import { exec } from 'node:child_process'
import {
  copyFileSync,
  existsSync,
  readFileSync,
  readdirSync,
  renameSync,
  writeFileSync
} from 'node:fs'
import { join } from 'node:path'
import { promisify } from 'node:util'
import { parseVdf, stringifyVdf, type VdfNode } from './vdf'
import { getSteamPath } from './steam'

const execAsync = promisify(exec)

export async function isSteamRunning(): Promise<boolean> {
  try {
    const { stdout } = await execAsync(
      'tasklist /FI "IMAGENAME eq steam.exe" /FO CSV /NH',
      { windowsHide: true }
    )
    return /steam\.exe/i.test(stdout)
  } catch {
    return false
  }
}

async function getLocalConfigPaths(): Promise<string[]> {
  const steamPath = await getSteamPath()
  if (!steamPath) return []
  const userdataDir = join(steamPath, 'userdata')
  if (!existsSync(userdataDir)) return []
  let entries: string[] = []
  try {
    entries = readdirSync(userdataDir)
  } catch {
    return []
  }
  const paths: string[] = []
  for (const entry of entries) {
    if (!/^\d+$/.test(entry) || entry === '0') continue
    const p = join(userdataDir, entry, 'config', 'localconfig.vdf')
    if (existsSync(p)) paths.push(p)
  }
  return paths
}

function findKey(node: VdfNode, target: string): string | undefined {
  const lower = target.toLowerCase()
  for (const k of Object.keys(node)) {
    if (k.toLowerCase() === lower) return k
  }
  return undefined
}

function findCaseInsensitive(
  node: VdfNode,
  ...keys: string[]
): VdfNode | undefined {
  let cur: VdfNode = node
  for (const key of keys) {
    const found: string | undefined = findKey(cur, key)
    if (!found) return undefined
    const value: string | VdfNode = cur[found]
    if (typeof value !== 'object') return undefined
    cur = value
  }
  return cur
}

function findOrCreatePath(node: VdfNode, ...keys: string[]): VdfNode {
  let cur: VdfNode = node
  for (const key of keys) {
    const found: string | undefined = findKey(cur, key)
    if (found && typeof cur[found] === 'object') {
      cur = cur[found] as VdfNode
    } else {
      if (found) delete cur[found]
      cur[key] = {}
      cur = cur[key] as VdfNode
    }
  }
  return cur
}

function getAppNode(
  parsed: VdfNode,
  appId: string,
  create: boolean
): VdfNode | undefined {
  if (create) {
    const apps = findOrCreatePath(
      parsed,
      'UserLocalConfigStore',
      'Software',
      'Valve',
      'Steam',
      'apps'
    )
    if (typeof apps[appId] !== 'object') apps[appId] = {}
    return apps[appId] as VdfNode
  }
  const apps = findCaseInsensitive(
    parsed,
    'UserLocalConfigStore',
    'Software',
    'Valve',
    'Steam',
    'apps'
  )
  if (!apps) return undefined
  const v = apps[appId]
  return typeof v === 'object' ? v : undefined
}

function writeBackup(path: string): void {
  try {
    const bak = path + '.exr.bak'
    if (!existsSync(bak)) copyFileSync(path, bak)
  } catch {
    // best-effort
  }
}

async function atomicWrite(path: string, contents: string): Promise<void> {
  // Write to temp then rename (atomic on Windows for same directory). Retry a
  // few times on transient EBUSY/EPERM (AV scanners and OneDrive sometimes
  // hold a handle briefly during a Steam config rewrite).
  //
  // Раньше тут был busy-loop sleep — Steam-конфиги пишутся редко, но из main
  // process, и при попадании на занятый файл (Steam ещё держит handle) морозили
  // весь UI на 250мс. Заменили на async setTimeout-sleep.
  const tmp = path + '.exr.tmp'
  const delays = [0, 50, 200]
  let lastErr: unknown
  for (const delay of delays) {
    if (delay > 0) await new Promise<void>((r) => setTimeout(r, delay))
    try {
      writeFileSync(tmp, contents, 'utf-8')
      renameSync(tmp, path)
      return
    } catch (e) {
      lastErr = e
    }
  }
  throw lastErr
}

async function modifyLaunchOptions(
  configPath: string,
  appId: string,
  fn: (current: string) => string | null
): Promise<boolean> {
  let raw: string
  try {
    raw = readFileSync(configPath, 'utf-8')
  } catch {
    return false
  }
  let parsed: VdfNode
  try {
    parsed = parseVdf(raw)
  } catch {
    return false
  }

  // Read existing
  const app = getAppNode(parsed, appId, false)
  const loKey = app
    ? Object.keys(app).find((k) => k.toLowerCase() === 'launchoptions')
    : undefined
  const existing = app && loKey ? String(app[loKey] ?? '') : ''

  const next = fn(existing)
  if (next === null) return false
  if (next === existing) return true

  const targetApp = getAppNode(parsed, appId, true)!
  // Remove any existing variant of the key to keep canonical name.
  for (const k of Object.keys(targetApp)) {
    if (k.toLowerCase() === 'launchoptions') delete targetApp[k]
  }
  if (next.length > 0) {
    targetApp['LaunchOptions'] = next
  }

  writeBackup(configPath)
  try {
    await atomicWrite(configPath, stringifyVdf(parsed))
  } catch {
    return false
  }
  return true
}

export async function isLaunchOptionPresent(
  appId: string,
  option: string
): Promise<boolean> {
  const paths = await getLocalConfigPaths()
  for (const p of paths) {
    try {
      const raw = readFileSync(p, 'utf-8')
      const parsed = parseVdf(raw)
      const app = getAppNode(parsed, appId, false)
      if (!app) continue
      const loKey = Object.keys(app).find(
        (k) => k.toLowerCase() === 'launchoptions'
      )
      if (!loKey) continue
      const value = String(app[loKey] ?? '')
      if (value.includes(option)) return true
    } catch {
      // ignore
    }
  }
  return false
}

async function applyOptionToAllConfigs(
  appId: string,
  option: string
): Promise<void> {
  const paths = await getLocalConfigPaths()
  for (const p of paths) {
    await modifyLaunchOptions(p, appId, (current) => {
      if (current.includes(option)) return current
      return current.length > 0 ? `${current} ${option}` : option
    })
  }
}

async function removeOptionFromAllConfigs(
  appId: string,
  option: string
): Promise<void> {
  const paths = await getLocalConfigPaths()
  for (const p of paths) {
    await modifyLaunchOptions(p, appId, (current) => {
      if (!current.includes(option)) return current
      return current
        .split(/\s+/)
        .filter((tok) => tok !== option)
        .join(' ')
        .trim()
    })
  }
}

// Pending operations queue with a watcher that polls Steam and applies on exit.
type PendingOp = {
  appId: string
  option: string
  op: 'add' | 'remove'
}

const pending: PendingOp[] = []
let watchTimer: NodeJS.Timeout | null = null
let onAppliedCallback: (() => void) | null = null

export function onLaunchOptionsApplied(cb: () => void): void {
  onAppliedCallback = cb
}

export function hasPendingOperations(): boolean {
  return pending.length > 0
}

function dedupePush(op: PendingOp): void {
  // Remove conflicting entries (opposite op for same option) before adding.
  for (let i = pending.length - 1; i >= 0; i--) {
    if (pending[i].appId === op.appId && pending[i].option === op.option) {
      pending.splice(i, 1)
    }
  }
  pending.push(op)
}

function ensureWatcher(): void {
  if (watchTimer || pending.length === 0) return
  watchTimer = setInterval(() => {
    void tick()
  }, 5_000)
}

function stopWatcher(): void {
  if (watchTimer) {
    clearInterval(watchTimer)
    watchTimer = null
  }
}

async function tick(): Promise<void> {
  if (pending.length === 0) {
    stopWatcher()
    return
  }
  if (await isSteamRunning()) return
  const toApply = [...pending]
  pending.length = 0
  for (const op of toApply) {
    if (op.op === 'add') await applyOptionToAllConfigs(op.appId, op.option)
    else await removeOptionFromAllConfigs(op.appId, op.option)
  }
  stopWatcher()
  onAppliedCallback?.()
}

export type EnsureResult = 'applied' | 'queued' | 'no_user'

export async function ensureLaunchOption(
  appId: string,
  option: string
): Promise<EnsureResult> {
  if (await isLaunchOptionPresent(appId, option)) return 'applied'
  const paths = await getLocalConfigPaths()
  if (paths.length === 0) return 'no_user'
  if (await isSteamRunning()) {
    dedupePush({ appId, option, op: 'add' })
    ensureWatcher()
    return 'queued'
  }
  await applyOptionToAllConfigs(appId, option)
  return (await isLaunchOptionPresent(appId, option)) ? 'applied' : 'queued'
}

export async function ensureLaunchOptionRemoved(
  appId: string,
  option: string
): Promise<EnsureResult> {
  if (!(await isLaunchOptionPresent(appId, option))) return 'applied'
  if (await isSteamRunning()) {
    dedupePush({ appId, option, op: 'remove' })
    ensureWatcher()
    return 'queued'
  }
  await removeOptionFromAllConfigs(appId, option)
  return (await isLaunchOptionPresent(appId, option)) ? 'queued' : 'applied'
}