import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
import { computeDiff, createWhiteboardClient } from '../src/composables/useWhiteboard.js'

// ---------- computeDiff 纯函数 ----------
describe('computeDiff', () => {
  it('相同文本返回全长前后缀', () => {
    expect(computeDiff('abc', 'abc')).toEqual({ prefix: 3, suffixOld: 3, suffixNew: 3 })
  })

  it('前插：新文本在头部插入', () => {
    // old="bc", new="abc" -> prefix=0, suffixOld=0(newtext 无公共前缀... 实际 old[0]='b'!=new[0]='a')
    // 公共后缀: old="bc" new="abc" 从尾比: 'c'='c', 'b'='b' -> suffixOld=0, suffixNew=1
    const d = computeDiff('bc', 'abc')
    expect(d.prefix).toBe(0)
    // 后缀比较到 prefix=0 停止：suffixOld 从 2 递减，suffixNew 从 3 递减
    // old[1]='c'==new[2]='c' -> suffixOld=1,suffixNew=2; old[0]='b'==new[1]='b' -> suffixOld=0,suffixNew=1; 停
    expect(d.suffixOld).toBe(0)
    expect(d.suffixNew).toBe(1)
  })

  it('后插：新文本在尾部追加', () => {
    // old="ab", new="abc" -> prefix=2, suffixOld=2, suffixNew=3（后缀循环不进入因 suffixOld>prefix 即 2>2 false）
    const d = computeDiff('ab', 'abc')
    expect(d.prefix).toBe(2)
    expect(d.suffixOld).toBe(2)
    expect(d.suffixNew).toBe(3)
  })

  it('中间改：替换中间字符', () => {
    // old="abc", new="aXc" -> prefix=1('a'), 后缀 old[2]='c'==new[2]='c' -> suffixOld=2,suffixNew=2
    const d = computeDiff('abc', 'aXc')
    expect(d.prefix).toBe(1)
    expect(d.suffixOld).toBe(2)
    expect(d.suffixNew).toBe(2)
  })

  it('全替换：无公共前后缀', () => {
    const d = computeDiff('abc', 'xyz')
    expect(d.prefix).toBe(0)
    expect(d.suffixOld).toBe(3)
    expect(d.suffixNew).toBe(3)
  })

  it('空旧文本', () => {
    const d = computeDiff('', 'abc')
    expect(d.prefix).toBe(0)
    expect(d.suffixOld).toBe(0)
    expect(d.suffixNew).toBe(3)
  })

  it('空新文本（清空）', () => {
    const d = computeDiff('abc', '')
    expect(d.prefix).toBe(0)
    expect(d.suffixOld).toBe(3)
    expect(d.suffixNew).toBe(0)
  })
})

// ---------- createWhiteboardClient ----------
// 用 mock WebSocket + mock fetch + mock sessionStorage/location/document 测同步状态机

function makeMockWs() {
  const instances = []
  class MockWebSocket {
    constructor(url) {
      this.url = url
      this.readyState = 0 // CONNECTING
      this.OPEN = 1
      this.onopen = null
      this.onmessage = null
      this.onclose = null
      this.onerror = null
      this.sent = []
      instances.push(this)
    }
    _open() {
      this.readyState = 1
      if (this.onopen) this.onopen()
    }
    _receive(data) {
      if (this.onmessage) this.onmessage({ data })
    }
    _close() {
      this.readyState = 3
      if (this.onclose) this.onclose()
    }
    send(data) {
      this.sent.push(data)
    }
    close() {}
  }
  MockWebSocket.OPEN = 1
  return { MockWebSocket, instances }
}

function makeMockStorage() {
  const store = {}
  return {
    getItem: (k) => (k in store ? store[k] : null),
    setItem: (k, v) => {
      store[k] = String(v)
    },
    removeItem: (k) => {
      delete store[k]
    },
    _store: store,
  }
}

function makeClient(overrides = {}) {
  const { MockWebSocket, instances } = makeMockWs()
  const ss = makeMockStorage()
  const fetchMock = vi.fn(async () => ({
    ok: true,
    json: async () => ({ content: '' }),
  }))
  const loc = { protocol: 'http:', host: 'localhost' }
  const doc = {
    visibilityState: 'visible',
    addEventListener: vi.fn(),
    removeEventListener: vi.fn(),
    activeElement: null,
  }
  const client = createWhiteboardClient({
    fetch: fetchMock,
    WebSocket: MockWebSocket,
    sessionStorage: ss,
    location: loc,
    document: doc,
    ...overrides,
  })
  return { client, instances, ss, fetchMock, loc, doc, MockWebSocket }
}

describe('createWhiteboardClient', () => {
  beforeEach(() => {
    vi.useFakeTimers()
  })
  afterEach(() => {
    vi.useRealTimers()
  })

  it('clientId 用 sessionStorage 持久化（c_ 前缀）', () => {
    const { ss } = makeClient()
    const cid = ss._store['wb_cid']
    expect(cid).toMatch(/^c_/)
  })

  it('connectBoard 先 GET /api/wb/{id} 预取，再连 WS 并发 hello', async () => {
    const { client, instances, fetchMock } = makeClient()
    await client.connectBoard('share', null)
    // 预取
    expect(fetchMock).toHaveBeenCalledWith(
      '/api/wb/share',
      expect.objectContaining({ headers: { accept: 'application/json' } })
    )
    // WS 已创建
    expect(instances.length).toBe(1)
    const ws = instances[0]
    expect(ws.url).toBe('ws://localhost/api/ws/wb/share')
    // 模拟 onopen -> 应发 hello
    ws._open()
    expect(ws.sent).toContainEqual(JSON.stringify({ type: 'hello', client_id: client.clientId }))
  })

  it('收到 init 填充 content（无编辑器时）', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    ws._receive(JSON.stringify({ type: 'init', content: 'hello world', version: 1, edit_count: 1 }))
    expect(client.content.value).toBe('hello world')
    expect(client.connected.value).toBe(true)
  })

  it('sendEdit 400ms debounce 后发 edit，且 lastSentText 去重', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    // 初始化 lastSentText 为空
    ws._receive(JSON.stringify({ type: 'init', content: '', version: 0, edit_count: 0 }))
    // 编辑
    client.sendEdit('abc')
    // 立即未发
    expect(ws.sent.filter((s) => s.includes('"edit"'))).toHaveLength(0)
    // 推进 400ms
    vi.advanceTimersByTime(400)
    const edits = ws.sent.filter((s) => s.includes('"edit"'))
    expect(edits).toHaveLength(1)
    expect(JSON.parse(edits[0])).toEqual({ type: 'edit', content: 'abc' })
    expect(client._getLastSentText()).toBe('abc')

    // 再次发相同内容 -> 去重
    client.sendEdit('abc')
    vi.advanceTimersByTime(400)
    const edits2 = ws.sent.filter((s) => s.includes('"edit"'))
    expect(edits2).toHaveLength(1) // 仍只有 1 条
  })

  it('心跳每 3s 发 ping', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    const pingsBefore = ws.sent.filter((s) => s.includes('"ping"')).length
    vi.advanceTimersByTime(3000)
    expect(ws.sent.filter((s) => s.includes('"ping"')).length).toBe(pingsBefore + 1)
    vi.advanceTimersByTime(3000)
    expect(ws.sent.filter((s) => s.includes('"ping"')).length).toBe(pingsBefore + 2)
  })

  it('sendClear 发 clear 帧', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    client.sendClear()
    expect(ws.sent).toContainEqual(JSON.stringify({ type: 'clear' }))
  })

  it('收到 update 应用 applyRemoteUpdate（无编辑器时更新 content）', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    ws._receive(JSON.stringify({ type: 'init', content: 'abc', version: 1, edit_count: 1 }))
    ws._receive(JSON.stringify({ type: 'update', content: 'abcd', version: 2, client_id: 'other' }))
    expect(client.content.value).toBe('abcd')
  })

  it('收到 cleared 清空 content', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    ws._receive(JSON.stringify({ type: 'init', content: 'abc', version: 1, edit_count: 1 }))
    ws._receive(JSON.stringify({ type: 'cleared', client_id: 'other' }))
    expect(client.content.value).toBe('')
  })

  it('断线 2s 后重连（创建新 WS）', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    expect(instances.length).toBe(1)
    // 模拟断线
    ws._close()
    expect(client.connected.value).toBe(false)
    // 2s 内未重连
    vi.advanceTimersByTime(1999)
    expect(instances.length).toBe(1)
    // 满 2s 重连
    vi.advanceTimersByTime(1)
    expect(instances.length).toBe(2)
  })

  it('flushSend 立即补发未发送编辑', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    ws._receive(JSON.stringify({ type: 'init', content: '', version: 0, edit_count: 0 }))
    client.sendEdit('pending')
    // 未到 400ms，立即 flush
    client.flushSend()
    const edits = ws.sent.filter((s) => s.includes('"edit"'))
    expect(edits).toHaveLength(1)
    expect(JSON.parse(edits[0])).toEqual({ type: 'edit', content: 'pending' })
  })

  it('init 时本地有未发送编辑 -> 发本地编辑（last-writer-wins）', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    // 先 open（此时 lastSentText=''）
    ws._open()
    // 模拟本地有未发送编辑：直接调 sendEdit 但不推进定时器，再手动设 lastSentText 为旧值模拟 pending
    client.sendEdit('local-edit')
    // 不推进 debounce，直接收到 init（带服务端旧内容）
    ws._receive(JSON.stringify({ type: 'init', content: 'server-old', version: 5, edit_count: 5 }))
    // 应发本地编辑覆盖
    const edits = ws.sent.filter((s) => s.includes('"edit"'))
    expect(edits.some((s) => s.includes('local-edit'))).toBe(true)
  })

  it('disconnect 停心跳/重连并关闭', async () => {
    const { client, instances } = makeClient()
    await client.connectBoard('share', null)
    const ws = instances[0]
    ws._open()
    client.disconnect()
    // 断线重连定时器不应再触发
    vi.advanceTimersByTime(5000)
    expect(instances.length).toBe(1) // 无新 WS
    expect(client.connected.value).toBe(false)
  })
})