chore: remove old and unused code

highlight.go

@@ -6,18 +6,67 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/alecthomas/chroma/v2/lexers"
 	"github.com/alecthomas/chroma/v2/quick"
 )
 
 const reviewContextLines = 3
+const highlightedDiffCacheLimit = 256
 
 var codeHighlightTheme = "github-dark"
 var colorEnabled = true
 
 var hunkHeaderPattern = regexp.MustCompile(`^@@ -(\d+)(?:,\d+)? \+(\d+)(?:,\d+)? @@`)
 
+type highlightedDiffCacheKey struct {
+	path, hunk, side, theme string
+	startLine, endLine      int
+	color                   bool
+}
+
+type highlightedDiffCache struct {
+	mu      sync.Mutex
+	entries map[highlightedDiffCacheKey][]highlightedDiffLine
+	order   []highlightedDiffCacheKey
+}
+
+var highlightedDiffs = highlightedDiffCache{
+	entries: make(map[highlightedDiffCacheKey][]highlightedDiffLine),
+}
+
+func (c *highlightedDiffCache) get(key highlightedDiffCacheKey) ([]highlightedDiffLine, bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	lines, ok := c.entries[key]
+	return append([]highlightedDiffLine(nil), lines...), ok
+}
+
+func (c *highlightedDiffCache) put(
+	key highlightedDiffCacheKey, lines []highlightedDiffLine,
+) []highlightedDiffLine {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if cached, ok := c.entries[key]; ok {
+		return append([]highlightedDiffLine(nil), cached...)
+	}
+	if len(c.entries) >= highlightedDiffCacheLimit {
+		delete(c.entries, c.order[0])
+		c.order = c.order[1:]
+	}
+	c.entries[key] = append([]highlightedDiffLine(nil), lines...)
+	c.order = append(c.order, key)
+	return append([]highlightedDiffLine(nil), lines...)
+}
+
+func (c *highlightedDiffCache) clear() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.entries = make(map[highlightedDiffCacheKey][]highlightedDiffLine)
+	c.order = nil
+}
+
 type highlightedDiffLine struct {
 	gutter   string
 	code     string
@@ -34,6 +83,17 @@ type parsedDiffLine struct {
 }
 
 func highlightDiff(path, hunk string, startLine, endLine int, side string) []highlightedDiffLine {
+	key := highlightedDiffCacheKey{
+		path: path, hunk: hunk, side: side, theme: codeHighlightTheme,
+		startLine: startLine, endLine: endLine, color: colorEnabled,
+	}
+	if cached, ok := highlightedDiffs.get(key); ok {
+		return cached
+	}
+	return highlightedDiffs.put(key, highlightDiffUncached(path, hunk, startLine, endLine, side))
+}
+
+func highlightDiffUncached(path, hunk string, startLine, endLine int, side string) []highlightedDiffLine {
 	if hunk == "" {
 		return []highlightedDiffLine{{code: "(GitHub did not return a diff hunk)"}}
 	}