# mysql/reflection.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

import re
from ... import log, util
from ... import types as sqltypes
from .enumerated import _EnumeratedValues, SET
from .types import DATETIME, TIME, TIMESTAMP


class ReflectedState(object):
    """Stores raw information about a SHOW CREATE TABLE statement."""

    def __init__(self):
        self.columns = []
        self.table_options = {}
        self.table_name = None
        self.keys = []
        self.fk_constraints = []
        self.ck_constraints = []


@log.class_logger
class MySQLTableDefinitionParser(object):
    """Parses the results of a SHOW CREATE TABLE statement."""

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

    def parse(self, show_create, charset):
        state = ReflectedState()
        state.charset = charset
        for line in re.split(r'\r?\n', show_create):
            if line.startswith('  ' + self.preparer.initial_quote):
                self._parse_column(line, state)
            # a regular table options line
            elif line.startswith(') '):
                self._parse_table_options(line, state)
            # an ANSI-mode table options line
            elif line == ')':
                pass
            elif line.startswith('CREATE '):
                self._parse_table_name(line, state)
            # Not present in real reflection, but may be if
            # loading from a file.
            elif not line:
                pass
            else:
                type_, spec = self._parse_constraints(line)
                if type_ is None:
                    util.warn("Unknown schema content: %r" % line)
                elif type_ == 'key':
                    state.keys.append(spec)
                elif type_ == 'fk_constraint':
                    state.fk_constraints.append(spec)
                elif type_ == 'ck_constraint':
                    state.ck_constraints.append(spec)
                else:
                    pass
        return state

    def _parse_constraints(self, line):
        """Parse a KEY or CONSTRAINT line.

        :param line: A line of SHOW CREATE TABLE output
        """

        # KEY
        m = self._re_key.match(line)
        if m:
            spec = m.groupdict()
            # convert columns into name, length pairs
            # NOTE: we may want to consider SHOW INDEX as the
            # format of indexes in MySQL becomes more complex
            spec['columns'] = self._parse_keyexprs(spec['columns'])
            return 'key', spec

        # FOREIGN KEY CONSTRAINT
        m = self._re_fk_constraint.match(line)
        if m:
            spec = m.groupdict()
            spec['table'] = \
                self.preparer.unformat_identifiers(spec['table'])
            spec['local'] = [c[0]
                             for c in self._parse_keyexprs(spec['local'])]
            spec['foreign'] = [c[0]
                               for c in self._parse_keyexprs(spec['foreign'])]
            return 'fk_constraint', spec

        # CHECK constraint
        m = self._re_ck_constraint.match(line)
        if m:
            spec = m.groupdict()
            return 'ck_constraint', spec

        # PARTITION and SUBPARTITION
        m = self._re_partition.match(line)
        if m:
            # Punt!
            return 'partition', line

        # No match.
        return (None, line)

    def _parse_table_name(self, line, state):
        """Extract the table name.

        :param line: The first line of SHOW CREATE TABLE
        """

        regex, cleanup = self._pr_name
        m = regex.match(line)
        if m:
            state.table_name = cleanup(m.group('name'))

    def _parse_table_options(self, line, state):
        """Build a dictionary of all reflected table-level options.

        :param line: The final line of SHOW CREATE TABLE output.
        """

        options = {}

        if not line or line == ')':
            pass

        else:
            rest_of_line = line[:]
            for regex, cleanup in self._pr_options:
                m = regex.search(rest_of_line)
                if not m:
                    continue
                directive, value = m.group('directive'), m.group('val')
                if cleanup:
                    value = cleanup(value)
                options[directive.lower()] = value
                rest_of_line = regex.sub('', rest_of_line)

        for nope in ('auto_increment', 'data directory', 'index directory'):
            options.pop(nope, None)

        for opt, val in options.items():
            state.table_options['%s_%s' % (self.dialect.name, opt)] = val

    def _parse_column(self, line, state):
        """Extract column details.

        Falls back to a 'minimal support' variant if full parse fails.

        :param line: Any column-bearing line from SHOW CREATE TABLE
        """

        spec = None
        m = self._re_column.match(line)
        if m:
            spec = m.groupdict()
            spec['full'] = True
        else:
            m = self._re_column_loose.match(line)
            if m:
                spec = m.groupdict()
                spec['full'] = False
        if not spec:
            util.warn("Unknown column definition %r" % line)
            return
        if not spec['full']:
            util.warn("Incomplete reflection of column definition %r" % line)

        name, type_, args = spec['name'], spec['coltype'], spec['arg']

        try:
            col_type = self.dialect.ischema_names[type_]
        except KeyError:
            util.warn("Did not recognize type '%s' of column '%s'" %
                      (type_, name))
            col_type = sqltypes.NullType

        # Column type positional arguments eg. varchar(32)
        if args is None or args == '':
            type_args = []
        elif args[0] == "'" and args[-1] == "'":
            type_args = self._re_csv_str.findall(args)
        else:
            type_args = [int(v) for v in self._re_csv_int.findall(args)]

        # Column type keyword options
        type_kw = {}

        if issubclass(col_type, (DATETIME, TIME, TIMESTAMP)):
            if type_args:
                type_kw['fsp'] = type_args.pop(0)

        for kw in ('unsigned', 'zerofill'):
            if spec.get(kw, False):
                type_kw[kw] = True
        for kw in ('charset', 'collate'):
            if spec.get(kw, False):
                type_kw[kw] = spec[kw]
        if issubclass(col_type, _EnumeratedValues):
            type_args = _EnumeratedValues._strip_values(type_args)

            if issubclass(col_type, SET) and '' in type_args:
                type_kw['retrieve_as_bitwise'] = True

        type_instance = col_type(*type_args, **type_kw)

        col_kw = {}

        # NOT NULL
        col_kw['nullable'] = True
        # this can be "NULL" in the case of TIMESTAMP
        if spec.get('notnull', False) == 'NOT NULL':
            col_kw['nullable'] = False

        # AUTO_INCREMENT
        if spec.get('autoincr', False):
            col_kw['autoincrement'] = True
        elif issubclass(col_type, sqltypes.Integer):
            col_kw['autoincrement'] = False

        # DEFAULT
        default = spec.get('default', None)

        if default == 'NULL':
            # eliminates the need to deal with this later.
            default = None

        comment = spec.get('comment', None)

        if comment is not None:
            comment = comment.replace("\\\\", "\\").replace("''", "'")

        col_d = dict(name=name, type=type_instance, default=default,
                     comment=comment)
        col_d.update(col_kw)
        state.columns.append(col_d)

    def _describe_to_create(self, table_name, columns):
        """Re-format DESCRIBE output as a SHOW CREATE TABLE string.

        DESCRIBE is a much simpler reflection and is sufficient for
        reflecting views for runtime use.  This method formats DDL
        for columns only- keys are omitted.

        :param columns: A sequence of DESCRIBE or SHOW COLUMNS 6-tuples.
          SHOW FULL COLUMNS FROM rows must be rearranged for use with
          this function.
        """

        buffer = []
        for row in columns:
            (name, col_type, nullable, default, extra) = \
                [row[i] for i in (0, 1, 2, 4, 5)]

            line = [' ']
            line.append(self.preparer.quote_identifier(name))
            line.append(col_type)
            if not nullable:
                line.append('NOT NULL')
            if default:
                if 'auto_increment' in default:
                    pass
                elif (col_type.startswith('timestamp') and
                      default.startswith('C')):
                    line.append('DEFAULT')
                    line.append(default)
                elif default == 'NULL':
                    line.append('DEFAULT')
                    line.append(default)
                else:
                    line.append('DEFAULT')
                    line.append("'%s'" % default.replace("'", "''"))
            if extra:
                line.append(extra)

            buffer.append(' '.join(line))

        return ''.join([('CREATE TABLE %s (\n' %
                         self.preparer.quote_identifier(table_name)),
                        ',\n'.join(buffer),
                        '\n) '])

    def _parse_keyexprs(self, identifiers):
        """Unpack '"col"(2),"col" ASC'-ish strings into components."""

        return self._re_keyexprs.findall(identifiers)

    def _prep_regexes(self):
        """Pre-compile regular expressions."""

        self._re_columns = []
        self._pr_options = []

        _final = self.preparer.final_quote

        quotes = dict(zip(('iq', 'fq', 'esc_fq'),
                          [re.escape(s) for s in
                           (self.preparer.initial_quote,
                            _final,
                            self.preparer._escape_identifier(_final))]))

        self._pr_name = _pr_compile(
            r'^CREATE (?:\w+ +)?TABLE +'
            r'%(iq)s(?P<name>(?:%(esc_fq)s|[^%(fq)s])+)%(fq)s +\($' % quotes,
            self.preparer._unescape_identifier)

        # `col`,`col2`(32),`col3`(15) DESC
        #
        self._re_keyexprs = _re_compile(
            r'(?:'
            r'(?:%(iq)s((?:%(esc_fq)s|[^%(fq)s])+)%(fq)s)'
            r'(?:\((\d+)\))?(?: +(ASC|DESC))?(?=\,|$))+' % quotes)

        # 'foo' or 'foo','bar' or 'fo,o','ba''a''r'
        self._re_csv_str = _re_compile(r'\x27(?:\x27\x27|[^\x27])*\x27')

        # 123 or 123,456
        self._re_csv_int = _re_compile(r'\d+')

        # `colname` <type> [type opts]
        #  (NOT NULL | NULL)
        #   DEFAULT ('value' | CURRENT_TIMESTAMP...)
        #   COMMENT 'comment'
        #  COLUMN_FORMAT (FIXED|DYNAMIC|DEFAULT)
        #  STORAGE (DISK|MEMORY)
        self._re_column = _re_compile(
            r"  "
            r"%(iq)s(?P<name>(?:%(esc_fq)s|[^%(fq)s])+)%(fq)s +"
            r"(?P<coltype>\w+)"
            r"(?:\((?P<arg>(?:\d+|\d+,\d+|"
            r"(?:'(?:''|[^'])*',?)+))\))?"
            r"(?: +(?P<unsigned>UNSIGNED))?"
            r"(?: +(?P<zerofill>ZEROFILL))?"
            r"(?: +CHARACTER SET +(?P<charset>[\w_]+))?"
            r"(?: +COLLATE +(?P<collate>[\w_]+))?"
            r"(?: +(?P<notnull>(?:NOT )?NULL))?"
            r"(?: +DEFAULT +(?P<default>"
            r"(?:NULL|'(?:''|[^'])*'|[\w\(\)]+"
            r"(?: +ON UPDATE [\w\(\)]+)?)"