from .._compat import basestring
from ..adapters.db2 import DB2
from .base import SQLDialect
from . import dialects, sqltype_for


@dialects.register_for(DB2)
class DB2Dialect(SQLDialect):
    @sqltype_for('text')
    def type_text(self):
        return 'CLOB'

    @sqltype_for('integer')
    def type_integer(self):
        return 'INT'

    @sqltype_for('bigint')
    def type_bigint(self):
        return 'BIGINT'

    @sqltype_for('float')
    def type_float(self):
        return 'REAL'

    @sqltype_for('id')
    def type_id(self):
        return 'INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY NOT NULL'

    @sqltype_for('big-id')
    def type_big_id(self):
        return 'BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY NOT NULL'

    @sqltype_for('reference')
    def type_reference(self):
        return 'INT, FOREIGN KEY (%(field_name)s) REFERENCES ' + \
            '%(foreign_key)s ON DELETE %(on_delete_action)s'

    @sqltype_for('big-reference')
    def type_big_reference(self):
        return 'BIGINT, FOREIGN KEY (%(field_name)s) REFERENCES ' + \
            '%(foreign_key)s ON DELETE %(on_delete_action)s'

    @sqltype_for('reference FK')
    def type_reference_fk(self):
        return ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY ' + \
            '(%(field_name)s) REFERENCES %(foreign_key)s ' + \
            'ON DELETE %(on_delete_action)s'

    @sqltype_for('reference TFK')
    def type_reference_tfk(self):
        return ' CONSTRAINT FK_%(constraint_name)s_PK FOREIGN KEY ' + \
            '(%(field_name)s) REFERENCES %(foreign_table)s' + \
            '(%(foreign_key)s) ON DELETE %(on_delete_action)s'

    def left_join(self, val, query_env={}):
        # Left join must always have an ON clause
        if not isinstance(val, basestring):
            val = self.expand(val, query_env=query_env)
        return 'LEFT OUTER JOIN %s' % val

    @property
    def random(self):
        return 'RAND()'

    def select(self, fields, tables, where=None, groupby=None, having=None,
               orderby=None, limitby=None, distinct=False, for_update=False):
        dst, whr, grp, order, limit, offset, upd = '', '', '', '', '', '', ''
        if distinct is True:
            dst = ' DISTINCT'
        elif distinct:
            dst = ' DISTINCT ON (%s)' % distinct
        if where:
            whr = ' %s' % self.where(where)
        if groupby:
            grp = ' GROUP BY %s' % groupby
            if having:
                grp += ' HAVING %s' % having
        if orderby:
            order = ' ORDER BY %s' % orderby
        if limitby:
            (lmin, lmax) = limitby
            limit = ' FETCH FIRST %i ROWS ONLY' % lmax
        if for_update:
            upd = ' FOR UPDATE'
        return 'SELECT%s %s FROM %s%s%s%s%s%s%s;' % (
            dst, fields, tables, whr, grp, order, limit, offset, upd)