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

> Configuration: settings.yml

Usage:
  clonedb.py [-v] [-y] [<dbname>]
  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 os
import re
import threading
from subprocess import Popen, PIPE, CalledProcessError
import sys

import pymysql
import yaml
from docopt import docopt
from path import Path
from sshtunnel import SSHTunnelForwarder

import logging_
from locker import Lockfile

__VERSION__ = "0.1"

HERE = Path(__file__).parent

# Start logger
logger = logging.getLogger('clonedb')
logging_.start("clonedb", replace=True)

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

# Options
VERBOSE_DUMP = True


# Utilities

def load_settings():
    # Load settings
    with open(HERE / 'settings.yml', 'r') as f:
        settings = yaml.load(f, Loader=yaml.FullLoader)
    return settings


class StderrPipeHandler(threading.Thread):
    """ Handle the stderr output from a Popen object """

    def __init__(self, logger_name, default_level=logging.INFO):
        """Setup the object with a logger and a loglevel
        and start the thread
        """
        threading.Thread.__init__(self)
        self.logger = logging.getLogger(logger_name)
        self.daemon = False
        self.default_level = default_level
        self.fdRead, self.fdWrite = os.pipe()
        self.pipeReader = os.fdopen(self.fdRead)
        self.start()

    def fileno(self):
        """Return the write file descriptor of the pipe
        """
        return self.fdWrite

    def process(self, line):
        self.logger.log(self.default_level, line.strip('\n'))

    def run(self):
        """Run the thread, logging everything.
        """
        for line in iter(self.pipeReader.readline, ''):
            self.process(line)

        self.pipeReader.close()

    def close(self):
        """Close the write end of the pipe.
        """
        os.close(self.fdWrite)


class StderrMysqlDumpHandler(StderrPipeHandler):
    """ Handle  and process the stderr output from a mysqldump process """
    _rx_newtable = re.compile(r'Retrieving table structure for table (\w+)')

    def process(self, line):
        line = line.strip('\n')
        match = self._rx_newtable.search(line)
        if match:
            print('.', end="", flush=True)
            # logger.info('** %s', match.group(1))
        logger.debug(line)

    def close(self):
        print('', flush=True)
        super().close()


class SshTunnel:
    LOCAL_ADRESS = ('127.0.0.1', 6000)

    def __init__(self, host, remote_port, port=22, user="root", key_file="~/.ssh/id_rsa"):
        self.host = host
        self.remote_port = remote_port
        self.port = int(port)
        self.user = user
        self.key_file = key_file

        self._tunnel = SSHTunnelForwarder(
            (self.host, self.port),
            ssh_username=self.user,
            ssh_pkey=self.key_file,
            local_bind_address=self.LOCAL_ADRESS,
            remote_bind_address=('127.0.0.1', self.remote_port)
        )

    def start(self):
        self._tunnel.start()
        if not self._tunnel.tunnel_is_up[self.LOCAL_ADRESS]:
            raise RuntimeError('Unable to open the SSH Tunnel')

    def stop(self):
        self._tunnel.stop()


class MySqlServer:
    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 or "no description"
        self.ssh_tunnel = ssh_tunnel

        self.cnn = None
        self.active_db = ""

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

    def connect(self, autocommit=True):
        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)

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

        return self.cnn

    def set_constraints(self, active):
        self.exec_query(f"SET FOREIGN_KEY_CHECKS={int(bool(active))};")

    def warmup(self):
        self.set_constraints(True)
        self.exec_query(""" SET MAX_ALLOWED_PACKETS=1073741824;
                            SET CONNECT_TIMEOUT=28800;
                            SET WAIT_TIMEOUT=28800;
                            SET INTERACTIVE_TIMEOUT=28800;
                            """)

    def set_active_db(self, dbname):
        self.cnn.select_db(dbname)
        self.active_db = dbname

    def close(self):
        if self.cnn:
            self.cnn.close()
        if self.ssh_tunnel:
            self.ssh_tunnel.stop()

    def exec_query(self, sql):
        """ Execute the sql code and return the cursor """
        cursor = self.cnn.cursor()
        logger.debug(sql)
        cursor.execute(sql)
        return cursor

    def db_exists(self, dbname):
        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 (not views!)
        for either the current database or the given one"""
        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 current database or the given one"""
        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):
        cursor = self.exec_query(f"show create view {view_name}")
        return cursor.fetchone()[1]


IGNORE = 0
STRUCTURE_ONLY = 1
STRUCTURE_AND_DATA = 2  # default


class CloningOperation:
    def __init__(self, dbname, from_server, to_server, is_default=True, ignore_tables=None, structure_only=None,
                 filter_tables=None, ignore_views=None, ignore_procedures=None, ignore_functions=None):
        self.dbname = dbname
        self.from_server = from_server
        self.to_server = to_server
        self.is_default = is_default

        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.ignore_procedures = [re.compile(r) for r in ignore_procedures] if ignore_procedures else []
        self.ignore_functions = [re.compile(r) for r in ignore_functions] if ignore_functions else []

        self.table_count = None

    def __repr__(self):
        return f"Clone {self.dbname} from {self.from_server} to {self.to_server} [ignored tables: {len(self.ignore_tables)}]"

    def _build_dump_command(self, dump_options=None, tables=None):
        # > 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}",
                    # "--compress"
                    ]

        if VERBOSE_DUMP:
            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):
        return ["mysql",
                "-h", self.to_server.host,
                "-P", str(self.to_server.port),
                "-u", self.to_server.username,
                f"--password={self.to_server.password}",
                "-D", self.dbname
                ]

    def _run_piped_processes(self, dump_cmd, restore_cmd):
        logger.debug("Run: %s | %s", " ".join(map(str, dump_cmd)), " ".join(map(str, restore_cmd)))

        logger.debug("Dump command: %s", " ".join(map(str, dump_cmd)))
        logger.debug("Piped into: %s", " ".join(map(str, restore_cmd)))

        stderr_handler = StderrMysqlDumpHandler(logger.name)

        try:
            # noinspection PyTypeChecker
            with Popen(restore_cmd, stdin=PIPE, stdout=PIPE, stderr=stderr_handler) as mysql:
                # noinspection PyTypeChecker
                with Popen(dump_cmd, stdout=PIPE, stderr=stderr_handler) as mysqldump:
                    mysql.stdin.write(mysqldump.stdout.read())

            if mysqldump.returncode or mysql.returncode:
                raise RuntimeError

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

        finally:
            stderr_handler.close()

    def run(self):
        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(["--single-transaction", "--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)

                    # force the definer
                    definition = re.sub(r'DEFINER=`\w+`@`[\w\-.]+`',
                                        f"DEFINER=`{self.to_server.username}`@`localhost`",
                                        definition)

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

                logger.info("> the database was successfully cloned")
            except RuntimeError:
                logger.error(f"<!> An error happened while cloning the '{self.dbname}' database")

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


def ask_confirmation(msg):
    logger.debug('Ask for confirmation...')
    msg += "\nWould you like to continue? (yes/no)"
    while 1:
        answer = input(msg)
        if answer in ('oui', 'yes', 'y', 'o'):
            logger.debug(f"> user confirmed by answering '{answer}'")
            return True
        elif answer in ('non', 'no', 'n'):
            logger.debug(f"> user cancelled by answering '{answer}'")
            return False
        else:
            msg = "The answer could'nt be understood. Continue? (yes/no)"


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

    logger.info("Start db cloning utility...")
    logger.debug(f"Settings: {settings}")
    logger.debug(f"Arguments: {arguments}")

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

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

    # Operations to launch
    if arguments.get('<dbname>', None):
        selected_ops = [ops[arguments['<dbname>']]]
    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:
        # 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

    for op in selected_ops:
        op.run()


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)