"""

   Firebird database specific implementations of changeset classes.

"""

from sqlalchemy.databases import firebird as sa_base

from sqlalchemy.schema import PrimaryKeyConstraint

from kallithea.lib.dbmigrate.migrate import exceptions

from kallithea.lib.dbmigrate.migrate.changeset import ansisql

FBSchemaGenerator = sa_base.FBDDLCompiler

class FBColumnGenerator(FBSchemaGenerator, ansisql.ANSIColumnGenerator):

    """Firebird column generator implementation."""

class FBColumnDropper(ansisql.ANSIColumnDropper):

    """Firebird column dropper implementation."""

    def visit_column(self, column):

        """Firebird supports 'DROP col' instead of 'DROP COLUMN col' syntax

        Drop primary key and unique constraints if dropped column is referencing it."""

        if column.primary_key:

            if column.table.primary_key.columns.contains_column(column):

                column.table.primary_key.drop()

                # TODO: recreate primary key if it references more than this column

        for index in column.table.indexes:

            # "column in index.columns" causes problems as all

            # column objects compare equal and return a SQL expression

            if column.name in [col.name for col in index.columns]:

                index.drop()

                # TODO: recreate index if it references more than this column

        for cons in column.table.constraints:

            if isinstance(cons,PrimaryKeyConstraint):

                # will be deleted only when the column its on

                # is deleted!

                continue

            should_drop = column.name in cons.columns

            if should_drop:

                self.start_alter_table(column)

                self.append("DROP CONSTRAINT ")

                self.append(self.preparer.format_constraint(cons))

                self.execute()

        self.start_alter_table(column)

        self.append('DROP %s' % self.preparer.format_column(column))

        self.execute()

class FBSchemaChanger(ansisql.ANSISchemaChanger):

    """Firebird schema changer implementation."""

    def visit_table(self, table):

        """Rename table not supported"""

        raise exceptions.NotSupportedError(

            "Firebird does not support renaming tables.")

    def _visit_column_name(self, table, column, delta):

        self.start_alter_table(table)

        col_name = self.preparer.quote(delta.current_name, table.quote)

        new_name = self.preparer.format_column(delta.result_column)

        self.append('ALTER COLUMN %s TO %s' % (col_name, new_name))

    def _visit_column_nullable(self, table, column, delta):

        """Changing NULL is not supported"""

        # TODO: http://www.firebirdfaq.org/faq103/

        raise exceptions.NotSupportedError(

            "Firebird does not support altering NULL behavior.")

class FBConstraintGenerator(ansisql.ANSIConstraintGenerator):

    """Firebird constraint generator implementation."""

class FBConstraintDropper(ansisql.ANSIConstraintDropper):

    """Firebird constraint dropper implementation."""

    def cascade_constraint(self, constraint):

        """Cascading constraints is not supported"""

        raise exceptions.NotSupportedError(

            "Firebird does not support cascading constraints")

class FBDialect(ansisql.ANSIDialect):

    columngenerator = FBColumnGenerator

    columndropper = FBColumnDropper

    schemachanger = FBSchemaChanger

    constraintgenerator = FBConstraintGenerator

    constraintdropper = FBConstraintDropper