# encoding: utf8
from django.test import TransactionTestCase
from django.db.migrations.autodetector import MigrationAutodetector
from django.db.migrations.state import ProjectState, ModelState
from django.db import models


class AutodetectorTests(TransactionTestCase):
    """
    Tests the migration autodetector.
    """

    author_empty = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True))])

    def make_project_state(self, model_states):
        "Shortcut to make ProjectStates from lists of predefined models"
        project_state = ProjectState()
        for model_state in model_states:
            project_state.add_model_state(model_state)
        return project_state

    def test_new_model(self):
        "Tests autodetection of new models"
        # Make state
        before = self.make_project_state([])
        after = self.make_project_state([self.author_empty])
        autodetector = MigrationAutodetector(before, after)
        changes = autodetector.changes()
        # Right number of migrations?
        self.assertEqual(len(changes), 1)
        # Right number of actions?
        migration = changes.pop()
        self.assertEqual(len(migration.operations), 1)
        # Right action?
        action = migration.operations[0]
        self.assertEqual(action.__class__.__name__, "CreateModel")
        self.assertEqual(action.name, "Author")

    def test_old_model(self):
        "Tests deletion of old models"
        # Make state
        before = self.make_project_state([self.author_empty])
        after = self.make_project_state([])
        autodetector = MigrationAutodetector(before, after)
        changes = autodetector.changes()
        # Right number of migrations?
        self.assertEqual(len(changes), 1)
        # Right number of actions?
        migration = changes.pop()
        self.assertEqual(len(migration.operations), 1)
        # Right action?
        action = migration.operations[0]
        self.assertEqual(action.__class__.__name__, "DeleteModel")
        self.assertEqual(action.name, "Author")