import { describe, expect, it } from 'bun:test'
import { readLines } from './stream.ts'

function streamOf(chunks: string[]): ReadableStream<Uint8Array> {
  const encoder = new TextEncoder()
  return new ReadableStream({
    start(controller) {
      for (const chunk of chunks) controller.enqueue(encoder.encode(chunk))
      controller.close()
    },
  })
}

async function collect(chunks: string[]): Promise<string[]> {
  const lines: string[] = []
  for await (const line of readLines(streamOf(chunks))) lines.push(line)
  return lines
}

describe('按行读流', () => {
  it('一块里有好几行就拆开', async () => {
    expect(await collect(['a\nb\nc\n'])).toEqual(['a', 'b', 'c'])
  })

  it('半行留在缓冲里，等下一块补齐', async () => {
    // 分块边界和行边界无关，这是这个模块存在的全部理由
    expect(await collect(['{"up":1,"do', 'wn":2}\n{"up":3}\n'])).toEqual([
      '{"up":1,"down":2}',
      '{"up":3}',
    ])
  })

  it('流结束时缓冲里剩的半行也交出去', async () => {
    expect(await collect(['a\nb'])).toEqual(['a', 'b'])
  })

  it('空行丢弃，\\r\\n 换行的 \\r 去掉', async () => {
    expect(await collect(['a\r\n\n\nb\n'])).toEqual(['a', 'b'])
  })

  it('多字节字符跨块也不会读坏', async () => {
    const bytes = new TextEncoder().encode('香港01\n')
    const stream = new ReadableStream<Uint8Array>({
      start(controller) {
        // 故意从「港」字中间切开
        controller.enqueue(bytes.slice(0, 4))
        controller.enqueue(bytes.slice(4))
        controller.close()
      },
    })
    const lines: string[] = []
    for await (const line of readLines(stream)) lines.push(line)
    expect(lines).toEqual(['香港01'])
  })
})