fix: scrolling on suggestions

suggestions.go

@@ -2,10 +2,15 @@ package main
 
 import (
 	"strings"
+	"sync"
 
 	"github.com/charmbracelet/x/ansi"
 )
 
+const suggestionRenderCacheLimit = 256
+
+var renderedSuggestions = newSuggestionRenderCache(suggestionRenderCacheLimit)
+
 type parsedCommentBody struct {
 	Prose       string
 	Suggestions []string
@@ -16,6 +21,98 @@ type codeRange struct {
 	End   int
 }
 
+type suggestionRenderCacheKey struct {
+	path         string
+	removed      string
+	removedLines int
+	replacement  string
+	width        int
+}
+
+type suggestionRenderCacheEntry struct {
+	removed []detailLine
+	added   []detailLine
+}
+
+type suggestionRenderCache struct {
+	mu      sync.Mutex
+	limit   int
+	entries map[suggestionRenderCacheKey]suggestionRenderCacheEntry
+	order   []suggestionRenderCacheKey
+}
+
+func newSuggestionRenderCache(limit int) *suggestionRenderCache {
+	return &suggestionRenderCache{
+		limit: limit, entries: make(map[suggestionRenderCacheKey]suggestionRenderCacheEntry),
+	}
+}
+
+func (c *suggestionRenderCache) get(
+	key suggestionRenderCacheKey,
+) (suggestionRenderCacheEntry, bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	entry, ok := c.entries[key]
+	return cloneSuggestionRenderEntry(entry), ok
+}
+
+func (c *suggestionRenderCache) put(
+	key suggestionRenderCacheKey, entry suggestionRenderCacheEntry,
+) suggestionRenderCacheEntry {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if cached, ok := c.entries[key]; ok {
+		return cloneSuggestionRenderEntry(cached)
+	}
+	if len(c.entries) >= c.limit {
+		delete(c.entries, c.order[0])
+		c.order = c.order[1:]
+	}
+	c.entries[key] = cloneSuggestionRenderEntry(entry)
+	c.order = append(c.order, key)
+	return cloneSuggestionRenderEntry(entry)
+}
+
+func (c *suggestionRenderCache) clear() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.entries = make(map[suggestionRenderCacheKey]suggestionRenderCacheEntry)
+	c.order = nil
+}
+
+func cloneSuggestionRenderEntry(entry suggestionRenderCacheEntry) suggestionRenderCacheEntry {
+	return suggestionRenderCacheEntry{
+		removed: append([]detailLine(nil), entry.removed...),
+		added:   append([]detailLine(nil), entry.added...),
+	}
+}
+
+func renderSuggestion(
+	path string, reviewed []string, replacement string, width int,
+) suggestionRenderCacheEntry {
+	key := suggestionRenderCacheKey{
+		path: path, removed: strings.Join(reviewed, "\n"), removedLines: len(reviewed),
+		replacement: replacement, width: width,
+	}
+	if cached, ok := renderedSuggestions.get(key); ok {
+		return cached
+	}
+	removed, added := normalizeSuggestion(reviewed, replacement)
+	removedRanges, addedRanges := suggestionChangedRanges(removed, added)
+	entry := suggestionRenderCacheEntry{}
+	for index, source := range removed {
+		entry.removed = append(entry.removed, wrapSuggestionLine(
+			path, source, '-', removedRanges[index], width,
+		)...)
+	}
+	for index, source := range added {
+		entry.added = append(entry.added, wrapSuggestionLine(
+			path, source, '+', addedRanges[index], width,
+		)...)
+	}
+	return renderedSuggestions.put(key, entry)
+}
+
 func parseCommentBody(body string) parsedCommentBody {
 	var (
 		result       parsedCommentBody