#!/usr/bin/env python
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Autogenerate documentation for all process endpoints spawned by a
Mesos master and agent.
"""

import argparse
import atexit
import json
import os
import posixpath
import re
import shutil
import subprocess
import sys
import time
import urllib2


# The host ip and master and agent ports.
HOST_IP = "127.0.0.1"
MASTER_PORT = 5050
AGENT_PORT = 5051

# The master and agent programs to launch.
# We considered making the parameters to these commands something that
# a user could specify on the command line, but ultimately chose to
# hard code them.  Different parameters may cause different endpoints
# to become available, and we should modify this script to ensure that
# we cover all of them instead of leaving that up to the user.
MASTER_COMMAND = [
    'mesos-master.sh',
    '--ip=%s' % (HOST_IP),
    '--registry=in_memory',
    '--work_dir=/tmp/mesos'
]

# NOTE: The agent flags here ensure that this script can run inside docker.
AGENT_COMMAND = [
    'mesos-agent.sh',
    '--master=%s:%s' % (HOST_IP, MASTER_PORT),
    '--work_dir=/tmp/mesos',
    '--systemd_enable_support=false',
    '--launcher=posix'
]


# A header to add onto all generated markdown files.
MARKDOWN_HEADER = """---
title: %s
layout: documentation
---
<!--- This is an automatically generated file. DO NOT EDIT! --->
"""

# A template of the title to add onto all generated markdown files.
MARKDOWN_TITLE = "Apache Mesos - HTTP Endpoints%s"

# A global timeout as well as a retry interval when hitting any http
# endpoints on the master or agent (in seconds).
RECEIVE_TIMEOUT = 10
RETRY_INTERVAL = 0.10


class Subprocess(object):
    """The process running using this script."""
    def __init__(self):
        self.current = None

    def cleanup(self):
        """Kill the process running once the script is done."""
        if self.current:
            self.current.kill()


# A pointer to the top level directory of the mesos project.
GIT_TOP_DIR = subprocess.check_output(
    ['git', 'rev-parse', '--show-cdup']).strip()

with open(os.path.join(GIT_TOP_DIR, 'CHANGELOG'), 'r') as f:
    if 'mesos' not in f.readline().lower():
        print >> sys.stderr, ('You must run this command from within'
                              ' the Mesos source repository!')
        sys.exit(1)


def parse_options():
    """Parses command line options and populates the dictionary."""

    options = {}

    parser = argparse.ArgumentParser(
        formatter_class=argparse.RawTextHelpFormatter,
        description='Generate markdown files from all installed HTTP '
                    'endpoints on a Mesos master and agent process.')

    parser.add_argument(
        '-c', '--command-path',
        metavar='COMMAND_PATH',
        default=os.path.join(GIT_TOP_DIR, "build/bin"),
        help='Path to the Mesos master and agent commands.\n'
             '(default: %(default)s)')

    parser.add_argument(
        '-o', '--output-path',
        metavar='OUTPUT_PATH',
        default=os.path.join(GIT_TOP_DIR, "docs/endpoints"),
        help='Path to the top level directory where all\n'
             'generated markdown files will be placed.\n'
             '(default: %(default)s)')

    args = parser.parse_args()

    options['command_path'] = args.command_path
    options['output_path'] = args.output_path

    return options


def get_url_until_success(url):
    """Continuously tries to open a url until it succeeds or times out."""
    time_spent = 0
    while time_spent < RECEIVE_TIMEOUT:
        try:
            helps = urllib2.urlopen(url)
            break
        except Exception:
            time.sleep(RETRY_INTERVAL)
            time_spent += RETRY_INTERVAL

    if time_spent >= RECEIVE_TIMEOUT:
        print >> sys.stderr, 'Timeout attempting to hit url: %s' % (url)
        sys.exit(1)

    return helps.read()


def get_help(ip, port):
    """
    Grabs the help strings for all endpoints at http://ip:port as a JSON object.
    """
    url = 'http://%s:%d/help?format=json' % (ip, port)
    return json.loads(get_url_until_success(url))


def generalize_endpoint_id(p_id):
    """Generalizes the id of the form e.g. process(1) to process(id)."""
    return re.sub(r'\([0-9]+\)', '(id)', p_id)


def normalize_endpoint_id(p_id):
    """Normalizes the id of the form e.g. process(id) to process."""
    return re.sub(r'\([0-9]+\)', '', p_id)


def get_endpoint_path(p_id, name):
    """
    Generates the canonical endpoint path, given id and name.

    Examples: ('process', '/')         -> '/process'
              ('process(id)', '/')     -> '/process(id)'
              ('process', '/endpoint') -> '/process/endpoint'
    """
    # Tokenize the endpoint by '/' (filtering
    # out any empty strings between '/'s)
    path_parts = filter(None, name.split('/'))

    # Conditionally prepend the 'id' to the list of path parts.
    # Following the notion of a 'delegate' in Mesos, we want our
    # preferred endpoint paths for the delegate process to be
    # '/endpoint' instead of '/process/endpoint'. Since this script only
    # starts 1 master and 1 agent, our only delegate processes are
    # "master" and "slave(id)". If the id matches one of these, we don't
    # prepend it, otherwise we do.
    p_id = generalize_endpoint_id(p_id)
    delegates = ["master", "slave(id)"]
    if p_id not in delegates:
        path_parts = [p_id] + path_parts

    return posixpath.join('/', *path_parts)


def get_relative_md_path(p_id, name):
    """
    Generates the relative path of the generated .md file from id and name.

    This path is relative to the options['output_path'] directory.

    Examples: master/health.md
              master/maintenance/schedule.md
              registrar/registry.md
              version.md
    """
    new_id = normalize_endpoint_id(p_id)
    # Strip the leading slash
    new_name = name[1:]

    if new_name:
        return os.path.join(new_id, new_name + '.md')
    else:
        return os.path.join(new_id + '.md')


def write_markdown(path, output, title):
    """Writes 'output' to the file at 'path'."""
    print 'generating: %s' % (path)

    dirname = os.path.dirname(path)
    if not os.path.exists(dirname):
        os.makedirs(dirname)

    outfile = open(path, 'w+')

    # Add our header and remove all '\n's at the end of the output if
    # there are any.
    output = (MARKDOWN_HEADER % title) + '\n' + output.rstrip()

    outfile.write(output)
    outfile.close()


def dump_index_markdown(master_help, agent_help, options):
    """
    Dumps an index for linking to the master and agent help files.

    This file is dumped into a directory rooted at
    options['output_path'].
    """

    # The output template for the HTTP endpoints index.
    # We use a helper function below to insert text into the '%s' format
    # strings contained in the "Master Endpoints" and "Agent Endpoints"
    # sections of this template.
    output = """# HTTP Endpoints #

Below is a list of HTTP endpoints available for a given Mesos process.

Depending on your configuration, some subset of these endpoints will be
available on your Mesos master or agent. Additionally, a `/help`
endpoint will be available that displays help similar to what you see
below.

** NOTE: ** If you are using Mesos 1.1 or later, we recommend using the
new [v1 Operator HTTP API](../operator-http-api.md) instead of the
unversioned REST endpoints listed below. These endpoints will be
deprecated in the future.


** NOTE: ** The documentation for these endpoints is auto-generated from
the Mesos source code. See `support/generate-endpoint-help.py`.

## Master Endpoints ##

Below are the endpoints that are available on a Mesos master. These
endpoints are reachable at the address `http://ip:port/endpoint`.

For example, `http://master.com:5050/files/browse`.

%s

## Agent Endpoints ##

Below are the endpoints that are available on a Mesos agent. These
endpoints are reachable at the address `http://ip:port/endpoint`.

For example, `http://agent.com:5051/files/browse`.

%s
"""

    def generate_links(master_or_agent_help):
        """
        Iterates over the input JSON and creates a list of links to
        to the markdown files generated by this script. These links
        are grouped per process, with the process's name serving as a
        header for each group. All links are relative to
        options['output_path'].

        For example:
        ### profiler ###
        * [/profiler/start] (profiler/start.md)
        * [/profiler/stop] (profiler/stop.md)

        ### version ###
        * [/version] (version.md)
        """
        output = ""
        for process in master_or_agent_help['processes']:
            p_id = process['id']
            output += '### %s ###\n' % (generalize_endpoint_id(p_id))
            for endpoint in process['endpoints']:
                name = endpoint['name']
                output += '* [%s](%s)\n' % (get_endpoint_path(p_id, name),
                                            get_relative_md_path(p_id, name))
            output += '\n'

        # Remove any trailing newlines
        return output.rstrip()

    output = output % (generate_links(master_help),
                       generate_links(agent_help))

    path = os.path.join(options['output_path'], 'index.md')
    write_markdown(path, output, MARKDOWN_TITLE % "")


def dump_markdown(master_or_agent_help, options):
    """
    Dumps JSON encoded help strings into markdown files.

    These files are dumped into a directory rooted at
    options['output_path'].
    """
    for process in master_or_agent_help['processes']:
        p_id = process['id']
        for endpoint in process['endpoints']:
            name = endpoint['name']
            text = endpoint['text']
            title = get_endpoint_path(p_id, name)

            relative_path = get_relative_md_path(p_id, name)
            path = os.path.join(options['output_path'], relative_path)
            write_markdown(path, text, MARKDOWN_TITLE % (" - " + title))


def start_master(options):
    """
    Starts the Mesos master using the specified command.

    This method returns the Popen object used to start it so it can
    be killed later on.
    """
    cmd = os.path.join('.', options['command_path'], MASTER_COMMAND[0])
    master = subprocess.Popen([cmd] + MASTER_COMMAND[1:])

    # Wait for the master to become responsive
    get_url_until_success("http://%s:%d/health" % (HOST_IP, MASTER_PORT))
    return master


def start_agent(options):
    """
    Starts the Mesos agent using the specified command.

    This method returns the Popen object used to start it so it can
    be killed later on.
    """
    cmd = os.path.join('.', options['command_path'], AGENT_COMMAND[0])
    agent = subprocess.Popen([cmd] + AGENT_COMMAND[1:])

    # Wait for the agent to become responsive.
    get_url_until_success('http://%s:%d/health' % (HOST_IP, AGENT_PORT))
    return agent


def main():
    """
    Called when the Python script is used, we do not directly write code
    after 'if __name__ == "__main__"' as we cannot set variables in that case.
    """
    # A dictionary of the command line options passed in.
    options = parse_options()

    # A pointer to the current subprocess for the master or agent.
    # This is useful for tracking the master or agent subprocesses so
    # that we can kill them if the script exits prematurely.
    subproc = Subprocess()
    atexit.register(subproc.cleanup())
    subproc.current = start_master(options)
    master_help = get_help(HOST_IP, MASTER_PORT)
    subproc.current.kill()

    subproc.current = start_agent(options)
    agent_help = get_help(HOST_IP, AGENT_PORT)
    subproc.current.kill()

    shutil.rmtree(options['output_path'], ignore_errors=True)
    os.makedirs(options['output_path'])

    dump_index_markdown(master_help, agent_help, options)
    dump_markdown(master_help, options)
    dump_markdown(agent_help, options)

if __name__ == '__main__':
    main()