import { execFile } from 'node:child_process'
import { existsSync } from 'node:fs'
import { fileURLToPath } from 'node:url'
import { promisify } from 'node:util'
import { describe, expect, it } from 'vitest'
import { logTruncationMarker, WIRE_FRAME_FIELDS } from '../src/protocol.ts'

/**
 * Cross-language mirror check between `src/protocol.ts` and `py/protocol.py`,
 * spawning a real `python3` to read the Python side. Two things are asserted:
 * the runtime surfaces both sides EXECUTE against — `PROTOCOL_FD` and the log
 * truncation marker text, where a drift silently corrupts a live run — and the
 * per-frame wire field sets (required/optional keys of each `TypedDict`), which
 * turns the otherwise review-only shape mirror into an executable check that
 * catches the round-12 kind of drift (a renamed/dropped field, or one side
 * making a field optional the other requires). Self-skips when no `python3` is
 * on PATH — CI provides one; the pure-TS `protocol.spec.ts` covers the host
 * codec unconditionally.
 */

const execFileAsync = promisify(execFile)
const pyDir = fileURLToPath(new URL('../py', import.meta.url))

async function hasPython3(): Promise<boolean> {
  try {
    await execFileAsync('python3', ['--version'])
    return true
  } catch {
    return false
  }
}

const python3Available = await hasPython3()

describe.skipIf(!python3Available)('protocol.py mirrors protocol.ts at runtime', () => {
  it('agrees on PROTOCOL_FD and the log truncation marker across byte budgets', async () => {
    const budgets = [1, 65536, 1048576]
    const probe = [
      'import json, sys',
      `sys.path.insert(0, ${JSON.stringify(pyDir)})`,
      'from protocol import PROTOCOL_FD, log_truncation_marker',
      `budgets = ${JSON.stringify(budgets)}`,
      'print(json.dumps({',
      '  "fd": PROTOCOL_FD,',
      '  "markers": [log_truncation_marker(b) for b in budgets],',
      '}))',
    ].join('\n')
    const { stdout } = await execFileAsync('python3', ['-I', '-c', probe])
    const seen = JSON.parse(stdout) as { fd: number; markers: string[] }
    // fd 3 is the wire contract, not a tunable: the host pins it positionally
    // when it spawns the child.
    expect(seen.fd).toBe(3)
    expect(seen.markers).toEqual(budgets.map(budget => logTruncationMarker(budget)))
  })

  it('agrees on every frame type\'s wire field set between the TS and Python declarations', async () => {
    // Turn the TypedDict mirror from a review-only obligation into an executable
    // check: read each Python TypedDict's required/optional key sets and assert
    // them against WIRE_FRAME_FIELDS — the TS-side source of truth bound to the
    // frame interfaces by `satisfies` in protocol.ts, so a rename or a removed
    // field on the TS side breaks typecheck and an added field breaks this
    // comparison (the Python side would carry it). Covers the reply frames too.
    // `global` is the reserved-keyword wire key the Python side carries via a
    // functional TypedDict. This catches the round-12 kind of drift on EITHER
    // side of the wire.
    const pyNames = Object.keys(WIRE_FRAME_FIELDS)
    const probe = [
      'import json, sys',
      `sys.path.insert(0, ${JSON.stringify(pyDir)})`,
      'import protocol as p',
      'def keys(td): return {"required": sorted(td.__required_keys__), "optional": sorted(td.__optional_keys__)}',
      `names = ${JSON.stringify(pyNames)}`,
      'print(json.dumps({n: keys(getattr(p, n)) for n in names}))',
    ].join('\n')
    const { stdout } = await execFileAsync('python3', ['-I', '-c', probe])
    const seen = JSON.parse(stdout) as Record<string, { required: string[]; optional: string[] }>
    // Normalize the TS source of truth to the same sorted shape Python reports.
    const expected = Object.fromEntries(
      Object.entries(WIRE_FRAME_FIELDS).map(([name, sets]) => [
        name,
        { required: [...sets.required].sort(), optional: [...sets.optional].sort() },
      ]),
    )
    expect(seen).toEqual(expected)
  })
})

it('names the py/ directory that ships with the package', () => {
  // Resolves py/ relative to this test file; the same directory ships in the
  // package.json `files` whitelist (`py/**/*.py`). The tests/ directory itself
  // is not published — this asserts the source-tree layout the mirror test
  // depends on, so it holds even when python3 is absent from the runner.
  expect(existsSync(pyDir)).toBe(true)
})