#!@PYTHON@

# Copyright (C) 2012  Internet Systems Consortium.
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SYSTEMS CONSORTIUM
# DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
# INTERNET SYSTEMS CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
# FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
# WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""
@file Dabase Utilities

This file holds the "dbutil" program, a general utility program for doing
management of the BIND 10 database.  There are two modes of operation:

      b10-dbutil --check [--verbose] database
      b10-dbutil --upgrade [--noconfirm] [--verbose] database

The first form checks the version of the given database.  The second form
upgrades the database to the latest version of the schema, omitting the
warning prompt if --noconfirm is given.

For maximum safety, prior to the upgrade a backup database is created.
The is the database name with ".backup" appended to it (or ".backup-n" if
".backup" already exists).  This is used to restore the database if the
upgrade fails.
"""

# Exit codes
# These are defined here because one of them is already used before most
# of the import statements.
EXIT_SUCCESS = 0
EXIT_NEED_UPDATE = 1
EXIT_VERSION_TOO_HIGH = 2
EXIT_COMMAND_ERROR = 3
EXIT_READ_ERROR = 4
EXIT_UPGRADE_ERROR = 5
EXIT_UNCAUGHT_EXCEPTION = 6

import sys; sys.path.append("@@PYTHONPATH@@")

# Normally, python exits with a status code of 1 on uncaught exceptions
# Since we reserve exit status 1 for 'database needs upgrade', we
# override the excepthook to exit with a different status
def my_except_hook(a, b, c):
    sys.__excepthook__(a,b,c)
    sys.exit(EXIT_UNCAUGHT_EXCEPTION)
sys.excepthook = my_except_hook

import os, sqlite3, shutil
from optparse import OptionParser
import isc.util.process
import isc.log
from isc.log_messages.dbutil_messages import *

isc.log.init("b10-dbutil")
logger = isc.log.Logger("dbutil")
isc.util.process.rename()

TRACE_BASIC = logger.DBGLVL_TRACE_BASIC


# @brief Version String
# This is the version displayed to the user.  It comprises the module name,
# the module version number, and the overall BIND 10 version number (set in
# configure.ac)
VERSION = "b10-dbutil 20120319 (BIND 10 @PACKAGE_VERSION@)"

# @brief Statements to Update the Database
# These are in the form of a list of dictionaries, each of which contains the
# information to perform an incremental upgrade from one version of the
# database to the next.  The information is:
#
# a) from: (major, minor) version that the database is expected to be at
#    to perform this upgrade.
# b) to: (major, minor) version of the database to which this set of statements
#    upgrades the database to.  (This is used for documentation purposes,
#    and to update the schema_version table when the upgrade is complete.)
# c) statements: List of SQL statments to perform the upgrade.
#
# The incremental upgrades are performed one after the other.  If the version
# of the database does not exactly match that required for the incremental
# upgrade, the upgrade is skipped.  For this reason, the list must be in
# ascending order (e.g. upgrade 1.0 to 2.0, 2.0 to 2.1, 2.1 to 2.2 etc.).
#
# Note that apart from the 1.0 to 2.0 upgrade, no upgrade need alter the
# schema_version table: that is done by the upgrade process using the
# information in the "to" field.
UPGRADES = [
    {'from': (1, 0), 'to': (2, 0),
        'statements': [

            # Move to the latest "V1" state of the database if not there
            # already.
            "CREATE TABLE IF NOT EXISTS diffs (" +
                "id INTEGER PRIMARY KEY, " +
                "zone_id INTEGER NOT NULL," +
                "version INTEGER NOT NULL, " +
                "operation INTEGER NOT NULL, " +
                "name STRING NOT NULL COLLATE NOCASE, " +
                "rrtype STRING NOT NULL COLLATE NOCASE, " +
                "ttl INTEGER NOT NULL, " +
                "rdata STRING NOT NULL)",

            # Within SQLite with can only rename tables and add columns; we
            # can't drop columns nor can we alter column characteristics.
            # So the strategy is to rename the table, create the new table,
            # then copy all data across.  This means creating new indexes
            # as well; these are created after the data has been copied.

            # zones table
            "DROP INDEX zones_byname",
            "ALTER TABLE zones RENAME TO old_zones",
            "CREATE TABLE zones (" +
                "id INTEGER PRIMARY KEY, " +
                "name TEXT NOT NULL COLLATE NOCASE, " +
                "rdclass TEXT NOT NULL COLLATE NOCASE DEFAULT 'IN', " +
                "dnssec BOOLEAN NOT NULL DEFAULT 0)",
            "INSERT INTO ZONES " +
                "SELECT id, name, rdclass, dnssec FROM old_zones",
            "CREATE INDEX zones_byname ON zones (name)",
            "DROP TABLE old_zones",

            # records table
            "DROP INDEX records_byname",
            "DROP INDEX records_byrname",
            "ALTER TABLE records RENAME TO old_records",
            "CREATE TABLE records (" +
                "id INTEGER PRIMARY KEY, " +
                "zone_id INTEGER NOT NULL, " +
                "name TEXT NOT NULL COLLATE NOCASE, " +
                "rname TEXT NOT NULL COLLATE NOCASE, " +
                "ttl INTEGER NOT NULL, " +
                "rdtype TEXT NOT NULL COLLATE NOCASE, " +
                "sigtype TEXT COLLATE NOCASE, " +
                "rdata TEXT NOT NULL)",
            "INSERT INTO records " +
                "SELECT id, zone_id, name, rname, ttl, rdtype, sigtype, " +
                    "rdata FROM old_records",
            "CREATE INDEX records_byname ON records (name)",
            "CREATE INDEX records_byrname ON records (rname)",
            "CREATE INDEX records_bytype_and_rname ON records (rdtype, rname)",
            "DROP TABLE old_records",

            # nsec3 table
            "DROP INDEX nsec3_byhash",
            "ALTER TABLE nsec3 RENAME TO old_nsec3",
            "CREATE TABLE nsec3 (" +
                "id INTEGER PRIMARY KEY, " +
                "zone_id INTEGER NOT NULL, " +
                "hash TEXT NOT NULL COLLATE NOCASE, " +
                "owner TEXT NOT NULL COLLATE NOCASE, " +
                "ttl INTEGER NOT NULL, " +
                "rdtype TEXT NOT NULL COLLATE NOCASE, " +
                "rdata TEXT NOT NULL)",
            "INSERT INTO nsec3 " +
                "SELECT id, zone_id, hash, owner, ttl, rdtype, rdata " +
                    "FROM old_nsec3",
            "CREATE INDEX nsec3_byhash ON nsec3 (hash)",
            "DROP TABLE old_nsec3",

            # diffs table
            "ALTER TABLE diffs RENAME TO old_diffs",
            "CREATE TABLE diffs (" +
                "id INTEGER PRIMARY KEY, " +
                "zone_id INTEGER NOT NULL, " +
                "version INTEGER NOT NULL, " +
                "operation INTEGER NOT NULL, " +
                "name TEXT NOT NULL COLLATE NOCASE, " +
                "rrtype TEXT NOT NULL COLLATE NOCASE, " +
                "ttl INTEGER NOT NULL, " +
                "rdata TEXT NOT NULL)",
            "INSERT INTO diffs " +
                "SELECT id, zone_id, version, operation, name, rrtype, " +
                    "ttl, rdata FROM old_diffs",
            "DROP TABLE old_diffs",

            # Schema table.  This is updated to include a second column for
            # future changes.  The idea is that if a version of BIND 10 is
            # written for schema M.N, it should be able to work for all
            # versions of N; if not, M must be incremented.
            #
            # For backwards compatibility, the column holding the major
            # version number is left named "version".
            "ALTER TABLE schema_version " +
                "ADD COLUMN minor INTEGER NOT NULL DEFAULT 0"
        ]
    }

# To extend this, leave the above statements in place and add another
# dictionary to the list.  The "from" version should be (2, 0), the "to"
# version whatever the version the update is to, and the SQL statements are
# the statements required to perform the upgrade.  This way, the upgrade
# program will be able to upgrade both a V1.0 and a V2.0 database.
]

class DbutilException(Exception):
    """
    @brief Exception class to indicate error exit
    """
    pass

class Database:
    """
    @brief Database Encapsulation

    Encapsulates the SQL database, both the connection and the cursor.  The
    methods will cause a program exit on any error.
    """
    def __init__(self, db_file):
        """
        @brief Constructor

        @param db_file Name of the database file
        """
        self.connection = None
        self.cursor = None
        self.db_file = db_file
        self.backup_file = None

    def open(self):
        """
        @brief Open Database

        Opens the passed file as an sqlite3 database and stores a connection
        and a cursor.
        """
        if not os.path.exists(self.db_file):
            raise DbutilException("database " + self.db_file +
                                 " does not exist");

        try:
            self.connection = sqlite3.connect(self.db_file)
            self.connection.isolation_level = None  # set autocommit
            self.cursor = self.connection.cursor()
        except sqlite3.OperationalError as ex:
            raise DbutilException("unable to open " + self.db_file +
                                  " - " + str(ex))

    def close(self):
        """
        @brief Closes the database
        """
        if self.connection is not None:
            self.connection.close()

    def execute(self, statement):
        """
        @brief Execute Statement

        Executes the given statement, exiting the program on error.

        @param statement SQL statement to execute
        """
        logger.debug(TRACE_BASIC, DBUTIL_EXECUTE, statement)

        try:
            self.cursor.execute(statement)
        except Exception as ex:
            logger.error(DBUTIL_STATEMENT_ERROR, statement, ex)
            raise DbutilException(str(ex))

    def result(self):
        """
        @brief Return result of last execute

        Returns a single row that is the result of the last "execute".
        """
        return self.cursor.fetchone()

    def backup(self):
        """
        @brief Backup Database

        Attempts to copy the given database file to a backup database, the
        backup database file being the file name with ".backup" appended.
        If the ".backup" file exists, a new name is constructed by appending
        ".backup-n" (n starting at 1) and the action repeated until an
        unused filename is found.

        @param db_file Database file to backup
        """
        if not os.path.exists(self.db_file):
            raise DbutilException("database " + self.db_file +
                                  " does not exist");

        self.backup_file = self.db_file + ".backup"
        count = 0
        while os.path.exists(self.backup_file):
            count = count + 1
            self.backup_file = self.db_file + ".backup-" + str(count)

        # Do the backup
        shutil.copyfile(self.db_file, self.backup_file)
        logger.info(DBUTIL_BACKUP, self.db_file, self.backup_file)

def prompt_user():
    """
    @brief Prompt the User

    Explains about the upgrade and requests authorisation to continue.

    @return True if user entered 'Yes', False if 'No'
    """
    sys.stdout.write(
"""You have selected the upgrade option.  This will upgrade the schema of the
selected BIND 10 zone database to the latest version.

The utility will take a copy of the zone database file before executing so, in
the event of a problem, you will be able to restore the zone database from
the backup.  To ensure that the integrity of this backup, please ensure that
BIND 10 is not running before continuing.
""")
    yes_entered = False
    no_entered = False
    while (not yes_entered) and (not no_entered):
        sys.stdout.write("Enter 'Yes' to proceed with the upgrade, " +
                         "'No' to exit the program: \n")
        response = sys.stdin.readline()
        if response.lower() == "yes\n":
            yes_entered = True
        elif response.lower() == "no\n":
            no_entered = True
        else:
            sys.stdout.write("Please enter 'Yes' or 'No'\n")

    return yes_entered


def version_string(version):
    """
    @brief Format Database Version

    Converts a (major, minor) tuple into a 'Vn.m' string.

    @param version Version tuple to convert

    @return Version string
    """
    return "V" + str(version[0]) + "." + str(version[1])


def compare_versions(first, second):
    """
    @brief Compare Versions

    Compares two database version numbers.

    @param first First version number to check (in the form of a
           "(major, minor)" tuple).
    @param second Second version number to check (in the form of a
           "(major, minor)" tuple).

    @return -1, 0, +1 if "first" is <, ==, > "second"
    """
    if first == second:
        return 0

    elif ((first[0] < second[0]) or
          ((first[0] == second[0]) and (first[1] < second[1]))):
        return -1

    else:
        return 1


def get_latest_version():
    """
    @brief Returns the version to which this utility can upgrade the database

    This is the 'to' version held in the last element of the upgrades list
    """
    return UPGRADES[-1]['to']


def get_version(db):
    """
    @brief Return version of database

    @return Version of database in form (major version, minor version)
    """

    # Get the version information.
    db.execute("SELECT * FROM schema_version")
    result = db.result()
    if result is None:
        raise DbutilException("nothing in schema_version table")

    major = result[0]
    if (major == 1):
        # If the version number is 1, there will be no "minor" column, so
        # assume a minor version number of 0.
        minor = 0
    else:
        minor = result[1]

    result = db.result()
    if result is not None:
        raise DbutilException("too many rows in schema_version table")

    return (major, minor)


def check_version(db):
    """
    @brief Check the version

    Checks the version of the database and the latest version, and advises if
    an upgrade is needed.

    @param db Database object

    returns 0 if the database is up to date
    returns EXIT_NEED_UPDATE if the database needs updating
    returns EXIT_VERSION_TOO_HIGH if the database is at a later version
            than this program knows about
    These return values are intended to be passed on to sys.exit.
    """
    current = get_version(db)
    latest = get_latest_version()

    match = compare_versions(current, latest)
    if match == 0:
        logger.info(DBUTIL_VERSION_CURRENT, version_string(current))
        logger.info(DBUTIL_CHECK_OK)
        return EXIT_SUCCESS
    elif match < 0:
        logger.info(DBUTIL_VERSION_LOW, version_string(current),
                    version_string(latest))
        logger.info(DBUTIL_CHECK_UPGRADE_NEEDED)
        return EXIT_NEED_UPDATE
    else:
        logger.warn(DBUTIL_VERSION_HIGH, version_string(current),
                    version_string(get_latest_version()))
        logger.info(DBUTIL_UPGRADE_DBUTIL)
        return EXIT_VERSION_TOO_HIGH

def perform_upgrade(db, upgrade):
    """
    @brief Perform upgrade

    Performs the upgrade.  At the end of the upgrade, updates the schema_version
    table with the expected version.

    @param db Database object
    @param upgrade Upgrade dictionary, holding "from", "to" and "statements".
    """
    logger.info(DBUTIL_UPGRADING, version_string(upgrade['from']),
         version_string(upgrade['to']))
    for statement in upgrade['statements']:
        db.execute(statement)

    # Update the version information
    db.execute("DELETE FROM schema_version")
    db.execute("INSERT INTO schema_version VALUES (" +
                    str(upgrade['to'][0]) + "," + str(upgrade['to'][1]) + ")")


def perform_all_upgrades(db):
    """
    @brief Performs all the upgrades

    @brief db Database object

    For each upgrade, checks that the database is at the expected version.
    If so, calls perform_upgrade to update the database.
    """
    match = compare_versions(get_version(db), get_latest_version())
    if match == 0:
        logger.info(DBUTIL_UPGRADE_NOT_NEEDED)

    elif match > 0:
        logger.warn(DBUTIL_UPGRADE_NOT_POSSIBLE)

    else:
        # Work our way through all upgrade increments
        count = 0
        for upgrade in UPGRADES:
            if compare_versions(get_version(db), upgrade['from']) == 0:
                perform_upgrade(db, upgrade)
                count = count + 1

        if count > 0:
            logger.info(DBUTIL_UPGRADE_SUCCESFUL)
        else:
            # Should not get here, as we established earlier that the database
            # was not at the latest version so we should have upgraded.
            raise DbutilException("internal error in upgrade tool - no " +
                                  "upgrade was performed on an old version " +
                                  "the database")


def parse_command():
    """
    @brief Parse Command

    Parses the command line and sets the global command options.

    @return Tuple of parser options and parser arguments
    """
    usage = ("usage: %prog --check [options] db_file\n" +
             "       %prog --upgrade [--noconfirm] [options] db_file")
    parser = OptionParser(usage = usage, version = VERSION)
    parser.add_option("-c", "--check", action="store_true",
                      dest="check", default=False,
                      help="Print database version and check if it " +
                           "needs upgrading")
    parser.add_option("-n", "--noconfirm", action="store_true",
                      dest="noconfirm", default=False,
                      help="Do not prompt for confirmation before upgrading")
    parser.add_option("-u", "--upgrade", action="store_true",
                      dest="upgrade", default=False,
                      help="Upgrade the database file to the latest version")
    parser.add_option("-v", "--verbose", action="store_true",
                      dest="verbose", default=False,
                      help="Print SQL statements as they are executed")
    parser.add_option("-q", "--quiet", action="store_true",
                      dest="quiet", default=False,
                      help="Don't print any info, warnings or errors")
    (options, args) = parser.parse_args()

    # Set the database file on which to operate
    if (len(args) > 1):
        logger.error(DBUTIL_TOO_MANY_ARGUMENTS)
        parser.print_usage()
        sys.exit(EXIT_COMMAND_ERROR)
    elif len(args) == 0:
        logger.error(DBUTIL_NO_FILE)
        parser.print_usage()
        sys.exit(EXIT_COMMAND_ERROR)

    # Check for conflicting options.  If some are found, output a suitable
    # error message and print the usage.
    if options.check and options.upgrade:
        logger.error(DBUTIL_COMMAND_UPGRADE_CHECK)
    elif (not options.check) and (not options.upgrade):
        logger.error(DBUTIL_COMMAND_NONE)
    elif (options.check and options.noconfirm):
        logger.error(DBUTIL_CHECK_NOCONFIRM)
    else:
        return (options, args)

    # Only get here on conflicting options
    parser.print_usage()
    sys.exit(EXIT_COMMAND_ERROR)


if __name__ == "__main__":
    (options, args) = parse_command()

    if options.verbose:
        isc.log.init("b10-dbutil", "DEBUG", 99)
        logger = isc.log.Logger("dbutil")
    elif options.quiet:
        # We don't use FATAL, so setting the logger to use
        # it should essentially make it silent.
        isc.log.init("b10-dbutil", "FATAL")
        logger = isc.log.Logger("dbutil")

    db = Database(args[0])
    exit_code = EXIT_SUCCESS

    logger.info(DBUTIL_FILE, args[0])
    if options.check:
        # Check database - open, report, and close
        try:
            db.open()
            exit_code = check_version(db)
            db.close()
        except Exception as ex:
            logger.error(DBUTIL_CHECK_ERROR, ex)
            exit_code = EXIT_READ_ERROR

    elif options.upgrade:
        # Upgrade.  Check if this is what they really want to do
        if not options.noconfirm:
            proceed = prompt_user()
            if not proceed:
                logger.info(DBUTIL_UPGRADE_CANCELED)
                sys.exit(EXIT_SUCCESS)

        # It is.  Do a backup then do the upgrade.
        in_progress = False
        try:
            db.backup()
            db.open()
            in_progress = True
            perform_all_upgrades(db)
            db.close()
        except Exception as ex:
            if in_progress:
                logger.error(DBUTIL_UPGRADE_FAILED, ex)
                logger.warn(DBUTIL_DATABASE_MAY_BE_CORRUPT, db.db_file,
                            db.backup_file)
            else:
                logger.error(DBUTIL_UPGRADE_PREPARATION_FAILED, ex)
                logger.info(DBUTIL_UPGRADE_NOT_ATTEMPTED)
            exit_code = EXIT_UPGRADE_ERROR

    sys.exit(exit_code)
