'use strict'

const fs = require('../fs')
const path = require('path')
const util = require('util')
const atLeastNode = require('at-least-node')

const nodeSupportsBigInt = atLeastNode('10.5.0')
const stat = (file) => nodeSupportsBigInt ? fs.stat(file, { bigint: true }) : fs.stat(file)
const statSync = (file) => nodeSupportsBigInt ? fs.statSync(file, { bigint: true }) : fs.statSync(file)

function getStats (src, dest) {
  return Promise.all([
    stat(src),
    stat(dest).catch(err => {
      if (err.code === 'ENOENT') return null
      throw err
    })
  ]).then(([srcStat, destStat]) => ({ srcStat, destStat }))
}

function getStatsSync (src, dest) {
  let destStat
  const srcStat = statSync(src)
  try {
    destStat = statSync(dest)
  } catch (err) {
    if (err.code === 'ENOENT') return { srcStat, destStat: null }
    throw err
  }
  return { srcStat, destStat }
}

function checkPaths (src, dest, funcName, cb) {
  util.callbackify(getStats)(src, dest, (err, stats) => {
    if (err) return cb(err)
    const { srcStat, destStat } = stats
    if (destStat && areIdentical(srcStat, destStat)) {
      return cb(new Error('Source and destination must not be the same.'))
    }
    if (srcStat.isDirectory() && isSrcSubdir(src, dest)) {
      return cb(new Error(errMsg(src, dest, funcName)))
    }
    return cb(null, { srcStat, destStat })
  })
}

function checkPathsSync (src, dest, funcName) {
  const { srcStat, destStat } = getStatsSync(src, dest)
  if (destStat && areIdentical(srcStat, destStat)) {
    throw new Error('Source and destination must not be the same.')
  }
  if (srcStat.isDirectory() && isSrcSubdir(src, dest)) {
    throw new Error(errMsg(src, dest, funcName))
  }
  return { srcStat, destStat }
}

// recursively check if dest parent is a subdirectory of src.
// It works for all file types including symlinks since it
// checks the src and dest inodes. It starts from the deepest
// parent and stops once it reaches the src parent or the root path.
function checkParentPaths (src, srcStat, dest, funcName, cb) {
  const srcParent = path.resolve(path.dirname(src))
  const destParent = path.resolve(path.dirname(dest))
  if (destParent === srcParent || destParent === path.parse(destParent).root) return cb()
  const callback = (err, destStat) => {
    if (err) {
      if (err.code === 'ENOENT') return cb()
      return cb(err)
    }
    if (areIdentical(srcStat, destStat)) {
      return cb(new Error(errMsg(src, dest, funcName)))
    }
    return checkParentPaths(src, srcStat, destParent, funcName, cb)
  }
  if (nodeSupportsBigInt) fs.stat(destParent, { bigint: true }, callback)
  else fs.stat(destParent, callback)
}

function checkParentPathsSync (src, srcStat, dest, funcName) {
  const srcParent = path.resolve(path.dirname(src))
  const destParent = path.resolve(path.dirname(dest))
  if (destParent === srcParent || destParent === path.parse(destParent).root) return
  let destStat
  try {
    destStat = statSync(destParent)
  } catch (err) {
    if (err.code === 'ENOENT') return
    throw err
  }
  if (areIdentical(srcStat, destStat)) {
    throw new Error(errMsg(src, dest, funcName))
  }
  return checkParentPathsSync(src, srcStat, destParent, funcName)
}

function areIdentical (srcStat, destStat) {
  if (destStat.ino && destStat.dev && destStat.ino === srcStat.ino && destStat.dev === srcStat.dev) {
    if (nodeSupportsBigInt || destStat.ino < Number.MAX_SAFE_INTEGER) {
      // definitive answer
      return true
    }
    // Use additional heuristics if we can't use 'bigint'.
    // Different 'ino' could be represented the same if they are >= Number.MAX_SAFE_INTEGER
    // See issue 657
    if (destStat.size === srcStat.size &&
        destStat.mode === srcStat.mode &&
        destStat.nlink === srcStat.nlink &&
        destStat.atimeMs === srcStat.atimeMs &&
        destStat.mtimeMs === srcStat.mtimeMs &&
        destStat.ctimeMs === srcStat.ctimeMs &&
        destStat.birthtimeMs === srcStat.birthtimeMs) {
      // heuristic answer
      return true
    }
  }
  return false
}

// return true if dest is a subdir of src, otherwise false.
// It only checks the path strings.
function isSrcSubdir (src, dest) {
  const srcArr = path.resolve(src).split(path.sep).filter(i => i)
  const destArr = path.resolve(dest).split(path.sep).filter(i => i)
  return srcArr.reduce((acc, cur, i) => acc && destArr[i] === cur, true)
}

function errMsg (src, dest, funcName) {
  return `Cannot ${funcName} '${src}' to a subdirectory of itself, '${dest}'.`
}

module.exports = {
  checkPaths,
  checkPathsSync,
  checkParentPaths,
  checkParentPathsSync,
  isSrcSubdir
}