""" Handlers for implementing v1beta2 of the taskqueue REST API. """
import json
import re

import tornado.escape
from tornado import gen
from tornado.web import MissingArgumentError, RequestHandler

from appscale.common.constants import HTTPCodes

from appscale.taskqueue.constants import QueueNotFound
from appscale.taskqueue.statistics import service_stats, stats_lock, REST_API

from .constants import TaskNotFound
from .task import InvalidTaskInfo, Task, TASK_FIELDS
from .queue import (InvalidLeaseRequest,
                    LONG_QUEUE_FORM,
                    PostgresPullQueue,
                    QUEUE_FIELDS)

# The prefix for all of the handlers of the pull queue REST API.
REST_PREFIX = '/taskqueue/v1beta2/projects/(?:.~)?([a-z0-9-]+)/taskqueues'

# Matches commas that are outside of parentheses.
FIELD_DELIMITERS_RE = re.compile(r',(?=[^)]*(?:\(|$))')

# Matches strings that only contain the URL-safe Base64 alphabet.
BASE64_CHARS_RE = re.compile(r'^[a-zA-Z0-9-_=]*$')


def parse_fields(fields_string):
  """ Converts a fields string to a tuple.

  Args:
    fields_string: A string extracted from a URL parameter.
  Returns:
    A tuple containing the fields to use. If a field contains sub-fields, it is
    represented as a dictionary.
  """
  fields = []
  for main_field in FIELD_DELIMITERS_RE.split(fields_string):
    if '(' not in main_field:
      fields.append(main_field)
      continue

    section, sub_fields = main_field.split('(')
    fields.append({section: tuple(sub_fields[:-1].split(','))})

  return tuple(fields)


def write_error(request, code, message):
  """ Sets the response headers and body for error messages.

  Args:
    request: A tornado request object.
    code: The HTTP response code.
    message: The error message to use in the body of the request.
  """
  error = {'error': {'code': code, 'message': message}}
  request.set_status(code)
  request.write(json.dumps(error))


class TrackedRequestHandler(RequestHandler):
  AREA = None

  @gen.coroutine
  def prepare(self):
    rest_method = "{}_{}".format(self.request.method, self.AREA).lower()
    with (yield stats_lock.acquire()):
      self.stats_info = service_stats.start_request()
      self.stats_info.api = REST_API
      self.stats_info.rest_method = rest_method
      self.stats_info.pb_method = None
      self.stats_info.pb_status = None
      self.stats_info.rest_status = None

  @gen.coroutine
  def on_finish(self):
    with (yield stats_lock.acquire()):
      self.stats_info.rest_status = self.get_status()
      self.stats_info.finalize()


class QueueList(TrackedRequestHandler):
  """ Provides a list of all pull queues.

  This method was never part of the v1beta2 API. """
  def initialize(self, queue_handler):
    """ Provide access to the queue handler. """
    self.queue_handler = queue_handler

  def get(self, project_id):
    """ Returns a list of existing pull queues.

    Args:
      project_id: A string specifying a project ID.
    """
    try:
      project_queues = self.queue_handler.queue_manager[project_id]
    except KeyError:
      write_error(self, HTTPCodes.NOT_FOUND, 'Project ID not found')
      return

    pull_queues = [queue_name for queue_name, queue in project_queues.items()
                   if isinstance(queue, PostgresPullQueue)]
    json.dump(pull_queues, self)


class RESTQueue(TrackedRequestHandler):
  PATH = '{}/([a-zA-Z0-9-]+)'.format(REST_PREFIX)
  AREA = 'queue'  # Area name is used in stats

  def initialize(self, queue_handler):
    """ Provide access to the queue handler. """
    self.queue_handler = queue_handler

  def get(self, project, queue):
    """ Return info about an existing queue.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
    """
    try:
      queue = self.queue_handler.get_queue(project, queue)
    except QueueNotFound:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    if not isinstance(queue, PostgresPullQueue):
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'The REST API is only applicable to pull queues.')
      return

    get_stats = bool(self.get_argument('getStats', False))

    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = QUEUE_FIELDS
    else:
      fields = parse_fields(requested_fields)

    self.write(queue.to_json(include_stats=get_stats, fields=fields))


class RESTTasks(TrackedRequestHandler):
  PATH = '{}/([a-zA-Z0-9-]+)/tasks'.format(REST_PREFIX)
  AREA = 'tasks'  # Area name is used in stats

  def initialize(self, queue_handler):
    """ Provide access to the queue handler. """
    self.queue_handler = queue_handler

  def get(self, project, queue):
    """ List all non-deleted tasks in a queue, whether or not they are
    currently leased, up to a maximum of 100.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
    """
    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = ('kind', {'items': TASK_FIELDS})
    else:
      fields = parse_fields(requested_fields)

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    tasks = queue.list_tasks()
    task_list = {}
    if 'kind' in fields:
      task_list['kind'] = 'taskqueues#tasks'

    for field in fields:
      if isinstance(field, dict) and 'items' in field and tasks:
        task_list['items'] = [task.json_safe_dict(fields=field['items'])
                              for task in tasks]

    self.write(json.dumps(task_list))

  def post(self, project, queue):
    """ Insert a task into an existing queue.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
    """
    try:
      task_info = tornado.escape.json_decode(self.request.body)
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'The request body must contain a task.')
      return

    if 'payloadBase64' not in task_info:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'payloadBase64 must be specified.')
      return

    if not BASE64_CHARS_RE.match(task_info['payloadBase64']):
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'Invalid payloadBase64 value.')
      return

    try:
      task = Task(task_info)
    except TypeError:
      write_error(self, HTTPCodes.BAD_REQUEST, 'Invalid payloadBase64 value.')
      return

    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = TASK_FIELDS
    else:
      fields = parse_fields(requested_fields)

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    try:
      queue.add_task(task)
    except InvalidTaskInfo as insert_error:
      write_error(self, HTTPCodes.BAD_REQUEST, str(insert_error))
      return

    self.write(json.dumps(task.json_safe_dict(fields=fields)))


class RESTLease(TrackedRequestHandler):
  PATH = '{}/([a-zA-Z0-9-]+)/tasks/lease'.format(REST_PREFIX)
  AREA = 'lease'  # Area name is used in stats

  def initialize(self, queue_handler):
    """ Provide access to the queue handler. """
    self.queue_handler = queue_handler

  def post(self, project, queue):
    """ Acquire a lease on the topmost N unowned tasks in a queue.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
    """
    try:
      lease_seconds = int(self.get_argument('leaseSecs'))
    except MissingArgumentError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'Required parameter leaseSecs not specified.')
      return
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST, 'leaseSecs must be an integer.')
      return

    try:
      num_tasks = int(self.get_argument('numTasks'))
    except MissingArgumentError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'Required parameter numTasks not specified.')
      return
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST, 'numTasks must be an integer.')
      return

    try:
      group_by_tag = bool(self.get_argument('groupByTag', False))
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST, 'groupByTag must be a boolean.')
      return

    tag = self.get_argument('tag', None)

    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = ('kind', {'items': TASK_FIELDS})
    else:
      fields = parse_fields(requested_fields)

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    try:
      tasks = queue.lease_tasks(num_tasks, lease_seconds, group_by_tag, tag)
    except InvalidLeaseRequest as lease_error:
      write_error(self, HTTPCodes.BAD_REQUEST, str(lease_error))
      return
    except TransientError as lease_error:
      write_error(self, HTTPCodes.INTERNAL_ERROR, str(lease_error))
      return

    task_list = {}
    if 'kind' in fields:
      task_list['kind'] = 'taskqueues#tasks'

    for field in fields:
      if isinstance(field, dict) and 'items' in field and tasks:
        task_list['items'] = [task.json_safe_dict(fields=field['items'])
                              for task in tasks]

        for task in task_list['items']:
          task.update({
            'queueName': LONG_QUEUE_FORM.format(app=project,
                                                queue=task['queueName'])})

    self.write(json.dumps(task_list))


class RESTTask(TrackedRequestHandler):
  PATH = '{}/([a-zA-Z0-9-]+)/tasks/([a-zA-Z0-9_-]+)'.format(REST_PREFIX)
  AREA = 'task'  # Area name is used in stats

  def initialize(self, queue_handler):
    """ Provide access to the queue handler. """
    self.queue_handler = queue_handler

  def get(self, project, queue, task):
    """ Get the named task in a queue.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
      task: A string containing a task ID.
    """
    task = Task({'id': task, 'queueName': queue})

    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = TASK_FIELDS
    else:
      fields = parse_fields(requested_fields)

    omit_payload = False
    if 'payloadBase64' not in fields:
      omit_payload = True

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    task = queue.get_task(task, omit_payload=omit_payload)
    self.write(json.dumps(task.json_safe_dict(fields=fields)))

  def post(self, project, queue, task):
    """ Update the duration of a task lease.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
      task: A string containing a task ID.
    """
    try:
      task_info = tornado.escape.json_decode(self.request.body)
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'The request body must contain a task.')
      return

    if 'leaseTimestamp' not in task_info:
      write_error(self, HTTPCodes.BAD_REQUEST, 'leaseTimestamp is required.')
      return

    # GAE uses the ID from the post body and ignores the value in the URL.
    if 'id' not in task_info:
      write_error(self, HTTPCodes.BAD_REQUEST, 'id is required.')
      return
    provided_task = Task(task_info)

    try:
      new_lease_seconds = int(self.get_argument('newLeaseSeconds'))
    except MissingArgumentError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'Required parameter newLeaseSeconds not specified.')
      return
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'newLeaseSeconds must be an integer.')
      return

    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = TASK_FIELDS
    else:
      fields = parse_fields(requested_fields)

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    try:
      task = queue.update_lease(provided_task, new_lease_seconds)
    except InvalidLeaseRequest as lease_error:
      write_error(self, HTTPCodes.BAD_REQUEST, str(lease_error))
      return
    except TaskNotFound as error:
      write_error(self, HTTPCodes.NOT_FOUND, str(error))
      return

    self.write(json.dumps(task.json_safe_dict(fields=fields)))

  def delete(self, project, queue, task):
    """ Delete a task from a queue.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
      task: A string containing a task ID.
    """
    task = Task({'id': task})

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    queue.delete_task(task)

  def patch(self, project, queue, task):
    """ Update tasks that are leased out of a queue.

    Args:
      project: A string containing an application ID.
      queue: A string containing a queue name.
      task: A string containing a task ID.
    """
    try:
      task_info = tornado.escape.json_decode(self.request.body)
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'The request body must contain a task.')
      return

    # GAE requires the queueName to be part of the PATCH.
    if 'queueName' not in task_info:
      write_error(self, HTTPCodes.BAD_REQUEST, 'queueName is invalid.')
      return
    if task_info['queueName'] != queue:
      write_error(self, HTTPCodes.BAD_REQUEST, 'queueName cannot be updated.')
      return

    if 'id' in task_info and task_info['id'] != task:
      write_error(self, HTTPCodes.BAD_REQUEST, 'Task ID cannot be updated.')
      return
    task_info['id'] = task

    try:
      new_task = Task(task_info)
    except InvalidTaskInfo as task_error:
      write_error(self, HTTPCodes.BAD_REQUEST, str(task_error))
      return

    try:
      new_lease_seconds = int(self.get_argument('newLeaseSeconds'))
    except MissingArgumentError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'Required parameter newLeaseSeconds not specified.')
      return
    except ValueError:
      write_error(self, HTTPCodes.BAD_REQUEST,
                  'newLeaseSeconds must be an integer.')
      return

    requested_fields = self.get_argument('fields', None)
    if requested_fields is None:
      fields = TASK_FIELDS
    else:
      fields = parse_fields(requested_fields)

    queue = self.queue_handler.get_queue(project, queue)
    if queue is None:
      write_error(self, HTTPCodes.NOT_FOUND, 'Queue not found.')
      return

    try:
      task = queue.update_task(new_task, new_lease_seconds)
    except InvalidLeaseRequest as lease_error:
      write_error(self, HTTPCodes.BAD_REQUEST, str(lease_error))
      return
    except TaskNotFound as error:
      write_error(self, HTTPCodes.NOT_FOUND, str(error))
      return

    self.write(json.dumps(task.json_safe_dict(fields=fields)))