Added transactions and updated models to reflect transactions

equipment_tracker/transactions/admin.py

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+from django.contrib import admin
+from .models import Transaction
+from accounts.models import CustomUser
+
+
+class TransactionAdmin(admin.ModelAdmin):
+    def formfield_for_foreignkey(self, db_field, request, **kwargs):
+        if db_field.name == "borrower":
+            kwargs["queryset"] = CustomUser.objects.exclude(
+                is_technician=True).exclude(is_teacher=True)
+        elif db_field.name == "teacher":
+            kwargs["queryset"] = CustomUser.objects.filter(is_teacher=True)
+        return super().formfield_for_foreignkey(db_field, request, **kwargs)
+
+
+admin.site.register(Transaction, TransactionAdmin)

equipment_tracker/transactions/apps.py

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+from django.apps import AppConfig
+
+
+class TransactionsConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'transactions'

equipment_tracker/transactions/migrations/0001_initial.py

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+# Generated by Django 4.2.7 on 2023-12-08 14:41
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('equipments', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Transaction',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('transaction_status', models.CharField(choices=[('Pending Approval', 'Pending Approval'), ('Approved', 'Approved'), ('Rejected', 'Rejected'), ('Cancelled', 'Cancelled'), ('Borrowed', 'Borrowed'), ('Returned: Pending Checking', 'Returned: Pending Checking'), ('With Breakages: Pending Resolution', 'With Breakages: Pending Resolution'), ('Finalized', 'Finalized')], default='Pending', max_length=40)),
+                ('timestamp', models.DateTimeField(default=django.utils.timezone.now, editable=False)),
+                ('borrower', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='borrowed_transactions', to=settings.AUTH_USER_MODEL)),
+                ('equipments', models.ManyToManyField(to='equipments.equipmentinstance')),
+                ('teacher', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='teacher_transactions', to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

equipment_tracker/transactions/models.py

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+from django.db import models
+from accounts.models import CustomUser
+from equipments.models import EquipmentInstance
+from django.utils.timezone import now
+
+
+class Transaction(models.Model):
+    TRANSACTION_STATUS_CHOICES = (
+        # Transaction is pending approval
+        ('Pending Approval', 'Pending Approval'),
+        # Transaction has been approved, pending delivery by labtech
+        ('Approved', 'Approved'),
+        # Tranasction has been rejected
+        ('Rejected', 'Rejected'),
+        # Transaction has been approved but has been cancelled due to rare circumstances
+        ('Cancelled', 'Cancelled'),
+        # Transaction has been delivered and is on borrow
+        ('Borrowed', 'Borrowed'),
+        # Transaction has been returned, pending checking
+        ('Returned: Pending Checking', 'Returned: Pending Checking'),
+        # Transaction has been breakages after being returned, pending resolution
+        ('With Breakages: Pending Resolution',
+            'With Breakages: Pending Resolution'),
+        # Transaction has been finalized
+        ('Finalized', 'Finalized'),
+    )
+
+    borrower = models.ForeignKey(
+        CustomUser, on_delete=models.SET_NULL, null=True, related_name='borrowed_transactions')
+    teacher = models.ForeignKey(
+        CustomUser, on_delete=models.SET_NULL, null=True, related_name='teacher_transactions')
+    equipments = models.ManyToManyField(EquipmentInstance)
+    transaction_status = models.CharField(
+        max_length=40, choices=TRANSACTION_STATUS_CHOICES, default='Pending')
+    timestamp = models.DateTimeField(default=now, editable=False)
+
+    def __str__(self):
+        return f"Transaction #{self.id} under {self.teacher} by {self.borrower}"

equipment_tracker/transactions/serializers.py

@@ -0,0 +1,156 @@
+from rest_framework import serializers
+from accounts.models import CustomUser
+from equipments.models import EquipmentInstance
+from .models import Transaction
+from accounts.models import CustomUser
+from config.settings import DEBUG
+
+
+class TransactionSerializer(serializers.HyperlinkedModelSerializer):
+    borrower = serializers.SlugRelatedField(
+        many=False, slug_field='id', queryset=CustomUser.objects.all(), required=False, allow_null=True)
+
+    equipments = serializers.SlugRelatedField(
+        many=True, slug_field='id', queryset=EquipmentInstance.objects.filter(status="Working"), required=False)
+
+    transaction_status = serializers.ChoiceField(
+        choices=Transaction.TRANSACTION_STATUS_CHOICES)
+
+    class Meta:
+        model = Transaction
+        fields = ['id', 'borrower', 'teacher',
+                  'equipments', 'transaction_status', 'timestamp']
+        read_only_fields = ['id', 'timestamp']
+
+    def create(self, validated_data):
+        # Any transactions created will be associated with the one sending the POST/CREATE request
+        user = self.context['request'].user
+        validated_data.data['borrower'] = user
+
+        # All created transactions will be labelled as Pending
+        validated_data['transaction_status'] = 'Pending'
+
+        # If no teacher responsible for the borrow transaction is selected, raise an error
+        if 'teacher' not in validated_data:
+            raise serializers.ValidationError(
+                "You have not selected a teacher responsible for your borrow transaction")
+
+        # If no borrower responsible for the borrow transaction is selected, raise an error
+        if 'borrower' not in validated_data:
+            raise serializers.ValidationError(
+                "No borrower assigned for this transaction!")
+
+        # If the user in the teacher field != actually a teacher, raise an error
+        borrower = validated_data.get('borrower')
+        if borrower and borrower.is_teacher or borrower.is_technician:
+            raise serializers.ValidationError(
+                "The borrower must be a student. Not a teacher or techician")
+
+        # If the user in the teacher field != actually a teacher, raise an error
+        teacher = validated_data.get('teacher')
+        if teacher and not teacher.is_teacher:
+            raise serializers.ValidationError(
+                "The assigned teacher != a valid teacher")
+
+        # If the user in the teacher field != actually a teacher, raise an error
+        teacher = validated_data.get('teacher')
+        if teacher and not teacher.is_teacher:
+            raise serializers.ValidationError(
+                "The specified user != a teacher.")
+
+        # If there are no equipments specified, raise an error
+        if 'equipments' in validated_data and validated_data['equipments'] == []:
+            raise serializers.ValidationError(
+                "You cannot create a transaction without any equipments selected"
+            )
+
+        return super().create(validated_data)
+
+    def update(self, instance, validated_data):
+        user = self.context['request'].user
+        equipments = validated_data['equipments']
+
+       # Check if any of the equipment instances are already in a non-finalized transaction
+        for equipment in equipments:
+            existing__pending_transactions = Transaction.objects.filter(
+                equipments=equipment, status__in=['Pending', 'Approved', 'Borrowed', 'With Breakages: Pending Resolution'])
+            if existing__pending_transactions.exists():
+                raise serializers.ValidationError(
+                    f"Equipment {equipment.id} is still part of a non-finalized transaction")
+
+        # If user != a teacher or a technician, forbid them from changing the status of a transaction
+        if not user.is_teacher and not user.technician and 'transaction_status' in validated_data and validated_data['transaction_status'] != instance.status:
+            raise serializers.ValidationError(
+                "You are not a teacher or technician. You do not have permission to change the status of transactions"
+            )
+
+        # If user != a teacher, forbid them from changing the status of a transaction
+        if not user.is_teacher and 'transaction_status' in validated_data and validated_data['transaction_status'] != instance.status:
+            raise serializers.ValidationError(
+                "You do not have permission to change the status of a transaction"
+            )
+        # Do not allow changes to equipments on created transactions
+        if 'equipments' in validated_data and instance.equipments != validated_data['equipments']:
+            raise serializers.ValidationError(
+                "You cannot change the equipments of an already created transaction"
+            )
+
+        # For already finalized/done transactions (Rejected or Finalized ones)
+        # Do not allow any changes to already finalized transactions
+        if instance.status in ['Rejected', 'Finalized']:
+            raise serializers.ValidationError(
+                "Unable to update rejected or finalized transaction. Please create a new one"
+            )
+
+        # Check if the update involves the transaction status
+        if 'transaction_status' in validated_data:
+
+            # For Pending transactions
+            # If not changing to Approved or Rejected, throw an error
+            if instance.status == 'Pending' and validated_data['transaction_status'] != 'Approved' or validated_data['transaction_status'] != 'Rejected':
+                raise serializers.ValidationError(
+                    "A pending transaction can only change to Approved or Rejected"
+                )
+
+            # For Approved transactions,
+            # If not changing to Borrowed or Cancelled, throw an error
+            # Already approved transactions can only be moved to Borrowed or Cancelled
+            if instance.status == 'Approved' and validated_data['transaction_status'] != 'Borrowed' or validated_data != 'Cancelled':
+                raise serializers.ValidationError(
+                    "An already approved transaction can only changed to Borrowed (On borrow) or Cancelled"
+                )
+
+            # For Borrowed transactions,
+            # If not changing to returned, throw an error
+            # Borrowed transactions that can only be changed to returned, pending checking for broken items
+            if instance.status == 'Borrowed' and validated_data['transaction_status'] != 'Finalized' or validated_data != 'With Breakages: Pending Resolution':
+                raise serializers.ValidationError(
+                    "A borrowed transaction can only changed to status of Finalized or With Breakages: Pending Resolution"
+                )
+
+            # For Return: Pending Checking transactions,
+            # If not changing to With Breakages: Pending Resolution or Finalized, throw an error
+            # Returned transactions can only be finalized without any issues or be marked as with breakages
+            if instance.status == 'Returned: Pending Checking' and validated_data['transaction_status'] != 'Finalized' or validated_data != 'With Breakages: Pending Resolution':
+                raise serializers.ValidationError(
+                    "A borrowed transaction can only changed to status of Finalized or With Breakages: Pending Resolution"
+                )
+
+            # For transactions with pending breakage resolutions,
+            # Do not allow updating of status. It should be updated within its respective breakage report
+            # If it has been resolved there, this field will automatically update to Finalized
+            if instance.status == 'With Breakages: Pending Resolution':
+                raise serializers.ValidationError(
+                    "A transaction with pending breakage resolutions must be updated or resolved in its respective breakage report"
+                )
+
+            # If there are no issues and a transaction changes from Approved to Borrowed, label the selected equipment's statuses as Borrowed
+            if instance.status == 'Approved' and validated_data['transaction_status'] == 'Borrowed':
+                equipments = validated_data.get('equipments', [])
+                for equipment in equipments:
+                    equipment.status = 'Borrowed'
+                    equipment.save()
+                return super().update(validated_data)
+            # Changing equipment status of broken items when returned is handled in breakage reports
+
+        return super().update(instance, validated_data)

equipment_tracker/transactions/tests.py

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+from django.test import TestCase
+
+# Create your tests here.

equipment_tracker/transactions/urls.py

@@ -0,0 +1,10 @@
+from django.urls import include, path
+from rest_framework import routers
+from . import views
+
+router = routers.DefaultRouter()
+router.register(r'', views.TransactionViewSet)
+
+urlpatterns = [
+    path('', include(router.urls)),
+]

equipment_tracker/transactions/views.py

@@ -0,0 +1,13 @@
+from rest_framework.permissions import IsAuthenticated
+from rest_framework import viewsets, generics
+from .serializers import TransactionSerializer
+from .models import Transaction
+
+
+class TransactionViewSet(viewsets.ModelViewSet):
+    # Only allow GET, POST/CREATE
+    # Transactions cannot be deleted
+    http_method_names = ['get', 'post']
+    permission_classes = [IsAuthenticated]
+    serializer_class = TransactionSerializer
+    queryset = Transaction.objects.all()