import crypto from 'node:crypto'
import fs from 'node:fs'
import path from 'node:path'

// ── Windows VC++ runtime for the managed Python ─────────────────────────────
//
// Voice features load native wheels (onnxruntime for the wake word,
// ctranslate2 for local speech-to-text) that link against msvcp140.dll and
// msvcp140_1.dll. The managed CPython only ships vcruntime140*.dll, so on a
// Windows install without the system-wide VC++ Redistributable those imports
// fail with "DLL load failed / The specified module could not be found".
//
// The desktop package carries the Microsoft-signed VC143 CRT set and copies it
// next to the managed python.exe before every local backend start. That
// directory is the process image directory, which Windows searches first for
// extension-module dependencies, so a stale msvcp140.dll elsewhere on PATH can
// never win. Existing installs are healed on their next launch.

export interface VcRuntimeFile {
  name: string
  size: number
  sha256: string
  // Files the managed CPython already ships. Never overwrite an existing copy:
  // the interpreter owns it and replacing a loaded DLL is not possible anyway.
  ownedByPython?: boolean
}

export interface VcRuntimeManifest {
  schemaVersion: 1
  version: string
  architecture: string
  files: VcRuntimeFile[]
}

export type VcRuntimeResult =
  | { status: 'skipped'; reason: string }
  | { status: 'ok' | 'repaired'; pythonHome: string; copied: string[] }
  | { status: 'failed'; pythonHome: string | null; copied: string[]; error: string }

const FILE_NAME_RE = /^[a-z0-9_]+\.dll$/i
const SHA256_RE = /^[0-9a-f]{64}$/

export function readPythonHome(venvRoot: string): string | null {
  let text: string

  try {
    text = fs.readFileSync(path.join(venvRoot, 'pyvenv.cfg'), 'utf8')
  } catch {
    return null
  }

  for (const line of text.split(/\r?\n/)) {
    const match = /^\s*home\s*=\s*(.+?)\s*$/i.exec(line)

    if (match) {
      return match[1]
    }
  }

  return null
}

export function loadVcRuntimeManifest(sourceDir: string): VcRuntimeManifest {
  const manifest = JSON.parse(fs.readFileSync(path.join(sourceDir, 'manifest.json'), 'utf8'))

  if (manifest?.schemaVersion !== 1 || !Array.isArray(manifest.files) || manifest.files.length === 0) {
    throw new Error('invalid VC++ runtime manifest')
  }

  for (const file of manifest.files) {
    if (!FILE_NAME_RE.test(file?.name) || !SHA256_RE.test(file?.sha256) || !Number.isInteger(file?.size)) {
      throw new Error(`invalid VC++ runtime manifest entry: ${JSON.stringify(file?.name)}`)
    }
  }

  return manifest
}

function sha256File(filePath: string): string {
  return crypto.createHash('sha256').update(fs.readFileSync(filePath)).digest('hex')
}

function matches(filePath: string, file: VcRuntimeFile): boolean {
  try {
    return fs.statSync(filePath).size === file.size && sha256File(filePath) === file.sha256
  } catch {
    return false
  }
}

function installFile(sourceDir: string, pythonHome: string, file: VcRuntimeFile) {
  const source = path.join(sourceDir, file.name)

  if (!matches(source, file)) {
    throw new Error(`bundled ${file.name} does not match its manifest digest`)
  }

  const target = path.join(pythonHome, file.name)
  const temp = `${target}.aiturk-${process.pid}.tmp`

  try {
    fs.copyFileSync(source, temp)

    if (!matches(temp, file)) {
      throw new Error(`copied ${file.name} failed digest verification`)
    }

    fs.renameSync(temp, target)
  } finally {
    fs.rmSync(temp, { force: true })
  }
}

export function ensureWindowsVcRuntime({
  platform,
  venvRoot,
  sourceDir
}: {
  platform: NodeJS.Platform
  venvRoot: string
  sourceDir: string
}): VcRuntimeResult {
  if (platform !== 'win32') {
    return { status: 'skipped', reason: 'not windows' }
  }

  const pythonHome = readPythonHome(venvRoot)

  if (!pythonHome || !fs.existsSync(path.join(pythonHome, 'python.exe'))) {
    return { status: 'failed', pythonHome, copied: [], error: 'managed python home not found' }
  }

  const copied: string[] = []

  try {
    const manifest = loadVcRuntimeManifest(sourceDir)

    for (const file of manifest.files) {
      const target = path.join(pythonHome, file.name)

      if (file.ownedByPython ? fs.existsSync(target) : matches(target, file)) {
        continue
      }

      installFile(sourceDir, pythonHome, file)
      copied.push(file.name)
    }
  } catch (error) {
    return { status: 'failed', pythonHome, copied, error: error instanceof Error ? error.message : String(error) }
  }

  return { status: copied.length ? 'repaired' : 'ok', pythonHome, copied }
}

export function describeVcRuntimeResult(result: VcRuntimeResult): string {
  if (result.status === 'skipped') {
    return `skipped (${result.reason})`
  }

  if (result.status === 'failed') {
    return `failed for ${result.pythonHome ?? 'unknown python home'}: ${result.error}` +
      (result.copied.length ? ` (copied before failure: ${result.copied.join(', ')})` : '')
  }

  return result.status === 'repaired'
    ? `installed ${result.copied.join(', ')} into ${result.pythonHome}`
    : `verified in ${result.pythonHome}`
}