#!@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 [database]
#       b10-dbutil --upgrade [--noconfirm] [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.  In both cases, if the databas
# file is not given on the command line, the default database will be accessed.
#
# 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.

import sys; sys.path.append("@@PYTHONPATH@@")
import os, sqlite3, shutil
from optparse import OptionParser
import isc.util.process

isc.util.process.rename()

# Default database to use if the database is not given on the command line.
# (This is the same string as in "auth.spec.pre.in".)
DEFAULT_DATABASE_FILE = "@@LOCALSTATEDIR@@/@PACKAGE@/zone.sqlite3"

# 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@)"

# 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.
]

# Exception class to indicate error exit
class DbutilException(Exception):
    pass

# Functions for outputting messages in a consistent format.  As this is intended
# to be an interactive utility, it was not considered necessary to use the full
# logging framework for messages.

def output(writer, prefix, text, ex = None):
    """
    @brief Write error message to output stream

    @param writer Function to do the writing
    @param prefix Prefix to the message
    @param text Text to output
    @param ex Possible exception holding additiona information
    """
    writer(prefix + ": " + text)
    if ex is not None:
        writer(" - " + str(ex))
    writer("\n")


def error(text, ex = None):
    """
    @brief Write error message to stderr.

    @param text Text to output
    @param ex Possible exception holding additiona information
    """
    output(sys.stderr.write, "ERROR", text, ex)


def warn(text, ex = None):
    """
    @brief Write warning message to stderr.

    @param text Text to output
    @param ex Possible exception holding additiona information
    """
    output(sys.stderr.write, "WARN", text, ex)


def info(text, ex = None):
    """
    @brief Write informational message to stdout.

    @param text Text to output
    @param ex Possible exception holding additiona information
    """
    output(sys.stdout.write, "INFO", text, ex)


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

        @param db_file Name of the database file
        @param verbose If True, print all SQL statements to stdout before
               executing them.
        """
        self.connection = None
        self.cursor = None
        self.db_file = db_file
        self.backup_file = None
        self.verbose = verbose

    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, what = None):
        """
        @brief Execute Statement

        Executes the given statement, exiting the program on error.  If
        verbose mode is set, the statement is printed to stdout before
        execution.

        @param statement SQL statement to execute
        @param what Reason for the action (used in the error message if the
               action fails)
        """
        if self.verbose:
            sys.stdout.write(statement + "\n")

        try:
            self.cursor.execute(statement)
        except Exception as ex:
            if (what is None):
                raise DbutilException("SQL Error - " + str(ex))
            else:
                raise DbutilException("failed to " + what + " - " + 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)
        info("database " + self.db_file + " backed up to " + 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: ")
        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 get_latest_version():
    """
    @brief Returns the latest version of 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)
    """

    # Check only one row of data in the version table.
    db.execute("SELECT COUNT(*) FROM schema_version", "get database version")
    result = db.result()
    if result[0] == 0:
        raise DbutilException("unable to determine database version - " +
                              "nothing in schema_version table")
    elif result[0] > 1:
        raise DbutilException("unable to determine database version - " +
                              "too many rows in schema_version table")

    # Get the version information.
    db.execute("SELECT * FROM schema_version", "get database version")
    result = db.result()
    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]

    return (major, minor)


def match_version(db, expected):
    """
    @brief Check database version against that expected
    
    Checks whether the version of the database matches that expected for
    the upgrade.  Both the major and minor versions must match.

    @param db Database
    @param expected Expected version of the database in form (major, minor)

    @return True if the versions match, false if they don't.
    """
    current = get_version(db)
    return expected == current


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".
    """
    increment = (version_string(upgrade['from']) + " to " +
                 version_string(upgrade['to']))
    action = "upgrading database from " + increment
    info(action)
    for statement in upgrade['statements']:
        db.execute(statement, "upgrade database from " + increment)

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


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.
    """
    if match_version(db, get_latest_version()):
        info("database already at latest version, no upgrade necessary")

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

        if count > 0:
            info("database upgrade successfully completed")
        else:
            # Should not get here, as we established earlier that the database
            # was not at the latest version so we should have upgraded.
            # (Although it is possible that as version checks are for equality,
            # an older version of dbutil was being run against a newer version
            # of the database.)
            raise DbutilException("database not at latest version but no " +
                                  "upgrade was performed")


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
    """
    current = get_version(db);
    latest = get_latest_version()

    if current == latest:
        info("database version " + version_string(current))
        info("this is the latest version of the database schema, " +
             "no upgrade is required")
    else:
        info("database version " + version_string(current) +
             ", latest version is " + version_string(latest))
        info("re-run this program with the --upgrade switch to upgrade")


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")
    (options, args) = parser.parse_args()

    # Set the database file on which to operate
    if (len(args) > 1):
        error("too many arguments to the command, maximum of one expected")
        parser.print_usage()
        sys.exit(1)
    elif len(args) == 0:
        args.append(DEFAULT_DATABASE_FILE)

    # Check for conflicting options.  If some are found, output a suitable
    # error message and print the usage.
    if options.check and options.upgrade:
        error("--upgrade is not compatible with --check")
    elif (not options.check) and (not options.upgrade):
        error("must select one of --check or --upgrade")
    elif (options.check and options.noconfirm):
        error("--noconfirm is not compatible with --check")
    else:
        return (options, args)

    # Only get here on conflicting options
    parser.print_usage()
    sys.exit(1)


if __name__ == "__main__":
    (options, args) = parse_command()
    db = Database(args[0], options.verbose)

    if options.check:
        # Check database - open, report, and close
        try:
            db.open()
            check_version(db)
            db.close()
        except Exception as ex:
            error("unable to check database version - " + str(ex))
            sys.exit(1)

    elif options.upgrade:
        # Upgrade.  Check if this is what they really want to do
        if not options.noconfirm:
            proceed = prompt_user()
            if not proceed:
                info("upgrade abandoned - database has not been changed\n")
                sys.exit(0)

        # 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:
                error("upgrade failed - " + str(ex))
                warn("database may be corrupt, restore it from backup")
            else:
                error("upgrade preparation failed - " + str(ex))
                info("database upgrade was not attempted")
            sys.exit(1)
    else:
        error("internal error, neither --check nor --upgrade selected")
        sys.exit(1)