# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""This library manages the interfaces to the signer for update payloads."""

from __future__ import print_function

import logging
import os
import re
import shutil
import tempfile
import time
import threading

from chromite.lib import cros_build_lib
from chromite.lib import gs
from chromite.lib.paygen import gslock
from chromite.lib.paygen import gspaths
from chromite.lib.paygen import utils


# How long to sleep between polling GS to see if signer results are present.
DELAY_CHECKING_FOR_SIGNER_RESULTS_SECONDS = 10

# Signer priority value, slightly higher than the common value 50.
SIGNER_PRIORITY = 45


class SignerPayloadsClientGoogleStorage(object):
  """This class implements the Google Storage signer interface for payloads."""

  def __init__(self, channel, board, version, bucket=None, unique=None,
               ctx=None):
    """This initializer identifies the build an payload that need signatures.

    Args:
      channel: Channel of the build whose payload is being signed.
      board: Board of the build whose payload is being signed.
      version: Version of the build whose payload is being signed.
      bucket: Bucket used to reach the signer. [defaults 'chromeos-releases']
      unique: Force known 'unique' id. Mostly for unittests.
      ctx: GS Context to use for GS operations.
    """
    self.channel = channel
    self.board = board
    self.version = version
    self.bucket = bucket if bucket else gspaths.ChromeosReleases.BUCKET
    self._ctx = ctx if ctx is not None else gs.GSContext()

    build_signing_uri = gspaths.ChromeosReleases.BuildPayloadsSigningUri(
        channel,
        board,
        version,
        bucket=bucket)

    # Uniquify the directory using our pid/thread-id. This can't collide
    # with other hosts because the build is locked to our host in
    # paygen_build.
    if unique is None:
      unique = '%d-%d' % (os.getpid(), threading.current_thread().ident)

    # This is a partial URI that is extended for a lot of other URIs we use.
    self.signing_base_dir = os.path.join(build_signing_uri, unique)

    self.archive_uri = os.path.join(self.signing_base_dir,
                                    'payload.hash.tar.bz2')

  def _CleanSignerFilesByKeyset(self, hashes, keyset, timeout=600):
    """Helper method that cleans up GS files associated with a single keyset.

    Args:
      hashes: A list of hash values to be signed by the signer in string
              format. They are all expected to be 32 bytes in length.
      keyset: keyset to have the hashes signed with.
      timeout: Timeout for acquiring the lock on the files to clean.

    Raises:
      gslock.LockNotAcquired if we can't get a lock on the data within timeout.
    """
    hash_names = self._CreateHashNames(len(hashes))

    instructions_uri = self._CreateInstructionsURI(keyset)
    request_uri = self._SignerRequestUri(instructions_uri)
    signature_uris = self._CreateSignatureURIs(hash_names, keyset)

    paths = [instructions_uri, request_uri]
    paths += signature_uris
    paths += [s + '.md5' for s in signature_uris]

    end_time = time.time() + timeout

    while True:
      try:
        with gslock.Lock(request_uri + '.lock'):
          for path in paths:
            self._ctx.Remove(path, ignore_missing=True)

          return
      except gslock.LockNotAcquired:
        # If we have timed out.
        if time.time() > end_time:
          raise

        time.sleep(DELAY_CHECKING_FOR_SIGNER_RESULTS_SECONDS)

  def _CleanSignerFiles(self, hashes, keysets):
    """Helper method that cleans up all GS files associated with a signing.

    Safe to call repeatedly.

    Args:
      hashes: A list of hash values to be signed by the signer in string
              format. They are all expected to be 32 bytes in length.
      keysets: list of keysets to have the hashes signed with.

    Raises:
      May raise GSLibError if there is an extraordinary GS problem.
    """
    for keyset in keysets:
      self._CleanSignerFilesByKeyset(hashes, keyset)

    # After all keysets have been cleaned up, clean up the archive.
    self._ctx.Remove(self.signing_base_dir, recursive=True, ignore_missing=True)

  def _CreateInstructionsURI(self, keyset):
    """Construct the URI used to upload a set of instructions.

    Args:
      keyset: name of the keyset contained in this instruction set.

    Result:
      URI for the given instruction set as a string.
    """
    return os.path.join(self.signing_base_dir,
                        '%s.payload.signer.instructions' % keyset)

  def _CreateHashNames(self, hash_count):
    """Helper method that creates file names for each hash in GS.

    These names are arbitrary, and only used when working with the signer.

    Args:
      hash_count: How many hash names are needed?
    """
    result = []
    for i in xrange(1, hash_count + 1):
      result.append('%d.payload.hash' % i)
    return result

  def _CreateSignatureURIs(self, hash_names, keyset):
    """Helper method that creates URIs for the signature output files.

    These names are the actual URIs the signer will populate with ".bin"
    already included.

    Args:
      hash_names: The list of input_names passed to the signer.
      keyset: Keyset name passed to the signer.
    Result:
      List of URIs expected back from the signer.
    """
    result = []
    for hash_name in hash_names:
      # Based on the pattern defined in _CreateInstructions.
      expanded_name = '%s.%s.signed.bin' % (hash_name, keyset)
      result.append(os.path.join(self.signing_base_dir, expanded_name))
    return result

  def _CreateArchive(self, archive_file, hashes, hash_names):
    """Take the hash strings and bundle them in the signer request format.

    Take the contents of an array of strings, and put them into a specified
    file in .tar.bz2 format. Each string is named with a specified name in
    the tar file.

    The number of hashes and number of hash_names must be equal. The
    archive_file will be created or overridden as needed. It's up to
    the caller to ensure it's cleaned up.

    Args:
      archive_file: Name of file to put the tar contents into.
      hashes: List of hashes to sign, stored in strings.
      hash_names: File names expected in the signer request.
    """
    try:
      tmp_dir = tempfile.mkdtemp()

      # Copy hash files into tmp_dir with standard hash names.
      for h, hash_name in zip(hashes, hash_names):
        with open(os.path.join(tmp_dir, hash_name), 'wb') as f:
          f.write(h)

      cmd = ['tar', '-cjf', archive_file] + hash_names
      utils.RunCommand(cmd,
                       redirect_stdout=True,
                       redirect_stderr=True,
                       cwd=tmp_dir)
    finally:
      # Cleanup.
      shutil.rmtree(tmp_dir)

  def _CreateInstructions(self, hash_names, keyset):
    """Create the signing instructions to send to the signer.

    Args:
      hash_names: The names of the hash files in the archive to sign.
      keyset: Which keyset to sign the hashes with. Valid keysets are
              defined on the signer. 'update_signer' is currently valid.

    Returns:
      A string that contains the contents of the instructions to send.
    """

    pattern = """
# Auto-generated instruction file for signing payload hashes.

[insns]
generate_metadata = false
keyset = %(keyset)s
channel = %(channel)s

input_files = %(input_files)s
output_names = @BASENAME@.@KEYSET@.signed

[general]
archive = metadata-disable.instructions
type = update_payload
board = %(board)s

archive = %(archive_name)s

# We reuse version for version rev because we may not know the
# correct versionrev "R24-1.2.3"
version = %(version)s
versionrev = %(version)s
"""

    # foo-channel -> foo
    channel = self.channel.replace('-channel', '')

    archive_name = os.path.basename(self.archive_uri)
    input_files = ' '.join(hash_names)

    return pattern % {
        'channel': channel,
        'board': self.board,
        'version': self.version,
        'archive_name': archive_name,
        'input_files': input_files,
        'keyset': keyset,
    }

  def _SignerRequestUri(self, instructions_uri):
    """Find the URI of the empty file to create to ask the signer to sign."""

    exp = r'^gs://%s/(?P<postbucket>.*)$' % self.bucket
    m = re.match(exp, instructions_uri)
    relative_uri = m.group('postbucket')

    return 'gs://%s/tobesigned/%d,%s' % (
        self.bucket,
        SIGNER_PRIORITY,
        relative_uri.replace('/', ','))

  def _WaitForSignatures(self, signature_uris, timeout=1800):
    """Wait until all uris exist, or timeout.

    Args:
      signature_uris: list of uris to check for.
      timeout: time in seconds to wait for all uris to be created.

    Returns:
      True if the signatures all exist, or False.
    """
    end_time = time.time() + timeout

    missing_signatures = signature_uris[:]

    while missing_signatures and time.time() < end_time:
      while missing_signatures and self._ctx.Exists(missing_signatures[0]):
        missing_signatures.pop(0)

      if missing_signatures:
        time.sleep(DELAY_CHECKING_FOR_SIGNER_RESULTS_SECONDS)

    # If none are missing, we found them all.
    return not missing_signatures

  def _DownloadSignatures(self, signature_uris):
    """Download the list of URIs to in-memory strings.

    Args:
      signature_uris: List of URIs to download.

    Returns:
      List of signatures in strings.
    """

    results = []
    for uri in signature_uris:
      with tempfile.NamedTemporaryFile(delete=False) as sig_file:
        sig_file_name = sig_file.name
      try:
        self._ctx.Copy(uri, sig_file_name)
        with open(sig_file_name) as sig_file:
          results.append(sig_file.read())
      finally:
        # Cleanup the temp file, in case it's still there.
        if os.path.exists(sig_file_name):
          os.remove(sig_file_name)

    return results

  def GetHashSignatures(self, hashes, keysets=('update_signer',)):
    """Take an arbitrary list of hash files, and get them signed.

    Args:
      hashes: A list of hash values to be signed by the signer in string
              format. They are all expected to be 32 bytes in length.
      keysets: list of keysets to have the hashes signed with. The default
               is almost certainly what you want. These names must match
               valid keysets on the signer.

    Returns:
      A dictionary keyed by hash with a list of signatures in string format.
      The list of signatures will correspond to the list of keysets passed
      in.

      hashes, keysets=['update_signer', 'update_signer-v2'] ->

      { hashes[0] : [sig_update_signer, sig_update_signer-v2], ... }

      Returns None if the process failed.

    Raises:
      Can raise a variety of GSLibError errors in extraordinary conditions.
    """

    try:
      # Hash and signature names.
      hash_names = self._CreateHashNames(len(hashes))

      # Create and upload the archive of hashes to sign.
      with tempfile.NamedTemporaryFile() as archive_file:
        self._CreateArchive(archive_file.name, hashes, hash_names)
        self._ctx.Copy(archive_file.name, self.archive_uri)

      # [sig_uri, ...]
      all_signature_uris = []

      # { hash : [sig_uri, ...], ... }
      hash_signature_uris = dict([(h, []) for h in hashes])

      # Upload one signing instruction file and signing request for
      # each keyset.
      for keyset in keysets:
        instructions_uri = self._CreateInstructionsURI(keyset)

        self._ctx.CreateWithContents(
            instructions_uri,
            self._CreateInstructions(hash_names, keyset))

        # Create signer request file with debug friendly contents.
        self._ctx.CreateWithContents(
            self._SignerRequestUri(instructions_uri),
            cros_build_lib.MachineDetails())

        # Remember which signatures we just requested.
        uris = self._CreateSignatureURIs(hash_names, keyset)

        all_signature_uris += uris
        for h, sig_uri in zip(hashes, uris):
          hash_signature_uris[h].append(sig_uri)

      # Wait for the signer to finish all keysets.
      if not self._WaitForSignatures(all_signature_uris):
        logging.error('Signer request timed out.')
        return None

      # Download the results.
      return [self._DownloadSignatures(hash_signature_uris[h]) for h in hashes]

    finally:
      # Clean up the signature related files from this run.
      self._CleanSignerFiles(hashes, keysets)