More work on initial backend models

sse_library/library/migrations/0002_add_patrons_and_transactions.py

@@ -0,0 +1,115 @@
+# -*- coding: utf-8 -*-
+import datetime
+from south.db import db
+from south.v2 import SchemaMigration
+from django.db import models
+
+
+class Migration(SchemaMigration):
+
+    def forwards(self, orm):
+        # Adding model 'Transaction'
+        db.create_table('library_transaction', (
+            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
+            ('book', self.gf('django.db.models.fields.related.ForeignKey')(related_name='transactions', to=orm['library.Book'])),
+            ('borrower', self.gf('django.db.models.fields.related.ForeignKey')(related_name='transactions', to=orm['library.Patron'])),
+            ('checkout_date', self.gf('django.db.models.fields.DateField')(default=datetime.datetime(2012, 9, 24, 0, 0))),
+            ('due_date', self.gf('django.db.models.fields.DateField')(default=datetime.datetime(2012, 10, 15, 0, 0))),
+            ('return_date', self.gf('django.db.models.fields.DateField')(default=None, null=True, blank=True)),
+            ('is_transaction_completed', self.gf('django.db.models.fields.BooleanField')(default=False)),
+        ))
+        db.send_create_signal('library', ['Transaction'])
+
+        # Adding model 'Patron'
+        db.create_table('library_patron', (
+            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
+            ('name', self.gf('django.db.models.fields.CharField')(max_length=254)),
+            ('email', self.gf('django.db.models.fields.EmailField')(max_length=7)),
+            ('uid', self.gf('django.db.models.fields.CharField')(max_length=9)),
+        ))
+        db.send_create_signal('library', ['Patron'])
+
+        # Adding field 'Book.is_missing'
+        db.add_column('library_book', 'is_missing',
+                      self.gf('django.db.models.fields.BooleanField')(default=False),
+                      keep_default=False)
+
+
+        # Changing field 'Book.publisher'
+        db.alter_column('library_book', 'publisher_id', self.gf('django.db.models.fields.related.ForeignKey')(null=True, to=orm['library.Publisher']))
+
+        # Changing field 'Book.isbn'
+        db.alter_column('library_book', 'isbn', self.gf('django.db.models.fields.CharField')(unique=True, max_length=17))
+        # Adding unique constraint on 'Book', fields ['isbn']
+        db.create_unique('library_book', ['isbn'])
+
+
+        # Changing field 'Book.condition'
+        db.alter_column('library_book', 'condition', self.gf('django.db.models.fields.CharField')(max_length=254))
+
+    def backwards(self, orm):
+        # Removing unique constraint on 'Book', fields ['isbn']
+        db.delete_unique('library_book', ['isbn'])
+
+        # Deleting model 'Transaction'
+        db.delete_table('library_transaction')
+
+        # Deleting model 'Patron'
+        db.delete_table('library_patron')
+
+        # Deleting field 'Book.is_missing'
+        db.delete_column('library_book', 'is_missing')
+
+
+        # User chose to not deal with backwards NULL issues for 'Book.publisher'
+        raise RuntimeError("Cannot reverse this migration. 'Book.publisher' and its values cannot be restored.")
+
+        # Changing field 'Book.isbn'
+        db.alter_column('library_book', 'isbn', self.gf('django.db.models.fields.CharField')(max_length=16))
+
+        # Changing field 'Book.condition'
+        db.alter_column('library_book', 'condition', self.gf('django.db.models.fields.CharField')(max_length=1))
+
+    models = {
+        'library.author': {
+            'Meta': {'object_name': 'Author'},
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '254'})
+        },
+        'library.book': {
+            'Meta': {'object_name': 'Book'},
+            'authors': ('django.db.models.fields.related.ManyToManyField', [], {'related_name': "'books'", 'symmetrical': 'False', 'to': "orm['library.Author']"}),
+            'condition': ('django.db.models.fields.CharField', [], {'default': "'Good'", 'max_length': '254'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'is_missing': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'is_required_text': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'isbn': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '17'}),
+            'publish_date': ('django.db.models.fields.DateField', [], {'default': 'datetime.datetime(2012, 9, 24, 0, 0)'}),
+            'publisher': ('django.db.models.fields.related.ForeignKey', [], {'default': 'None', 'related_name': "'books'", 'null': 'True', 'blank': 'True', 'to': "orm['library.Publisher']"}),
+            'title': ('django.db.models.fields.CharField', [], {'max_length': '254'})
+        },
+        'library.patron': {
+            'Meta': {'object_name': 'Patron'},
+            'email': ('django.db.models.fields.EmailField', [], {'max_length': '7'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '254'}),
+            'uid': ('django.db.models.fields.CharField', [], {'max_length': '9'})
+        },
+        'library.publisher': {
+            'Meta': {'object_name': 'Publisher'},
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '254'})
+        },
+        'library.transaction': {
+            'Meta': {'object_name': 'Transaction'},
+            'book': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'transactions'", 'to': "orm['library.Book']"}),
+            'borrower': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'transactions'", 'to': "orm['library.Patron']"}),
+            'checkout_date': ('django.db.models.fields.DateField', [], {'default': 'datetime.datetime(2012, 9, 24, 0, 0)'}),
+            'due_date': ('django.db.models.fields.DateField', [], {'default': 'datetime.datetime(2012, 10, 15, 0, 0)'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'is_transaction_completed': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'return_date': ('django.db.models.fields.DateField', [], {'default': 'None', 'null': 'True', 'blank': 'True'})
+        }
+    }
+
+    complete_apps = ['library']

sse_library/library/models.py

@@ -1,6 +1,18 @@
 from django.db import models
 from django.utils import timezone
-from datetime import timedelta
+import datetime, sha
+
+DEFAULT_CHECKOUT_DURATION = datetime.timedelta(weeks=3)
+
+class CheckoutException(Exception):
+  pass
+
+class CheckinException(Exception):
+  pass
+
+class ConsistencyError(Exception):
+  pass
+
 class Author(models.Model):
   """ Author of a book.
 
@@ -20,47 +32,120 @@ class Publisher(models.Model):
 class Book(models.Model):
   """ Book model.
 
-      Constants:
-      * DB_GOOD database shortand for a book in good condition
-      * DB_POOR database shortand for a book in poor condition
-      * CONDITIONS mapping from database shorthands to human-readable name
-
       Relations:
       * has many authors
       * has one publisher
+      * has many transactions
   """
 
-  DB_GOOD = '+'
-  DB_POOR = '-'
-  CONDITIONS = (
-      (DB_GOOD, 'Good'),
-      (DB_POOR, 'Poor'))
-
   # Foreign Keys
   authors = models.ManyToManyField('Author', related_name='books')
-  publisher = models.ForeignKey('Publisher', related_name='books')
+  publisher = models.ForeignKey('Publisher',
+      related_name='books',
+      null=True,
+      blank=True,
+      default=None)
 
   # Fields
   title = models.CharField(max_length=254)
-  isbn = models.CharField(max_length=16)
+  isbn = models.CharField(max_length=17, unique=True)
   publish_date = models.DateField(default=timezone.now())
-  condition = models.CharField(max_length=1, choices=CONDITIONS, default=DB_GOOD)
-  is_required_text = models.BooleanField()
+  condition = models.CharField(max_length=254, default='Good')
+  is_missing = models.BooleanField(default=False)
+  is_required_text = models.BooleanField(default=False)
+
+class Patron(models.Model):
+  """ Library user who borrows books.
+
+      Relations:
+        * has many transactions
+  """
+
+  # Fields
+  name = models.CharField(max_length=254)
+  email = models.EmailField(max_length=7)
+  uid = models.CharField(max_length=9)
+
+  def checked_out_books(self):
+    """ Returns the patron's currently checked out books.
+
+    Returns a generator.
+
+    Returns:
+      collection of books checked out
+    """
+
+    return (t.book for t in self.transactions.filter(
+        is_transaction_completed=False))
+
+  def checkout(self, book):
+    """ Attempt to check out a book.
+
+    Exceptions:
+      Book is already checked out by someone
+      Book is missing
+    """
+
+    if book.is_missing:
+      raise CheckoutException("{0} is missing.".format(book.title))
+
+    if book.is_required_text:
+      raise CheckoutException("{0} is a required textbook.".format(book.title))
+
+    active_book_transactions = Transaction.objects.filter(
+        book=book, is_transaction_completed=False)
+
+    if active_book_transactions.exists():
+      existing_transaction = active_book_transactions.all()[0]
+      raise CheckoutException("{0} is currently checked out by {1}".format(
+          book.title, existing_transaction.borrower.name))
+
+    # Create and save transaction
+    checkout_transaction = Transaction.objects.create(
+        book=book, borrower=self)
+
+  def checkin(self, book):
+    """ Attempt to check in (return) a book.
+
+    Exceptions:
+      There is no existing transaction for this user and book.
+    """
+
+    book_transaction = Transaction.objects.filter(
+        is_transaction_completed=False, book=book, borrower=self)
+
+    if not book_transaction.exists():
+      raise CheckinException(
+          "{0} is not checked out by {1} or is already returned".format(
+              book.title, self.name))
+
+    # This should never happen
+    if book_transaction.count() != 1:
+      raise ConsistencyError("{0} has multiple transactions with {1}".format(
+          self.name, book.title))
+
+    book_transaction = book_transaction[0]
+
+    book_transaction.is_transaction_completed = True
+    book_transaction.return_date = timezone.now()
+
+    book_transaction.save()
 
 class Transaction(models.Model):
-
-  ACTIONS = (
-    ('Renew', 'Renew'),
-    ('ChkOut', 'Check Out'),
-    ('ChkIn', 'Check in'))
-
-  #Foreign Keys
-  #TODO:Add in FKs to users
-  book = models.ForeignKey(Book)
-
-  #Fields
-  date= models.DateTimeField(db_column='Date of Transaction', default = timezone.now())
-  due_date = models.DateTimeField(db_column='Due Back',default= timezone.now() + timedelta(days=7))
-  #TODO:Make tables for conditions/actions to make the site more configurable and so that things (such as conditions) can be used in multiple objects
-  action = models.CharField(max_length=90, choices=ACTIONS, default='ChkOut')
-  trans_notes = models.CharField(max_length=500)
+  """ Check out a book.
+
+      Relations:
+      * belongs to a book
+      * belongs to a borrower
+  """
+
+  # Foreign Keys
+  book = models.ForeignKey('Book', related_name='transactions')
+  borrower = models.ForeignKey('Patron', related_name='transactions')
+
+  # Fields
+  checkout_date = models.DateField(default=timezone.now())
+  due_date = models.DateField(default=timezone.now() +
+      DEFAULT_CHECKOUT_DURATION)
+  return_date = models.DateField(default=None, blank=True, null=True)
+  is_transaction_completed = models.BooleanField(default=False)