import os, sys, types
from glob import glob
from time import asctime, localtime, time
from MiddleKit.Core.ObjRefAttr import objRefJoin
from MiscUtils import AbstractError, StringTypes, CSVParser
from CodeGenerator import *

try: # for Python < 2.3
	True, False
except NameError:
	True, False = 1, 0


class SampleError:

	def __init__(self, line, error):
		self._line = line
		self._error = error

	def write(self, filename):
		print '%s:%d: %s' % (filename, self._line, self._error)


class SQLGenerator(CodeGenerator):
	"""The MiddleKit SQL Generator class.

	This class and its associated mix-ins are responsible for generating:
		- Create.sql
		- InsertSample.sql
		- Info.text

	A subclass and further mix-ins are required for specific databases
	(since SQL varies from product to product).

	The main method to invoke is generate():

		gen = SomeSQLGenerator()
		gen.readModelFileNamed(filename)
		gen.generate(dirname)

	For subclassers:
		- Subclasses should be named <DATABASE>SQLGenerator where <DATABASE>
		  is the name of the particular database product.
		- A good example of a custom subclass is MySQLSQLGenerator.py.
		  Be sure to take a look at it.
		- Candidates for customization include:
			Klasses
				dropDatabaseSQL()
				createDatabaseSQL()
				useDatabaseSQL()
			StringAttr
			EnumAttr
	"""

	def sqlDatabaseName(self):
		"""Return the name of the database by asking the generator's model."""
		return self.model().sqlDatabaseName()

	def generate(self, dirname):
		self.requireDir(dirname)
		self.writeInfoFile(os.path.join(dirname, 'Info.text'))
		self._model.writeCreateSQL(self, dirname)
		self._model.writeInsertSamplesSQL(self, dirname)

	def sqlSupportsDefaultValues(self):
		"""Return whether SQL default values are supported.

		Subclasses must override to return True or False, indicating their
		SQL variant supports DEFAULT <value> in the CREATE statement.
		Subclass responsibility.

		"""
		raise AbstractError


class ModelObject:
	pass


class Model:

	def writeCreateSQL(self, generator, dirname):
		"""Write SQL create statements.

		Creates the directory if necessary, sets the klasses' generator, and
		tells klasses to writeCreateSQL().

		"""
		if not os.path.exists(dirname):
			os.mkdir(dirname)
		assert os.path.isdir(dirname)
		self._klasses.setSQLGenerator(generator)
		self._klasses.writeCreateSQL(generator, os.path.join(dirname, 'Create.sql'))

	def sqlDatabaseName(self):
		"""Return the name of the database.

		This is either the 'Database' setting or self.name().

		"""
		name = self.setting('Database', None)
		if name is None:
			name = self.name()
		return name

	def writeConnectToDatabase(self, generator, output, databasename):
		output.write('use %s;\n\n' % databasename)

	def writeInsertSamplesSQL(self, generator, dirname):
		if self._filename is not None:
			file = open(os.path.join(dirname, 'InsertSamples.sql'), 'w')
			self.writeConnectToDatabase(generator, file, self.sqlDatabaseName())

			if self.setting('DoNotSortSQLCreateStatementsByDependency', False):
				allKlasses = self.allKlassesInOrder()
			else:
				allKlasses = self.allKlassesInDependencyOrder()

			# delete the existing data
			wr = file.write
			if 0:
				# Woops. Our only auxiliary table is _MKClassIds, which we
				# *don't* want to delete. In the future we will likely
				# have other aux tables for lists and relationships. When
				# that happens, we'll need more granularity regarding
				# aux tables.
				names = self.auxiliaryTableNames()[:]
				names.reverse()
				for tableName in names:
					wr('delete from %s;\n' % tableName)
			reverseKlasses = allKlasses[:]
			reverseKlasses.reverse()
			for klass in reverseKlasses:
				if not klass.isAbstract():
					wr('delete from %s;\n' % klass.sqlTableName())
			wr('\n')

			self._klassSamples = {} # keyed by klass,
			# value is list of SQL strings (comments or INSERT statements)

			filenames = glob(os.path.join(self._filename, 'Sample*.csv'))
			for filename in filenames:
				lines = open(filename).readlines()
				try:
					self.writeInsertSamplesSQLForLines(lines, generator, file, filename)
				except SampleError, s:
					s.write(filename)
					sys.exit(1)

			# at this point the klassSamples dict has the collected samples for each klass
			# write the samples file
			for klass in allKlasses:
				samples = self._klassSamples.get(klass)
				if samples is not None:
					for line in samples:
						file.write(line)
				self.writePostKlassSamplesSQL(generator, file)

			self.writePostSamplesSQL(generator, file)
			file.close()

			del self._klassSamples

	def writePostKlassSamplesSQL(self, generator, file):
		pass

	def writeInsertSamplesSQLForLines(self, lines, generator, file, filename):
		readColumns = True
		parse = CSVParser.CSVParser().parse
		linenum = 0
		klass = None
		attrs = []
		try:
			for line in lines:
				linenum += 1
				try:
					fields = parse(line)
				except CSVParser.ParseError, err:
					raise SampleError(linenum, 'Syntax error: %s' % err)
				if fields is None:	# parser got embedded newline; continue with next line
					continue

				try:
					if self.areFieldsBlank(fields):
						pass # skip blank lines
					elif fields[0] and str(fields[0])[0] == '#':
						pass
					elif fields[0].lower().endswith(' objects'):
						klassName = fields[0].split()[0]
						try:
							klass = self.klass(klassName)
						except KeyError:
							raise SampleError(linenum,
								"Class '%s' is not defined" % klassName)
						samples = self._klassSamples.get(klass, None)
						if samples is None:
							samples = self._klassSamples[klass] = []
							samples.append('\n\n/* %s */\n\n' % klass.name())
						tableName = klass.sqlTableName()
						# print '>> table:', tableName
						readColumns = True
						for attr in attrs:
							attr.refByAttrName = None
						attrs = []
					elif readColumns:
							if klass is None:
								raise SampleError(linenum,
									"Have not yet seen an 'objects' declaration.")
							names = [name for name in fields if name]
							for name in names:
								if name == klass.sqlSerialColumnName():
									attrs.append(PrimaryKey(name, klass))
								else:
									# support "foo by bar"
									name = name.strip()
									parts = name.split(' ')
									if len(parts) == 1:
										refByAttrName = None
									else:
										parts = [p.strip() for p in parts]
										if len(parts) != 3 \
												or parts[1].lower() != 'by' \
												or len(parts[2]) == 0:
											raise SampleError(linenum,
												"Attribute '%s' of class '%s'"
												" is not in format 'foo' or 'foo-by-bar'"
												% (name, klass.name()))
										name = parts[0]
										refByAttrName = parts[2]
										# print '>> refByAttrName:', name, refByAttrName
									# locate the attr definiton
									try:
										attr = klass.lookupAttr(name)
										attrs.append(attr)
									except KeyError:
										raise SampleError(linenum,
											"Class '%s' has no attribute '%s'"
											% (klass.name(), name))
									# error checking for "foo by bar" and set refByAttre
									if refByAttrName:
										from MiddleKit.Core.ObjRefAttr \
											import ObjRefAttr as ObjRefAttrClass
										if not isinstance(attr, ObjRefAttrClass):
											raise SampleError(linenum,
												"Cannot use 'by' feature with non-obj ref attributes."
												" Attr %r of class %r is a %r."
												% (name, klass.name(), attr.__class__.__name__))
										try:
											refByAttr = attr.targetKlass().lookupAttr(refByAttrName)
										except KeyError:
											raise SampleError(linenum,
												"Attribute %r of class %r has a 'by' of %r,"
												" but no such attribute can be found in target class %r."
												% (name, klass.name(),
													refByAttrName, attr.targetKlass().name()))
										attr.refByAttr = refByAttr
									else:
										attr.refByAttr = None

							# @@ 2000-10-29 ce: check that each attr.hasSQLColumn()
							for attr in attrs:
								assert not attr.get('isDerived', False)
							colNames = [attr.sqlName() for attr in attrs]
							# print '>> cols:', columns
							colSql = ','.join(colNames)
							readColumns = False
					else:
						if klass is None:
							raise SampleError(linenum,
								"Have not yet seen an 'objects' declaration.")
						values = fields[:len(attrs)]
						preinsertSQL = []
						i = 0
						for attr in attrs:
							try:
								value = values[i]
							except IndexError:
								if i == 0:
									# too early to accept nulls?
									raise SampleError(linenum,
										"Couldn't find value for attribute"
										" '%s'\nattrs = %r\nvalues for line = %r"
										% (attr.name(), [a.name() for a in attrs], values))
								else:
									# assume blank
									# (Excel sometimes doesn't include all the commas)
									value = ''
							value = attr.sqlForSampleInput(value)
							if isinstance(value, types.TupleType):
								# sqlForSampleInput can return a 2 tuple: (presql, sqlValue)
								assert len(value) == 2
								preinsertSQL.append(value[0])
								value = value[1]
							assert value, 'sql value cannot be blank: %r' % value
							try:
								values[i] = value
							except IndexError:
								values.append(value)
							i += 1
						values = ', '.join(values)
						for stmt in preinsertSQL:
							#print '>>', stmt
							samples.append(stmt)
						stmt = 'insert into %s (%s) values (%s);\n' % (tableName, colSql, values)
						# print '>>', stmt
						samples.append(stmt)
				except Exception:
					print
					print 'Samples error:'
					try:
						print '%s:%s' % (filename, linenum)
						print line
					except Exception:
						pass
					print
					raise
		finally:
			for attr in attrs:
				attr.refByAttr = None

	def areFieldsBlank(self, fields):
		"""Utility method for writeInsertSamplesSQLForLines()."""
		if len(fields) == 0:
			return True
		for field in fields:
			if field:
				return False
		return True

	def writePostSamplesSQL(self, generator, output):
		pass


class Klasses:

	def sqlGenerator(self):
		return generator

	def setSQLGenerator(self, generator):
		self._sqlGenerator = generator

	def auxiliaryTableNames(self):
		"""Return a list of table names in addition to the tables that hold objects.

		One popular user of this method is dropTablesSQL().

		"""
		return ['_MKClassIds']

	def writeKeyValue(self, out, key, value):
		"""Used by willCreateWriteSQL()."""
		key = key.ljust(12)
		out.write('# %s = %s\n' % (key, value))

	def writeCreateSQL(self, generator, out):
		"""Write the SQL to define the tables for a set of classes.

		The target can be a file or a filename.

		"""
		if type(out) in StringTypes:
			out = open(out, 'w')
			close = True
		else:
			close = False
		self.willWriteCreateSQL(generator, out)
		self._writeCreateSQL(generator, out)
		self.didWriteCreateSQL(generator, out)
		if close:
			out.close()

	def willWriteCreateSQL(self, generator, out):
		# @@ 2001-02-04 ce: break up this method
		wr = out.write
		kv = self.writeKeyValue
		wr('/*\nStart of generated SQL.\n\n')
		kv(out, 'Date', asctime(localtime(time())))
		kv(out, 'Python ver', sys.version)
		kv(out, 'Op Sys', os.name)
		kv(out, 'Platform', sys.platform)
		kv(out, 'Cur dir', os.getcwd())
		kv(out, 'Num classes', len(self._klasses))
		wr('\nClasses:\n')
		for klass in self._model.allKlassesInOrder():
			wr('\t%s\n' % klass.name())
		wr('*/\n\n')

		sql = generator.setting('PreSQL', None)
		if sql:
			wr('/* PreSQL start */\n' + sql + '\n/* PreSQL end */\n\n')

		dbName = generator.sqlDatabaseName()
		drop = generator.setting('DropStatements')
		if drop == 'database':
			wr(self.dropDatabaseSQL(dbName))
			wr(self.createDatabaseSQL(dbName))
			wr(self.useDatabaseSQL(dbName))
		elif drop == 'tables':
			wr(self.useDatabaseSQL(dbName))
			wr(self.dropTablesSQL())
		else:
			raise Exception, 'Invalid value for DropStatements setting: %r' % drop

	def dropDatabaseSQL(self, dbName):
		"""Return SQL code that will remove the database with the given name.

		Used by willWriteCreateSQL().
		Subclass responsibility.

		"""
		raise AbstractError, self.__class__

	def dropTablesSQL(self):
		"""Return SQL code that will remove each of the tables in the database.

		Used by willWriteCreateSQL().
		Subclass responsibility.

		"""
		raise AbstractError, self.__class__

	def createDatabaseSQL(self, dbName):
		"""Return SQL code that will create the database with the given name.

		Used by willWriteCreateSQL().
		Subclass responsibility.

		"""
		raise AbstractError, self.__class__

	def useDatabaseSQL(self, dbName):
		"""Return SQL code that will use the database with the given name.

		Used by willWriteCreateSQL().
		Subclass responsibility.

		"""
		raise AbstractError, self.__class__

	def _writeCreateSQL(self, generator, out):
		# assign the class ids up-front, so that we can resolve forward object references
		self.assignClassIds(generator)
		self.writeClassIdsSQL(generator, out)

		if self._model.setting('DoNotSortSQLCreateStatementsByDependency', False):
			# Generates the CREATE TABLEs in the order the classes were declared
			# but if you're not careful, than foreign keys will cause "unknown table" errors
			allKlasses = self._model.allKlassesInOrder()
		else:
			allKlasses = self._model.allKlassesInDependencyOrder()

		for klass in allKlasses:
			klass.writeCreateSQL(self._sqlGenerator, out)

	def writeClassIdsSQL(self, generator, out):
		wr = out.write
		wr('''\
create table _MKClassIds (
	id int not null primary key,
	name varchar(100)
);
''')
		values = []
		for klass in self._model._allKlassesInOrder:
			wr('insert into _MKClassIds (id, name) values ')
			wr("\t(%s, '%s');\n" % (klass.id(), klass.name()))
		wr('\n')

	def listTablesSQL(self):
		# return a SQL command to list all tables in the database
		# this is database-specific, so by default we return nothing
		return ''

	def didWriteCreateSQL(self, generator, out):
		sql = generator.setting('PostSQL', None)
		if sql:
			out.write('/* PostSQL start */\n' + sql + '\n/* PostSQL end */\n\n')
		out.write(self.listTablesSQL())
		out.write('/* end of generated SQL */\n')


import KlassSQLSerialColumnName


class Klass:

	def writeCreateSQL(self, generator, out):
		for attr in self.attrs():
			attr.writeAuxiliaryCreateTable(generator, out)
		if not self.isAbstract():
			self.writeCreateTable(generator, out)
			self.writePostCreateTable(generator, out)

	def writeCreateTable(self, generator, out):
		name = self.name()
		wr = out.write
		wr('create table %s (\n' % self.sqlTableName())
		wr(self.primaryKeySQLDef(generator))
		if generator.model().setting('DeleteBehavior', 'delete') == 'mark':
			self.writeDeletedSQLDef(generator, out)
			wr(',\n')
		first = True
		sqlAttrs = []
		nonSQLAttrs = []
		for attr in self.allAttrs():
			attr.containingKlass = self # as opposed to the declaring klass of the attr
			if attr.hasSQLColumn():
				sqlAttrs.append(attr)
			else:
				nonSQLAttrs.append(attr)
		for attr in sqlAttrs:
			if first:
				first = False
			else:
				wr(',\n')
			attr.writeCreateSQL(generator, out)
		self.writeIndexSQLDefsInTable(wr)
		for attr in nonSQLAttrs:
			attr.writeCreateSQL(generator, out)
			wr('\n')
		wr(');\n')
		self.writeIndexSQLDefsAfterTable(wr)
		wr('\n\n')
		# cleanup
		for attr in self.allAttrs():
			attr.containingKlass = None

	def writePostCreateTable(self, generator, out):
		pass

	def primaryKeySQLDef(self, generator):
		"""Return SQL for primary key.

		Returns a one-liner that becomes part of the CREATE statement for
		creating the primary key of the table. SQL generators often override
		this mix-in method to customize the creation of the primary key for
		their SQL variant. This method should use self.sqlSerialColumnName()
		and often ljust()s it by self.maxNameWidth().

		"""
		return '    %s int not null primary key,\n' \
			% self.sqlSerialColumnName().ljust(self.maxNameWidth())

	def writeDeletedSQLDef(self, generator, out):
		"""Return SQL for deleted timestamp.

		Returns a the column definition that becomes part of the CREATE
		statement for the deleted timestamp field of the table.
		This is used if DeleteBehavior is set to "mark".

		"""
		row = {'Attribute': 'deleted', 'Type': 'DateTime'}
		# create a "DateTimeAttr", so that the correct database type is used
		# depending on the backend database.
		datetime = generator.model().coreClass('DateTimeAttr')(row)
		datetime.setKlass(self)
		datetime.writeCreateSQL(generator, out)

	def maxNameWidth(self):
		return 30 # @@ 2000-09-15 ce: Ack! Duplicated from Attr class below

	def writeIndexSQLDefsInTable(self, wr):
		"""Return SQL for creating indexes in table.

		Subclasses should override this or writeIndexSQLDefsAfterTable,
		or no indexes will be created.

		"""
		pass

	def writeIndexSQLDefsAfterTable(self, wr):
		""""Return SQL for creating indexes after table.

		Subclasses should override this or writeIndexSQLDefsInTable,
		or no indexes will be created.

		"""
		pass

	def sqlTableName(self):
		"""Return table name.

		Can be overidden to allow for table names that do not conflict
		with SQL reserved words. dr 08-08-2002 - MSSQL uses [tablename]
		"""
		return self.name()


class Attr:

	def sqlName(self):
		return self.name()

	def hasSQLColumn(self):
		"""Return whether attribute corresponds to table column.

		Returns true if the attribute has a direct correlating SQL column
		in its class' SQL table definition. Most attributes do.
		Those of type list do not.

		"""
		return not self.get('isDerived', False)

	def sqlForSampleInput(self, input):
		"""Return SQL for sample input.

		Users of Attr should invoke this method, but subclasses and mixins
		should implement sqlForNonNoneSampleInput() instead.

		"""
		input = input.strip()
		if input == '':
			input = self.get('Default', '')
		if input in (None, 'None', 'none'):
			return self.sqlForNone()
		else:
			s = self.sqlForNonNoneSampleInput(input)
			assert type(s) in StringTypes + (types.TupleType,), \
				'%r, %r, %r' % (s, type(s), self)
			return s

	def sqlForNone(self):
		return 'NULL'

	def sqlForNonNoneSampleInput(self, input):
		return input

	def writeCreateSQL(self, generator, out):
		"""Write SQL create command.

		The klass argument is the containing klass of the attribute
		which can be different than the declaring klass.

		"""
		try:
			if self.hasSQLColumn():
				self.writeRealCreateSQLColumn(generator, out)
			else:
				out.write('\t/* %(Name)s %(Type)s - not a SQL column */' % self)
		except Exception:
			bar = '*'*78
			print
			print bar
			print 'exception for attribute:'
			print '%s.%s' % (self.klass().name(), self.name())
			print
			try:
				from pprint import pprint
				pprint(self.data)
			except Exception:
				pass
			print bar
			print
			raise

	def writeRealCreateSQLColumn(self, generator, out):
		name = self.sqlName().ljust(self.maxNameWidth())
		if self.isRequired():
			notNullSQL = ' not null'
		else:
			notNullSQL = self.sqlNullSpec()
		if generator.sqlSupportsDefaultValues():
			defaultSQL = self.createDefaultSQL()
			if defaultSQL:
				defaultSQL = ' ' + defaultSQL
		else:
			defaultSQL = ''
		out.write('\t%s %s%s%s%s' % (name, self.sqlTypeOrOverride(),
			self.uniqueSQL(), notNullSQL, defaultSQL))

	def writeAuxiliaryCreateTable(self, generator, out):
		# most attribute types have no such beast
		pass

	def sqlNullSpec(self):
		return ''

	def createDefaultSQL(self):
		default = self.get('SQLDefault', None)
		if default is None:
			default = self.get('Default', None)
			if default is not None:
				default = self.sqlForSampleInput(str(default))
		if default:
			default = str(default).strip()
			if default.lower() == 'none':  # kind of redundant
				default = None
			return 'default ' + default
		else:
			return ''

	def maxNameWidth(self):
		return 30 # @@ 2000-09-14 ce: should compute that from names rather than hard code

	def sqlTypeOrOverride(self):
		"""Return SQL type.

		Returns the SQL type as specified by the attribute class, or
		the SQLType that the user can specify in the model to override that.
		For example, SQLType='image' for a string attribute.
		Subclasses should not override this method, but sqlType() instead.

		"""
		return self.get('SQLType') or self.sqlType()

	def sqlType(self):
		raise AbstractError, self.__class__

	def sqlColumnName(self):
		"""Return SQL column name.

		Returns the SQL column name corresponding to this attribute
		which simply defaults to the attribute's name. Subclasses may
		override to customize.

		"""
		if not self._sqlColumnName:
			self._sqlColumnName = self.name()
		return self._sqlColumnName

	def uniqueSQL(self):
		"""Return SQL to use within a column definition to make it unique."""
		return self.boolForKey('isUnique') and ' unique' or ''


class BoolAttr:

	def sqlType(self):
		# @@ 2001-02-04 ce: is this ANSI SQL? or at least common SQL?
		return 'bool'

	def sqlForNonNoneSampleInput(self, input):
		try:
			input = input.upper()
		except Exception:
			pass
		if input in (False, 'FALSE', 'NO', '0', '0.0', 0, 0.0):
			value = 0
		elif input in (True, 'TRUE', 'YES', '1', '1.0', 1, 1.0):
			value = 1
		else:
			raise ValueError, "invalid bool input: %r" % input
		assert value in (0, 1), value
		return str(value)


class IntAttr:

	def sqlType(self):
		return 'int'

	def sqlForNonNoneSampleInput(self, input):
		if not isinstance(input, types.IntType):
			value = str(input)
			if value.endswith('.0'):
				# numeric values from Excel-based models are always float
				value = value[:-2]
			try:
				int(value) # raises exception if value is invalid
			except ValueError, e:
				raise ValueError, str(e)+'. attr is '+self.name()
			return str(value)


class LongAttr:

	def sqlType(self):
		# @@ 2000-10-18 ce: is this ANSI SQL?
		return 'bigint'

	def sqlForNonNoneSampleInput(self, input):
		long(input) # raises exception if value is invalid
		return str(input)


class FloatAttr:

	def sqlType(self):
		return 'double precision'

	def sqlForNonNoneSampleInput(self, input):
		float(input) # raises exception if value is invalid
		return str(input)


class DecimalAttr:

	def sqlType(self):
		# the keys 'Precision' and 'Scale' are used because all the
		# SQL docs I read say:  decimal(precision, scale)
		precision = self.get('Precision', None)
		if precision is None:
			# the following setting is for backwards compatibility
			if self.klass().klasses()._model.setting('UseMaxForDecimalPrecision', False):
				precision = self.get('Max', None)
				if not precision:
					precision = None
			if precision is None:
				precision = 11
		scale = self.get('Scale', None)
		if scale is None:
			scale = self.get('numDecimalPlaces', 3)
		return 'decimal(%s,%s)' % (precision, scale)

	def sqlForNonNoneSampleInput(self, input):
		return str(input)


class StringAttr:

	def sqlType(self):
		"""Return SQL type.

		Subclass responsibility.
		Subclasses should take care that if self['Max'] == self['Min']
		then the "char" type is preferred over "varchar".
		Also, most (if not all) SQL databases require different types
		depending on the length of the string.

		"""
		raise AbstractError, self.__class__

	def sqlForNonNoneSampleInput(self, input):
		value = input
		if value == "''":
			value = ''
		elif value.find('\\') != -1:
			if 1:
				# add spaces before and after, to prevent
				# syntax error if value begins or ends with "
				value = eval('""" '+str(value)+' """')
				value = repr(value[1:-1]) # trim off the spaces
				value = value.replace('\\011', '\\t')
				value = value.replace('\\012', '\\n')
				return value
		value = repr(value)
		#print '>> value:', value
		return value


class AnyDateTimeAttr:

	def sqlType(self):
		return self['Type'] # e.g., date, time and datetime

	def sqlForNonNoneSampleInput(self, input):
		return repr(input)


class ObjRefAttr:

	def sqlName(self):
		if self.setting('UseBigIntObjRefColumns', False):
			return self.name() + 'Id'  # old way: one 64 bit column
		else:
			# new way: 2 int columns for class id and obj id
			name = self.name()
			classIdName, objIdName = self.setting('ObjRefSuffixes')
			classIdName = name + classIdName
			objIdName = name + objIdName
			return '%s,%s' % (classIdName, objIdName)

	def writeRealCreateSQLColumn(self, generator, out):
		if self.setting('UseBigIntObjRefColumns', False):
			# the old technique of having both the class id and the obj id in one 64 bit reference
			name = self.sqlName().ljust(self.maxNameWidth())
			if self.get('Ref', None):
				refs = ' references %(Type)s(%(Type)sId)' % self
			else:
				refs = ''
			if self.isRequired():
				notNull = ' not null'
			else:
				notNull = self.sqlNullSpec()
			out.write('\t%s %s%s%s' % (name, self.sqlTypeOrOverride(), refs, notNull))
		else:
			# the new technique uses one column for each part of the obj ref: class id and obj id
			classIdName = self.name()+self.setting('ObjRefSuffixes')[0]
			classIdName = classIdName.ljust(self.maxNameWidth())
			objIdName = self.name()+self.setting('ObjRefSuffixes')[1]
			objIdName = objIdName.ljust(self.maxNameWidth())
			if self.isRequired():
				notNull = ' not null'
			else:
				notNull = self.sqlNullSpec()
			classIdDefault = ' default %s' % self.targetKlass().id()
			# ^ this makes the table a little to easier to work with in some cases
			# (you can often just insert the obj id)
			objIdRef = ''
			if self.get('Ref', None) or (
					self.setting('GenerateSQLReferencesForObjRefsToSingleClasses', False)
						and len(self.targetKlass().subklasses()) == 0):
				if self.get('Ref', None) not in ('0', 0, 0.0, False):
					objIdRef = self.objIdReferences()
			out.write('\t%s %s%s%s%s, /* %s */ \n' % (
				classIdName, self.sqlTypeOrOverride(), notNull, classIdDefault,
					self.classIdReferences(), self.targetClassName()))
			out.write('\t%s %s%s%s' % (objIdName, self.sqlTypeOrOverride(),
				notNull, objIdRef))

	def classIdReferences(self):
		return ' references _MKClassIds'

	def objIdReferences(self):
		targetKlass = self.targetKlass()
		return ' references %s(%s) ' % (
			targetKlass.sqlTableName(), targetKlass.sqlSerialColumnName())

	def sqlForNone(self):
		if self.setting('UseBigIntObjRefColumns', False):
			return 'NULL'
		else:
			return 'NULL,NULL'

	def sqlForNonNoneSampleInput(self, input):
		"""Get SQL for non-None sample input.

		Obj ref sample data format is "Class.serialNum", such as "Thing.3".
		If the Class and period are missing, then the obj ref's type is assumed.

		Also, a comment can follow the value after a space:
		"User.3 Joe Schmoe" or "User.3 - Joe Schmoe"
		This is useful so that you can look at the sample later and know
		what the obj ref value is referring to without having to look it up.
		MiddleKit only looks at the first part ("User.3").

		"""
		if self.refByAttr:
			# the column was spec'ed as "foo by bar".
			# so match by "bar" value, not serial number.
			# refByAttr holds the "bar" attr
			targetKlass = self.targetKlass()
			refByAttr = self.refByAttr
			assert targetKlass is refByAttr.klass()
			sql = '(select %s from %s where %s=%s)' % (
				targetKlass.sqlSerialColumnName(), targetKlass.sqlTableName(), refByAttr.sqlColumnName(), refByAttr.sqlForSampleInput(input))
			sql = str(targetKlass.id()) + ',' + sql
			# print '>> sql =', sql
			return sql
			# caveat: this only works if the object is found directly in the
			# target class. i.e., inheritance is not supported
			# caveat: this does not work if the UseBigIntObjRefColumns setting
			# is true (by default it is false)
			# caveat: MS SQL Server supports subselects but complains
			# "Subqueries are not allowed in this context. Only scalar expressions are allowed."
			# so more work is needed in its SQL generator
		else:
			# the de facto technique of <serialnum> or <class name>.<serial num>
			input = input.split()
			# this gets rid of the sample value comment described above
			if input:
				input = input[0]
			else:
				input = ''
			parts = input.split('.')
			if len(parts) == 2:
				className = parts[0]
				objSerialNum = parts[1]
			else:
				className = self.targetClassName()
				objSerialNum = input or 'null'
			klass = self.klass().klasses()._model.klass(className)
			klassId = klass.id()
			if self.setting('UseBigIntObjRefColumns', False):
				objRef = objRefJoin(klassId, objSerialNum)
				return str(objRef)
			else:
				return '%s,%s' % (klassId, objSerialNum)


class ListAttr:

	def sqlType(self):
		raise Exception, 'Lists do not have a SQL type.'

	def hasSQLColumn(self):
		return False

	def sqlForSampleInput(self, input):
		raise Exception, 'Lists are implicit. They cannot have sample values.'


class EnumAttr:

	def sqlType(self):
		if self.usesExternalSQLEnums():
			tableName, valueColName, nameColName = self.externalEnumsSQLNames()
			return 'int references %s(%s)' % (tableName, valueColName)
		else:
			return self.nativeEnumSQLType()

	def nativeEnumSQLType(self):
		maxLen = max([len(e) for e in self.enums()])
		return 'varchar(%s)' % maxLen

	def sqlForNonNoneSampleInput(self, input):
		if self.usesExternalSQLEnums():
			return str(self.intValueForString(input))
		else:
			assert input in self._enums, 'input=%r, enums=%r' % (input, self._enums)
			return repr(input)

	def writeAuxiliaryCreateTable(self, generator, out):
		if self.usesExternalSQLEnums():
			tableName, valueColName, nameColName = self.externalEnumsSQLNames()
			out.write('create table %s (\n' % tableName)
			out.write('\t%s int not null primary key,\n' % valueColName)
			out.write('\t%s varchar(255)\n' % nameColName)
			out.write(');\n')
			i = 0
			sep = ''
			for enum in self.enums():
				out.write("insert into %(tableName)s values (%(i)i, '%(enum)s');\n" % locals())
				i += 1
			out.write('\n')


	## Settings ##

	def usesExternalSQLEnums(self):
		flag = getattr(self, '_usesExternalSQLEnums', None)
		if flag is None:
			flag = self.model().usesExternalSQLEnums()
			self._usesExternalSQLEnums = flag
		return flag

	def externalEnumsSQLNames(self):
		"""Return the tuple (tableName, valueColName, nameColName).

		This is derived from the model setting ExternalEnumsSQLNames.

		"""
		names = getattr(self, '_externalEnumsSQLNames', None)
		if names is None:
			_ClassName = self.klass().name()
			ClassName  = _ClassName[0].upper() + _ClassName[1:]
			className  = _ClassName[0].lower() + _ClassName[1:]
			_AttrName  = self.name()
			AttrName   = _AttrName[0].upper()  + _AttrName[1:]
			attrName   = _AttrName[0].lower()  + _AttrName[1:]
			values = locals()
			names = self.setting('ExternalEnumsSQLNames')
			names = [names['TableName'], names['ValueColName'], names['NameColName']]
			for i in range(len(names)):
				names[i] %= values
			self._externalEnumsSQLNames = names
		return names


class PrimaryKey:
	"""Help class for dealing with primary keys.

	This class is not a 'standard' attribute, but just a helper class for the
	writeInsertSamplesSQLForLines method, in case the samples.csv file contains
	a primary key column (i.e. the serial numbers are specified explicitly).

	"""

	def __init__(self, name, klass):
		self._name = name
		self._klassid = klass.id()
		self._props = {'isDerived': False}

		# this is for PostgreSQLSQLGenerator, but it's awkward to keep it there
		self._klass = klass
		if not hasattr(klass, '_maxSerialNum'):
			klass._maxSerialNum = 0

	def name(self):
		return self._name

	def sqlName(self):
		return self.name()

	def get(self, key, default=0):
		return self._props.get(key, default)

	def sqlForSampleInput(self, input):
		return input
