Add Employee Leave Management module

modules/elm/api/urls.py

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+"""URL patterns for Employee Leave Management."""
+
+from django.urls import path
+
+from modules.elm.api.views import (
+    DecideLeaveApplicationView,
+    MyLeaveApplicationsView,
+    SubmitLeaveApplicationView,
+)
+
+app_name = "elm"
+
+urlpatterns = [
+    path(
+        "my-leaves/",
+        MyLeaveApplicationsView.as_view(),
+        name="my-leaves",
+    ),
+    path(
+        "apply/",
+        SubmitLeaveApplicationView.as_view(),
+        name="apply",
+    ),
+    path(
+        "applications/<uuid:application_id>/decision/",
+        DecideLeaveApplicationView.as_view(),
+        name="decide-application",
+    ),
+]

modules/elm/api/views.py

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+"""API views for Employee Leave Management."""
+
+from datetime import date
+from uuid import UUID
+
+from rest_framework import status
+from rest_framework.response import Response
+from rest_framework.views import APIView
+
+from modules.elm.models import LeaveApplication
+from modules.elm.services.applications import (
+    LeaveApplicationError,
+    decide_leave,
+    submit_leave,
+)
+from modules.elm.services.authz import require
+
+
+def serialize_application(application):
+    """Convert a leave application to a JSON-compatible dictionary."""
+    return {
+        "id": str(application.id),
+        "employee_id": application.employee_id,
+        "leave_type": application.leave_type,
+        "start_date": application.start_date.isoformat(),
+        "end_date": application.end_date.isoformat(),
+        "reason": application.reason,
+        "status": application.status,
+        "approver_id": application.approver_id,
+        "decision_note": application.decision_note,
+        "submitted_at": (
+            application.submitted_at.isoformat()
+            if application.submitted_at
+            else None
+        ),
+        "decided_at": (
+            application.decided_at.isoformat()
+            if application.decided_at
+            else None
+        ),
+    }
+
+
+def get_actor(request):
+    """Return the authenticated principal supplied by the platform."""
+    return getattr(request, "principal", None)
+
+
+class MyLeaveApplicationsView(APIView):
+    """List leave applications belonging to the current employee."""
+
+    def get(self, request):
+        actor = get_actor(request)
+        require(actor, "elm.application.view_self")
+
+        employee_id = str(getattr(actor, "id", ""))
+
+        if not employee_id:
+            return Response(
+                {"detail": "Employee identity is unavailable."},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        applications = LeaveApplication.objects.filter(
+            employee_id=employee_id
+        )
+
+        return Response(
+            [serialize_application(item) for item in applications]
+        )
+
+
+class SubmitLeaveApplicationView(APIView):
+    """Submit a leave application."""
+
+    def post(self, request):
+        actor = get_actor(request)
+        require(actor, "elm.application.create")
+
+        data = request.data
+
+        try:
+            start_date = date.fromisoformat(data.get("start_date", ""))
+            end_date = date.fromisoformat(data.get("end_date", ""))
+
+            application = submit_leave(
+                employee_id=str(getattr(actor, "id", "")),
+                leave_type=str(data.get("leave_type", "")),
+                start_date=start_date,
+                end_date=end_date,
+                reason=str(data.get("reason", "")),
+            )
+        except (ValueError, TypeError, LeaveApplicationError) as exc:
+            return Response(
+                {"detail": str(exc)},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        return Response(
+            serialize_application(application),
+            status=status.HTTP_201_CREATED,
+        )
+
+
+class DecideLeaveApplicationView(APIView):
+    """Approve or reject a submitted leave application."""
+
+    def post(self, request, application_id):
+        actor = get_actor(request)
+        require(actor, "elm.application.approve")
+
+        try:
+            UUID(str(application_id))
+            decision = request.data.get("decision", "")
+            if decision not in ("approve", "reject"):
+                return Response(
+                    {"detail": "Decision must be 'approve' or 'reject'."},
+                    status=status.HTTP_400_BAD_REQUEST,
+                )
+
+            application = decide_leave(
+                application_id=application_id,
+                approver_id=str(getattr(actor, "id", "")),
+                approve=(decision == "approve"),
+                decision_note=str(request.data.get("decision_note", "")),
+            )
+        except LeaveApplication.DoesNotExist:
+            return Response(
+                {"detail": "Leave application not found."},
+                status=status.HTTP_404_NOT_FOUND,
+            )
+        except (ValueError, TypeError, LeaveApplicationError) as exc:
+            return Response(
+                {"detail": str(exc)},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        return Response(serialize_application(application))

modules/elm/apps.py

@@ -0,0 +1,9 @@
+
+from django.apps import AppConfig
+
+
+class ElmConfig(AppConfig):
+    default_auto_field = "django.db.models.BigAutoField"
+    name = "modules.elm"
+    label = "elm"
+    verbose_name = "Employee Leave Management"

modules/elm/domain/entities.py

@@ -0,0 +1,42 @@
+
+"""Domain types for Employee Leave Management."""
+
+from dataclasses import dataclass
+from datetime import date
+from enum import StrEnum
+from uuid import UUID
+
+
+class LeaveStatus(StrEnum):
+    DRAFT = "draft"
+    SUBMITTED = "submitted"
+    PENDING_APPROVAL = "pending_approval"
+    APPROVED = "approved"
+    REJECTED = "rejected"
+    WITHDRAWN = "withdrawn"
+    CANCELLED = "cancelled"
+    EXTENSION_REQUESTED = "extension_requested"
+    RESUMED = "resumed"
+
+
+@dataclass(frozen=True)
+class LeavePeriod:
+    start_date: date
+    end_date: date
+
+    def __post_init__(self) -> None:
+        if self.end_date < self.start_date:
+            raise ValueError("Leave end date cannot be before start date.")
+
+    @property
+    def calendar_days(self) -> int:
+        return (self.end_date - self.start_date).days + 1
+
+
+@dataclass(frozen=True)
+class LeaveApplicationSummary:
+    id: UUID
+    employee_id: str
+    leave_type: str
+    period: LeavePeriod
+    status: LeaveStatus

modules/elm/migrations/0001_initial.py

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+# Generated by Django 5.2.18 on 2026-10-12 13:18
+
+import uuid
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='LeaveApplication',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('employee_id', models.CharField(db_index=True, max_length=128)),
+                ('leave_type', models.CharField(max_length=32)),
+                ('start_date', models.DateField()),
+                ('end_date', models.DateField()),
+                ('reason', models.TextField()),
+                ('status', models.CharField(choices=[('draft', 'Draft'), ('submitted', 'Submitted'), ('pending_approval', 'Pending Approval'), ('approved', 'Approved'), ('rejected', 'Rejected'), ('withdrawn', 'Withdrawn'), ('cancelled', 'Cancelled'), ('extension_requested', 'Extension Requested'), ('resumed', 'Resumed')], db_index=True, default='draft', max_length=32)),
+                ('approver_id', models.CharField(blank=True, default='', max_length=128)),
+                ('decision_note', models.TextField(blank=True, default='')),
+                ('submitted_at', models.DateTimeField(blank=True, null=True)),
+                ('decided_at', models.DateTimeField(blank=True, null=True)),
+                ('created_at', models.DateTimeField(auto_now_add=True)),
+                ('updated_at', models.DateTimeField(auto_now=True)),
+            ],
+            options={
+                'ordering': ['-created_at'],
+                'indexes': [models.Index(fields=['employee_id', 'status'], name='elm_emp_status_idx'), models.Index(fields=['start_date', 'end_date'], name='elm_leave_dates_idx')],
+            },
+        ),
+    ]

modules/elm/models/__init__.py

@@ -0,0 +1,6 @@
+
+"""Database models for Employee Leave Management."""
+
+from .leave_application import LeaveApplication
+
+__all__ = ["LeaveApplication"]

modules/elm/models/leave_application.py

@@ -0,0 +1,62 @@
+
+"""Database model for Employee Leave Management applications."""
+
+import uuid
+
+from django.db import models
+
+
+class LeaveApplication(models.Model):
+    class Status(models.TextChoices):
+        DRAFT = "draft", "Draft"
+        SUBMITTED = "submitted", "Submitted"
+        PENDING_APPROVAL = "pending_approval", "Pending Approval"
+        APPROVED = "approved", "Approved"
+        REJECTED = "rejected", "Rejected"
+        WITHDRAWN = "withdrawn", "Withdrawn"
+        CANCELLED = "cancelled", "Cancelled"
+        EXTENSION_REQUESTED = "extension_requested", "Extension Requested"
+        RESUMED = "resumed", "Resumed"
+
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+
+    employee_id = models.CharField(max_length=128, db_index=True)
+    leave_type = models.CharField(max_length=32)
+    start_date = models.DateField()
+    end_date = models.DateField()
+    reason = models.TextField()
+
+    status = models.CharField(
+        max_length=32,
+        choices=Status.choices,
+        default=Status.DRAFT,
+        db_index=True,
+    )
+
+    approver_id = models.CharField(max_length=128, blank=True, default="")
+    decision_note = models.TextField(blank=True, default="")
+    submitted_at = models.DateTimeField(null=True, blank=True)
+    decided_at = models.DateTimeField(null=True, blank=True)
+
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        app_label = "elm"
+        ordering = ["-created_at"]
+        indexes = [
+            models.Index(
+                fields=["employee_id", "status"],
+                name="elm_emp_status_idx",
+            ),
+            models.Index(
+                fields=["start_date", "end_date"],
+                name="elm_leave_dates_idx",
+            ),
+        ]
+
+    def __str__(self):
+        return (
+            f"{self.employee_id}: {self.leave_type} "
+            f"({self.start_date} to {self.end_date})"
+        )