#!/usr/bin/env python2.7
# -*- 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

import json
import logging
import os
import time
from six.moves import urllib

import sys

try:
    import dateutil.parser
    import dateutil.tz
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):
    """
    Request a resource through the Asana API, authenticating using
    HTTP basic auth.
    """
    auth = base64.encodestring('%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)
    result = urllib.request.urlopen(request)

    return json.load(result)

def send_zulip(topic, content):
    """
    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):
    """
    Given an ISO 8601 datestring, return the corresponding datetime object.
    """
    return dateutil.parser.parse(datestring).replace(
        tzinfo=dateutil.tz.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):
        return self.get(field)

def format_topic(task, projects):
    """
    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):
    """
    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):
    """
    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):
    """
    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):
    """
    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():
    """
    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():
        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: %s" % (
                    e.message or e.strerror,))
            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():
    """
    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(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