from rope.base import pynames, evaluate, exceptions, worder
from rope.refactor.rename import Rename


class LocalToField(object):

    def __init__(self, project, resource, offset):
        self.project = project
        self.pycore = project.pycore
        self.resource = resource
        self.offset = offset

    def get_changes(self):
        name = worder.get_name_at(self.resource, self.offset)
        this_pymodule = self.pycore.resource_to_pyobject(self.resource)
        pyname = evaluate.eval_location(this_pymodule, self.offset)
        if not self._is_a_method_local(pyname):
            raise exceptions.RefactoringError(
                'Convert local variable to field should be performed on \n'
                'a local variable of a method.')

        pymodule, lineno = pyname.get_definition_location()
        function_scope = pymodule.get_scope().get_inner_scope_for_line(lineno)
        # Not checking redefinition
        #self._check_redefinition(name, function_scope)

        new_name = self._get_field_name(function_scope.pyobject, name)
        changes = Rename(self.project, self.resource, self.offset).\
                  get_changes(new_name, resources=[self.resource])
        return changes

    def _check_redefinition(self, name, function_scope):
        class_scope = function_scope.parent
        if name in class_scope.pyobject:
            raise exceptions.RefactoringError(
                'The field %s already exists' % name)

    def _get_field_name(self, pyfunction, name):
        self_name = pyfunction.get_param_names()[0]
        new_name = self_name + '.' + name
        return new_name

    def _is_a_method_local(self, pyname):
        pymodule, lineno = pyname.get_definition_location()
        holding_scope = pymodule.get_scope().get_inner_scope_for_line(lineno)
        parent = holding_scope.parent
        return isinstance(pyname, pynames.AssignedName) and \
               pyname in list(holding_scope.get_names().values()) and \
               holding_scope.get_kind() == 'Function' and \
               parent is not None and parent.get_kind() == 'Class'
