import { execFileSync } from 'node:child_process'
import fs from 'node:fs'
import path from 'node:path'

/**
 * Regenerates src/services/contract.ts from the backend wire contract.
 * Source of truth: `cargo run -p clash-verge --bin frontend-contract` inside
 * src-tauri, which serializes the same enum variants and event payloads the
 * app emits at runtime. CI reruns this and fails on a non-empty diff.
 */

const ROOT = path.resolve(import.meta.dirname, '..')
const OUT = path.join(ROOT, 'src/services/contract.ts')

const contract = JSON.parse(
  execFileSync(
    'cargo',
    ['run', '-p', 'clash-verge', '--bin', 'frontend-contract', '-q'],
    {
      cwd: path.join(ROOT, 'src-tauri'),
      encoding: 'utf8',
      maxBuffer: 16 * 1024 * 1024,
    },
  ),
)

if (contract.version !== 1) {
  throw new Error(`unsupported wire contract version: ${contract.version}`)
}

/** TS type per event, derived from the serialized sample payload's JSON shape. */
const payloadType = (name, sample) => {
  if (sample === null) return 'null'
  if (typeof sample === 'string') return 'string'
  if (Array.isArray(sample)) {
    if (name === 'verge://notice-message') return '[NoticeStatus, string]'
    throw new Error(`unexpected array payload for ${name}`)
  }
  if (typeof sample === 'object') {
    const keys = Object.keys(sample)
    if (keys.length === 1 && keys[0] === 'uid') return '{ uid: string }'
    if (name === 'verge://run-state-changed') return 'RunState'
    throw new Error(`unexpected object payload for ${name}: ${keys.join(',')}`)
  }
  throw new Error(`unexpected payload for ${name}`)
}

const needsRunState = contract.events.some(
  (e) => e.name === 'verge://run-state-changed',
)
if (!needsRunState)
  throw new Error('run-state-changed event missing from contract')

const lines = []
lines.push(
  '// @generated by scripts/gen-contract.mjs from the backend wire contract. DO NOT EDIT.',
)
lines.push('// Regen: pnpm gen:contract')
lines.push('')
lines.push("import type { RunState } from './cmds'")
lines.push('')
lines.push(
  '/** Wire status strings from NoticeStatus; keep in sync via `pnpm gen:contract`. */',
)
lines.push('export type NoticeStatus =')
for (const status of contract.noticeStatuses) {
  lines.push(`  | ${JSON.stringify(status)}`)
}
lines.push('')
lines.push('/** Event name → payload type for every backend-emitted event. */')
lines.push('export interface VergeEventPayloads {')
for (const event of contract.events) {
  const key = JSON.stringify(event.name)
  lines.push(`  ${key}: ${payloadType(event.name, event.sample)}`)
}
lines.push('}')
lines.push('')

const content = `${lines.join('\n')}\n`
fs.writeFileSync(OUT, content)

// Match the repo's biome style so CI parity (`git diff --exit-code`) is stable.
execFileSync(
  process.platform === 'win32' ? 'pnpm.cmd' : 'pnpm',
  ['exec', 'biome', 'format', '--write', path.relative(ROOT, OUT)],
  { cwd: ROOT, stdio: 'ignore' },
)

console.log(
  `[gen-contract] wrote ${path.relative(ROOT, OUT)}: ${contract.events.length} events, ${contract.noticeStatuses.length} statuses`,
)