import { describe, expect, test, vi } from 'vitest'

import type {
  EventConnection,
  EventSocket,
  EventSocketListener,
  PublicApi,
} from '../api/client'
import type {
  DeletionOperationDto,
  EventTicketDto,
  JobPageDto,
  JobResourceDto,
} from '../api/contracts'
import type { Session, SessionState } from '../auth/session'
import { WebClientRuntime, type Scheduler } from './runtime'
import { heartbeat, job, jobChanged, observedAt } from './test-fixtures'

describe('web client runtime', () => {
  test('loads a snapshot, deduplicates events, and resyncs on a gap', async () => {
    const fixture = runtimeFixture()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)

    fixture.socket.frame(jobChanged(1, 'event_000001', 2, 20))
    await vi.waitFor(() => {
      expect(fixture.api.jobRequests).toEqual(['job_00000001'])
    })
    expect(fixture.runtime.snapshot.jobs[0]?.resource).toEqual(job(2))

    fixture.socket.frame(jobChanged(2, 'event_000001', 2, 20))
    await flush()
    expect(fixture.api.jobRequests).toHaveLength(1)

    fixture.socket.frame(heartbeat(4, 'event_000004'))
    await vi.waitFor(() => {
      expect(fixture.api.listRequests).toBe(2)
    })
  })

  test('clears state and ignores stale work on logout', async () => {
    const fixture = runtimeFixture()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)

    fixture.session.emit({ kind: 'signed_out' })

    expect(fixture.runtime.snapshot.status).toBe('signed_out')
    expect(fixture.runtime.snapshot.jobs).toEqual([])
    expect(fixture.socket.connections[0]?.closed).toBe(true)
  })

  test('takes a fresh snapshot when authorization material changes', async () => {
    const fixture = runtimeFixture()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)

    fixture.api.snapshot = job(5, { label: 'New authorization' })
    fixture.session.emit(authenticated('token-two'))
    await vi.waitFor(() => {
      expect(fixture.runtime.snapshot.status).toBe('live')
      expect(fixture.runtime.snapshot.jobs[0]?.resource).toEqual(
        fixture.api.snapshot,
      )
    })
    expect(fixture.api.tokens).toEqual(['token-one', 'token-two'])
    expect(fixture.socket.connections[0]?.closed).toBe(true)
  })

  test('does not serialize a new session behind stale event work', async () => {
    const fixture = runtimeFixture()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)
    fixture.api.nextJob = new Promise(() => {})
    fixture.socket.frame(jobChanged(1, 'event_000001', 2, 20))
    await vi.waitFor(() => {
      expect(fixture.api.jobRequests).toEqual(['job_00000001'])
    })

    fixture.session.emit({ kind: 'signed_out' })
    fixture.api.snapshot = job(5)
    fixture.session.emit(authenticated('token-two'))
    await live(fixture)
    fixture.api.nextJob = Promise.resolve(job(6))
    fixture.socket.frame(jobChanged(1, 'event_000006', 6, 60))

    await vi.waitFor(() => {
      expect(fixture.runtime.snapshot.jobs[0]?.resource).toEqual(job(6))
    })
  })

  test('refetches deletion invalidations and reconnects from the latest cursor', async () => {
    const fixture = runtimeFixture()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)
    fixture.socket.frame({
      schema_version: 1,
      kind: 'deletion_changed',
      event_id: 'event_000001',
      sequence: 1,
      cursor: 'cursor-event-0001',
      occurred_at: observedAt,
      job_id: 'job_00000001',
      operation_id: 'deletion_001',
      state: 'running',
    })
    await vi.waitFor(() => {
      expect(fixture.runtime.snapshot.deletions).toEqual([fixture.api.deletion])
    })
    fixture.socket.frame(heartbeat(2, 'event_000002'))
    await vi.waitFor(() => {
      expect(fixture.runtime.snapshot.cursor).toBe('cursor-event-0002')
    })
    fixture.socket.disconnect()

    await vi.waitFor(() => {
      expect(fixture.socket.cursors).toEqual([
        'cursor-snapshot-0001',
        'cursor-event-0002',
      ])
    })
    expect(fixture.api.ticketRequests).toBe(2)
  })

  test('replays an invalidation whose refetch was interrupted by reconnect', async () => {
    const fixture = runtimeFixture()
    const staleRequest = deferred<JobResourceDto | null>()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)
    fixture.api.nextJob = staleRequest.promise

    fixture.socket.frame(jobChanged(1, 'event_000001', 2, 20))
    await vi.waitFor(() => {
      expect(fixture.api.jobRequests).toEqual(['job_00000001'])
    })
    fixture.socket.disconnect()
    await vi.waitFor(() => {
      expect(fixture.socket.cursors).toEqual([
        'cursor-snapshot-0001',
        'cursor-snapshot-0001',
      ])
    })

    fixture.socket.frame(jobChanged(1, 'event_000001', 2, 20))
    await vi.waitFor(() => {
      expect(fixture.api.jobRequests).toHaveLength(2)
      expect(fixture.runtime.snapshot.jobs[0]?.resource).toEqual(job(2))
      expect(fixture.runtime.snapshot.cursor).toBe('cursor-event-0001')
    })
    staleRequest.resolve(job(9))
    await flush()
    expect(fixture.runtime.snapshot.jobs[0]?.resource).toEqual(job(2))
  })

  test('does not serialize a reconnected socket behind a hung refetch', async () => {
    const fixture = runtimeFixture()
    await fixture.runtime.start()
    fixture.session.emit(authenticated('token-one'))
    await live(fixture)
    fixture.api.nextJob = new Promise(() => {})

    fixture.socket.frame(jobChanged(1, 'event_000001', 2, 20))
    await vi.waitFor(() => {
      expect(fixture.api.jobRequests).toEqual(['job_00000001'])
    })
    fixture.socket.disconnect()
    await vi.waitFor(() => {
      expect(fixture.socket.connections).toHaveLength(2)
    })
    fixture.socket.frame({
      schema_version: 1,
      kind: 'resync_required',
      event_id: 'event_000002',
      sequence: 1,
      cursor: 'cursor-event-0002',
      occurred_at: observedAt,
      reason: 'history_unavailable',
    })

    await vi.waitFor(() => {
      expect(fixture.api.listRequests).toBe(2)
      expect(fixture.runtime.snapshot.status).toBe('live')
    })
  })
})

function runtimeFixture(): {
  runtime: WebClientRuntime
  session: FakeSession
  api: FakeApi
  socket: FakeSocket
} {
  const session = new FakeSession()
  const api = new FakeApi()
  const socket = new FakeSocket()
  return {
    runtime: new WebClientRuntime(
      session,
      api,
      socket,
      new ImmediateScheduler(),
    ),
    session,
    api,
    socket,
  }
}

async function live(fixture: ReturnType<typeof runtimeFixture>): Promise<void> {
  await vi.waitFor(() => {
    expect(fixture.runtime.snapshot.status).toBe('live')
  })
}

async function flush(): Promise<void> {
  await Promise.resolve()
  await Promise.resolve()
}

function deferred<T>(): {
  promise: Promise<T>
  resolve(value: T): void
} {
  let resolve!: (value: T) => void
  const promise = new Promise<T>((complete) => {
    resolve = complete
  })
  return { promise, resolve }
}

function authenticated(accessToken: string): SessionState {
  return {
    kind: 'authenticated',
    session: { accessToken, identity: 'issuer\u0000subject' },
  }
}

class FakeSession implements Session {
  state: SessionState = { kind: 'loading' }
  readonly #listeners = new Set<(state: SessionState) => void>()

  async start(): Promise<void> {}
  async signIn(): Promise<void> {}
  async signOut(): Promise<void> {}

  subscribe(listener: (state: SessionState) => void): () => void {
    this.#listeners.add(listener)
    listener(this.state)
    return () => {
      this.#listeners.delete(listener)
    }
  }

  emit(state: SessionState): void {
    this.state = state
    for (const listener of this.#listeners) listener(state)
  }
}

class FakeApi implements PublicApi {
  snapshot = job(1)
  readonly deletion: DeletionOperationDto = {
    id: 'deletion_001',
    job_id: 'job_00000001',
    state: 'running',
    problem: null,
    created_at: observedAt,
    updated_at: observedAt,
  }
  nextJob: Promise<JobResourceDto | null> | null = null
  listRequests = 0
  ticketRequests = 0
  readonly tokens: string[] = []
  readonly jobRequests: string[] = []

  async listJobs(accessToken: string): Promise<JobPageDto> {
    this.listRequests += 1
    this.tokens.push(accessToken)
    return {
      items: [this.snapshot],
      next_cursor: null,
      event_cursor: 'cursor-snapshot-0001',
    }
  }

  async getJob(
    _accessToken: string,
    jobId: string,
  ): Promise<JobResourceDto | null> {
    this.jobRequests.push(jobId)
    if (this.nextJob !== null) {
      const response = this.nextJob
      this.nextJob = null
      return response
    }
    this.snapshot = job(2)
    return this.snapshot
  }

  async getDeletion(
    _accessToken: string,
    _operationId: string,
  ): Promise<DeletionOperationDto | null> {
    return this.deletion
  }

  async createEventTicket(_accessToken: string): Promise<EventTicketDto> {
    this.ticketRequests += 1
    return {
      ticket: 'ticket_00001',
      expires_at: '2026-07-17T00:01:00Z',
    }
  }
}

interface FakeConnection extends EventConnection {
  closed: boolean
}

class FakeSocket implements EventSocket {
  readonly connections: FakeConnection[] = []
  readonly cursors: string[] = []
  #listener: EventSocketListener | null = null

  connect(
    _ticket: string,
    cursor: string,
    listener: EventSocketListener,
  ): EventConnection {
    this.#listener = listener
    const connection: FakeConnection = {
      closed: false,
      close(): void {
        connection.closed = true
      },
    }
    this.connections.push(connection)
    this.cursors.push(cursor)
    listener.opened()
    return connection
  }

  frame(frame: Parameters<EventSocketListener['frame']>[0]): void {
    this.#listener?.frame(frame)
  }

  disconnect(): void {
    this.#listener?.closed()
  }
}

class ImmediateScheduler implements Scheduler {
  schedule(callback: () => void): () => void {
    queueMicrotask(callback)
    return () => {}
  }
}