templates: add basic string functions

Some clients are sending a text/plain part that contains nothing but the text/html part. This is rather suboptimal when replying. To be able to filter these, it is important to be able to detect things like <!doctype html>. Add basic string operations to the template functions. Signed-off-by: Moritz Poldrack <[email protected]> Tested-by: Koni Marti <[email protected]> Acked-by: Robin Jarry <[email protected]>
rjarry · Jan 19, 2024 · 2d9d7e0 · 2d9d7e0
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diff --git a/doc/aerc-templates.7.scd b/doc/aerc-templates.7.scd
@@ -440,6 +440,41 @@ aerc provides the following additional functions:
 	{{compactDir .Folder}}
 	```
 
+*contains*
+	Checks if a string contains a substring.
+
+	```
+	{{contains "<!DOCTYPE html>" .OriginalText}}
+	```
+
+*hasPrefix*
+	Checks if a string has a prefix.
+
+	```
+	{{hasPrefix "Business" .Folder}}
+	```
+
+*toLower*
+	Convert a string to lowercase.
+
+	```
+	{{toLower "SPECIAL OFFER!"}}
+	```
+
+*toUpper*
+	Convert a string to uppercase.
+
+	```
+	{{toUpper "important"}}
+	```
+
+*replace*
+	Perform a regular expression substitution on the passed string.
+
+	```
+	{{replace `(.+) - .+ at .+\..+` `$1` ((index .OriginalFrom 0).Name)}}
+	```
+
 *.Style*
 	Apply a user-defined style (see *aerc-stylesets*(7)) to a string.
 

diff --git a/lib/templates/functions.go b/lib/templates/functions.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"regexp"
 	"strings"
 	"text/template"
 	"time"
@@ -241,11 +242,7 @@ func join(sep string, elems []string) string {
 }
 
 func split(sep string, s string) []string {
-	sp := strings.Split(s, sep)
-	for i := range sp {
-		sp[i] = strings.TrimSpace(sp[i])
-	}
-	return sp
+	return strings.Split(s, sep)
 }
 
 // removes a signature from the piped in message
@@ -324,6 +321,19 @@ top:
 	return mapped
 }
 
+func replace(pattern, subst, value string) string {
+	re := regexp.MustCompile(pattern)
+	return re.ReplaceAllString(value, subst)
+}
+
+func contains(substring, s string) bool {
+	return strings.Contains(s, substring)
+}
+
+func hasPrefix(prefix, s string) bool {
+	return strings.HasPrefix(s, prefix)
+}
+
 var templateFuncs = template.FuncMap{
 	"quote":         quote,
 	"wrapText":      wrapText,
@@ -352,4 +362,9 @@ var templateFuncs = template.FuncMap{
 	"default":       default_,
 	"map":           map_,
 	"exclude":       exclude,
+	"contains":      contains,
+	"hasPrefix":     hasPrefix,
+	"toLower":       strings.ToLower,
+	"toUpper":       strings.ToUpper,
+	"replace":       replace,
 }