/**
 * Graceful shutdown handler - registers cleanup functions and handles shutdown signals.
 */

import { SHUTDOWN_TIMEOUT_MS } from './constants.js'

const cleanupFunctions = []
const shutdownState = {
  isShuttingDown: false,
}

export function clearCleanup() {
  cleanupFunctions.length = 0
  shutdownState.isShuttingDown = false
}

export function registerCleanup(fn) {
  if (typeof fn !== 'function') throw new TypeError('Cleanup function must be a function')
  cleanupFunctions.push(fn)
}

const executeCleanupFunction = async (fn, index) => {
  try {
    await fn()
  }
  catch (error) {
    console.error(`[shutdown] Cleanup function ${index} failed:`, error?.message || String(error))
  }
}

const executeCleanupReverse = async (functions, index = functions.length - 1) => {
  if (index < 0) return
  await executeCleanupFunction(functions[index], index)
  return executeCleanupReverse(functions, index - 1)
}

async function executeCleanup() {
  if (shutdownState.isShuttingDown) return
  shutdownState.isShuttingDown = true
  await executeCleanupReverse(cleanupFunctions)
}

export async function graceful(error) {
  if (error) {
    console.error('[shutdown] Shutting down due to error:', error?.message || String(error))
    if (error.stack) console.error('[shutdown] Stack trace:', error.stack)
  }
  else {
    console.log('[shutdown] Initiating graceful shutdown')
  }
  const timeout = setTimeout(() => {
    console.error('[shutdown] Shutdown timeout exceeded, forcing exit')
    process.exit(1)
  }, SHUTDOWN_TIMEOUT_MS)
  try {
    await executeCleanup()
    clearTimeout(timeout)
    console.log('[shutdown] Cleanup complete')
    process.exit(error ? 1 : 0)
  }
  catch (err) {
    clearTimeout(timeout)
    console.error('[shutdown] Error during cleanup:', err?.message || String(err))
    process.exit(1)
  }
}

export function initShutdownHandlers() {
  for (const signal of ['SIGTERM', 'SIGINT']) {
    process.on(signal, () => {
      console.log(`[shutdown] Received ${signal}`)
      graceful().catch((err) => {
        console.error('[shutdown] Error in graceful shutdown:', err)
        process.exit(1)
      })
    })
  }
}