# sql/compiler.py
# Copyright (C) 2005-2018 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""Base SQL and DDL compiler implementations.

Classes provided include:

:class:`.compiler.SQLCompiler` - renders SQL
strings

:class:`.compiler.DDLCompiler` - renders DDL
(data definition language) strings

:class:`.compiler.GenericTypeCompiler` - renders
type specification strings.

To generate user-defined SQL strings, see
:doc:`/ext/compiler`.

"""

import contextlib
import re
from . import schema, sqltypes, operators, functions, visitors, \
    elements, selectable, crud
from .. import util, exc
import itertools

RESERVED_WORDS = set([
    'all', 'analyse', 'analyze', 'and', 'any', 'array',
    'as', 'asc', 'asymmetric', 'authorization', 'between',
    'binary', 'both', 'case', 'cast', 'check', 'collate',
    'column', 'constraint', 'create', 'cross', 'current_date',
    'current_role', 'current_time', 'current_timestamp',
    'current_user', 'default', 'deferrable', 'desc',
    'distinct', 'do', 'else', 'end', 'except', 'false',
    'for', 'foreign', 'freeze', 'from', 'full', 'grant',
    'group', 'having', 'ilike', 'in', 'initially', 'inner',
    'intersect', 'into', 'is', 'isnull', 'join', 'leading',
    'left', 'like', 'limit', 'localtime', 'localtimestamp',
    'natural', 'new', 'not', 'notnull', 'null', 'off', 'offset',
    'old', 'on', 'only', 'or', 'order', 'outer', 'overlaps',
    'placing', 'primary', 'references', 'right', 'select',
    'session_user', 'set', 'similar', 'some', 'symmetric', 'table',
    'then', 'to', 'trailing', 'true', 'union', 'unique', 'user',
    'using', 'verbose', 'when', 'where'])

LEGAL_CHARACTERS = re.compile(r'^[A-Z0-9_$]+$', re.I)
ILLEGAL_INITIAL_CHARACTERS = {str(x) for x in range(0, 10)}.union(['$'])

BIND_PARAMS = re.compile(r'(?<![:\w\$\x5c]):([\w\$]+)(?![:\w\$])', re.UNICODE)
BIND_PARAMS_ESC = re.compile(r'\x5c(:[\w\$]*)(?![:\w\$])', re.UNICODE)

BIND_TEMPLATES = {
    'pyformat': "%%(%(name)s)s",
    'qmark': "?",
    'format': "%%s",
    'numeric': ":[_POSITION]",
    'named': ":%(name)s"
}


OPERATORS = {
    # binary
    operators.and_: ' AND ',
    operators.or_: ' OR ',
    operators.add: ' + ',
    operators.mul: ' * ',
    operators.sub: ' - ',
    operators.div: ' / ',
    operators.mod: ' % ',
    operators.truediv: ' / ',
    operators.neg: '-',
    operators.lt: ' < ',
    operators.le: ' <= ',
    operators.ne: ' != ',
    operators.gt: ' > ',
    operators.ge: ' >= ',
    operators.eq: ' = ',
    operators.is_distinct_from: ' IS DISTINCT FROM ',
    operators.isnot_distinct_from: ' IS NOT DISTINCT FROM ',
    operators.concat_op: ' || ',
    operators.match_op: ' MATCH ',
    operators.notmatch_op: ' NOT MATCH ',
    operators.in_op: ' IN ',
    operators.notin_op: ' NOT IN ',
    operators.comma_op: ', ',
    operators.from_: ' FROM ',
    operators.as_: ' AS ',
    operators.is_: ' IS ',
    operators.isnot: ' IS NOT ',
    operators.collate: ' COLLATE ',

    # unary
    operators.exists: 'EXISTS ',
    operators.distinct_op: 'DISTINCT ',
    operators.inv: 'NOT ',
    operators.any_op: 'ANY ',
    operators.all_op: 'ALL ',

    # modifiers
    operators.desc_op: ' DESC',
    operators.asc_op: ' ASC',
    operators.nullsfirst_op: ' NULLS FIRST',
    operators.nullslast_op: ' NULLS LAST',

}

FUNCTIONS = {
    functions.coalesce: 'coalesce%(expr)s',
    functions.current_date: 'CURRENT_DATE',
    functions.current_time: 'CURRENT_TIME',
    functions.current_timestamp: 'CURRENT_TIMESTAMP',
    functions.current_user: 'CURRENT_USER',
    functions.localtime: 'LOCALTIME',
    functions.localtimestamp: 'LOCALTIMESTAMP',
    functions.random: 'random%(expr)s',
    functions.sysdate: 'sysdate',
    functions.session_user: 'SESSION_USER',
    functions.user: 'USER',
    functions.cube: 'CUBE%(expr)s',
    functions.rollup: 'ROLLUP%(expr)s',
    functions.grouping_sets: 'GROUPING SETS%(expr)s',
}

EXTRACT_MAP = {
    'month': 'month',
    'day': 'day',
    'year': 'year',
    'second': 'second',
    'hour': 'hour',
    'doy': 'doy',
    'minute': 'minute',
    'quarter': 'quarter',
    'dow': 'dow',
    'week': 'week',
    'epoch': 'epoch',
    'milliseconds': 'milliseconds',
    'microseconds': 'microseconds',
    'timezone_hour': 'timezone_hour',
    'timezone_minute': 'timezone_minute'
}

COMPOUND_KEYWORDS = {
    selectable.CompoundSelect.UNION: 'UNION',
    selectable.CompoundSelect.UNION_ALL: 'UNION ALL',
    selectable.CompoundSelect.EXCEPT: 'EXCEPT',
    selectable.CompoundSelect.EXCEPT_ALL: 'EXCEPT ALL',
    selectable.CompoundSelect.INTERSECT: 'INTERSECT',
    selectable.CompoundSelect.INTERSECT_ALL: 'INTERSECT ALL'
}


class Compiled(object):

    """Represent a compiled SQL or DDL expression.

    The ``__str__`` method of the ``Compiled`` object should produce
    the actual text of the statement.  ``Compiled`` objects are
    specific to their underlying database dialect, and also may
    or may not be specific to the columns referenced within a
    particular set of bind parameters.  In no case should the
    ``Compiled`` object be dependent on the actual values of those
    bind parameters, even though it may reference those values as
    defaults.
    """

    _cached_metadata = None

    execution_options = util.immutabledict()
    """
    Execution options propagated from the statement.   In some cases,
    sub-elements of the statement can modify these.
    """

    def __init__(self, dialect, statement, bind=None,
                 schema_translate_map=None,
                 compile_kwargs=util.immutabledict()):
        """Construct a new :class:`.Compiled` object.

        :param dialect: :class:`.Dialect` to compile against.

        :param statement: :class:`.ClauseElement` to be compiled.

        :param bind: Optional Engine or Connection to compile this
          statement against.

        :param schema_translate_map: dictionary of schema names to be
         translated when forming the resultant SQL

         .. versionadded:: 1.1

         .. seealso::

            :ref:`schema_translating`

        :param compile_kwargs: additional kwargs that will be
         passed to the initial call to :meth:`.Compiled.process`.


        """

        self.dialect = dialect
        self.bind = bind
        self.preparer = self.dialect.identifier_preparer
        if schema_translate_map:
            self.preparer = self.preparer._with_schema_translate(
                schema_translate_map)

        if statement is not None:
            self.statement = statement
            self.can_execute = statement.supports_execution
            if self.can_execute:
                self.execution_options = statement._execution_options
            self.string = self.process(self.statement, **compile_kwargs)

    @util.deprecated("0.7", ":class:`.Compiled` objects now compile "
                     "within the constructor.")
    def compile(self):
        """Produce the internal string representation of this element.
        """
        pass

    def _execute_on_connection(self, connection, multiparams, params):
        if self.can_execute:
            return connection._execute_compiled(self, multiparams, params)
        else:
            raise exc.ObjectNotExecutableError(self.statement)

    @property
    def sql_compiler(self):
        """Return a Compiled that is capable of processing SQL expressions.

        If this compiler is one, it would likely just return 'self'.

        """

        raise NotImplementedError()

    def process(self, obj, **kwargs):
        return obj._compiler_dispatch(self, **kwargs)

    def __str__(self):
        """Return the string text of the generated SQL or DDL."""

        return self.string or ''

    def construct_params(self, params=None):
        """Return the bind params for this compiled object.

        :param params: a dict of string/object pairs whose values will
                       override bind values compiled in to the
                       statement.
        """

        raise NotImplementedError()

    @property
    def params(self):
        """Return the bind params for this compiled object."""
        return self.construct_params()

    def execute(self, *multiparams, **params):
        """Execute this compiled object."""

        e = self.bind
        if e is None:
            raise exc.UnboundExecutionError(
                "This Compiled object is not bound to any Engine "
                "or Connection.", code="2afi")
        return e._execute_compiled(self, multiparams, params)

    def scalar(self, *multiparams, **params):
        """Execute this compiled object and return the result's
        scalar value."""

        return self.execute(*multiparams, **params).scalar()


class TypeCompiler(util.with_metaclass(util.EnsureKWArgType, object)):
    """Produces DDL specification for TypeEngine objects."""

    ensure_kwarg = r'visit_\w+'

    def __init__(self, dialect):
        self.dialect = dialect

    def process(self, type_, **kw):
        return type_._compiler_dispatch(self, **kw)


class _CompileLabel(visitors.Visitable):

    """lightweight label object which acts as an expression.Label."""

    __visit_name__ = 'label'
    __slots__ = 'element', 'name'

    def __init__(self, col, name, alt_names=()):
        self.element = col
        self.name = name
        self._alt_names = (col,) + alt_names

    @property
    def proxy_set(self):
        return self.element.proxy_set

    @property
    def type(self):
        return self.element.type

    def self_group(self, **kw):
        return self


class SQLCompiler(Compiled):
    """Default implementation of :class:`.Compiled`.

    Compiles :class:`.ClauseElement` objects into SQL strings.

    """

    extract_map = EXTRACT_MAP

    compound_keywords = COMPOUND_KEYWORDS

    isdelete = isinsert = isupdate = False
    """class-level defaults which can be set at the instance
    level to define if this Compiled instance represents
    INSERT/UPDATE/DELETE
    """

    isplaintext = False

    returning = None
    """holds the "returning" collection of columns if
    the statement is CRUD and defines returning columns
    either implicitly or explicitly
    """

    returning_precedes_values = False