templates: move signature from compose to templates

Currently, when composing a new message, everything is read from the
template files, except the signature, which is added directly in the
compose code. Add a new template variable {{.Signature}}, by moving the
logic of reading signature from command or file from compose to
templates. Update the various default template files to preserve the
original placement of signatures. Users using the default templates
should not notice the change. Users with custom compose templates will
need to update their templates with {{.Signature}}.

Changelog-changed: Signature placement is now controlled via the
 `{{.Signature}}` template variable and not hardcoded.
Signed-off-by: Bence Ferdinandy <bence@ferdinandy.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 66 insertions, 0 deletions

diff --git a/lib/state/templates.go b/lib/state/templates.go
index 22cdbfa6..ac701e9f 100644
--- a/lib/state/templates.go
+++ b/lib/state/templates.go
@@ -1,12 +1,18 @@
 package state
 
 import (
+	"bufio"
+	"bytes"
 	"fmt"
+	"os"
+	"os/exec"
 	"strings"
 	"time"
 
 	"git.sr.ht/~rjarry/aerc/config"
 	"git.sr.ht/~rjarry/aerc/lib/parse"
+	"git.sr.ht/~rjarry/aerc/lib/xdg"
+	"git.sr.ht/~rjarry/aerc/log"
 	"git.sr.ht/~rjarry/aerc/models"
 	"github.com/danwakefield/fnmatch"
 	sortthread "github.com/emersion/go-imap-sortthread"
@@ -651,3 +657,63 @@ top:
 	}
 	return mapped
 }
+
+func (d *templateData) Signature() string {
+	if d.account == nil {
+		return ""
+	}
+	var signature []byte
+	if d.account.SignatureCmd != "" {
+		var err error
+		signature, err = d.readSignatureFromCmd()
+		if err != nil {
+			signature = d.readSignatureFromFile()
+		}
+	} else {
+		signature = d.readSignatureFromFile()
+	}
+	if len(bytes.TrimSpace(signature)) == 0 {
+		return ""
+	}
+	signature = d.ensureSignatureDelimiter(signature)
+	return string(signature)
+}
+
+func (d *templateData) readSignatureFromCmd() ([]byte, error) {
+	sigCmd := d.account.SignatureCmd
+	cmd := exec.Command("sh", "-c", sigCmd)
+	signature, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+	return signature, nil
+}
+
+func (d *templateData) readSignatureFromFile() []byte {
+	sigFile := d.account.SignatureFile
+	if sigFile == "" {
+		return nil
+	}
+	sigFile = xdg.ExpandHome(sigFile)
+	signature, err := os.ReadFile(sigFile)
+	if err != nil {
+		log.Errorf(" Error loading signature from file: %v", sigFile)
+		return nil
+	}
+	return signature
+}
+
+func (d *templateData) ensureSignatureDelimiter(signature []byte) []byte {
+	buf := bytes.NewBuffer(signature)
+	scanner := bufio.NewScanner(buf)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "-- " {
+			// signature contains standard delimiter, we're good
+			return signature
+		}
+	}
+	// signature does not contain standard delimiter, prepend one
+	sig := "\n\n-- \n" + strings.TrimLeft(string(signature), " \t\r\n")
+	return []byte(sig)
+}