#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Asana integration for Zulip
#
# Copyright © 2014 Zulip, Inc.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
# The "zulip_asana_mirror" script is run continuously, possibly on a work computer
# or preferably on a server.
#
# When restarted, it will attempt to pick up where it left off.
#
# python-dateutil is a dependency for this script.

from __future__ import print_function
import base64
from datetime import datetime, timedelta
from typing import List, Dict, Optional, Any, Tuple

import json
import logging
import os
import time
from six.moves import urllib
from six.moves.urllib import request as urllib_request
import sys


try:
    import dateutil.parser
    from dateutil.tz import gettz
except ImportError as e:
    print(e, file=sys.stderr)
    print("Please install the python-dateutil package.", file=sys.stderr)
    exit(1)

sys.path.insert(0, os.path.dirname(__file__))
import zulip_asana_config as config
VERSION = "0.9"

if config.ZULIP_API_PATH is not None:
    sys.path.append(config.ZULIP_API_PATH)
import zulip

if config.LOG_FILE:
    logging.basicConfig(filename=config.LOG_FILE, level=logging.WARNING)
else:
    logging.basicConfig(level=logging.INFO)

client = zulip.Client(email=config.ZULIP_USER, api_key=config.ZULIP_API_KEY,
                      site=config.ZULIP_SITE, client="ZulipAsana/" + VERSION)

def fetch_from_asana(path):
    # type: (str) -> Optional[Dict[str, Any]]
    """
    Request a resource through the Asana API, authenticating using
    HTTP basic auth.
    """
    auth = base64.encodestring(b'%s:' % (config.ASANA_API_KEY,))
    headers = {"Authorization": "Basic %s" % auth}

    url = "https://app.asana.com/api/1.0" + path
    request = urllib_request.Request(url, None, headers) # type: ignore
    result = urllib_request.urlopen(request) # type: ignore

    return json.load(result)

def send_zulip(topic, content):
    # type: (str, str) -> Dict[str, str]
    """
    Send a message to Zulip using the configured stream and bot credentials.
    """
    message = {"type": "stream",
               "sender": config.ZULIP_USER,
               "to": config.ZULIP_STREAM_NAME,
               "subject": topic,
               "content": content,
               }
    return client.send_message(message)

def datestring_to_datetime(datestring):
    # type: (str) -> datetime
    """
    Given an ISO 8601 datestring, return the corresponding datetime object.
    """
    return dateutil.parser.parse(datestring).replace(
        tzinfo=gettz('Z'))

class TaskDict(dict):
    """
    A helper class to turn a dictionary with task information into an
    object where each of the keys is an attribute for easy access.
    """
    def __getattr__(self, field):
        # type: (TaskDict, str) -> Any
        return self.get(field)

def format_topic(task, projects):
    # type: (TaskDict, Dict[str, str]) -> str
    """
    Return a string that will be the Zulip message topic for this task.
    """
    # Tasks can be associated with multiple projects, but in practice they seem
    # to mostly be associated with one.
    project_name = projects[task.projects[0]["id"]]
    return "%s: %s" % (project_name, task.name)

def format_assignee(task, users):
    # type: (TaskDict, Dict[str, str]) -> str
    """
    Return a string describing the task's assignee.
    """
    if task.assignee:
        assignee_name = users[task.assignee["id"]]
        assignee_info = "**Assigned to**: %s (%s)" % (
            assignee_name, task.assignee_status)
    else:
        assignee_info = "**Status**: Unassigned"

    return assignee_info

def format_due_date(task):
    # type: (TaskDict) -> str
    """
    Return a string describing the task's due date.
    """
    if task.due_on:
        due_date_info = "**Due on**: %s" % (task.due_on,)
    else:
        due_date_info = "**Due date**: None"
    return due_date_info

def format_task_creation_event(task, projects, users):
    # type: (TaskDict, Dict[str, str], Dict[str, str]) -> Tuple[str, str]
    """
    Format the topic and content for a newly-created task.
    """
    topic = format_topic(task, projects)
    assignee_info = format_assignee(task, users)
    due_date_info = format_due_date(task)

    content = """Task **%s** created:

~~~ quote
%s
~~~

%s
%s
""" % (task.name, task.notes, assignee_info, due_date_info)
    return topic, content

def format_task_completion_event(task, projects, users):
    # type: (TaskDict, Dict[str, str], Dict[str, str]) -> Tuple[str, str]
    """
    Format the topic and content for a completed task.
    """
    topic = format_topic(task, projects)
    assignee_info = format_assignee(task, users)
    due_date_info = format_due_date(task)

    content = """Task **%s** completed. :white_check_mark:

%s
%s
""" % (task.name, assignee_info, due_date_info)
    return topic, content

def since():
    # type: () -> datetime
    """
    Return a newness threshold for task events to be processed.
    """
    # If we have a record of the last event processed and it is recent, use it,
    # else process everything from ASANA_INITIAL_HISTORY_HOURS ago.
    def default_since():
        # type: () -> datetime
        return datetime.utcnow() - timedelta(
            hours=config.ASANA_INITIAL_HISTORY_HOURS)

    if os.path.exists(config.RESUME_FILE):
        try:
            with open(config.RESUME_FILE, "r") as f:
                datestring = f.readline().strip()
                timestamp = float(datestring)
                max_timestamp_processed = datetime.fromtimestamp(timestamp)
                logging.info("Reading from resume file: " + datestring)
        except (ValueError, IOError) as e:
            logging.warn("Could not open resume file: " + str(e))
            max_timestamp_processed = default_since()
    else:
        logging.info("No resume file, processing an initial history.")
        max_timestamp_processed = default_since()

    # Even if we can read a timestamp from RESUME_FILE, if it is old don't use
    # it.
    return max(max_timestamp_processed, default_since())

def process_new_events():
    # type: () -> None
    """
    Forward new Asana task events to Zulip.
    """
    # In task queries, Asana only exposes IDs for projects and users, so we need
    # to look up the mappings.
    projects = dict((elt["id"], elt["name"]) for elt in
                    fetch_from_asana("/projects")["data"])
    users = dict((elt["id"], elt["name"]) for elt in
                 fetch_from_asana("/users")["data"])

    cutoff = since()
    max_timestamp_processed = cutoff
    time_operations = (("created_at", format_task_creation_event),
                       ("completed_at", format_task_completion_event))
    task_fields = ["assignee", "assignee_status", "created_at", "completed_at",
                   "modified_at", "due_on", "name", "notes", "projects"]

    # First, gather all of the tasks that need processing. We'll
    # process them in order.
    new_events = []

    for project_id in projects:
        project_url = "/projects/%d/tasks?opt_fields=%s" % (
            project_id, ",".join(task_fields))
        tasks = fetch_from_asana(project_url)["data"]

        for task in tasks:
            task = TaskDict(task)

            for time_field, operation in time_operations:
                if task[time_field]:
                    operation_time = datestring_to_datetime(task[time_field])
                    if operation_time > cutoff:
                        new_events.append((operation_time, time_field, operation, task))

    new_events.sort()
    now = datetime.utcnow()

    for operation_time, time_field, operation, task in new_events:
        # Unfortunately, creating an Asana task is not an atomic operation. If
        # the task was just created, or is missing basic information, it is
        # probably because the task is still being filled out -- wait until the
        # next round to process it.
        if (time_field == "created_at") and \
                (now - operation_time < timedelta(seconds=30)):
            # The task was just created, give the user some time to fill out
            # more information.
            return

        if (time_field == "created_at") and (not task.name) and \
                (now - operation_time < timedelta(seconds=60)):
            # If this new task hasn't had a name for a full 30 seconds, assume
            # you don't plan on giving it one.
            return

        topic, content = operation(task, projects, users)
        logging.info("Sending Zulip for " + topic)
        result = send_zulip(topic, content)

        # If the Zulip wasn't sent successfully, don't update the
        # max timestamp processed so the task has another change to
        # be forwarded. Exit, giving temporary issues time to
        # resolve.
        if not result.get("result"):
            logging.warn("Malformed result, exiting:")
            logging.warn(str(result))
            return

        if result["result"] != "success":
            logging.warn(result["msg"])
            return

        if operation_time > max_timestamp_processed:
            max_timestamp_processed = operation_time

    if max_timestamp_processed > cutoff:
        max_datestring = max_timestamp_processed.strftime("%s.%f")
        logging.info("Updating resume file: " + max_datestring)
        open(config.RESUME_FILE, 'w').write(max_datestring)

while True:
    try:
        process_new_events()
        time.sleep(5)
    except KeyboardInterrupt:
        logging.info("Shutting down...")
        logging.info("Set LOG_FILE to log to a file instead of stdout.")
        break