templates: add switch/case functions

This allows much shorter templates.

Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Tim Culverhouse <tim@timculverhouse.com>

3 files changed, 45 insertions, 0 deletions

diff --git a/doc/aerc-templates.7.scd b/doc/aerc-templates.7.scd
index 401c04e7..7f3d6410 100644
--- a/doc/aerc-templates.7.scd
+++ b/doc/aerc-templates.7.scd
@@ -392,6 +392,15 @@ aerc provides the following additional functions:
 	{{if match .Subject `^(\[[\w-]+\]\s*)?\[(RFC )?PATCH`}}{{.Style .Subject "cyan"}}{{else}}{{.Subject}}{{end}}
 	```
 
+*switch*
+	Do swich/case/default control flows. The switch value is compared with
+	regular expressions. If none of the case/default arms match, an empty
+	string is returned.
+
+	```
+	{{switch .Folder (case `^INBOX$` "📥") (case `^Archive/.*` "🗃") (default "📁")}}
+	```
+
 *Function chaining*
 	All of the template functions can be chained together if needed.
 
diff --git a/lib/templates/functions.go b/lib/templates/functions.go
index 8bd8f37b..b331dc85 100644
--- a/lib/templates/functions.go
+++ b/lib/templates/functions.go
@@ -12,6 +12,7 @@ import (
 
 	"git.sr.ht/~rjarry/aerc/lib/format"
 	"git.sr.ht/~rjarry/aerc/lib/parse"
+	"git.sr.ht/~rjarry/aerc/models"
 	"github.com/emersion/go-message/mail"
 )
 
@@ -251,6 +252,33 @@ func compactDir(path string) string {
 	return format.CompactPath(path, os.PathSeparator)
 }
 
+type (
+	Case    struct{ expr, value string }
+	Default struct{ value string }
+)
+
+func (c *Case) Matches(s string) bool    { return parse.MatchCache(s, c.expr) }
+func (c *Case) Value() string            { return c.value }
+func (d *Default) Matches(s string) bool { return true }
+func (d *Default) Value() string         { return d.value }
+
+func switch_(value string, cases ...models.Case) string {
+	for _, c := range cases {
+		if c.Matches(value) {
+			return c.Value()
+		}
+	}
+	return ""
+}
+
+func case_(expr, value string) models.Case {
+	return &Case{expr: expr, value: value}
+}
+
+func default_(value string) models.Case {
+	return &Default{value: value}
+}
+
 var templateFuncs = template.FuncMap{
 	"quote":         quote,
 	"wrapText":      wrapText,
@@ -273,4 +301,7 @@ var templateFuncs = template.FuncMap{
 	"trimSignature": trimSignature,
 	"compactDir":    compactDir,
 	"match":         parse.MatchCache,
+	"switch":        switch_,
+	"case":          case_,
+	"default":       default_,
 }
diff --git a/models/templates.go b/models/templates.go
index 54537a31..dc984fc4 100644
--- a/models/templates.go
+++ b/models/templates.go
@@ -44,3 +44,8 @@ type TemplateData interface {
 	PendingKeys() string
 	Style(string, string) string
 }
+
+type Case interface {
+	Matches(string) bool
+	Value() string
+}