Start adding support to download twitch emotes

The code has been transferred over from the utility, and should work,
but it hasn't been tested nor has it been linked to the command.

common/chatcommands.go

@@ -35,6 +35,7 @@ var (
 	CNReloadEmotes ChatCommandNames = []string{"reloademotes"}
 	CNModpass      ChatCommandNames = []string{"modpass"}
 	CNIP           ChatCommandNames = []string{"iplist"}
+	CNAddEmotes    ChatCommandNames = []string{"addemotes"}
 )
 
 var ChatCommands = []ChatCommandNames{

emotes.go

@@ -0,0 +1,165 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strings"
+)
+
+type twitchChannel struct {
+	ChannelName     string            `json:"channel_name"`
+	DisplayName     string            `json:"display_name"`
+	ChannelId       string            `json:"channel_id"`
+	BroadcasterType string            `json:"broadcaster_type"`
+	Plans           map[string]string `json:"plans"`
+	Emotes          []struct {
+		Code string `json:"code"`
+		Set  string `json:"emoticon_set"`
+		Id   int    `json:"id"`
+	} `json:"emotes"`
+	BaseSetId   string `json:"base_set_id"`
+	GeneratedAt string `json:"generated_at"`
+}
+
+// Used in settings
+type EmoteSet struct {
+	Channel string // channel name
+	Prefix  string // emote prefix
+	Found   bool   `json:"-"`
+}
+
+const subscriberJson string = `subscribers.json`
+
+// Download a single channel's emote set
+func (tc *twitchChannel) downloadEmotes() (*EmoteSet, error) {
+	es := &EmoteSet{Channel: strings.ToLower(tc.ChannelName)}
+	for _, emote := range tc.Emotes {
+		url := fmt.Sprintf(`https://static-cdn.jtvnw.net/emoticons/v1/%d/1.0`, emote.Id)
+		png := `static/emotes/` + emote.Code + `.png`
+
+		if len(es.Prefix) == 0 {
+			// For each letter
+			for i := 0; i < len(emote.Code); i++ {
+				// Find the first capital
+				b := emote.Code[i]
+				if b >= 'A' && b <= 'Z' {
+					es.Prefix = emote.Code[0 : i-1]
+					fmt.Printf("Found prefix for channel %q: %q (%q)\n", es.Channel, es.Prefix, emote)
+					break
+				}
+			}
+		}
+
+		resp, err := http.Get(url)
+		if err != nil {
+			return nil, err
+		}
+
+		f, err := os.Create(png)
+		if err != nil {
+			return nil, err
+		}
+
+		_, err = io.Copy(f, resp.Body)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return es, nil
+}
+
+func GetEmotes(names []string) ([]*EmoteSet, error) {
+	// Do this up-front
+	for i := 0; i < len(names); i++ {
+		names[i] = strings.ToLower(names[i])
+	}
+
+	channels, err := findChannels(names)
+	if err != nil {
+		return nil, fmt.Errorf("Error reading %q: %v", subscriberJson, err)
+	}
+
+	emoteSets := []*EmoteSet{}
+	for _, c := range channels {
+		es, err := c.downloadEmotes()
+		if err != nil {
+			return nil, fmt.Errorf("Error downloading emotes: %v", err)
+		}
+		emoteSets = append(emoteSets, es)
+	}
+
+	for _, es := range emoteSets {
+		found := false
+		for _, name := range names {
+			if es.Channel == name {
+				found = true
+				break
+			}
+		}
+		if !found {
+			es.Found = false
+		}
+	}
+
+	return emoteSets, nil
+}
+
+func findChannels(names []string) ([]twitchChannel, error) {
+	file, err := os.Open(subscriberJson)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	data := []twitchChannel{}
+	dec := json.NewDecoder(file)
+
+	// Open bracket
+	_, err = dec.Token()
+	if err != nil {
+		return nil, err
+	}
+
+	done := false
+	for dec.More() && !done {
+		// opening bracket of channel
+		_, err = dec.Token()
+		if err != nil {
+			return nil, err
+		}
+
+		// Decode the channel stuff
+		var c twitchChannel
+		err = dec.Decode(&c)
+		if err != nil {
+			return nil, err
+		}
+
+		// Is this a channel we are looking for?
+		found := false
+		for _, search := range names {
+			if strings.ToLower(c.ChannelName) == search {
+				found = true
+				break
+			}
+		}
+
+		// Yes it is.  Add it to the data
+		if found {
+			data = append(data, c)
+		}
+
+		// Check for completion.  Don't bother parsing the rest of
+		// the json file if we've already found everything that we're
+		// looking for.
+		if len(data) == len(names) {
+			done = true
+		}
+	}
+
+	return data, nil
+}

settings.go

@@ -28,6 +28,7 @@ type Settings struct {
 	AdminPassword   string
 	StreamKey       string
 	ListenAddress   string
+	ApprovedEmotes  []EmoteSet // list of channels that have been approved for emote use.  Global emotes are always "approved".
 	Bans            []BanInfo
 	LogLevel        common.LogLevel
 	LogFile         string