Add area function

area.go

@@ -0,0 +1,44 @@
+package radiko
+
+import (
+	"net/http"
+
+	"golang.org/x/net/html"
+)
+
+const (
+	areaURL = "http://radiko.jp/area"
+)
+
+// AreaID returns areaID.
+func AreaID() (string, error) {
+	resp, err := http.Get(areaURL)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	doc, err := html.Parse(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	return processSpanNode(doc), nil
+}
+
+func processSpanNode(n *html.Node) string {
+	var areaID string
+
+	var f func(*html.Node)
+	f = func(n *html.Node) {
+		if n.Type == html.ElementNode && n.Data == "span" && len(n.Attr) > 0 {
+			areaID = n.Attr[0].Val
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			f(c)
+		}
+	}
+	f(n)
+
+	return areaID
+}

area_test.go

@@ -0,0 +1,32 @@
+package radiko
+
+import (
+	"strings"
+	"testing"
+
+	"golang.org/x/net/html"
+)
+
+func TestAreaID(t *testing.T) {
+	areaID, err := AreaID()
+	if err != nil {
+		t.Errorf("Failed to download player.swf: %s", err)
+	}
+	if areaID == "" {
+		t.Errorf("Invalid area id: %s", areaID)
+	}
+}
+
+func TestProcessSpanNode(t *testing.T) {
+	s := `document.write('<span class="JP13">TOKYO JAPAN</span>');`
+	doc, err := html.Parse(strings.NewReader(s))
+	if err != nil {
+		t.Errorf("Parse HTML: %s", err)
+	}
+
+	areaID := processSpanNode(doc)
+	if areaID != "JP13" {
+		t.Errorf("Failed to process span node.\nAreaID: %s",
+			areaID)
+	}
+}

client.go

@@ -55,7 +55,7 @@ func New() (*Client, error) {
 	}
 
 	if httpClient == nil {
-		return nil, errors.New("HTTP Client is nil")
+		return nil, errors.New("A HTTP client is nil.")
 	}
 
 	return &Client{