import { readFileSync } from 'fs'
import { describe, expect, it } from 'vitest'

const readClientFile = (path: string) => readFileSync(`packages/client/src/${path}`, 'utf8')

// 从 `computed(` 的左括号开始做括号配平，精确切出这个表达式的范围。
// 用空行切分不行：箭头函数写成单行后，紧邻的下一个顶层声明只隔一个空行。
function balancedBlock(source: string, header: string): string {
  const start = source.indexOf(header)
  expect(start, `${header} not found`).toBeGreaterThan(-1)

  let depth = 0
  for (let i = start + header.length - 1; i < source.length; i += 1) {
    if (source[i] === '(') depth += 1
    if (source[i] === ')') {
      depth -= 1
      if (depth === 0) return source.slice(start, i + 1)
    }
  }
  return source.slice(start)
}

// known-issues #1: `providerOptions` 的 computed getter 内部给 customProvider
// 赋值。用户手动挑好的 provider 会被下一次 getter 重算无声改回去，表现为
// 「自己跳」。修法是把同步移进 watch，让 getter 恢复成纯读。
describe('ModelSelector provider selection', () => {
  it('keeps the providerOptions getter free of side effects', () => {
    const source = readClientFile('components/layout/ModelSelector.vue')
    const block = balancedBlock(source, 'const providerOptions = computed(')

    expect(block).not.toContain('customProvider.value =')
  })

  it('syncs customProvider from the store through a watch', () => {
    const source = readClientFile('components/layout/ModelSelector.vue')
    const block = balancedBlock(source, 'watch(')

    // 同步点必须挂在 selectedProvider 上，而不是挂在 providerOptions 上 ——
    // 后者等于把同一个副作用换个地方写一遍。
    expect(block.slice(0, 200)).toContain('appStore.selectedProvider')
    expect(block).toContain('customProvider.value =')
  })

  it('still initialises the provider when the picker opens', () => {
    // watch 是懒的：不会在初始渲染时触发。openModal 的这一次赋值是首帧
    // 唯一来源，不能跟着一起去掉。
    const source = readClientFile('components/layout/ModelSelector.vue')

    expect(source).toMatch(/function openModal\(\)[\s\S]*?customProvider\.value = appStore\.selectedProvider/)
  })
})