# This code is part of Ansible, but is an independent component.
# This particular file snippet, and this file snippet only, is BSD licensed.
# Modules you write using this snippet, which is embedded dynamically by Ansible
# still belong to the author of the module, and may assign their own license
# to the complete work.
#
# Copyright (c) 2014, Toshio Kuratomi <tkuratomi@ansible.com>
#
# Simplified BSD License (see licenses/simplified_bsd.txt or https://opensource.org/licenses/BSD-2-Clause)

from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import re


# Input patterns for is_input_dangerous function:
#
# 1. '"' in string and '--' in string or
# "'" in string and '--' in string
PATTERN_1 = re.compile(r'(\'|\").*--')

# 2. union \ intersect \ except + select
PATTERN_2 = re.compile(r'(UNION|INTERSECT|EXCEPT).*SELECT', re.IGNORECASE)

# 3. ';' and any KEY_WORDS
PATTERN_3 = re.compile(r';.*(SELECT|UPDATE|INSERT|DELETE|DROP|TRUNCATE|ALTER)', re.IGNORECASE)


class SQLParseError(Exception):
    pass


class UnclosedQuoteError(SQLParseError):
    pass


# maps a type of identifier to the maximum number of dot levels that are
# allowed to specify that identifier.  For example, a database column can be
# specified by up to 4 levels: database.schema.table.column
_PG_IDENTIFIER_TO_DOT_LEVEL = dict(
    database=1,
    schema=2,
    table=3,
    column=4,
    role=1,
    tablespace=1,
    sequence=3,
    publication=1,
)
_MYSQL_IDENTIFIER_TO_DOT_LEVEL = dict(database=1, table=2, column=3, role=1, vars=1)


def _find_end_quote(identifier, quote_char):
    accumulate = 0
    while True:
        try:
            quote = identifier.index(quote_char)
        except ValueError:
            raise UnclosedQuoteError
        accumulate = accumulate + quote
        try:
            next_char = identifier[quote + 1]
        except IndexError:
            return accumulate
        if next_char == quote_char:
            try:
                identifier = identifier[quote + 2:]
                accumulate = accumulate + 2
            except IndexError:
                raise UnclosedQuoteError
        else:
            return accumulate


def _identifier_parse(identifier, quote_char):
    if not identifier:
        raise SQLParseError('Identifier name unspecified or unquoted trailing dot')

    already_quoted = False
    if identifier.startswith(quote_char):
        already_quoted = True
        try:
            end_quote = _find_end_quote(identifier[1:], quote_char=quote_char) + 1
        except UnclosedQuoteError:
            already_quoted = False
        else:
            if end_quote < len(identifier) - 1:
                if identifier[end_quote + 1] == '.':
                    dot = end_quote + 1
                    first_identifier = identifier[:dot]
                    next_identifier = identifier[dot + 1:]
                    further_identifiers = _identifier_parse(next_identifier, quote_char)
                    further_identifiers.insert(0, first_identifier)
                else:
                    raise SQLParseError('User escaped identifiers must escape extra quotes')
            else:
                further_identifiers = [identifier]

    if not already_quoted:
        try:
            dot = identifier.index('.')
        except ValueError:
            identifier = identifier.replace(quote_char, quote_char * 2)
            identifier = ''.join((quote_char, identifier, quote_char))
            further_identifiers = [identifier]
        else:
            if dot == 0 or dot >= len(identifier) - 1:
                identifier = identifier.replace(quote_char, quote_char * 2)
                identifier = ''.join((quote_char, identifier, quote_char))
                further_identifiers = [identifier]
            else:
                first_identifier = identifier[:dot]
                next_identifier = identifier[dot + 1:]
                further_identifiers = _identifier_parse(next_identifier, quote_char)
                first_identifier = first_identifier.replace(quote_char, quote_char * 2)
                first_identifier = ''.join((quote_char, first_identifier, quote_char))
                further_identifiers.insert(0, first_identifier)

    return further_identifiers


def pg_quote_identifier(identifier, id_type):
    identifier_fragments = _identifier_parse(identifier, quote_char='"')
    if len(identifier_fragments) > _PG_IDENTIFIER_TO_DOT_LEVEL[id_type]:
        raise SQLParseError('PostgreSQL does not support %s with more than %i dots' % (id_type, _PG_IDENTIFIER_TO_DOT_LEVEL[id_type]))
    return '.'.join(identifier_fragments)


def mysql_quote_identifier(identifier, id_type):
    identifier_fragments = _identifier_parse(identifier, quote_char='`')
    if (len(identifier_fragments) - 1) > _MYSQL_IDENTIFIER_TO_DOT_LEVEL[id_type]:
        raise SQLParseError('MySQL does not support %s with more than %i dots' % (id_type, _MYSQL_IDENTIFIER_TO_DOT_LEVEL[id_type]))

    special_cased_fragments = []
    for fragment in identifier_fragments:
        if fragment == '`*`':
            special_cased_fragments.append('*')
        else:
            special_cased_fragments.append(fragment)

    return '.'.join(special_cased_fragments)


def is_input_dangerous(string):
    """Check if the passed string is potentially dangerous.
    Can be used to prevent SQL injections.

    Note: use this function only when you can't use
      psycopg2's cursor.execute method parametrized
      (typically with DDL queries).
    """
    if not string:
        return False

    for pattern in (PATTERN_1, PATTERN_2, PATTERN_3):
        if re.search(pattern, string):
            return True

    return False


def check_input(module, *args):
    """Wrapper for is_input_dangerous function."""
    needs_to_check = args

    dangerous_elements = []

    for elem in needs_to_check:
        if isinstance(elem, str):
            if is_input_dangerous(elem):
                dangerous_elements.append(elem)

        elif isinstance(elem, list):
            for e in elem:
                if is_input_dangerous(e):
                    dangerous_elements.append(e)

        elif elem is None or isinstance(elem, bool):
            pass

        else:
            elem = str(elem)
            if is_input_dangerous(elem):
                dangerous_elements.append(elem)

    if dangerous_elements:
        module.fail_json(msg="Passed input '%s' is "
                             "potentially dangerous" % ', '.join(dangerous_elements))
