// mainHandler responds to an HTTP request.
func mainHandler(w http.ResponseWriter, req *http.Request) {
log.SetPrefix(fmt.Sprintf("[%s %s] ", req.Method, req.URL))
if req.Method != "GET" {
fail(w, "invalid request method")
return
}
ifModSince := req.Header.Get("If-Modified-Since")
cacheTime, err := time.Parse(http.TimeFormat, ifModSince)
if err == nil && modifiedTime.Unix() <= cacheTime.Unix() {
w.WriteHeader(http.StatusNotModified)
return
}
w.Header().Set("Last-Modified", modifiedTime.Format(http.TimeFormat))
params := parseParams(req.URL)
log.Printf("Rendering %+v\n", params)
svg, err := renderSVG(params)
if err != nil {
fail(w, err.Error())
return
}
if params.onlySVG {
w.Header().Set("Content-Type", "image/svg+xml")
io.WriteString(w, svg)
} else {
depth, _ := strconv.Atoi(params.depth)
max := system.Named(params.name).MaxDepth()
query := "?" + req.URL.RawQuery
if query == "?" {
query = ""
}
page := pageData{
Name: params.name,
Thickness: params.thickness,
Color: params.color,
Query: query,
Depth: depth,
MaxDepth: max,
StepFactor: system.StepFactor,
PadFactor: system.PadFactor,
SVG: template.HTML(svg),
Systems: systemNames,
}
display(w, "index", page)
}
}
// renderSVG generates the SVG data for the specified curve.
func renderSVG(params parameters) (string, error) {
sys := system.Named(params.name)
if sys == nil {
return "", fmt.Errorf("no system named %q", params.name)
}
depth, err := strconv.Atoi(params.depth)
if err != nil {
return "", err
}
if depth < minimumDepth || depth > sys.MaxDepth() {
return "", fmt.Errorf("invalid depth %d", depth)
}
thickness, err := strconv.ParseFloat(params.thickness, 64)
if err != nil {
return "", err
}
if thickness <= 0 {
return "", fmt.Errorf("invalid thickness %f", thickness)
}
if params.color == "" {
return "", fmt.Errorf("invalid color \"\"")
}
precision, err := strconv.Atoi(params.precision)
if err != nil {
return "", err
}
if precision < minimumPrecision || precision > maximumPrecision {
return "", fmt.Errorf("invalid precision %d", precision)
}
opts := system.Options{
Depth: depth,
Thickness: thickness,
Color: params.color,
Precision: precision,
}
return sys.SVG(&opts), nil
}