#!/usr/bin/python

import argparse
from flask import Flask
from flask import Response
from flask import redirect
from flask import request
from flask import send_from_directory
from flask import session
import flask
from functools import wraps
import logging
import os
import re
import signal

import db_controller as dbc
import rz_api
import rz_api_rest
import rz_feedback
from rz_kernel import RZ_Kernel
from rz_mesh import init_ws_interface
from rz_req_handling import make_response__http__empty
import rz_server_ctrl
import rz_user
import rz_blob
from rz_user_db import User_DB


class Config(object):
    """
    rhizi-server configuration

    TODO: config option documentation
    
        listen_address
        listen_port
        log_level: upper/lower case log level as specified by the logging module
        neo4j_url
        root_path: root path from which the server will server content
        user_db_path: absolute path to a Berkeley DB file used to store user accounts & password hash values
    """

    @staticmethod
    def init_from_file(file_path):

        if False == os.path.exists(file_path):
            raise Exception('config file not found: ' + file_path)

        # apply defaults
        cfg = {}
        cfg['access_control'] = True
        cfg['config_dir'] = os.path.abspath(os.path.dirname(file_path))  # bypass prop restriction
        cfg['development_mode'] = False
        cfg['listen_address'] = '127.0.0.1'
        cfg['listen_port'] = 8080
        cfg['log_level'] = 'INFO'
        cfg['root_path'] = os.getcwd()
        cfg['static_url_path'] = '/static'
        cfg['user_db_path'] = os.path.join(cfg['config_dir'], 'user_db.db')

        # client configuration
        cfg['optimized_main'] = False

        # Mail settings
        cfg['mail_hostname'] = 'localhost'
        cfg['mail_port'] = 25

        # User feedback settings
        cfg['feedback_recipient'] = 'feedback@localhost'

        # Flask keys
        cfg['SECRET_KEY'] = ''

        with open(file_path, 'r') as f:
            for line in f:
                if re.match('(^#)|(\s+$)', line):
                    continue

                kv_arr = line.split('=')
                if 2 != len(kv_arr):
                    raise Exception('failed to parse config line: ' + line)

                k, v = map(str.strip, kv_arr)

                if None != cfg.get(k):
                    # apply type conversion based on default value type
                    type_f = type(cfg[k])
                    if bool == type_f:
                        v = v in ("True", "true")  # workaround bool('false') = True
                    else:
                        v = type_f(v)

                # [!] we can't use k.lower() as we are loading Flask configuration
                # keys which are expected to be capitalized
                cfg[k] = v

        ret = Config()
        ret.__dict__ = cfg  # allows setting of @property attributes

        # validate config
        if False == os.path.isabs(ret.root_path):
            ret.root_path = os.path.abspath(ret.root_path)

        return ret

    def __str__(self):
        kv_item_set = []
        for k, v in self.__dict__.items():
            if k == 'SECRET_KEY':  # exclude key from logs
                v = v[:3] + '...'
            kv_item_set.append('%s: %s' % (k, v))

        kv_item_set.sort()
        return '\n'.join(kv_item_set)

    @property
    def db_base_url(self):
        return self.neo4j_url

    @property
    def tx_api_path(self):
        return '/db/data/transaction'

    @property
    def config_dir_path(self):
        return self.config_dir

    @property
    def secret_key(self):
        return self.SECRET_KEY

class FlaskExt(Flask):
    """
    Flask server customization
    """

    def __init__(self, import_name, *args, **kwargs):
        """
        reserved for future use
        """
        super(FlaskExt, self).__init__(import_name, *args, **kwargs)

    def before_request(self, *args, **kwargs):
        # TODO impl
        pass

    def make_default_options_response(self):
        ret = Flask.make_default_options_response(self)

        ret.headers['Access-Control-Allow-Origin'] = 'http://rhizi.net'
        ret.headers['Access-Control-Allow-Headers'] = "Accept, Authorization, Content-Type, Origin"
        ret.headers['Access-Control-Allow-Credentials'] = 'true'

        # ret.headers['Access-Control-Allow-Methods'] = ', '.join(m_list)
        return ret

def init_log(cfg):
    """
    init log file, location derived from configuration
    """
    log = logging.getLogger('rhizi')

    log_level = logging._levelNames.get(cfg.log_level.upper())
    assert None != log_level, 'failed to determine log level'

    log.setLevel(log_level)
    log_handler_c = logging.StreamHandler()
    log_handler_f = logging.FileHandler(cfg.log_path)

    formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
    log_handler_c.setFormatter(formatter)
    log_handler_f.setFormatter(formatter)

    log.addHandler(log_handler_c)
    log.addHandler(log_handler_f)
    return log

def init_rest_interface(cfg, flask_webapp):
    """
    Initialize REST interface
    """

    def rest_entry(path, f, flask_args={'methods': ['POST']}):
        return (path, f, flask_args)

    def login_decorator(f):
        """
        security boundary: assert logged-in user before executing REST api call
        """
        @wraps(f)
        def wrapped_function(*args, **kw):
            if not 'username' in session:
                return redirect('/login')
            return f(*args, **kw)

        return wrapped_function


    def localhost_access_decorator__ipv4(f):
        """
        security boundary: assert request originated from localhost 
        """

        @wraps(f)
        def wrapped_function(*args, **kw):

            if '127.0.0.1' != request.remote_addr:
                log.warning('unauthorized attempt to access localhost restricted path: %s' % (request.path))
                return make_response__http__empty(stauts=403)

            return f(*args, **kw)

        return wrapped_function

    rest_entry_set = [
                      # REST endpoints
                      rest_entry('/feedback', rz_feedback.rest__send_user_feedback__email),
                      rest_entry('/graph/clone', rz_api.rz_clone),
                      rest_entry('/graph/diff-commit-set', rz_api.diff_commit__set),
                      rest_entry('/graph/diff-commit-topo', rz_api_rest.diff_commit__topo),
                      rest_entry('/graph/diff-commit-attr', rz_api_rest.diff_commit__attr),
                      rest_entry('/graph/diff-commit-vis', rz_api_rest.diff_commit__vis),
                      rest_entry('/index', rz_api.index, {'methods': ['GET']}),
                      rest_entry('/load/node-set-by-id', rz_api.load_node_set_by_id_attr),
                      rest_entry('/load/link-set/by_link_ptr_set', rz_api.load_link_set_by_link_ptr_set),
                      rest_entry('/login', rz_user.rest__login, {'methods': ['GET', 'POST']}),
                      rest_entry('/logout', rz_user.rest__logout, {'methods': ['GET', 'POST']}),
                      rest_entry('/match/node-set', rz_api.match_node_set_by_attr_filter_map),
                      rest_entry('/pw-reset', rz_user.rest__pw_reset, {'methods': ['GET', 'POST']}),
                      rest_entry('/signup', rz_user.rest__user_signup, {'methods': ['GET', 'POST']}),

                      # upload endpoints - this might change to external later, keep minimal and separate
                      rest_entry('/blob/upload', rz_blob.upload, {'methods': ['POST']}),
                      # [!] this is for development only. served from frontend web server in production
                      rest_entry('/blob/uploads/<path:path>', rz_blob.retreive, {'methods': ['GET', 'DELETE']}),

                      # server administration: access restricted to localhost
                      rest_entry('/monitor/server-info', rz_server_ctrl.monitor__server_info, {'methods': ['GET']}),
                      rest_entry('/monitor/user/list', rz_server_ctrl.rest__list_users, {'methods': ['GET']}),

                      # redirects - currently handled by reverse proxy
                  ]

    # FIXME: but should be rate limited (everything should be, regardless of login)
    no_login_paths = ['/feedback', '/login', '/pw-reset', '/signup']

    for re_entry in rest_entry_set:
        rest_path, f, flask_args = re_entry

        if cfg.access_control and rest_path not in no_login_paths:
            # currently require login on all but /login paths
            f = login_decorator(f)

        # apply local host access restriction
        if rest_path.startswith('/monitor'):
            f = localhost_access_decorator__ipv4(f)

        # [!] order seems important - apply route decorator last
        route_dec = flask_webapp.route(rest_path, **flask_args)
        f = route_dec(f)

        flask_webapp.f = f  # assign decorated function

def init_webapp(cfg, kernel, db_ctl=None):
    """
    Initialize webapp:
       - call init_rest_interface()
    """
    root_path = cfg.root_path
    assert os.path.exists(root_path), "root path doesn't exist: %s" % root_path

    webapp = FlaskExt(__name__,
                      static_folder='static',
                      template_folder=os.path.join(root_path, 'templates'),
                      static_url_path=cfg.static_url_path)
    webapp.config.from_object(cfg)
    webapp.root_path = root_path  # for some reason calling config.from_xxx() does not have effect

    if None == db_ctl:
        db_ctl = dbc.DB_Controller(cfg)
    rz_api.db_ctl = db_ctl
    rz_api_rest.db_ctl = db_ctl
    kernel.db_ctl = db_ctl

    webapp.rz_config = cfg
    webapp.kernel = kernel

    init_rest_interface(cfg, webapp)
    return webapp

def init_config(cfg_dir):
    cfg_path = os.path.join(cfg_dir, 'rhizi-server.conf')
    cfg = Config.init_from_file(cfg_path)
    return cfg

def init_user_db():
    global user_db

    try:
        user_db = User_DB(db_path=cfg.user_db_path)
        user_db.init(mode='c')  # dev default: create DB
    except Exception as e:
        log.exception('failed to init user_db, configured user_db path: %s' % (cfg.user_db_path))
        raise e

    log.info('user DB initialized: path: %s' % (cfg.user_db_path))
    return user_db

def init_signal_handlers():

    def signal_handler__exit(signum, frame):
        log.info('received exit signal: SIGINT/SIGTERM')
        shutdown()
        exit(0)

    signal.signal(signal.SIGINT, signal_handler__exit)
    signal.signal(signal.SIGTERM, signal_handler__exit)

def shutdown():
    user_db.shutdown()
    log.info('rz_server: shutting down')

class MinimalLog(object):
    """
    Minimal logger implementation to serve until init_log completes, which
    means init_config succeeded as well.
    """
    def exception(self, e):
        print(e)
    def info(self, msg):
        print(msg)

log = MinimalLog()

if __name__ == "__main__":

    p = argparse.ArgumentParser(description='rhizi-server')
    p.add_argument('--config-dir', help='path to Rhizi config dir', default='res/etc')
    args = p.parse_args()

    try:
        cfg = init_config(args.config_dir)
        log = init_log(cfg)
        cfg_indent_str = '   ' + str(cfg).replace('\n', '\n   ')
        log.info('loaded configuration:\n%s' % cfg_indent_str)  # print indented
        if False == cfg.access_control:
            log.warn('[!] access control disabled, all-granted access set on all URLs')

        init_signal_handlers()
        init_user_db()
    except Exception as e:
        log.exception('failed to initialize server')
        log.info('failed initialization, aborting')
        exit(-1)

    kernel = RZ_Kernel()
    webapp = init_webapp(cfg, kernel)
    ws_srv = init_ws_interface(cfg, kernel, webapp)

    webapp.user_db = user_db

    try:
        ws_srv.serve_forever()
    except Exception as e:
        log.exception(e)

    shutdown()