From 4a4ccb83a3556d7b3ee99d75fa0450226d20c173 Mon Sep 17 00:00:00 2001
From: Mechiel Lukkien <mechiel@ueber.net>
Date: Mon, 11 Sep 2023 14:41:50 +0200
Subject: [PATCH] when making a message preview, also recognize []-enclosed
 "horizontal ellipsis" unicode character as a snip

---
 webmail/message.go      | 17 +++++++++++------
 webmail/message_test.go | 28 ++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/webmail/message.go b/webmail/message.go
index 11283717ca..f9fb77e40e 100644
--- a/webmail/message.go
+++ b/webmail/message.go
@@ -45,7 +45,7 @@ func formatFirstLine(r io.Reader) (string, error) {
 	ensureLines()
 
 	isSnipped := func(s string) bool {
-		return s == "[...]" || s == "..."
+		return s == "[...]" || s == "[…]" || s == "..."
 	}
 
 	nextLineQuoted := func(i int) bool {
@@ -55,7 +55,8 @@ func formatFirstLine(r io.Reader) (string, error) {
 		return i+1 < len(lines) && (strings.HasPrefix(lines[i+1], ">") || isSnipped(lines[i+1]))
 	}
 
-	// remainder is signature if we see a line with only and minimum 2 dashes, and there are no more empty lines, and there aren't more than 5 lines left
+	// Remainder is signature if we see a line with only and minimum 2 dashes, and
+	// there are no more empty lines, and there aren't more than 5 lines left.
 	isSignature := func() bool {
 		if len(lines) == 0 || !strings.HasPrefix(lines[0], "--") || strings.Trim(strings.TrimSpace(lines[0]), "-") != "" {
 			return false
@@ -77,6 +78,10 @@ func formatFirstLine(r io.Reader) (string, error) {
 
 	result := ""
 
+	resultSnipped := func() bool {
+		return strings.HasSuffix(result, "[...]\n") || strings.HasSuffix(result, "[…]")
+	}
+
 	// Quick check for initial wrapped "On ... wrote:" line.
 	if len(lines) > 3 && strings.HasPrefix(lines[0], "On ") && !strings.HasSuffix(lines[0], "wrote:") && strings.HasSuffix(lines[1], ":") && nextLineQuoted(1) {
 		result = "[...]\n"
@@ -87,7 +92,7 @@ func formatFirstLine(r io.Reader) (string, error) {
 	for ; len(lines) > 0 && !isSignature(); ensureLines() {
 		line := lines[0]
 		if strings.HasPrefix(line, ">") {
-			if !strings.HasSuffix(result, "[...]\n") {
+			if !resultSnipped() {
 				result += "[...]\n"
 			}
 			lines = lines[1:]
@@ -101,14 +106,14 @@ func formatFirstLine(r io.Reader) (string, error) {
 		// line, with an optional empty line in between. If we don't have any text yet, we
 		// don't require the digits.
 		if strings.HasSuffix(line, ":") && (strings.ContainsAny(line, "0123456789") || result == "") && nextLineQuoted(0) {
-			if !strings.HasSuffix(result, "[...]\n") {
+			if !resultSnipped() {
 				result += "[...]\n"
 			}
 			lines = lines[1:]
 			continue
 		}
-		// Skip snipping by author.
-		if !(isSnipped(line) && strings.HasSuffix(result, "[...]\n")) {
+		// Skip possibly duplicate snipping by author.
+		if !isSnipped(line) || !resultSnipped() {
 			result += line + "\n"
 		}
 		lines = lines[1:]
diff --git a/webmail/message_test.go b/webmail/message_test.go
index 3d107ab555..e7d275a43a 100644
--- a/webmail/message_test.go
+++ b/webmail/message_test.go
@@ -1,11 +1,39 @@
 package webmail
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/mjl-/mox/dns"
 )
 
+func TestFormatFirstLine(t *testing.T) {
+	check := func(body, expLine string) {
+		t.Helper()
+
+		line, err := formatFirstLine(strings.NewReader(body))
+		tcompare(t, err, nil)
+		if line != expLine {
+			t.Fatalf("got %q, expected %q, for body %q", line, expLine, body)
+		}
+	}
+
+	check("", "")
+	check("single line", "single line\n")
+	check("single line\n", "single line\n")
+	check("> quoted\n", "[...]\n")
+	check("> quoted\nresponse\n", "[...]\nresponse\n")
+	check("> quoted\n[...]\nresponse after author snip\n", "[...]\nresponse after author snip\n")
+	check("[...]\nresponse after author snip\n", "[...]\nresponse after author snip\n")
+	check("[…]\nresponse after author snip\n", "[…]\nresponse after author snip\n")
+	check(">> quoted0\n> quoted1\n>quoted2\n[...]\nresponse after author snip\n", "[...]\nresponse after author snip\n")
+	check(">quoted\n\n>quoted\ncoalesce line-separated quotes\n", "[...]\ncoalesce line-separated quotes\n")
+	check("On <date> <user> wrote:\n> hi\nresponse", "[...]\nresponse\n")
+	check("On <longdate>\n<user> wrote:\n> hi\nresponse", "[...]\nresponse\n")
+	check("> quote\nresponse\n--\nsignature\n", "[...]\nresponse\n")
+	check("> quote\nline1\nline2\nline3\n", "[...]\nline1\nline2\nline3\n")
+}
+
 func TestParseListPostAddress(t *testing.T) {
 	check := func(s string, exp *MessageAddress) {
 		t.Helper()