parse http requests to image requests

proxy/proxy.go

@@ -0,0 +1,81 @@
+// Package proxy provides the image proxy.
+package proxy
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+// URLError reports a malformed URL error.
+type URLError struct {
+	Message string
+	URL     *url.URL
+}
+
+func (e URLError) Error() string {
+	return fmt.Sprintf("malformed URL %q: %s", e.URL, e.Message)
+}
+
+// Request is a request for an image.
+type Request struct {
+	URL    *url.URL // URL of the image to proxy
+	Width  int      // requested width, in pixels
+	Height int      // requested height, in pixels
+}
+
+// NewRequest parses an http.Request into an image request.
+func NewRequest(r *http.Request) (*Request, error) {
+	path := strings.SplitN(r.URL.Path, "/", 3)
+	if len(path) != 3 {
+		return nil, URLError{"too few path segments", r.URL}
+	}
+
+	var err error
+	req := new(Request)
+
+	req.URL, err = url.Parse(path[2])
+	if err != nil {
+		return nil, URLError{
+			fmt.Sprintf("unable to parse remote URL: %v", err),
+			r.URL,
+		}
+	}
+
+	if !req.URL.IsAbs() {
+		return nil, URLError{"must provide absolute remote URL", r.URL}
+	}
+
+	if req.URL.Scheme != "http" && req.URL.Scheme != "https" {
+		return nil, URLError{"remote URL must have http or https URL", r.URL}
+	}
+
+	// query string is always part of the remote URL
+	req.URL.RawQuery = r.URL.RawQuery
+
+	var h, w string
+	size := strings.SplitN(path[1], "x", 2)
+	w = size[0]
+	if len(size) > 1 {
+		h = size[1]
+	} else {
+		h = w
+	}
+
+	if w != "" {
+		req.Width, err = strconv.Atoi(w)
+		if err != nil {
+			return nil, URLError{"width must be an int", r.URL}
+		}
+	}
+	if h != "" {
+		req.Height, err = strconv.Atoi(h)
+		if err != nil {
+			return nil, URLError{"height must be an int", r.URL}
+		}
+	}
+
+	return req, nil
+}