Add custom sorting to the twitch channels widget

this allows the channels to be sorted as defined in the config while
still keeping the live channels on the top. the wording could probably
be improved, "custom" is too broad but i'm not sure what else to call
it.

docs/configuration.md

@@ -1063,6 +1063,7 @@ Preview:
 | ---- | ---- | -------- | ------- |
 | channels | array | yes | |
 | collapse-after | integer | no | 5 |
+| sort-by | string | no | viewers |
 
 ##### `channels`
 A list of channels to display.
@@ -1070,6 +1071,9 @@ A list of channels to display.
 ##### `collapse-after`
 How many channels are visible before the "SHOW MORE" button appears. Set to `-1` to never collapse.
 
+##### `sort-by`
+Can be used to specify the order in which the channels are displayed. Possible values are `viewers` and `custom`.
+
 ### Twitch top games
 Display a list of games with the most viewers on Twitch.
 

internal/feed/twitch.go

@@ -44,6 +44,12 @@ func (channels TwitchChannels) SortByViewers() {
 	})
 }
 
+func (channels TwitchChannels) SortByLive() {
+	sort.SliceStable(channels, func(i, j int) bool {
+		return channels[i].IsLive && !channels[j].IsLive
+	})
+}
+
 type twitchOperationResponse struct {
 	Data       json.RawMessage
 	Extensions struct {

internal/widget/twitch-channels.go

@@ -14,6 +14,7 @@ type TwitchChannels struct {
 	ChannelsRequest []string             `yaml:"channels"`
 	Channels        []feed.TwitchChannel `yaml:"-"`
 	CollapseAfter   int                  `yaml:"collapse-after"`
+	SortBy          string               `yaml:"sort-by"`
 }
 
 func (widget *TwitchChannels) Initialize() error {
@@ -23,6 +24,10 @@ func (widget *TwitchChannels) Initialize() error {
 		widget.CollapseAfter = 5
 	}
 
+	if widget.SortBy != "viewers" && widget.SortBy != "custom" {
+		widget.SortBy = "viewers"
+	}
+
 	return nil
 }
 
@@ -33,7 +38,12 @@ func (widget *TwitchChannels) Update(ctx context.Context) {
 		return
 	}
 
-	channels.SortByViewers()
+	if widget.SortBy == "viewers" {
+		channels.SortByViewers()
+	} else if widget.SortBy == "custom" {
+		channels.SortByLive()
+	}
+
 	widget.Channels = channels
 }