From 6a2587f5cebc7ad45b249bcbe6641221542ba5eb Mon Sep 17 00:00:00 2001
From: Aki Kareha <aki@kareha.org>
Date: Sun, 14 Sep 2025 13:50:57 +0900
Subject: [PATCH] Print diff more pretty

---
 internal/action/static/style.css | 18 +++++++++++
 internal/data/data.go            | 12 ++++---
 internal/format/diff.go          | 55 ++++++++++++++++++++++++++++++++
 templates/revisions.html         |  2 +-
 4 files changed, 82 insertions(+), 5 deletions(-)
 create mode 100644 internal/format/diff.go

diff --git a/internal/action/static/style.css b/internal/action/static/style.css
index 5a70c68..2b7d65e 100644
--- a/internal/action/static/style.css
+++ b/internal/action/static/style.css
@@ -20,3 +20,21 @@ em {
 	color: #25e;
 	font-size: 1.125em;
 }
+
+.plus {
+	color: #8cf;
+	font-size: 1.125em;
+}
+
+.plus-line {
+	color: #36f;
+}
+
+.minus {
+	color: #fc8;
+	font-size: 1.125em;
+}
+
+.minus-line {
+	color: #f63;
+}
diff --git a/internal/data/data.go b/internal/data/data.go
index 434c2ae..5240d07 100644
--- a/internal/data/data.go
+++ b/internal/data/data.go
@@ -3,6 +3,7 @@ package data
 import (
 	"context"
 	"fmt"
+	"html/template"
 	"log"
 	"net/url"
 	"strings"
@@ -11,6 +12,7 @@ import (
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"github.com/akikareha/himewiki/internal/config"
+	"github.com/akikareha/himewiki/internal/format"
 )
 
 var db *pgxpool.Pool
@@ -168,11 +170,12 @@ func LoadAll() ([]Name, error) {
 }
 
 type Revision struct {
-	ID        int
-	Name      string
-	Diff      string
+	ID int
+	Name string
+	Diff string
 	CreatedAt time.Time
-	Escaped   string
+	Escaped string
+	DiffHTML template.HTML
 }
 
 func LoadRevisions(name string) ([]Revision, error) {
@@ -193,6 +196,7 @@ func LoadRevisions(name string) ([]Revision, error) {
 			return nil, err
 		}
 		r.Escaped = url.PathEscape(r.Name)
+		r.DiffHTML = template.HTML(format.Diff(r.Diff))
 		revs = append(revs, r)
 	}
 	return revs, nil
diff --git a/internal/format/diff.go b/internal/format/diff.go
new file mode 100644
index 0000000..968bd5d
--- /dev/null
+++ b/internal/format/diff.go
@@ -0,0 +1,55 @@
+package format
+
+import (
+	"bytes"
+	"html/template"
+)
+
+func detectLine(data []byte) (int, int) {
+	lineFeed := bytes.IndexByte(data, '\n')
+	if lineFeed == -1 {
+		lineFeed = len(data)
+	}
+	lineEnd := lineFeed
+	if lineEnd > 0 {
+		c := data[lineEnd - 1]
+		if c == '\r' {
+			lineEnd -= 1
+		}
+	}
+	nextLine := lineFeed + 1
+	return lineEnd, nextLine
+}
+
+func Diff(text string) string {
+	data := []byte(text)
+	index := 0
+	var html bytes.Buffer
+
+	for index < len(data) {
+		lineEnd, nextLine := detectLine(data[index:])
+		lineEnd += index
+		nextLine += index
+		line := data[index:lineEnd]
+
+		if len(line) < 1 {
+			html.WriteString("\n");
+		} else {
+			c := line[0]
+			htmlLine := template.HTMLEscapeString(string(line[1:]))
+			if c == '+' {
+				html.WriteString("<span class=\"plus\">+</span>")
+				html.WriteString("<span class=\"plus-line\">" + htmlLine + "</span>\n")
+			} else if c == '-' {
+				html.WriteString("<span class=\"minus\">-</span>")
+				html.WriteString("<span class=\"minus-line\">" + htmlLine + "</span>\n")
+			} else {
+				html.WriteString("&nbsp;")
+				html.WriteString(htmlLine + "\n")
+			}
+		}
+		index = nextLine
+	}
+
+	return html.String()
+}
diff --git a/templates/revisions.html b/templates/revisions.html
index 31cf7b9..55cbff3 100644
--- a/templates/revisions.html
+++ b/templates/revisions.html
@@ -24,7 +24,7 @@
 <input type="hidden" name="i" value="{{.ID}}" />
 <input type="submit" value="View" />
 </form>
-<pre>{{.Diff}}</pre>
+<pre>{{.DiffHTML}}</pre>
 </li>
 {{else}}
 <li>No revisions found.</li>