# This file is part of python-sql. The COPYRIGHT file at the top level of

# this repository contains the full copyright notices and license terms.

from sql import CombiningQuery, Expression, Flavor, Select

__all__ = ['Case', 'Coalesce', 'NullIf', 'Greatest', 'Least']

class Conditional(Expression):

__slots__ = ()

_sql = ''

table = ''

name = ''

@staticmethod

def _format(value):

if isinstance(value, Expression):

return str(value)

elif isinstance(value, (Select, CombiningQuery)):

return '(%s)' % value

else:

return Flavor().get().param

class Case(Conditional):

__slots__ = ('whens', 'else_')

def __init__(self, *whens, **kwargs):

self.whens = whens

self.else_ = kwargs.get('else_')

def __str__(self):

case = 'CASE '

for cond, result in self.whens:

case += 'WHEN %s THEN %s ' % (

self._format(cond), self._format(result))

if self.else_ is not None:

case += 'ELSE %s ' % self._format(self.else_)

case += 'END'

return case

@property

def params(self):

p = []

for cond, result in self.whens:

if isinstance(cond, (Expression, Select, CombiningQuery)):

p.extend(cond.params)

else:

p.append(cond)

if isinstance(result, (Expression, Select, CombiningQuery)):

p.extend(result.params)

else:

p.append(result)

if self.else_ is not None:

if isinstance(self.else_, (Expression, Select, CombiningQuery)):

p.extend(self.else_.params)

else:

p.append(self.else_)

return tuple(p)

class Coalesce(Conditional):

__slots__ = ('values')

_conditional = 'COALESCE'

def __init__(self, *values):

self.values = values

def __str__(self):

return (self._conditional

+ '(' + ', '.join(map(self._format, self.values)) + ')')

@property

def params(self):

p = []

for value in self.values:

if isinstance(value, (Expression, Select, CombiningQuery)):

p.extend(value.params)

else:

p.append(value)

return tuple(p)

class NullIf(Coalesce):

__slots__ = ()

_conditional = 'NULLIF'

class Greatest(Coalesce):

__slots__ = ()

_conditional = 'GREATEST'

class Least(Coalesce):

__slots__ = ()

_conditional = 'LEAST'