Add url.go for handling irc file urls

url.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type IRCFileURL struct {
+	Network  string
+	Channel  string
+	UserName string
+	Slot     int
+}
+
+const ircFileURLFields = 4
+
+func parseSlot(slotStr string) (int, error) {
+	if !strings.HasPrefix(slotStr, "#") {
+		return -1, errors.New("invalid slot")
+	}
+	return strconv.Atoi(strings.TrimPrefix(slotStr, "#"))
+}
+
+// url has the following format: irc://network/channel/bot/#slot
+func parseIRCFileURl(url string) (*IRCFileURL, error) {
+	if !strings.HasPrefix(url, "irc://") {
+		return nil, errors.New("not an IRC url")
+	}
+
+	fields := strings.Split(strings.TrimPrefix(url, "irc://"), "/")
+	if len(fields) != ircFileURLFields {
+		return nil, errors.New("invalid IRC url")
+	}
+
+	slot, err := parseSlot(fields[3])
+	if err != nil {
+		return nil, err
+	}
+
+	return &IRCFileURL{
+		Network:  fields[0],
+		Channel:  fields[1],
+		UserName: fields[2],
+		Slot:     slot,
+	}, nil
+}
+
+func (url *IRCFileURL) String() string {
+	return fmt.Sprintf("irc://%s/%s/%s/#%d", url.Network, url.Channel, url.UserName, url.Slot)
+}