历史记录：每条可展开 diff，连续保存合并进 5 秒窗

备份存的是「改动前」，所以一条记录的 diff 两端是它自己和更新一份的状态（最新一条对比当前文件）。行级 diff 先掐公共前后缀再做 LCS，一次改动通常只碰几行，表撑得住；大面积不同时退化成整段删增。合并窗做在服务端而不是前端防抖：普通保存（opts.merge）发现最新备份还在窗内就不新建，连点删除共享一条历史、一步撤回。窗锚定在这一串的第一下，不滚雪球；还原、导入、撤回重做不合并，各占一条。合并时没有备份文件，重载失败的还原改用刚读出的原文写回。顺带消除了备份名只精确到秒、同秒保存互相覆盖的隐患。
2026-08-12 13:17:11 +08:00
parent 48e97bd91f
commit a40bd6a01b
8 changed files with 449 additions and 20 deletions
@@ -13,3 +13,17 @@ export function backupTime(name: string): string | null {
  if (!m) return null
  return `${m[1]}-${m[2]}-${m[3]} ${m[4]}:${m[5]}:${m[6]}`
 }
+
+/** 备份文件名里的时间戳解析成 Date（服务端本地时间）。名字不合预期时返回 null。 */
+export function backupDate(name: string): Date | null {
+  const m = STAMP.exec(name)
+  if (!m) return null
+  return new Date(
+    Number(m[1]),
+    Number(m[2]) - 1,
+    Number(m[3]),
+    Number(m[4]),
+    Number(m[5]),
+    Number(m[6]),
+  )
+}
@@ -0,0 +1,64 @@
+import { describe, expect, it } from 'bun:test'
+import { diffHunks, diffLines } from './diff.ts'
+
+const lines = (rows: ReturnType<typeof diffLines>) => rows.map((r) => `${r.kind}:${r.text}`)
+
+describe('行级 diff', () => {
+  it('相同的内容全是 same，折叠后没有片段', () => {
+    const rows = diffLines('a\nb\nc', 'a\nb\nc')
+    expect(rows.every((r) => r.kind === 'same')).toBe(true)
+    expect(diffHunks(rows)).toEqual([])
+  })
+
+  it('中间插入一行', () => {
+    expect(lines(diffLines('a\nc', 'a\nb\nc'))).toEqual(['same:a', 'add:b', 'same:c'])
+  })
+
+  it('中间删除一行', () => {
+    expect(lines(diffLines('a\nb\nc', 'a\nc'))).toEqual(['same:a', 'del:b', 'same:c'])
+  })
+
+  it('改一行等于删旧行加新行', () => {
+    expect(lines(diffLines('a\nx\nc', 'a\ny\nc'))).toEqual(['same:a', 'del:x', 'add:y', 'same:c'])
+  })
+
+  it('从空到有、从有到空', () => {
+    expect(lines(diffLines('', 'a'))).toEqual(['del:', 'add:a'])
+    expect(lines(diffLines('a\nb', ''))).toEqual(['del:a', 'del:b', 'add:'])
+  })
+
+  it('公共前后缀之外的多处改动都找得到', () => {
+    const before = ['p1', 'p2', 'x', 'm', 'y', 's1'].join('\n')
+    const after = ['p1', 'p2', 'x2', 'm', 'y2', 's1'].join('\n')
+    expect(lines(diffLines(before, after))).toEqual([
+      'same:p1',
+      'same:p2',
+      'del:x',
+      'add:x2',
+      'same:m',
+      'del:y',
+      'add:y2',
+      'same:s1',
+    ])
+  })
+})
+
+describe('折叠成片段', () => {
+  it('改动行带前后上下文，远处的未改动行不进片段', () => {
+    const rows = diffLines(
+      ['1', '2', '3', '4', '5', '6', '7', '8', '9'].join('\n'),
+      ['1', '2', '3', 'x', '5', '6', '7', '8', '9'].join('\n'),
+    )
+    const hunks = diffHunks(rows, 1)
+    expect(hunks).toHaveLength(1)
+    expect(hunks[0]!.map((r) => r.text)).toEqual(['3', '4', 'x', '5'])
+  })
+
+  it('相距很远的两处改动分成两个片段，挨得近就合并成一个', () => {
+    const before = ['a', '1', '2', '3', '4', '5', '6', '7', 'b'].join('\n')
+    const afterFar = ['a2', '1', '2', '3', '4', '5', '6', '7', 'b2'].join('\n')
+    expect(diffHunks(diffLines(before, afterFar), 1)).toHaveLength(2)
+    const afterNear = ['a2', '1', '2', '3', '4', '5', '6', '7b', 'b'].join('\n')
+    expect(diffHunks(diffLines(before, afterNear), 4)).toHaveLength(1)
+  })
+})
@@ -0,0 +1,103 @@
+/**
+ * 行级 diff，给历史记录的「这次改动改了什么」用。
+ *
+ * 先掐掉公共前后缀再对中段做 LCS：配置文件的一次改动通常只碰几行，中段一般
+ * 很小，LCS 的 O(n×m) 表因此撑得住。真遇到两份大面积不同的文件（中段乘积超过
+ * 上限），退化成「整段删除 + 整段新增」——依旧正确，只是不够精细。
+ */
+
+export interface DiffLine {
+  kind: 'same' | 'add' | 'del'
+  text: string
+}
+
+const LCS_LIMIT = 1_000_000
+
+export function diffLines(before: string, after: string): DiffLine[] {
+  const a = before.split('\n')
+  const b = after.split('\n')
+
+  let start = 0
+  while (start < a.length && start < b.length && a[start] === b[start]) start += 1
+  let endA = a.length
+  let endB = b.length
+  while (endA > start && endB > start && a[endA - 1] === b[endB - 1]) {
+    endA -= 1
+    endB -= 1
+  }
+
+  return [
+    ...a.slice(0, start).map((text): DiffLine => ({ kind: 'same', text })),
+    ...diffMiddle(a.slice(start, endA), b.slice(start, endB)),
+    ...a.slice(endA).map((text): DiffLine => ({ kind: 'same', text })),
+  ]
+}
+
+function diffMiddle(a: string[], b: string[]): DiffLine[] {
+  const allDel = a.map((text): DiffLine => ({ kind: 'del', text }))
+  const allAdd = b.map((text): DiffLine => ({ kind: 'add', text }))
+  if (a.length === 0 || b.length === 0 || a.length * b.length > LCS_LIMIT) {
+    return [...allDel, ...allAdd]
+  }
+
+  // LCS 长度表倒着填，回溯时从头正着走
+  const w = b.length + 1
+  const table = new Uint32Array((a.length + 1) * w)
+  for (let i = a.length - 1; i >= 0; i -= 1) {
+    for (let j = b.length - 1; j >= 0; j -= 1) {
+      table[i * w + j] =
+        a[i] === b[j]
+          ? table[(i + 1) * w + j + 1]! + 1
+          : Math.max(table[(i + 1) * w + j]!, table[i * w + j + 1]!)
+    }
+  }
+
+  const rows: DiffLine[] = []
+  let i = 0
+  let j = 0
+  while (i < a.length && j < b.length) {
+    if (a[i] === b[j]) {
+      rows.push({ kind: 'same', text: a[i]! })
+      i += 1
+      j += 1
+    } else if (table[(i + 1) * w + j]! >= table[i * w + j + 1]!) {
+      rows.push({ kind: 'del', text: a[i]! })
+      i += 1
+    } else {
+      rows.push({ kind: 'add', text: b[j]! })
+      j += 1
+    }
+  }
+  while (i < a.length) rows.push({ kind: 'del', text: a[i++]! })
+  while (j < b.length) rows.push({ kind: 'add', text: b[j++]! })
+  return rows
+}
+
+/**
+ * 折叠成只含改动的片段：每个片段是改动行加前后 context 行上下文，片段之间的
+ * 未改动区域丢弃（渲染端画省略号）。两份内容相同时返回空数组。
+ */
+export function diffHunks(rows: DiffLine[], context = 2): DiffLine[][] {
+  const keep = new Array<boolean>(rows.length).fill(false)
+  rows.forEach((row, index) => {
+    if (row.kind === 'same') return
+    const from = Math.max(0, index - context)
+    const to = Math.min(rows.length - 1, index + context)
+    for (let k = from; k <= to; k += 1) keep[k] = true
+  })
+
+  const hunks: DiffLine[][] = []
+  let current: DiffLine[] | null = null
+  rows.forEach((row, index) => {
+    if (!keep[index]) {
+      current = null
+      return
+    }
+    if (!current) {
+      current = []
+      hunks.push(current)
+    }
+    current.push(row)
+  })
+  return hunks
+}