#!/usr/bin/env python3
'''
Criticality: High
Checks the current state of the PostgreSQL database cluster.
'''

from pathlib import Path
import re
import socket
import subprocess
import sys
import time
import urllib
import uuid

try:
    import psycopg2
except ImportError:
    sys.exit(2)

sys.path.append(str(Path(__file__).parents[1].resolve()))

from utilities import logging as lg  # noqa: E402
from utilities.apt import Apt  # noqa: E402
from utilities.config import load_conf  # noqa: E402


def check_listen(host: str, port: int) -> bool:
    '''Check if server is listening (TCP only).

    :param host: The hostname or IP address to bind
    :param port: The port number to bind
    :type host: str
    :type port: int
    :return: Wether the `host` is listening on TCP/`port`
    :rtype: bool
    '''

    # try to connect to the port used by psql-primary frontend
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    result = client.connect_ex((host, port))
    client.close()

    return result == 0


def get_haproxy_conf(path: str = '/etc/haproxy/haproxy.cfg') -> dict:
    '''Get HAProxy configuration in a dictionary.

    :param path: HAProxy configuration file, defaults to '/etc/haproxy/haproxy.cfg'
    :type path: str
    :return: HAProxy configuration file content
    :rtype: dict
    '''

    # init configuration dictionary
    conf = {}

    # load configuration file
    try:
        with open(path) as data:
            lines = data.readlines()
    except EnvironmentError:
        return conf

    # define patterns
    pattern_block = re.compile(r'^([a-zA-Z0-9_.-]+ *[a-zA-Z0-9_.-]+)')
    pattern_param = re.compile(r'^\s+([ /:()|a-zA-Z0-9_.-]+)')

    # parse configuration file
    for line in lines:
        match_block = pattern_block.match(line)
        if match_block:
            block = match_block.group(1)
            conf[block] = []
        else:
            match_param = pattern_param.match(line)
            if match_param:
                param = match_param.group(1)
                conf[block].append(param)

    return conf


def get_nodes(conf: dict) -> dict:
    '''Get the list of nodes from HAProxy configuration.

    :param conf: The HAProxy configuration file content
    :type conf: dict
    :return: The list of nodes found in HAProxy configuration
    :rtype: dict
    '''

    servers = {}

    for item in conf.keys():
        if 'pgsql-primary' in item:
            # filter `server` lines
            server_lines = [x for x in conf[item] if x.startswith('server ')]
            for line in server_lines:
                # split line
                elements = line.split()

                # get needed elements
                name = elements[1]
                address = elements[2].split(':')
                host = address[0]
                port = int(address[1])
                rephacheck = elements[7]

                # update dictionary
                servers.update(
                    {name: {'host': host, 'port': port, 'rephacheck': rephacheck}}
                )

    return servers


def get_node_state(host: str, port: int) -> str:
    '''Get the curent state of node from its RepHACheck daemon.

    :param node: The node's hostname or IP address
    :param port: The node's port on which RepHACheck is listening
    :type node: str
    :type port: int
    :return: The current state of the node accordind to its RepHACheck daemon
    :rtype: str
    '''

    # connect and get tcp stream data
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.connect((host, port))
    data = client.recv(1024)
    client.close()
    # extract string from data output
    state = data.decode('utf-8').rstrip()

    return state


def check_fenced(nodes: dict) -> tuple:
    '''Check if the cluster have a fenced node.

    :param nodes: The dictionary containing nodes and their informations
    :type nodes: dict
    :return: Wether the nodes list contains a fenced server
    :rtype: tuple
    '''

    for node in nodes.keys():
        host = nodes[node]['host']
        port = int(nodes[node]['rephacheck'])
        if get_node_state(host, port) == 'fenced':
            return True, node

    return False, None


def check_psql(db_conn: dict, query: str) -> tuple:
    '''Check if we can write data on this node.

    :param db_conn: Database connection parameters
    :type db_conn: dict
    :param query: Query to execute
    :type query: str
    :return: Wether the query can be executed or not
    :rtype: tuple
    '''

    # build database connection uri
    if 'password' in db_conn:
        uri = 'postgresql://{}:{}@{}:{}/{}'.format(
            db_conn['user'],
            urllib.parse.quote_plus(db_conn['password']),
            db_conn['host'],
            db_conn['port'],
            db_conn['dbname'],
        )
    else:
        uri = 'postgresql:///{}'.format(db_conn['dbname'])

    # format command
    command = ['su -l postgres -c "psql {} -c \'{}\'"'.format(uri, query)]

    # execute
    try:
        subprocess.check_output(command, shell=True)
    except subprocess.CalledProcessError as psql_error:
        return False, str(psql_error).rstrip()

    return True, None


def check_replication(primary: dict, standby: dict) -> tuple:
    '''Check if replication is working between the primary and standby servers.

    :param primary: Database connection parameters for primary server
    :type primary: dict
    :param standby: Database connection parameters for standby server
    :type standby: dict
    :return: Wether replication between primary/stanbdy is working or not
    :rtype: tuple
    '''

    # connections
    try:
        primary_client = psycopg2.connect(**primary)
        standby_client = psycopg2.connect(**standby)
    except psycopg2.Error as repl_conn_error:
        return False, str(repl_conn_error).rstrip()

    # random id
    rand = uuid.uuid4().hex
    write_query = 'CREATE TABLE es_test_{} (id serial PRIMARY KEY);'.format(rand)
    read_query = 'SELECT * FROM es_test_{};'.format(rand)

    # write
    try:
        primary_psql = primary_client.cursor()
        primary_psql.execute(write_query)
    except psycopg2.Error as repl_write_error:
        return False, str(repl_write_error).rstrip()

    # read
    max_time = 6.0
    timer = 0.0
    while timer < max_time:
        time.sleep(timer)
        timer += 0.2
        try:
            standby_psql = primary_client.cursor()
            standby_psql.execute(read_query)
            msg = 'took ~{}s'.format(str(timer))
            break
        except psycopg2.Error as repl_read_error:
            msg = str(repl_read_error).rstrip()
    else:
        return False, msg

    # delete
    try:
        primary_psql.execute('DROP TABLE es_test_{};'.format(rand))
    except psycopg2.Error:
        pass

    # close
    primary_psql.close()
    standby_psql.close()
    primary_client.close()
    standby_client.close()

    return True, msg


def check_ha(db_conn: dict, errors: int = 0) -> int:
    '''Run all tests for a highly-available setup.

    :param db_conn: Database connection parameters
    :type db_conn: dict
    :param errors: Error counter, defaults to 0
    :param errors: int, optional
    :return: Number of errors
    :rtype: int
    '''

    # get haproxy conf
    ha_conf = get_haproxy_conf()

    # get nodes data
    nodes = get_nodes(ha_conf)

    # check haproxy
    lg.log('Checking local HAProxy frontends:')
    if not check_listen(db_conn['host'], 54321):
        lg.error('HAProxy pgsql-primary frontend is not listening')
        errors += 1
    else:
        lg.success('HAProxy pgsql-primary frontend is listening')
    if not check_listen(db_conn['host'], 54322):
        lg.error('HAProxy pgsql-standby frontend is not listening')
        errors += 1
    else:
        lg.success('HAProxy pgsql-standby frontend is listening')

    # check remotes
    lg.log('Checking remote PostgreSQL nodes:')
    for node in nodes:
        node_host = nodes[node]['host']
        node_port = nodes[node]['port']
        if not check_listen(node_host, node_port):
            lg.error('cannot bind {}:{}'.format(node_host, node_port))
            errors += 1
        else:
            lg.success('can bind {}:{}'.format(node_host, node_port))

    # check fenced
    lg.log('Checking cluster state:')
    fenced, node = check_fenced(nodes)
    if fenced:
        lg.error('Node `{}` is fenced'.format(node))
        errors += 1
    else:
        lg.success('No fenced node found')

    # check replication
    lg.log('Checking replication state:')
    primary = db_conn.copy()
    primary['port'] = 54321
    standby = db_conn.copy()
    standby['port'] = 54322
    status, info = check_replication(primary, standby)
    if not status:
        lg.error('cannot replicate between primary/standby ({})'.format(info))
        errors += 1
    else:
        lg.success('can replicate between primary/standby ({})'.format(info))

    return errors


def check_local(db_conn: dict, errors: int = 0) -> int:
    '''Run all tests for a highly-available setup.

    :param db_conn: Database connection parameters
    :type db_conn: dict
    :param errors: Error counter, defaults to 0
    :param errors: int, optional
    :return: Number of errors
    :rtype: int
    '''

    host = db_conn['host']
    port = db_conn['port']
    user = db_conn['user']

    # check listen
    lg.log('Checking local PostgreSQL node:')
    if not check_listen(host, port):
        lg.error('cannot connect to {}:{}'.format(host, port))
        errors += 1
    else:
        lg.success('can connect to {}:{}'.format(host, port))

    # check read
    lg.log('Checking read operation:')
    read_query = 'SELECT 1;'
    status, info = check_psql(db_conn, read_query)
    if not status:
        lg.error('cannot read from {}@{}:{} ({})'.format(user, host, port, info))
        errors += 1
    else:
        lg.success('can read from {}@{}:{}'.format(user, host, port))

    # get replication state if available
    if check_listen('127.0.0.1', 8543):
        state = get_node_state('127.0.0.1', 8543)
    else:
        state = 'primary'

    # check write
    lg.log('Checking write operation:')
    if state != 'primary':
        lg.info('this database is in {} state'.format(state))
    else:
        rand = uuid.uuid4().hex
        write_query = 'CREATE TABLE es_test_{} (id serial PRIMARY KEY);'.format(rand)
        status, info = check_psql(db_conn, write_query)
        if not status:
            lg.error('cannot write on {}@{}:{} ({})'.format(user, host, port, info))
            errors += 1
        else:
            lg.success('can write on {}@{}:{}'.format(user, host, port))
            # remove test table
            check_psql(db_conn, 'DROP TABLE es_test_{};'.format(rand))

    return errors


def main():
    '''Run all checks and exits with corresponding exit code.'''

    apt = Apt()
    pattern_postgresql_client = re.compile(r'postgresql-client.*')
    if not list(filter(pattern_postgresql_client.match, apt.installed_packages)):
        exit(2)

    # load configuration
    conf = load_conf()

    # get database configuration
    db_host = conf.get('DB_HOST') if conf.get('DB_HOST') else '127.0.0.1'
    db_port = 54321 if check_listen('127.0.0.1', 54321) else 5432
    db_user = conf.get('DB_USER') if conf.get('DB_USER') else 'postgres'
    db_pass = conf.get('DB_PG_ROOT_PWD')
    db_conn = {'dbname': db_user, 'host': db_host, 'port': db_port, 'user': db_user}
    if db_pass:
        db_conn.update({'password': db_pass})

    # determine if HA setup and run according tests
    lg.log('Checking availibility mode:')
    if check_listen('127.0.0.1', 54321) and check_listen('127.0.0.1', 54322):
        lg.info('this setup is using a primary and standby database')
        errors = check_ha(db_conn)
    else:
        lg.info('this setup is using a single database')
        errors = check_local(db_conn)

    if errors:
        sys.exit(1)
    else:
        sys.exit(0)


if __name__ == '__main__':
    main()