shows relative images in markdown

test/diff.test.ts

@@ -69,3 +69,33 @@ describe('makeDiff', () => {
     expect(deleted.added).toBe(false)
   })
 })
+
+describe('buildDiff on large files', () => {
+  it('diffs a 60k-line file without exhausting the heap', () => {
+    const base = Array.from({ length: 60_000 }, (_, i) => `line ${i}`)
+    const changed = base.slice()
+    changed[30_000] = 'line 30000 edited'
+    const d = buildDiff(base.join('\n'), changed.join('\n'))
+    expect(d.add).toBe(1)
+    expect(d.del).toBe(1)
+    expect(d.right[30_000].mark).toBe('add')
+  })
+
+  it('survives a full rewrite of a large file with no shared lines', () => {
+    const a = Array.from({ length: 40_000 }, (_, i) => `old ${i}`).join('\n')
+    const b = Array.from({ length: 40_000 }, (_, i) => `new ${i}`).join('\n')
+    const d = buildDiff(a, b)
+    expect(d.del).toBe(40_000)
+    expect(d.add).toBe(40_000)
+  })
+
+  it('keeps the unchanged head and tail of a large, heavily edited file', () => {
+    const head = Array.from({ length: 5_000 }, (_, i) => `head ${i}`)
+    const tail = Array.from({ length: 5_000 }, (_, i) => `tail ${i}`)
+    const mid = (p: string): string[] => Array.from({ length: 30_000 }, (_, i) => `${p} ${i % 7}`)
+    const d = buildDiff([...head, ...mid('x'), ...tail].join('\n'), [...head, ...mid('y'), ...tail].join('\n'))
+    expect(d.left.slice(0, 5_000).every((l) => l.mark === null)).toBe(true)
+    expect(d.left.slice(-5_000).every((l) => l.mark === null)).toBe(true)
+    expect(d.add).toBe(30_000)
+  })
+})