Feature/problem labels

backend/annotation/admin.py

@@ -1,3 +1,10 @@
 from django.contrib import admin
 
+from annotation.models import Label
+
+
 # Register your models here.
+@admin.register(Label)
+class LabelAdmin(admin.ModelAdmin):
+    list_display = ("text", "description")
+    search_fields = ("text",)

backend/annotation/fixtures/initial.json

@@ -0,0 +1,50 @@
+[
+    {
+        "model": "annotation.label",
+        "pk": 1,
+        "fields": {
+            "text": "Important",
+            "description": "This problem is particularly important."
+        }
+    },
+    {
+        "model": "annotation.label",
+        "pk": 2,
+        "fields": {
+            "text": "Review needed",
+            "description": "This problem needs to be reviewed by a master annotator."
+        }
+    },
+    {
+        "model": "annotation.label",
+        "pk": 3,
+        "fields": {
+            "text": "Ambiguous",
+            "description": "The problem statement is ambiguous and needs clarification."
+        }
+    },
+    {
+        "model": "annotation.label",
+        "pk": 4,
+        "fields": {
+            "text": "Incomplete knowledge",
+            "description": "Some knowledge base items are missing."
+        }
+    },
+    {
+        "model": "annotation.label",
+        "pk": 5,
+        "fields": {
+            "text": "Spelling",
+            "description": "The premises or hypothesis are misspelled, which may lead to wrong analyses."
+        }
+    },
+    {
+        "model": "annotation.label",
+        "pk": 6,
+        "fields": {
+            "text": "Wrong entailment label",
+            "description": "The entailment label is incorrect."
+        }
+    }
+]

backend/annotation/migrations/0002_label_labeling.py

@@ -0,0 +1,123 @@
+# Generated by Django 4.2.27 on 2025-12-11 15:10
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ("problem", "0007_alter_problem_options"),
+        ("annotation", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="Label",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("text", models.CharField(max_length=255)),
+                (
+                    "description",
+                    models.TextField(
+                        help_text="A detailed description of the label, indicating when it should be used."
+                    ),
+                ),
+            ],
+            options={
+                "ordering": ["text"],
+            },
+        ),
+        migrations.CreateModel(
+            name="Labeling",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("attached_at", models.DateTimeField(auto_now_add=True)),
+                (
+                    "removed_at",
+                    models.DateTimeField(
+                        blank=True,
+                        help_text="When this label was removed from the problem.",
+                        null=True,
+                    ),
+                ),
+                (
+                    "notes",
+                    models.TextField(
+                        blank=True,
+                        help_text="Optional notes explaining why this label was added or removed.",
+                    ),
+                ),
+                (
+                    "attached_by",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="labelings_attached",
+                        to=settings.AUTH_USER_MODEL,
+                    ),
+                ),
+                (
+                    "label",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="labelings",
+                        to="annotation.label",
+                    ),
+                ),
+                (
+                    "problem",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="labelings",
+                        to="problem.problem",
+                    ),
+                ),
+                (
+                    "removed_by",
+                    models.ForeignKey(
+                        blank=True,
+                        help_text="User who removed this label.",
+                        null=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="labelings_removed",
+                        to=settings.AUTH_USER_MODEL,
+                    ),
+                ),
+            ],
+            options={
+                "ordering": ["-attached_at"],
+                "permissions": [
+                    ("delete_own_labeling", "Can remove own labeling from problems"),
+                    ("delete_any_labeling", "Can remove any labeling from problems"),
+                ],
+                "indexes": [
+                    models.Index(
+                        fields=["problem", "removed_at"],
+                        name="annotation__problem_e7ac7b_idx",
+                    ),
+                    models.Index(
+                        fields=["label", "removed_at"],
+                        name="annotation__label_i_a229d2_idx",
+                    ),
+                ],
+            },
+        ),
+    ]

backend/annotation/models.py

@@ -81,3 +81,83 @@ class KnowledgeBaseAnnotation(models.Model):
     )
 
     created_at = models.DateTimeField(auto_now_add=True)
+
+
+class Label(models.Model):
+    text = models.CharField(max_length=255)
+    description = models.TextField(
+        help_text="A detailed description of the label, indicating when it should be used."
+    )
+
+    class Meta:
+        ordering = ["text"]
+
+    def __str__(self):
+        return self.text
+
+
+class Labeling(models.Model):
+    """
+    The attachment of a label to a problem.
+
+    Each time a label is attached to a problem, a new Labeling record is created.
+    When removed, the record is marked as removed (not deleted), so the history of labelings is preserved.
+    """
+
+    problem = models.ForeignKey(
+        Problem,
+        on_delete=models.CASCADE,
+        related_name="labelings",
+    )
+
+    label = models.ForeignKey(
+        Label,
+        on_delete=models.CASCADE,
+        related_name="labelings",
+    )
+
+    attached_at = models.DateTimeField(auto_now_add=True)
+    attached_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name="labelings_attached",
+    )
+
+    removed_at = models.DateTimeField(
+        null=True,
+        blank=True,
+        help_text="When this label was removed from the problem.",
+    )
+    removed_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name="labelings_removed",
+        null=True,
+        blank=True,
+        help_text="User who removed this label.",
+    )
+
+    notes = models.TextField(
+        blank=True,
+        help_text="Optional notes explaining why this label was added or removed.",
+    )
+
+    class Meta:
+        ordering = ["-attached_at"]
+        indexes = [
+            models.Index(fields=["problem", "removed_at"]),
+            models.Index(fields=["label", "removed_at"]),
+        ]
+        permissions = [
+            ("delete_own_labeling", "Can remove own labeling from problems"),
+            ("delete_any_labeling", "Can remove any labeling from problems"),
+        ]
+
+
+    def is_active(self) -> bool:
+        """Check if this labeling is currently active (not removed)."""
+        return self.removed_at is None
+
+    def __str__(self):
+        status = "active" if self.is_active() else f"removed at {self.removed_at}"
+        return f"Label '{self.label.text}' on Problem {self.problem.pk} ({status})"

backend/annotation/serializers.py

@@ -0,0 +1,121 @@
+from rest_framework import serializers
+
+from django.contrib.auth.models import AnonymousUser
+
+from annotation.models import Label, Labeling
+from problem.models import Problem
+from user.models import User
+
+
+class LabelSerializer(serializers.ModelSerializer):
+    """
+    Serializer for Label model.
+    """
+
+    class Meta:
+        model = Label
+        fields = ["id", "text", "description"]
+
+
+class ActiveLabelSerializer(serializers.Serializer):
+    """
+    Serializer for active labels attached to a problem.
+    Includes attachedInfo and removable status based on current user.
+    """
+
+    id = serializers.IntegerField(source="label.id")
+    text = serializers.CharField(source="label.text")
+    description = serializers.CharField(source="label.description")
+    attachedInfo = serializers.SerializerMethodField()
+    removable = serializers.SerializerMethodField()
+
+    def get_attachedInfo(self, labeling: Labeling) -> dict:
+        """Get attachment information for the label."""
+        request = self.context.get("request")
+        user: User | AnonymousUser | None = request.user if request else None
+
+        if user and user.is_anonymous is False:
+            attached_by_current_user = labeling.attached_by.pk == user.pk
+        else:
+            attached_by_current_user = False
+
+        return {
+            "userName": labeling.attached_by.username,
+            "date": labeling.attached_at.isoformat(),
+            "attachedByCurrentUser": attached_by_current_user,
+        }
+
+    def get_removable(self, labeling: Labeling) -> bool:
+        """Determine if the label is removable by the current user."""
+        request = self.context.get("request")
+        user: User | AnonymousUser | None = request.user if request else None
+
+        if user is None or user.is_anonymous:
+            return False
+
+        if user.is_superuser or user.has_perm("annotation.delete_any_labeling"):
+            return True
+
+        if user.has_perm("annotation.delete_own_labeling"):
+            return labeling.attached_by.pk == user.pk
+
+        return False
+
+
+class LabelingSerializer(serializers.ModelSerializer):
+    """
+    Serializer for Labeling model, including the full label details.
+    """
+
+    label = LabelSerializer(read_only=True)
+    attachedAt = serializers.DateTimeField(source="attached_at")
+    attachedBy = serializers.PrimaryKeyRelatedField(
+        source="attached_by", read_only=True
+    )
+    removedAt = serializers.DateTimeField(source="removed_at", allow_null=True)
+    removedBy = serializers.PrimaryKeyRelatedField(
+        source="removed_by", allow_null=True, read_only=True
+    )
+
+    class Meta:
+        model = Labeling
+        fields = [
+            "id",
+            "label",
+            "attached_at",
+            "attached_by",
+            "removed_at",
+            "removed_by",
+            "notes",
+        ]
+
+
+class SelectedLabelSerializer(serializers.Serializer):
+    """Serializer for a selected label in the save labels input."""
+
+    id = serializers.IntegerField()
+
+    def validate_id(self, value):
+        """Validate that the label exists."""
+        if not Label.objects.filter(id=value).exists():
+            raise serializers.ValidationError(f"Label with ID {value} does not exist.")
+        return value
+
+
+class SaveLabelsInputSerializer(serializers.Serializer):
+    """
+    Serializer for validating save labels input data.
+    Used when saving/updating labels for a problem.
+    """
+
+    problemId = serializers.IntegerField()
+    selectedLabels = SelectedLabelSerializer(many=True, allow_empty=True)
+    remarks = serializers.CharField(required=False, allow_blank=True, default="")
+
+    def validate_problemId(self, value):
+        """Validate that the problem exists."""
+        if not Problem.objects.filter(id=value).exists():
+            raise serializers.ValidationError(
+                f"Problem with ID {value} does not exist."
+            )
+        return value