}

	req.Format, err = parseFormat(req.Query)
	if err != nil {
		return nil, err
@@ -148,6 +153,37 @@ func parseBBOX(q url.Values) (BBOX, error) {
	return bbox, nil
}

func parseEPSGCode(q url.Values) (int, error) {
	srsStr := q.Get("SRS")
	if srsStr == "" {
		return 0, &MissingParamError{"SRS"}
	}

	if srsStr == "CRS:84" {
		return 4326, nil
	}

	srsParts := strings.Split(srsStr, ":")
	if len(srsParts) != 2 {
		return 0, &InvalidParamError{Param: "SRS", Value: srsStr}
	}

	if !strings.HasPrefix(strings.ToUpper(srsStr), "EPSG") {
		return 0, &InvalidParamError{Param: "SRS", Value: srsStr}
	}

	epsgCode, err := strconv.ParseUint(srsParts[1], 10, 32)
	if err != nil {
		return 0, &InvalidParamError{Param: "SRS", Value: srsStr}
	}

	if epsgCode == 900913 {
		epsgCode = 3857
	}

	return int(epsgCode), nil
}

func parseFormat(q url.Values) (string, error) {
	format := q.Get("FORMAT")
	if format == "" {