"""
Script de clonage des bases de données MySql
(requiert python 3.6+)

> Configuration: settings.yml

Usage:
  clonedb.py [-v] [-y] [<opname>...]
  clonedb.py (-h | --help)
  clonedb.py --version

Options:
  -y, --yes       Do not ask for confirmation
  -h --help       Show this screen.
  --version       Show version.

@author: olivier.massot, 05-2020
"""
import logging
import re
from subprocess import Popen, PIPE, CalledProcessError
import sys

import pymysql
import yaml
from docopt import docopt
from path import Path

from core import logging_
from core.docker import resolve_docker_ip
from core.locker import Lockfile
from core.pipe_handler import PipeHandler
from core.ssh import SshTunnel
from core.prompt import ask_confirmation

__VERSION__ = "0.2"

HERE = Path(__file__).parent

# Start logger
LOG_DIR = HERE / 'log'
LOG_DIR.mkdir_p()
logger = logging.getLogger('clonedb')
logging_.start("clonedb", filename=LOG_DIR / 'clonedb.log', replace=True)

# FIX the default ascii encoding on some linux dockers...
sys.stdout = open(sys.stdout.fileno(), mode='w', encoding='utf8', buffering=1)

# Options
SHOW_PROGRESSION = True
LOG_PIPES_OUTPUT = False
LOG_MYSQL_QUERIES = False

MY_CNF_FILE = Path(HERE / "my.cnf")

MAX_ALLOWED_PACKET = 1073741824


# Utilities

def load_settings():
    """ Load the settings from the 'settings.yml' file
    If there is no such file, the base settings.yml file is created
    """
    settings_file = HERE / 'settings.yml'
    if not settings_file.exists():
        Path(HERE / 'settings.yml.dist').copy(HERE / 'settings.yml')

    with open(settings_file, 'r') as f:
        return yaml.load(f, Loader=yaml.FullLoader)


class MysqldumpHandler(PipeHandler):
    """ Handle and process the stdout / stderr output from a mysqldump process
    """
    _rx_prog = re.compile(r'Retrieving table structure for table (\w+)')
    _log_all = LOG_PIPES_OUTPUT
    _action_name = "dumping"

    def process(self, line):
        """ Process the last line that was read
        """
        line = line.strip('\n')
        if SHOW_PROGRESSION:
            match = self._rx_prog.search(line)
            if match:
                logger.debug('... %s %s', self._action_name, match.group(1))
                print('.', end="", flush=True)
        if self._log_all:
            logger.debug(line)

    def close(self):
        """ Close the write end of the pipe.
        """
        print('', flush=True)
        super().close()


class MysqlHandler(MysqldumpHandler):
    """ Handle and process the stdout / stderr output from a mysql process
    """
    _rx_prog = re.compile(r'^((?:CREATE TABLE )|(?:INSERT INTO ))`(\w+)`')
    _log_all = LOG_PIPES_OUTPUT
    _action_name = "restoring"
    _last_logged = ""

    def process(self, line):
        """ Process the last line that was read
        """
        line = line.strip('\n')
        if SHOW_PROGRESSION:
            match = self._rx_prog.search(line)
            if match:
                tname = match.group(2)
                if tname != self._last_logged:
                    logger.debug('... %s %s %s', self._action_name,
                                 'structure of' if 'CREATE' in match.group(1) else 'data of',
                                 tname)
                    print('.', end="", flush=True)
                    self._last_logged = tname
        if self._log_all:
            logger.debug(line)


class MySqlServer:
    """ A server hosting a Mysql instance
    """

    def __init__(self, host, port, username, password, description="", ssh_tunnel=None):
        self.host = host
        self.port = port
        self.username = username
        self.password = password
        self.description = description[:30]
        self.ssh_tunnel = ssh_tunnel

        self.cnn = None
        self.active_db = ""

    def __repr__(self):
        s = f"{self.host}:{self.port} as {self.username}"
        if self.description:
            s = f"{self.description} ({s})"
        return s

    def connect(self, autocommit=True):
        """ Establish the connection to the Mysql server
        @see https://pymysql.readthedocs.io/en/latest/modules/connections.html
        """
        if self.ssh_tunnel:
            self.ssh_tunnel.start()
            host, port = self.ssh_tunnel.LOCAL_ADRESS
        else:
            host, port = self.host, self.port

        self.cnn = pymysql.connect(host=host,
                                   port=port,
                                   user=self.username,
                                   password=self.password,
                                   autocommit=autocommit,
                                   max_allowed_packet="32M",
                                   )

        if not self.cnn.open:
            raise RuntimeError(f'Unable to connect to {self}')

        return self.cnn

    def set_active_db(self, dbname):
        """ set the active database
        """
        self.cnn.select_db(dbname)
        self.active_db = dbname

    def close(self):
        """ Close the connection to the database
        and the ssh tunnel if one is opened
        """
        if self.cnn:
            self.cnn.close()
        if self.ssh_tunnel:
            self.ssh_tunnel.stop()
        logger.debug(f'{self} - connection closed')

    def exec_query(self, sql):
        """ Execute the sql code and return the resulting cursor
        @see https://pymysql.readthedocs.io/en/latest/modules/cursors.html
        """
        self.cnn.ping(reconnect=True)
        cursor = self.cnn.cursor()
        if LOG_MYSQL_QUERIES:
            logger.debug(sql)
        cursor.execute(sql)
        return cursor

    def db_exists(self, dbname):
        """ Return True if the database exists
        """
        cursor = self.exec_query(f"""SELECT SCHEMA_NAME
                           FROM INFORMATION_SCHEMA.SCHEMATA
                           WHERE SCHEMA_NAME = '{dbname}'""")
        row = cursor.fetchone()
        return row is not None

    def list_tables(self, dbname=""):
        """ Return a list of tables (but not views!)
        for either the currently selected database,
        or the one given as a parameter"""
        cursor = self.exec_query(
            "SHOW FULL TABLES{} WHERE Table_type='BASE TABLE';".format(f" FROM {dbname}" if dbname else ""))
        return (row[0] for row in cursor.fetchall())

    def list_views(self, dbname=""):
        """ Return a list of views
        for either the currently selected database,
        or the one given as a parameter"""
        cursor = self.exec_query(
            "SHOW FULL TABLES{} WHERE Table_type='VIEW';".format(f" FROM {dbname}" if dbname else ""))
        return (row[0] for row in cursor.fetchall())

    def get_view_definition(self, view_name, set_definer=""):
        """ Return the SQL create statement for the view
        If 'set_definer' is not empty, the username in the 'SET DEFINER' part
        of the create statement is replace by the one given
        """
        cursor = self.exec_query(f"show create view {view_name}")
        definition = cursor.fetchone()[1]
        if set_definer:
            # force a new definer
            definition = re.sub(r'DEFINER=`\w+`@`[\w\-.]+`',
                                f"DEFINER=`{set_definer}`@`\1`",
                                definition)
        return definition


# Operation status
UNKNOWN = 0
SUCCESS = 1
FAILURE = 2

# Behaviors for the tables cloning
IGNORE = 0
STRUCTURE_ONLY = 1
STRUCTURE_AND_DATA = 2  # -> default behavior


class CloningOperation:
    """ A database cloning operation between two Mysql servers
    """

    def __init__(self, name, dbname, from_server, to_server, is_default=True, ignore_tables=None, structure_only=None,
                 filter_tables=None, ignore_views=None, compress=True):
        self.name = name
        self.dbname = dbname
        self.from_server = from_server
        self.to_server = to_server

        self.is_default = is_default
        self.compress = compress
        self.ignore_tables = [re.compile(r) for r in ignore_tables] if ignore_tables else []
        self.structure_only = [re.compile(r) for r in structure_only] if structure_only else []
        self.filter_tables = [re.compile(r) for r in filter_tables] if filter_tables else []
        self.ignore_views = [re.compile(r) for r in ignore_views] if ignore_views else []

        self.status = UNKNOWN

    def __repr__(self):
        return f"Cloning {self.dbname} from {self.from_server} to {self.to_server}"

    def _build_dump_command(self, dump_options=None, tables=None):
        """ Build a mysqldump command line and return it as a
        ready-to-consume list for Popen
        @see https://dev.mysql.com/doc/refman/5.7/en/mysqldump.html#mysqldump-option-summary
        """
        tables = tables or []
        dump_options = dump_options or []

        base_cmd = ["mysqldump",
                    "--single-transaction",
                    "-u", self.from_server.username,
                    f"--password={self.from_server.password}",
                    f"--max-allowed-packet={MAX_ALLOWED_PACKET}",
                    "--skip-add-drop-table",
                    "--skip-add-locks",
                    "--skip-comments",
                    ]

        if self.compress:
            base_cmd.append("--compress")

        if SHOW_PROGRESSION:
            base_cmd.append("--verbose")

        if self.from_server.ssh_tunnel:
            host, port = self.from_server.ssh_tunnel.LOCAL_ADRESS
            base_cmd += ["--host", host,
                         "--port", str(port)]

        return base_cmd + dump_options + [self.dbname] + tables

    def _build_restore_command(self):
        """ Build a mysql command line and return it as a
        ready-to-consume list for Popen
        @see https://dev.mysql.com/doc/refman/8.0/en/mysql-command-options.html#option_mysql_quick
        """
        init_command = f"set global max_allowed_packet={MAX_ALLOWED_PACKET};" \
                       "set global wait_timeout=28800;" \
                       "set global interactive_timeout=28800;"

        cmd = ["mysql",
               "-h", self.to_server.host,
               "-P", str(self.to_server.port),
               "-u", self.to_server.username,
               f"--password={self.to_server.password}",
               f"--init-command={init_command}",
               "--reconnect",
               "--quick",
               "--unbuffered",
               "--wait",
               "--verbose",
               "-D", self.dbname
               ]

        # if LOG_PIPES_OUTPUT:
        #   cmd.append("--verbose")

        if self.compress:
            cmd.append("--compress")
        return cmd

    @staticmethod
    def _run_piped_processes(dump_cmd, restore_cmd):
        """ Run the dump and the restore commands by piping them
        The output of the mysqldump process is piped into the input of the mysql one
        """
        logger.debug(">>> Dump command: %s", " ".join(map(str, dump_cmd)))
        logger.debug(">>> Piped into: %s", " ".join(map(str, restore_cmd)))

        mysqldump_handler = MysqldumpHandler(logger.name)
        mysql_handler = MysqlHandler(logger.name)
        try:
            # noinspection PyTypeChecker
            with Popen(restore_cmd, stdin=PIPE, stdout=mysql_handler, stderr=mysql_handler) as mysql:
                # noinspection PyTypeChecker
                with Popen(dump_cmd, stdout=PIPE, stderr=mysqldump_handler) as mysqldump:
                    mysql.stdin.write(mysqldump.stdout.read())

            if mysqldump.returncode:
                raise RuntimeError('mysqldump returned a non zero code')
            if mysql.returncode:
                raise RuntimeError('mysql returned a non zero code')

        except (OSError, RuntimeError, CalledProcessError) as e:
            logger.error("Execution failed: %s", e)
            raise RuntimeError(f"An error happened at runtime: {e}")

        finally:
            mysqldump_handler.close()
            mysql_handler.close()

    def run(self):
        """ Run the cloning op
        """
        logger.info(f"*** Cloning {self.dbname} ***")
        logger.info(f"> From {self.from_server}")
        logger.info(f"> To {self.to_server}")

        try:
            self.from_server.connect()
            self.from_server.set_active_db(self.dbname)
            logger.debug('Connected to %s', self.from_server)

            self.to_server.connect()
            logger.debug('Connected to %s', self.to_server)

            tables = {}
            for tname in self.from_server.list_tables():
                if any(rx.match(tname) for rx in self.ignore_tables):
                    tables[tname] = IGNORE
                elif self.filter_tables and not any(rx.match(tname) for rx in self.filter_tables):
                    tables[tname] = IGNORE
                elif any(rx.match(tname) for rx in self.structure_only):
                    tables[tname] = STRUCTURE_ONLY
                else:
                    tables[tname] = STRUCTURE_AND_DATA

            restore_cmd = self._build_restore_command()

            # Dump structure: --single-transaction --no-data --routines {dbname} tbname1 tname2 ...
            dump_structure_for = [t for t, s in tables.items() if s != IGNORE]
            dump_structure_cmd = self._build_dump_command(["--no-data", "--routines"],
                                                          dump_structure_for)

            # Dump data: --no-create-info --skip-triggers {dbname} tbname1 tname2 ...
            dump_data_for = [t for t, s in tables.items() if s == STRUCTURE_AND_DATA]
            dump_data_cmd = self._build_dump_command(["--no-create-info", "--skip-triggers"],
                                                     dump_data_for)

            if tables and not dump_structure_for and not dump_data_for:
                logging.warning('No table will be cloned')

            # Recreate the target DB
            logger.info("(Re)create the database")
            self.to_server.exec_query(f"DROP DATABASE IF EXISTS `{self.dbname}`;")
            self.to_server.exec_query(f"CREATE SCHEMA `{self.dbname}`;")
            self.to_server.set_active_db(self.dbname)

            # Run mysqldump
            try:
                if dump_structure_for:
                    logger.info(f"Cloning structure for {len(dump_structure_for)} tables (on {len(tables)})...")
                    self._run_piped_processes(dump_structure_cmd, restore_cmd)

                if dump_data_for:
                    logger.info(f"Cloning data for {len(dump_data_for)} tables (on {len(tables)})...")
                    self._run_piped_processes(dump_data_cmd, restore_cmd)

                logger.info(f"Cloning views...")
                for v in self.from_server.list_views(self.dbname):
                    if any(rx.match(v) for rx in self.ignore_views):
                        continue
                    logger.debug('* cloning view %s', v)
                    definition = self.from_server.get_view_definition(v, self.to_server.username)

                    try:
                        self.to_server.exec_query(definition)
                    except (pymysql.err.ProgrammingError, pymysql.err.InternalError) as e:
                        logger.error('Unable to create the internal view %s: %s', v, e)

                self.status = SUCCESS
                logger.info("> the database was successfully cloned")
            except RuntimeError:
                self.status = FAILURE
                logger.error("<!> An error happened while cloning the '%s' database", self.dbname)

        finally:
            self.from_server.close()
            self.to_server.close()


def main(settings, arguments):
    prompt = not arguments["--yes"]

    logger.info("Start db cloning utility...")
    logger.debug(f"Settings: %s", str(settings).replace('\r', '').replace('\n', ''))
    logger.debug(f"Arguments: %s", str(arguments).replace('\r', '').replace('\n', ''))

    # Load the servers' configuration
    servers = {}
    for server_name, server_settings in settings['servers'].items():
        hostname = server_settings['host']

        match = re.search(r"^docker:(\w+)$", hostname)
        if match:
            logger.debug("resolve IP for docker %s", match.group(1))
            ip = resolve_docker_ip(match.group(1))
            logger.debug("substitute '%s' to '%s' as hostname", ip, hostname)
            hostname = ip

        if 'ssh' in server_settings:
            ssh_tunnel = SshTunnel(hostname, server_settings['mysql']['port'], **server_settings['ssh'])
        else:
            ssh_tunnel = None

        server = MySqlServer(hostname,
                             **server_settings['mysql'],
                             description=server_settings['description'],
                             ssh_tunnel=ssh_tunnel)

        servers[server_name] = server

    # Load the cloning ops' configuration
    ops = {}
    for name, args in settings['operations'].items():
        dbname = args['dbname']
        from_server = servers[args['from_server']]
        to_server = servers[args['to_server']]
        kwargs = {k: v for k, v in args.items() if k not in ('dbname', 'from_server', 'to_server')}

        op = CloningOperation(name, dbname, from_server, to_server, **kwargs)
        ops[name] = op

    # Operations to launch
    if arguments.get('<opname>', None):
        selected_ops = []
        for opname in arguments['<opname>']:
            try:
                selected_ops.append(ops[opname])
            except KeyError:
                logger.error('No operation found with name %s', opname)
    else:
        selected_ops = [op for op in ops.values() if op.is_default]

    if not selected_ops:
        raise RuntimeError('No operation to launch')

    # Ask for confirmation (except if '--yes' is in arguments)
    if prompt:
        logger.debug('Ask for confirmation...')
        msg = "The following operations will be launched:\n{}\n" \
              "WARNING: the existing local databases will be replaced" \
              "".format("\n".join(f"* {op}" for op in selected_ops))

        if not ask_confirmation(msg):
            logger.info("-- Operation cancelled by user --")
            return
        logger.debug('> User confirmed')

    # Run the cloning operations
    for op in selected_ops:
        op.run()

    failures = [op.name for op in selected_ops if op.status == FAILURE]
    if failures:
        logger.error("WARNING! the following operations failed: %s", ', '.join(failures))


if __name__ == '__main__':
    # load settings from settings.yml file
    settings = load_settings()

    # parse CLI arguments
    arguments = docopt(__doc__, help=__doc__, version=__VERSION__)

    with Lockfile(path=HERE / '.clonedb.lock',
                  on_error=lambda: logger.critical("A cloning process is already running, please wait...")):
        main(settings, arguments)