[templating] Add followAge function

Signed-off-by: Knut Ahlers <knut@ahlers.me>

functions_twitch.go

@@ -4,6 +4,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/pkg/errors"
+
 	"github.com/Luzifer/twitch-bot/v3/plugins"
 )
 
@@ -17,6 +19,10 @@ func init() {
 		return displayName, err
 	}))
 
+	tplFuncs.Register("followAge", plugins.GenericTemplateFunctionGetter(func(from, to string) (time.Duration, error) {
+		since, err := twitchClient.GetFollowDate(from, to)
+		return time.Since(since), errors.Wrap(err, "getting follow date")
+	}))
 	tplFuncs.Register("followDate", plugins.GenericTemplateFunctionGetter(func(from, to string) (time.Time, error) { return twitchClient.GetFollowDate(from, to) }))
 
 	tplFuncs.Register("recentGame", plugins.GenericTemplateFunctionGetter(func(username string, v ...string) (string, error) {

wiki/Templating.md

@@ -134,6 +134,19 @@ Example:
 < 5 hours, 33 minutes, 12 seconds - 5 hours, 33 minutes
 ```
 
+#### `followAge`
+
+Looks up when `from` followed `to` and returns the duration between then and now
+
+Syntax: `followAge <from> <to>`
+
+Example:
+
+```
+# {{ followAge "tezrian" "luziferus" }}
+< 15004h14m59.116620989s
+```
+
 #### `followDate`
 
 Looks up when `from` followed `to`