import { describe, expect, it, vi } from 'vitest'
import { useTransactionalFileWorker } from '../src/composables/useTransactionalFileWorker'

type TestResponse = {
  type: 'parsed'
  id: number
  value: string
} | {
  type: 'calculated'
  id: number
  value: string
} | {
  type: 'error'
  id: number
  operation: 'parse' | 'calculate'
  error: string
}

class FakeWorker {
  onmessage: ((event: MessageEvent<TestResponse>) => void) | null = null
  onerror: ((event: ErrorEvent) => void) | null = null
  onmessageerror: ((event: MessageEvent) => void) | null = null
  messages: Array<Record<string, unknown>> = []
  terminated = false

  postMessage(message: Record<string, unknown>) {
    this.messages.push(message)
  }

  terminate() {
    this.terminated = true
  }

  respond(response: TestResponse) {
    this.onmessage?.({ data: response } as MessageEvent<TestResponse>)
  }

  fail() {
    this.onerror?.({ preventDefault: vi.fn() } as unknown as ErrorEvent)
  }
}

function file(name: string): File {
  return { name, size: 1 } as File
}

function createHarness() {
  const workers: FakeWorker[] = []
  const parsed: string[] = []
  const calculated: string[] = []
  const parseErrors: string[] = []
  const calculationErrors: string[] = []
  const pendingWorkerErrors: boolean[] = []
  const activeWorkerError = vi.fn()
  const manager = useTransactionalFileWorker<Record<string, unknown>, TestResponse>({
    createWorker: () => {
      const worker = new FakeWorker()
      workers.push(worker)
      return worker as unknown as Worker
    },
    onParsed: (response, selected) => parsed.push(`${selected.name}:${response.value}`),
    onCalculated: (response) => calculated.push(response.value),
    onParseError: (message) => parseErrors.push(message),
    onCalculationError: (message) => calculationErrors.push(message),
    onPendingWorkerError: (hasCurrentFile) => pendingWorkerErrors.push(hasCurrentFile),
    onActiveWorkerError: activeWorkerError,
  })
  return {
    manager,
    workers,
    parsed,
    calculated,
    parseErrors,
    calculationErrors,
    pendingWorkerErrors,
    activeWorkerError,
  }
}

describe('transactional file Worker', () => {
  it('commits a parsed candidate and calculates with its Worker', () => {
    const harness = createHarness()
    expect(harness.manager.parseFile(file('first.hex'))).toBe(true)
    expect(harness.manager.parsing.value).toBe(true)
    expect(harness.workers[0].messages[0]).toMatchObject({ type: 'parse', id: 1 })

    harness.workers[0].respond({ type: 'parsed', id: 1, value: 'ready' })
    expect(harness.manager.parsing.value).toBe(false)
    expect(harness.parsed).toEqual(['first.hex:ready'])

    expect(harness.manager.calculate({ parameters: 'crc-32' })).toBe('started')
    expect(harness.manager.calculating.value).toBe(true)
    expect(harness.workers[0].messages[1]).toEqual({ type: 'calculate', id: 2, parameters: 'crc-32' })
    harness.workers[0].respond({ type: 'calculated', id: 2, value: 'result' })
    expect(harness.calculated).toEqual(['result'])
    expect(harness.manager.calculating.value).toBe(false)
  })

  it('supports an explicit parse-request payload without changing default callers', () => {
    const workers: FakeWorker[] = []
    const manager = useTransactionalFileWorker<Record<string, unknown>, TestResponse>({
      createWorker: () => {
        const worker = new FakeWorker()
        workers.push(worker)
        return worker as unknown as Worker
      },
      createParseRequest: (id, selected) => ({ type: 'parse', id, file: selected, mode: 'intel-hex' }),
      onParsed: vi.fn(),
      onCalculated: vi.fn(),
      onParseError: vi.fn(),
      onCalculationError: vi.fn(),
      onPendingWorkerError: vi.fn(),
      onActiveWorkerError: vi.fn(),
    })

    const selected = file('firmware.hex')
    manager.parseFile(selected)
    expect(workers[0].messages[0]).toEqual({ type: 'parse', id: 1, file: selected, mode: 'intel-hex' })
  })

  it('preserves the active Worker when a replacement parse fails', () => {
    const harness = createHarness()
    harness.manager.parseFile(file('first.hex'))
    harness.workers[0].respond({ type: 'parsed', id: 1, value: 'first' })

    harness.manager.parseFile(file('invalid.hex'))
    harness.workers[1].respond({ type: 'error', id: 2, operation: 'parse', error: 'bad checksum' })
    expect(harness.parseErrors).toEqual(['bad checksum'])
    expect(harness.workers[0].terminated).toBe(false)
    expect(harness.workers[1].terminated).toBe(true)
    expect(harness.manager.calculate({})).toBe('started')
  })

  it('atomically replaces the active Worker and ignores its stale result', () => {
    const harness = createHarness()
    harness.manager.parseFile(file('first.hex'))
    harness.workers[0].respond({ type: 'parsed', id: 1, value: 'first' })
    harness.manager.calculate({})

    harness.manager.parseFile(file('second.hex'))
    harness.workers[1].respond({ type: 'parsed', id: 3, value: 'second' })
    expect(harness.workers[0].terminated).toBe(true)
    expect(harness.parsed).toEqual(['first.hex:first', 'second.hex:second'])
    expect(harness.manager.calculating.value).toBe(false)

    harness.workers[0].respond({ type: 'calculated', id: 2, value: 'stale' })
    expect(harness.calculated).toEqual([])
  })

  it('distinguishes pending Worker failures with and without a current file', () => {
    const harness = createHarness()
    harness.manager.parseFile(file('first.hex'))
    harness.workers[0].fail()
    expect(harness.pendingWorkerErrors).toEqual([false])

    harness.manager.parseFile(file('current.hex'))
    harness.workers[1].respond({ type: 'parsed', id: 2, value: 'current' })
    harness.manager.parseFile(file('replacement.hex'))
    harness.workers[2].fail()
    expect(harness.pendingWorkerErrors).toEqual([false, true])
    expect(harness.workers[1].terminated).toBe(false)
  })

  it('terminates active and pending Workers and ignores late responses', () => {
    const harness = createHarness()
    harness.manager.parseFile(file('first.hex'))
    harness.workers[0].respond({ type: 'parsed', id: 1, value: 'first' })
    harness.manager.parseFile(file('second.hex'))
    harness.manager.destroyWorkers()

    expect(harness.workers.every((worker) => worker.terminated)).toBe(true)
    harness.workers[1].respond({ type: 'parsed', id: 2, value: 'late' })
    expect(harness.parsed).toEqual(['first.hex:first'])
    expect(harness.manager.parsing.value).toBe(false)
    expect(harness.manager.calculating.value).toBe(false)
  })

  it('reports Worker construction failure without entering a busy state', () => {
    const pendingWorkerErrors: boolean[] = []
    const manager = useTransactionalFileWorker<Record<string, unknown>, TestResponse>({
      createWorker: () => { throw new Error('unsupported') },
      onParsed: vi.fn(),
      onCalculated: vi.fn(),
      onParseError: vi.fn(),
      onCalculationError: vi.fn(),
      onPendingWorkerError: (hasCurrentFile) => pendingWorkerErrors.push(hasCurrentFile),
      onActiveWorkerError: vi.fn(),
    })

    expect(manager.parseFile(file('first.hex'))).toBe(false)
    expect(pendingWorkerErrors).toEqual([false])
    expect(manager.parsing.value).toBe(false)
  })
})