'use strict'

var core = require('./core')
var fs = require('fs')
var path = require('path')
var caller = require('./caller.js')
var nodeModulesPaths = require('./node-modules-paths.js')

var defaultIsFile = function isFile (file) {
  try {
    var stat = fs.statSync(file)
  } catch (e) {
    if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false
    throw e
  }
  return stat.isFile() || stat.isFIFO()
}

module.exports = function (x, options) {
  if (typeof x !== 'string') {
    throw new TypeError('Path must be a string.')
  }
  var opts = options || {}
  var isFile = opts.isFile || defaultIsFile
  var readFileSync = opts.readFileSync || fs.readFileSync

  var extensions = opts.extensions || ['.js']
  var basedir = opts.basedir || path.dirname(caller())

  opts.paths = opts.paths || []

  if (/^(?:\.\.?(?:\/|$)|\/|([A-Za-z]:)?[/\\])/.test(x)) {
    var res = path.resolve(basedir, x)
    if (x === '..' || x.slice(-1) === '/') res += '/'
    var m = loadAsFileSync(res) || loadAsDirectorySync(res)
    if (m) return m
  } else {
    var n = loadNodeModulesSync(x, basedir)
    if (n) return n
  }

  if (core[x]) return x

  var err = new Error("Cannot find module '" + x + "' from '" + basedir + "'")
  err.code = 'MODULE_NOT_FOUND'
  throw err

  function loadAsFileSync (x) {
    var pkg = loadpkg(path.dirname(x))

    if (pkg && pkg.dir && pkg.pkg && opts.pathFilter) {
      var rfile = path.relative(pkg.dir, x)
      var r = opts.pathFilter(pkg.pkg, x, rfile)
      if (r) {
        x = path.resolve(pkg.dir, r) // eslint-disable-line no-param-reassign
      }
    }

    if (isFile(x)) {
      return x
    }

    for (var i = 0; i < extensions.length; i++) {
      var file = x + extensions[i]
      if (isFile(file)) {
        return file
      }
    }
  }

  function loadpkg (dir) {
    if (dir === '' || dir === '/') return
    if (process.platform === 'win32' && (/^\w:[/\\]*$/).test(dir)) {
      return
    }
    if (/[/\\]node_modules[/\\]*$/.test(dir)) return

    var pkgfile = path.join(dir, 'package.json')

    if (!isFile(pkgfile)) {
      return loadpkg(path.dirname(dir))
    }

    var body = readFileSync(pkgfile)

    try {
      var pkg = JSON.parse(body)
    } catch (jsonErr) { }

    if (pkg && opts.packageFilter) {
      pkg = opts.packageFilter(pkg, dir)
    }

    return { pkg: pkg, dir: dir }
  }

  function loadAsDirectorySync (x) {
    var pkgfile = path.join(x, '/package.json')
    if (isFile(pkgfile)) {
      try {
        var body = readFileSync(pkgfile, 'UTF8')
        var pkg = JSON.parse(body)

        if (opts.packageFilter) {
          pkg = opts.packageFilter(pkg, x)
        }

        if (pkg.main) {
          if (pkg.main === '.' || pkg.main === './') {
            pkg.main = 'index'
          }
          var m = loadAsFileSync(path.resolve(x, pkg.main))
          if (m) return m
          var n = loadAsDirectorySync(path.resolve(x, pkg.main))
          if (n) return n
        }
      } catch (e) { }
    }

    return loadAsFileSync(path.join(x, '/index'))
  }

  function loadNodeModulesSync (x, start) {
    var dirs = nodeModulesPaths(start, opts)
    for (var i = 0; i < dirs.length; i++) {
      var dir = dirs[i]
      var m = loadAsFileSync(path.join(dir, '/', x))
      if (m) return m
      var n = loadAsDirectorySync(path.join(dir, '/', x))
      if (n) return n
    }
  }
}
