var fs = require('./fs.js')
var constants = require('constants')

var origCwd = process.cwd
var cwd = null
process.cwd = function() {
  if (!cwd)
    cwd = origCwd.call(process)
  return cwd
}
try {
  process.cwd()
} catch (er) {}

var chdir = process.chdir
process.chdir = function(d) {
  cwd = null
  chdir.call(process, d)
}

module.exports = patch

function patch (fs) {
  // (re-)implement some things that are known busted or missing.

  // lchmod, broken prior to 0.6.2
  // back-port the fix here.
  if (constants.hasOwnProperty('O_SYMLINK') &&
      process.version.match(/^v0\.6\.[0-2]|^v0\.5\./)) {
    patchLchmod(fs)
  }

  // lutimes implementation, or no-op
  if (!fs.lutimes) {
    patchLutimes(fs)
  }

  // https://github.com/isaacs/node-graceful-fs/issues/4
  // Chown should not fail on einval or eperm if non-root.
  // It should not fail on enosys ever, as this just indicates
  // that a fs doesn't support the intended operation.

  fs.chown = chownFix(fs.chown)
  fs.fchown = chownFix(fs.fchown)
  fs.lchown = chownFix(fs.lchown)

  fs.chmod = chownFix(fs.chmod)
  fs.fchmod = chownFix(fs.fchmod)
  fs.lchmod = chownFix(fs.lchmod)

  fs.chownSync = chownFixSync(fs.chownSync)
  fs.fchownSync = chownFixSync(fs.fchownSync)
  fs.lchownSync = chownFixSync(fs.lchownSync)

  fs.chmodSync = chownFix(fs.chmodSync)
  fs.fchmodSync = chownFix(fs.fchmodSync)
  fs.lchmodSync = chownFix(fs.lchmodSync)

  // if lchmod/lchown do not exist, then make them no-ops
  if (!fs.lchmod) {
    fs.lchmod = function (path, mode, cb) {
      process.nextTick(cb)
    }
    fs.lchmodSync = function () {}
  }
  if (!fs.lchown) {
    fs.lchown = function (path, uid, gid, cb) {
      process.nextTick(cb)
    }
    fs.lchownSync = function () {}
  }

  // on Windows, A/V software can lock the directory, causing this
  // to fail with an EACCES or EPERM if the directory contains newly
  // created files.  Try again on failure, for up to 1 second.
  if (process.platform === "win32") {
    fs.rename = (function (fs$rename) { return function (from, to, cb) {
      var start = Date.now()
      fs$rename(from, to, function CB (er) {
        if (er
            && (er.code === "EACCES" || er.code === "EPERM")
            && Date.now() - start < 1000) {
          return fs$rename(from, to, CB)
        }
        if (cb) cb(er)
      })
    }})(fs.rename)
  }

  // if read() returns EAGAIN, then just try it again.
  fs.read = (function (fs$read) { return function (fd, buffer, offset, length, position, callback_) {
    var callback
    if (callback_ && typeof callback_ === 'function') {
      var eagCounter = 0
      callback = function (er, _, __) {
        if (er && er.code === 'EAGAIN' && eagCounter < 10) {
          eagCounter ++
          return fs$read.call(fs, fd, buffer, offset, length, position, callback)
        }
        callback_.apply(this, arguments)
      }
    }
    return fs$read.call(fs, fd, buffer, offset, length, position, callback)
  }})(fs.read)

  fs.readSync = (function (fs$readSync) { return function (fd, buffer, offset, length, position) {
    var eagCounter = 0
    while (true) {
      try {
        return fs$readSync.call(fs, fd, buffer, offset, length, position)
      } catch (er) {
        if (er.code === 'EAGAIN' && eagCounter < 10) {
          eagCounter ++
          continue
        }
        throw er
      }
    }
  }})(fs.readSync)
}

function patchLchmod (fs) {
  fs.lchmod = function (path, mode, callback) {
    callback = callback || noop
    fs.open( path
           , constants.O_WRONLY | constants.O_SYMLINK
           , mode
           , function (err, fd) {
      if (err) {
        callback(err)
        return
      }
      // prefer to return the chmod error, if one occurs,
      // but still try to close, and report closing errors if they occur.
      fs.fchmod(fd, mode, function (err) {
        fs.close(fd, function(err2) {
          callback(err || err2)
        })
      })
    })
  }

  fs.lchmodSync = function (path, mode) {
    var fd = fs.openSync(path, constants.O_WRONLY | constants.O_SYMLINK, mode)

    // prefer to return the chmod error, if one occurs,
    // but still try to close, and report closing errors if they occur.
    var threw = true
    var ret
    try {
      ret = fs.fchmodSync(fd, mode)
      threw = false
    } finally {
      if (threw) {
        try {
          fs.closeSync(fd)
        } catch (er) {}
      } else {
        fs.closeSync(fd)
      }
    }
    return ret
  }
}

function patchLutimes (fs) {
  if (constants.hasOwnProperty("O_SYMLINK")) {
    fs.lutimes = function (path, at, mt, cb) {
      fs.open(path, constants.O_SYMLINK, function (er, fd) {
        cb = cb || noop
        if (er) return cb(er)
        fs.futimes(fd, at, mt, function (er) {
          fs.close(fd, function (er2) {
            return cb(er || er2)
          })
        })
      })
    }

    fs.lutimesSync = function (path, at, mt) {
      var fd = fs.openSync(path, constants.O_SYMLINK)
      var ret
      var threw = true
      try {
        ret = fs.futimesSync(fd, at, mt)
        threw = false
      } finally {
        if (threw) {
          try {
            fs.closeSync(fd)
          } catch (er) {}
        } else {
          fs.closeSync(fd)
        }
      }
      return ret
    }

  } else {
    fs.lutimes = function (_a, _b, _c, cb) { process.nextTick(cb) }
    fs.lutimesSync = function () {}
  }
}

function chownFix (orig) {
  if (!orig) return orig
  return function (target, uid, gid, cb) {
    return orig.call(fs, target, uid, gid, function (er, res) {
      if (chownErOk(er)) er = null
      cb(er, res)
    })
  }
}

function chownFixSync (orig) {
  if (!orig) return orig
  return function (target, uid, gid) {
    try {
      return orig.call(fs, target, uid, gid)
    } catch (er) {
      if (!chownErOk(er)) throw er
    }
  }
}

// ENOSYS means that the fs doesn't support the op. Just ignore
// that, because it doesn't matter.
//
// if there's no getuid, or if getuid() is something other
// than 0, and the error is EINVAL or EPERM, then just ignore
// it.
//
// This specific case is a silent failure in cp, install, tar,
// and most other unix tools that manage permissions.
//
// When running as root, or if other types of errors are
// encountered, then it's strict.
function chownErOk (er) {
  if (!er)
    return true

  if (er.code === "ENOSYS")
    return true

  var nonroot = !process.getuid || process.getuid() !== 0
  if (nonroot) {
    if (er.code === "EINVAL" || er.code === "EPERM")
      return true
  }

  return false
}