#!/usr/bin/python3
#
# Copyright 2008 Google Inc. All Rights Reserved.
#
# This file is part of Kamailio, a free SIP server.
#
# SPDX-License-Identifier: GPL-2.0-or-later
#
# Kamailio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version
#
# Kamailio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
#
"""SQL-like access layer for dbtext.

This module provides the glue for kamctl to interact with dbtext files
using basic SQL syntax thus avoiding special case handling of dbtext.

"""

import fcntl
import os
import shutil
import sys
import tempfile
import time

__author__ = 'herman@google.com (Herman Sheremetyev)'

if 'DBTEXTDB_DEBUG' in os.environ:
    DEBUG = os.environ['DBTEXTDB_DEBUG']
else:
    DEBUG = 0


def Debug(msg):
    """Debug print method."""
    if DEBUG:
        print(msg)


class DBText(object):
    """Provides connection to a dbtext database."""

    RESERVED_WORDS = ['SELECT', 'DELETE', 'UPDATE', 'INSERT', 'SET',
                      'VALUES', 'INTO', 'FROM', 'ORDER', 'BY', 'WHERE',
                      'COUNT', 'CONCAT', 'AND', 'AS']
    ALL_COMMANDS = ['SELECT', 'DELETE', 'UPDATE', 'INSERT']
    WHERE_COMMANDS = ['SELECT', 'DELETE', 'UPDATE']

    def __init__(self, location):
        self.location = location  # location of dbtext tables
        self.tokens = []      # query broken up into tokens
        self.conditions = {}  # args to the WHERE clause
        self.columns = []     # columns requested by SELECT
        self.table = ''       # name of the table being queried
        self.header = {}      # table header
        self.orig_data = []   # original table data used to diff after updates
        self.data = []        # table data as a list of dicts
        self.count = False    # where or not using COUNT()
        self.aliases = {}     # column aliases (SELECT AS)
        self.targets = {}     # target columns-value pairs for INSERT/UPDATE
        self.args = ''        # query arguments preceding the ;
        self.command = ''     # which command are we executing
        self.strings = []     # list of string literals parsed from the query
        self.parens = []      # list of parentheses parsed from the query
        self._str_placeholder = '__DBTEXTDB_PARSED_OUT_STRING__'
        self._paren_placeholder = '__DBTEXTDB_PARSED_OUT_PARENS__'
        if not os.path.isdir(location):
            raise ParseError(location + ' is not a directory')

    def __del__(self):
        if getattr(self, 'fd', False):
            self.fd.close()

    def _ParseOrderBy(self):
        """Parse out the column name to be used for ordering the dataset.

        Raises:
            ParseError: Invalid ORDER BY clause
        """
        self.order_by = ''
        if 'ORDER' in self.tokens:
            order_index = self.tokens.index('ORDER')
            if order_index != len(self.tokens) - 3:
                raise ParseError('ORDER must be followed with BY and column '
                                 'name')
            if self.tokens[order_index + 1] != 'BY':
                raise ParseError('ORDER must be followed with BY')
            self.order_by = self.tokens[order_index + 2]

            # strip off the order by stuff
            self.tokens.pop()  # column name
            self.tokens.pop()  # BY
            self.tokens.pop()  # ORDER

        elif 'BY' in self.tokens:
            raise ParseError('BY must be preceded by ORDER')

        Debug('Order by: ' + self.order_by)

    def _ParseConditions(self):
        """Parse out WHERE clause.

        Take everything after the WHERE keyword and convert it to a dict of
        name value pairs corresponding to the columns and their values that
        should be matched.

        Raises:
            ParseError: Invalid WHERE clause
            NotSupportedError: Unsupported syntax
        """
        self.conditions = {}
        Debug('self.tokens = %s' % self.tokens)
        if 'WHERE' not in self.tokens:
            return

        if self.command not in self.WHERE_COMMANDS:
            raise ParseError(self.command + ' cannot have a WHERE clause')
        if 'OR' in self.tokens:
            raise NotSupportedError('WHERE clause does not support OR '
                                    'operator')

        where_clause = self.tokens[self.tokens.index('WHERE') + 1:]
        self.conditions = self._ParsePairs(' '.join(where_clause), 'AND')
        for cond in self.conditions:
            self.conditions[cond] = self._EscapeChars(self.conditions[cond])
        Debug('Conditions are [%s]' % self.conditions)

        # pop off where clause
        a = self.tokens.pop()
        while a != 'WHERE':
            a = self.tokens.pop()

        Debug('self.tokens: %s' % self.tokens)

    def _ParseColumns(self):
        """Parse out the columns that need to be selected.

        Raises:
            ParseError: Invalid SELECT syntax
        """
        self.columns = []
        self.count = False
        self.aliases = {}
        col_end = 0
        # this is only valid for SELECT
        if self.command != 'SELECT':
            return

        if 'FROM' not in self.tokens:
            raise ParseError('SELECT must be followed by FROM')

        col_end = self.tokens.index('FROM')
        if not col_end:  # col_end == 0
            raise ParseError('SELECT must be followed by column name[s]')

        cols_str = ' '.join(self.tokens[0:col_end])
        # check if there is a function modifier on the columns
        if self.tokens[0] == 'COUNT':
            self.count = True
            if col_end == 1:
                raise ParseError('COUNT must be followed by column name[s]')
            if not self.tokens[1].startswith(self._paren_placeholder):
                raise ParseError('COUNT must be followed by ()')
            cols_str = self._ReplaceParens(self.tokens[1])

        cols = cols_str.split(',')
        for col in cols:
            if not col.strip():
                raise ParseError('Extra comma in columns')
            col_split = col.split()
            if col_split[0] == 'CONCAT':
                # found a concat statement, do the same overall steps
                # for those cols
                self._ParseColumnsConcatHelper(col_split)
            else:
                col_split = col.split()
                if len(col_split) > 2 and col_split[1] != 'AS':
                    raise ParseError('multiple columns must be separated '
                                     'by a comma')
                elif len(col_split) == 3:
                    if col_split[1] != 'AS':
                        raise ParseError('Invalid column alias, use AS')
                    my_key = self._ReplaceStringLiterals(col_split[2],
                                                         quotes=True)
                    my_val = self._ReplaceStringLiterals(col_split[0],
                                                         quotes=True)
                    self.aliases[my_key] = [my_val]
                    self.columns.append(my_key)
                elif len(col_split) > 3:
                    raise ParseError('multiple columns must be separated by '
                                     'a comma')
                elif len(col_split) == 2:  # alias
                    my_key = self._ReplaceStringLiterals(col_split[1],
                                                         quotes=True)
                    my_val = self._ReplaceStringLiterals(col_split[0],
                                                         quotes=True)
                    self.aliases[my_key] = [my_val]
                    self.columns.append(my_key)
                else:
                    col = self._ReplaceStringLiterals(col, quotes=True).strip()
                    if not col:  # col == ''
                        raise ParseError('empty column name not allowed')

                    self.columns.append(col)

        # pop off all the columns related junk
        self.tokens = self.tokens[col_end + 1:]

        Debug('Columns: %s' % self.columns)
        Debug('Aliases: %s' % self.aliases)
        Debug('self.tokens: %s' % self.tokens)

    def _ParseColumnsConcatHelper(self, col_split):
        """Handles the columns being CONCAT'd together.

        Args:
            col_split: ['column', 'column']

        Raises:
            ParseError: invalid CONCAT()
        """
        concat_placeholder = '_'
        split_len = len(col_split)
        if split_len == 1:
            raise ParseError('CONCAT() must be followed by column name[s]')
        if not col_split[1].startswith(self._paren_placeholder):
            raise ParseError('CONCAT must be followed by ()')
        if split_len > 2:
            if split_len == 4 and col_split[2] != 'AS':
                raise ParseError('CONCAT() must be followed by an AS clause')
            if split_len > 5:
                raise ParseError('CONCAT() AS clause takes exactly 1 arg. '
                                 'Extra args: [%s]' % (col_split[4:]))
            else:
                concat_placeholder = self._ReplaceStringLiterals(col_split[-1],
                                                                 quotes=True)

        # make sure this place hodler is unique
        while concat_placeholder in self.aliases:
            concat_placeholder += '_'
        concat_cols_str = self._ReplaceParens(col_split[1])
        concat_cols = concat_cols_str.split(',')
        concat_col_list = []
        for concat_col in concat_cols:
            if ' ' in concat_col.strip():
                raise ParseError('multiple columns must be separated by a '
                                 'comma inside CONCAT()')
            concat_col = self._ReplaceStringLiterals(concat_col,
                                                     quotes=True).strip()
            if not concat_col:
                raise ParseError('Attempting to CONCAT empty set')
            concat_col_list.append(concat_col)

        self.aliases[concat_placeholder] = concat_col_list
        self.columns.append(concat_placeholder)

    def _ParseTable(self):
        """Parse out the table name (multiple table names not supported).

        Raises:
        ParseError: Unable to parse table name
        """
        table_name = ''
        if (not self.tokens or  # len == 0
            (self.tokens[0] in self.RESERVED_WORDS and
             self.tokens[0] not in ['FROM', 'INTO'])):
            raise ParseError('Missing table name')

        # SELECT
        if self.command == 'SELECT':
            table_name = self.tokens.pop(0)

        # INSERT
        elif self.command == 'INSERT':
            table_name = self.tokens.pop(0)
            if table_name == 'INTO':
                table_name = self.tokens.pop(0)

        # DELETE
        elif self.command == 'DELETE':
            if self.tokens[0] != 'FROM':
                raise ParseError('DELETE command must be followed by FROM')

            self.tokens.pop(0)  # FROM
            table_name = self.tokens.pop(0)

        # UPDATE
        elif self.command == 'UPDATE':
            table_name = self.tokens.pop(0)

        if not self.table:
            self.table = table_name

        else:
            # multiple queries detected, make sure they're against same table
            if self.table != table_name:
                raise ParseError('Table changed between queries! %s -> %s' %
                                 (self.table, table_name))
        Debug('Table is [%s]' % self.table)
        Debug('self.tokens is %s' % self.tokens)

    def _ParseTargets(self):
        """Parse out name value pairs of columns and their values.

        Raises:
            ParseError: Unable to parse targets
        """
        self.targets = {}
        # UPDATE
        if self.command == 'UPDATE':
            if self.tokens.pop(0) != 'SET':
                raise ParseError('UPDATE command must be followed by SET')

            self.targets = self._ParsePairs(' '.join(self.tokens), ',')

        # INSERT
        if self.command == 'INSERT':
            if self.tokens[0] == 'SET':
                self.targets = self._ParsePairs(' '.join(self.tokens[1:]), ',')

            elif len(self.tokens) == 3 and self.tokens[1] == 'VALUES':
                if not self.tokens[0].startswith(self._paren_placeholder):
                    raise ParseError('INSERT column names must be inside '
                                     'parens')
                if not self.tokens[2].startswith(self._paren_placeholder):
                    raise ParseError('INSERT values must be inside parens')

                cols = self._ReplaceParens(self.tokens[0]).split(',')
                vals = self._ReplaceParens(self.tokens[2]).split(',')

                if len(cols) != len(vals):
                    raise ParseError('INSERT column and value numbers must '
                                     'match')
                if not cols:  # len == 0
                    raise ParseError('INSERT column number must be greater '
                                     'than 0')

                i = 0
                while i < len(cols):
                    val = vals[i].strip()
                    if not val:  # val == ''
                        raise ParseError('INSERT values cannot be empty')
                    if ' ' in val:
                        raise ParseError('INSERT values must be comma '
                                         'separated')
                    self.targets[cols[i].strip()] = \
                        self._ReplaceStringLiterals(val)
                    i += 1

            else:
                raise ParseError('Unable to parse INSERT targets')

        for target in self.targets:
            self.targets[target] = self._EscapeChars(self.targets[target])

        Debug('Targets are [%s]' % self.targets)

    def _EscapeChars(self, value):
        """Escape necessary chars before inserting into dbtext.

        Args:
            value: 'string'

        Returns:
            escaped: 'string' with chars escaped appropriately
        """
        # test that the value is string, if not return it as is
        try:
            value.find('a')
        except Exception:
            return value

        escaped = value
        escaped = escaped.replace('\\', '\\\\').replace('\0', '\\0')
        escaped = escaped.replace(':', '\\:').replace('\n', '\\n')
        escaped = escaped.replace('\r', '\\r').replace('\t', '\\t')
        return escaped

    def _UnEscapeChars(self, value):
        """Un-escape necessary chars before returning to user.

        Args:
            value: 'string'

        Returns:
            escaped: 'string' with chars escaped appropriately
        """
        # test that the value is string, if not return it as is
        try:
            value.find('a')
        except Exception:
            return value

        escaped = value
        escaped = escaped.replace('\\:', ':').replace('\\n', '\n')
        escaped = escaped.replace('\\r', '\r').replace('\\t', '\t')
        escaped = escaped.replace('\\0', '\0').replace('\\\\', '\\')
        return escaped

    def Execute(self, query, writethru=True):
        """Parse and execute the query.

        Args:
            query: e.g. 'select * from table;'
            writethru: bool

        Returns:
            dataset: [{col: val, col: val}, {col: val}, {col: val}]

        Raises:
            ExecuteError: unable to execute query
        """
        # parse the query
        self.ParseQuery(query)

        # get lock and execute the query
        self.OpenTable()
        Debug('Running ' + self.command)
        dataset = []
        if self.command == 'SELECT':
            dataset = self._RunSelect()
        elif self.command == 'UPDATE':
            dataset = self._RunUpdate()
        elif self.command == 'INSERT':
            dataset = self._RunInsert()
        elif self.command == 'DELETE':
            dataset = self._RunDelete()

        if self.command != 'SELECT' and writethru:
            self.WriteTempTable()
            self.MoveTableIntoPlace()

        Debug(dataset)
        return dataset

    def CleanUp(self):
        """Reset the internal variables (for multiple queries)."""
        self.tokens = []      # query broken up into tokens
        self.conditions = {}  # args to the WHERE clause
        self.columns = []     # columns requested by SELECT
        self.table = ''       # name of the table being queried
        self.header = {}      # table header
        self.orig_data = []   # original table data used to diff after updates
        self.data = []        # table data as a list of dicts
        self.count = False    # where or not using COUNT()
        self.aliases = {}     # column aliases (SELECT AS)
        self.targets = {}     # target columns-value pairs for INSERT/UPDATE
        self.args = ''        # query arguments preceding the ;
        self.command = ''     # which command are we executing
        self.strings = []     # list of string literals parsed from the query
        self.parens = []      # list of parentheses parsed from the query
        if getattr(self, 'fd', False):
            self.fd.close()

    def ParseQuery(self, query):
        """External wrapper for the query parsing routines.

        Args:
            query: string

        Raises:
            ParseError: Unable to parse query
        """
        self.args = query.split(';')[0]
        self._Tokenize()
        self._ParseCommand()
        self._ParseOrderBy()
        self._ParseConditions()
        self._ParseColumns()
        self._ParseTable()
        self._ParseTargets()

    def _ParseCommand(self):
        """Determine the command: SELECT, UPDATE, DELETE or INSERT.

        Raises:
            ParseError: unable to parse command
        """
        self.command = self.tokens[0]
        # Check that command is valid
        if self.command not in self.ALL_COMMANDS:
            raise ParseError('Unsupported command: ' + self.command)

        self.tokens.pop(0)
        Debug('Command is: %s' % self.command)
        Debug('self.tokens: %s' % self.tokens)

    def _Tokenize(self):
        """Turn the string query into a list of tokens.

        Split on '(', ')', ' ', ';', '=' and ','.
            In addition capitalize any SQL keywords found.
        """
        # horrible hack to handle now()
        time_now = '%s' % int(time.time())
        # round off the seconds for unittesting
        time_now = time_now[0:-2] + '00'
        while 'now()' in self.args.lower():
            start = self.args.lower().find('now()')
            self.args = ('%s%s%s' % (self.args[0:start], time_now,
                                     self.args[start + 5:]))
        # pad token separators with spaces
        pad = self.args.replace('(', ' ( ').replace(')', ' ) ')
        pad = pad.replace(',', ' , ').replace(';', ' ; ').replace('=', ' = ')
        self.args = pad
        # parse out all the blocks (string literals and parens)
        self._ParseOutBlocks()
        # split remaining into tokens
        self.tokens = self.args.split()

        # now capitalize
        i = 0
        while i < len(self.tokens):
            if self.tokens[i].upper() in self.RESERVED_WORDS:
                self.tokens[i] = self.tokens[i].upper()

            i += 1

        Debug('Tokens: %s' % self.tokens)

    def _ParseOutBlocks(self):
        """Parse out string literals and parenthesized values."""
        self.strings = []
        self.parens = []

        # set str placeholder to a value that's not present in the string
        while self._str_placeholder in self.args:
            self._str_placeholder = '%s_' % self._str_placeholder

        # set paren placeholder to a value that's not present in the string
        while self._paren_placeholder in self.args:
            self._paren_placeholder = '%s_' % self._paren_placeholder

        self.strings = self._ParseOutHelper(self._str_placeholder, ["'", '"'],
                                            'quotes')
        self.parens = self._ParseOutHelper(self._paren_placeholder, ['(', ')'],
                                           'parens')
        Debug('Strings: %s' % self.strings)
        Debug('Parens: %s' % self.parens)

    def _ParseOutHelper(self, placeholder, delims, mode):
        """Replace all text within delims with placeholders.

        Args:
            placeholder: string
            delims: list of strings
            mode: string
                'parens': if there are 2 delims treat the first as opening
                          and second as closing, such as with ( and )
                'quotes': treat each delim as either opening or
                          closing and require the same one to terminate the
                          block, such as with ' and "

        Returns:
            list: [value1, value2, ...]

        Raises:
            ParseError: unable to parse out delims
            ExecuteError: Invalid usage
        """
        if mode not in ['quotes', 'parens']:
            raise ExecuteError('_ParseOutHelper: invalid mode ' + mode)
        if mode == 'parens' and len(delims) != 2:
            raise ExecuteError('_ParseOutHelper: delims must have 2 values '
                               'in "parens" mode')
        values = []
        started = 0
        new_args = ''
        string = ''
        my_id = 0
        delim = ''
        for c in self.args:
            if c in delims:
                if not started:
                    if mode == 'parens' and c != delims[0]:
                        raise ParseError('Found closing delimiter %s before '
                                         'corresponding %s' % (c, delims[0]))
                    started += 1
                    delim = c
                else:
                    if ((mode == 'parens' and c == delim) or
                       (mode == 'quotes' and c != delim)):
                        string = '%s%s' % (string, c)
                        continue  # wait for matching delim

                    started -= 1
                    if not started:
                        values.append(string)
                        new_args = '%s %s' % (new_args, '%s%d' % (placeholder,
                                                                  my_id))
                        my_id += 1
                        string = ''

            else:
                if not started:
                    new_args = '%s%s' % (new_args, c)
                else:
                    string = '%s%s' % (string, c)

        if started:
            if mode == 'parens':
                waiting_for = delims[1]
            else:
                waiting_for = delim
            raise ParseError('Unterminated block, waiting for ' + waiting_for)

        self.args = new_args
        Debug('Values: %s' % values)
        return values

    def _ReplaceStringLiterals(self, s, quotes=False):
        """Replaces string placeholders with real values.

            If quotes is set to True surround the returned value with single
            quotes

        Args:
            s: string
            quotes: bool

        Returns:
            s: string
        """
        if s.strip().startswith(self._str_placeholder):
            str_index = int(s.split(self._str_placeholder)[1])
            s = self.strings[str_index]
            if quotes:
                s = "'" + s + "'"

        return s

    def _ReplaceParens(self, s):
        """Replaces paren placeholders with real values.

        Args:
            s: string

        Returns:
            s: string
        """
        if s.strip().startswith(self._paren_placeholder):
            str_index = int(s.split(self._paren_placeholder)[1])
            s = self.parens[str_index].strip()

        return s

    def _RunDelete(self):
        """Run the DELETE command.

        Go through the rows in self.data matching them against the conditions,
        if they fit delete the row leaving a placeholder value (in order to
        keep the iteration process sane).  Afterward clean up any empty values.

        Returns:
            dataset: [number of affected rows]
        """
        i = 0
        length = len(self.data)
        affected = 0
        while i < length:
            if self._MatchRow(self.data[i]):
                self.data[i] = None
                affected += 1

            i += 1

        # clean out the placeholders
        while None in self.data:
            self.data.remove(None)

        return [affected]

    def _RunUpdate(self):
        """Run the UPDATE command.

            Find the matching rows and update based on self.targets

        Returns:
            affected: [int]
        Raises:
            ExecuteError: failed to run UPDATE
        """
        i = 0
        length = len(self.data)
        affected = 0
        while i < length:
            if self._MatchRow(self.data[i]):
                for target in self.targets:
                    if target not in self.header:
                        raise ExecuteError(target + ' is an invalid column ' +
                                           'name')
                    if self.header[target]['auto']:
                        raise ExecuteError(target + ' is type auto and ' +
                                           'cannot be updated')

                    self.data[i][target] = \
                        self._TypeCheck(self.targets[target], target)
                affected += 1

            i += 1

        return [affected]

    def _RunInsert(self):
        """Run the INSERT command.

            Build up the row based on self.targets and table defaults, then
            append to self.data

        Returns:
            affected: [int]
        Raises:
            ExecuteError: failed to run INSERT
        """
        new_row = {}
        cols = self._SortHeaderColumns()
        for col in cols:
            if col in self.targets:
                if self.header[col]['auto']:
                    raise ExecuteError(col + ' is type auto: cannot be ' +
                                       'modified')
                new_row[col] = self.targets[col]

            elif self.header[col]['null']:
                new_row[col] = ''

            elif self.header[col]['auto']:
                new_row[col] = self._GetNextAuto(col)

            else:
                raise ExecuteError(col + ' cannot be empty or null')

        self.data.append(new_row)
        return [1]

    def _GetNextAuto(self, col):
        """Figure out the next value for col based on existing values.

            Scan all the current values and return the highest one + 1.

        Args:
            col: string

        Returns:
            next: int

        Raises:
            ExecuteError: Failed to get auto inc
        """
        highest = 0
        seen = []
        for row in self.data:
            if row[col] > highest:
                highest = row[col]

            if row[col] not in seen:
                seen.append(row[col])
            else:
                raise ExecuteError('duplicate value %s in %s' %
                                   (row[col], col))

        return highest + 1

    def _RunSelect(self):
        """Run the SELECT command.

        Returns:
            dataset: []

        Raises:
            ExecuteError: failed to run SELECT
        """
        dataset = []
        if ['*'] == self.columns:
            self.columns = self._SortHeaderColumns()

        for row in self.data:
            if self._MatchRow(row):
                match = []
                for col in self.columns:
                    if col in self.aliases:
                        concat = ''
                        for concat_col in self.aliases[col]:
                            if concat_col.startswith("'") and \
                               concat_col.endswith("'"):
                                concat += concat_col.strip("'")
                            elif concat_col not in self.header.keys():
                                raise ExecuteError('Table %s does not have ' +
                                                   'a column %s' %
                                                   (self.table, concat_col))
                            else:
                                concat = '%s%s' % (concat, row[concat_col])

                        if not concat.strip():
                            raise ExecuteError('Empty CONCAT statement')

                        my_match = concat

                    elif col.startswith("'") and col.endswith("'"):
                        my_match = col.strip("'")
                    elif col not in self.header.keys():
                        raise ExecuteError('Table %s does not have a column ' +
                                           '%s' % (self.table, col))
                    else:
                        my_match = row[col]

                    match.append(self._UnEscapeChars(my_match))

                dataset.append(match)

        if self.count:
            Debug('Dataset: %s' % dataset)
            dataset = [len(dataset)]

        if self.order_by:
            if self.order_by not in self.header.keys():
                raise ExecuteError('Unknown column %s in ORDER BY clause' %
                                   self.order_by)
            pos = self._PositionByCol(self.order_by)
            dataset = self._SortMatrixByCol(dataset, pos)

        return dataset

    def _SortMatrixByCol(self, dataset, pos):
        """Sorts the matrix (array or arrays) based on a given column value.

        That is, if given matrix that looks like:

        [[1, 2, 3], [6, 5, 4], [3, 2, 1]]

        given pos = 0 produce:

        [[1, 2, 3], [3, 2, 1], [6, 5, 4]]

        given pos = 1 produce:

        [[1, 2, 3], [3, 2, 1], [6, 5, 4]]

        given pos = 2 produce:

        [[3, 2, 1], [1, 2, 3], [6, 5, 4]]

        Works for both integer and string values of column.

        Args:
            dataset: [[], [], ...]
            pos: int

        Returns:
            sorted: [[], [], ...]
        """
        # prepend value in pos to the beginning of every row
        i = 0
        while i < len(dataset):
            dataset[i].insert(0, dataset[i][pos])
            i += 1

        # sort the matrix, which is done on the row we just prepended
        dataset.sort()

        # strip away the first value
        i = 0
        while i < len(dataset):
            dataset[i].pop(0)
            i += 1

        return dataset

    def _MatchRow(self, row):
        """Matches the row against self.conditions.

        Args:
            row: ['val', 'val']

        Returns:
            Bool
        """
        match = True
        # when there are no conditions we match everything
        if not self.conditions:
            return match

        for condition in self.conditions:
            cond_val = self.conditions[condition]
            if condition not in self.header.keys():
                match = False
                break
            else:
                if cond_val != row[condition]:
                    match = False
                    break

        return match

    def _ProcessHeader(self):
        """Parse out the header information.

        Returns:
            {col_name:
                {'type': string,
                 'null': string,
                 'auto': string,
                 'pos': int
                 }
            }
        """
        header = self.fd.readline().strip()
        cols = {}
        pos = 0
        for col in header.split():
            col_name = col.split('(')[0]
            col_type = col.split('(')[1].split(')')[0].split(',')[0]
            col_null = False
            col_auto = False
            if ',' in col.split('(')[1].split(')')[0]:
                if col.split('(')[1].split(')')[0].split(',')[1].lower() == \
                   'null':
                    col_null = True
                if col.split('(')[1].split(')')[0].split(',')[1].lower() == \
                   'auto':
                    col_auto = True

            cols[col_name] = {}
            cols[col_name]['type'] = col_type
            cols[col_name]['null'] = col_null
            cols[col_name]['auto'] = col_auto
            cols[col_name]['pos'] = pos
            pos += 1

        return cols

    def _GetData(self):
        """Reads table data into memory as a list of dicts keyed on column
        names.

        Returns:
            data: [{row}, {row}, ...]
        Raises:
            ExecuteError: failed to get data
        """
        data = []
        row_num = 0
        for row in self.fd:
            row = row.rstrip('\n')
            row_dict = {}
            i = 0
            field_start = 0
            field_num = 0
            while i < len(row):
                if row[i] == ':':
                    # the following block is executed again after the
                    # while is done
                    val = row[field_start:i]
                    col = self._ColByPosition(field_num)
                    val = self._TypeCheck(val, col)
                    row_dict[col] = val

                    field_start = i + 1  # skip the colon itself
                    field_num += 1
                if row[i] == '\\':
                    i += 2  # skip the next char since it's escaped
                else:
                    i += 1

            # handle the last field since we won't hit a : at the end
            # sucks to duplicate the code outside the loop but I can't think
            # of a better way :(

            val = row[field_start:i]
            col = self._ColByPosition(field_num)
            val = self._TypeCheck(val, col)
            row_dict[col] = val

            # verify that all columns were created
            for col in self.header:
                if col not in row_dict:
                    raise ExecuteError('%s is missing from row %d in %s' %
                                       (col, row_num, self.table))

            row_num += 1
            data.append(row_dict)

        return data

    def _TypeCheck(self, val, col):
        """Verify type of val based on the header.

        Make sure the value is returned in quotes if it's a string
        and as '' when it's empty and Null

        Args:
            val: string
            col: string

        Returns:
            val: string

        Raises:
            ExecuteError: invalid value or column
        """
        if not val and not self.header[col]['null']:
            raise ExecuteError(col + ' cannot be empty or null')

        hdr_t = self.header[col]['type'].lower()
        if hdr_t == 'int' or hdr_t == 'double':
            try:
                if val:
                    val = eval(val)
            except NameError as e:
                raise ExecuteError('Failed to parse %s in %s '
                                   '(unable to convert to type %s): %s' %
                                   (col, self.table, hdr_t, e))
            except SyntaxError as e:
                raise ExecuteError('Failed to parse %s in %s '
                                   '(unable to convert to type %s): %s' %
                                   (col, self.table, hdr_t, e))

        return val

    def _ColByPosition(self, pos):
        """Returns column name based on position.

        Args:
            pos: int

        Returns:
            column: string

        Raises:
            ExecuteError: invalid column
        """
        for col in self.header:
            if self.header[col]['pos'] == pos:
                return col

        raise ExecuteError('Header does not contain column %d' % pos)

    def _PositionByCol(self, col):
        """Returns position of the column based on the name.

        Args:
            col: string

        Returns:
            pos: int

        Raises:
            ExecuteError: invalid column
        """
        if col not in self.header.keys():
            raise ExecuteError(col + ' is not a valid column name')

        return self.header[col]['pos']

    def _SortHeaderColumns(self):
        """Sort column names by position.

        Returns:
            sorted: [col1, col2, ...]

        Raises:
            ExecuteError: unable to sort header
        """
        cols = self.header.keys()
        sorted_cols = [''] * len(cols)
        for col in cols:
            pos = self.header[col]['pos']
            sorted_cols[pos] = col

        if '' in sorted_cols:
            raise ExecuteError('Unable to sort header columns: %s' % cols)

        return sorted_cols

    def OpenTable(self):
        """Opens the table file and places its content into memory.

        Raises:
            ExecuteError: unable to open table
        """
        # if we already have a header assume multiple queries on same table
        # (can't use self.data in case the table was empty to begin with)
        if self.header:
            return

        try:
            self.fd = open(os.path.join(self.location, self.table), 'r')
            self.header = self._ProcessHeader()

            if self.command in ['INSERT', 'DELETE', 'UPDATE']:
                fcntl.flock(self.fd, fcntl.LOCK_EX)

            self.data = self._GetData()
            # save a copy of the data before modifying
            self.orig_data = self.data[:]

        except IOError as e:
            raise ExecuteError('Unable to open table %s: %s' % (self.table, e))

        Debug('Header is: %s' % self.header)

        # type check the conditions
        for cond in self.conditions:
            if cond not in self.header.keys():
                raise ExecuteError('unknown column %s in WHERE clause' % cond)
            self.conditions[cond] = self._TypeCheck(self.conditions[cond],
                                                    cond)

        # type check the targets
        for target in self.targets:
            if target not in self.header.keys():
                raise ExecuteError('unknown column in targets:  %s' % target)
            self.targets[target] = self._TypeCheck(self.targets[target],
                                                   target)

        Debug('Type checked conditions: %s' % self.conditions)

        Debug('Data is:')
        for row in self.data:
            Debug('=======================')
            Debug(row)
        Debug('=======================')

    def WriteTempTable(self):
        """Write table header and data.

        First write header and data to a temp file,
        then move the tmp file to replace the original table file.
        """
        self.temp_file = tempfile.NamedTemporaryFile()
        Debug('temp_file: ' + self.temp_file.name)
        # write header
        columns = self._SortHeaderColumns()
        header = ''
        for col in columns:
            header = '%s %s' % (header, col)
            header = '%s(%s' % (header, self.header[col]['type'])
            if self.header[col]['null']:
                header = '%s,null)' % header
            elif self.header[col]['auto']:
                header = '%s,auto)' % header
            else:
                header = '%s)' % header

        self.temp_file.write((header.strip() + '\n').encode())

        # write data
        for row in self.data:
            row_str = ''
            for col in columns:
                row_str = '%s:%s' % (row_str, row[col])

            self.temp_file.write((row_str[1:] + '\n').encode())

        self.temp_file.flush()

    def MoveTableIntoPlace(self):
        """Replace the real table with the temp one.

        Diff the new data against the original and replace the table when they
        are different.
        """
        if self.data != self.orig_data:
            temp_file = self.temp_file.name
            table_file = os.path.join(self.location, self.table)
            Debug('Copying %s to %s' % (temp_file, table_file))
            shutil.copy(self.temp_file.name, self.location + '/' + self.table)

    def _ParsePairs(self, s, delimiter):
        """Parses out name value pairs from a string.

        String contains name=value pairs
        separated by a delimiter (such as "and" or ",")

        Args:
            s: string
            delimiter: string

        Returns:
            my_dict: dictionary

        Raises:
            ParseError: unable to parse pairs
        """
        my_dict = {}
        Debug('parse pairs: [%s]' % s)
        pairs = s.split(delimiter)
        for pair in pairs:
            if '=' not in pair:
                raise ParseError('Invalid condition pair: ' + pair)

            split = pair.split('=')
            Debug('split: %s' % split)
            if len(split) != 2:
                raise ParseError('Invalid condition pair: ' + pair)

            col = split[0].strip()
            if not col or not split[1].strip() or ' ' in col:
                raise ParseError('Invalid condition pair: ' + pair)

            val = self._ReplaceStringLiterals(split[1].strip())
            my_dict[col] = val

        return my_dict


class Error(Exception):
    """DBText error."""


class ParseError(Error):
    """Parse error."""


class NotSupportedError(Error):
    """Not Supported error."""


class ExecuteError(Error):
    """Execute error."""


def main(argv):

    if len(argv) < 2:
        print('Usage %s query' % argv[0])
        sys.exit(1)

    if 'DBTEXT_PATH' not in os.environ or not os.environ['DBTEXT_PATH']:
        print('DBTEXT_PATH must be set')
        sys.exit(1)
    else:
        location = os.environ['DBTEXT_PATH']

    try:
        conn = DBText(location)
        dataset = conn.Execute(' '.join(argv[1:]))
        if dataset:
            for row in dataset:
                if conn.command != 'SELECT':
                    print('Updated %s, rows affected: %d' % (conn.table, row))
                else:
                    print(row)
    except Error as e:
        print(e)
        sys.exit(1)


if __name__ == '__main__':
    main(sys.argv)
