feat: add reusable solution library

backend/apps/solutions/__init__.py

@@ -0,0 +1 @@
+

backend/apps/solutions/api.py

@@ -0,0 +1,66 @@
+from ninja import Router
+
+from apps.solutions.models import Solution, TicketSolutionLink
+from apps.solutions.schemas import (
+    SolutionIn,
+    SolutionOut,
+    TicketSolutionLinkIn,
+    TicketSolutionLinkOut,
+)
+from apps.tickets.models import Ticket
+
+router = Router(tags=["solutions"])
+
+
+@router.post("", response=SolutionOut)
+def create_solution(request, payload: SolutionIn):
+    return Solution.objects.create(
+        title=payload.title,
+        problem_signature=payload.problem_signature,
+        related_system=payload.related_system,
+        environment_scope=payload.environment_scope,
+        root_cause=payload.root_cause,
+        solution=payload.solution,
+        risk_note=payload.risk_note,
+        status=payload.status,
+        created_by=request.user if request.user.is_authenticated else None,
+    )
+
+
+@router.get("", response=list[SolutionOut])
+def list_solutions(request, status: str | None = None):
+    queryset = Solution.objects.all()
+    if status:
+        queryset = queryset.filter(status=status)
+    return queryset[:100]
+
+
+@router.get("/{solution_id}", response=SolutionOut)
+def get_solution(request, solution_id: int):
+    return Solution.objects.get(id=solution_id)
+
+
+@router.post("/{solution_id}/link-ticket", response=TicketSolutionLinkOut)
+def link_solution_to_ticket(request, solution_id: int, payload: TicketSolutionLinkIn):
+    solution = Solution.objects.get(id=solution_id)
+    ticket = Ticket.objects.get(id=payload.ticket_id)
+    link, _ = TicketSolutionLink.objects.get_or_create(
+        ticket=ticket,
+        solution=solution,
+        link_type=payload.link_type,
+        defaults={
+            "agent_run_id": payload.agent_run_id,
+            "created_by": request.user if request.user.is_authenticated else None,
+        },
+    )
+    if payload.link_type == "adopted":
+        solution.usage_count = solution.ticket_links.filter(link_type="adopted").count()
+        solution.save(update_fields=["usage_count", "updated_at"])
+    return {
+        "id": link.id,
+        "ticket_id": ticket.id,
+        "solution_id": solution.id,
+        "link_type": link.link_type,
+        "solution_usage_count": solution.usage_count,
+        "created_at": link.created_at,
+    }

backend/apps/solutions/apps.py

@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class SolutionsConfig(AppConfig):
+    default_auto_field = "django.db.models.BigAutoField"
+    name = "apps.solutions"

backend/apps/solutions/migrations/0001_initial.py

@@ -0,0 +1,144 @@
+# Generated by Django 5.2.15 on 2026-06-30 10:43
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    initial = True
+
+    dependencies = [
+        ("tickets", "0001_initial"),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="Solution",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True, primary_key=True, serialize=False, verbose_name="ID"
+                    ),
+                ),
+                ("title", models.CharField(max_length=200)),
+                ("problem_signature", models.TextField()),
+                ("related_system", models.CharField(blank=True, max_length=120)),
+                ("environment_scope", models.CharField(blank=True, max_length=120)),
+                ("root_cause", models.TextField()),
+                ("solution", models.TextField()),
+                ("risk_note", models.TextField(blank=True)),
+                ("status", models.CharField(default="draft", max_length=40)),
+                ("usage_count", models.PositiveIntegerField(default=0)),
+                ("created_at", models.DateTimeField(auto_now_add=True)),
+                ("updated_at", models.DateTimeField(auto_now=True)),
+                (
+                    "category",
+                    models.ForeignKey(
+                        blank=True,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
+                        to="tickets.ticketcategory",
+                    ),
+                ),
+                (
+                    "created_by",
+                    models.ForeignKey(
+                        blank=True,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
+                        to=settings.AUTH_USER_MODEL,
+                    ),
+                ),
+            ],
+            options={
+                "ordering": ["-updated_at"],
+            },
+        ),
+        migrations.CreateModel(
+            name="TicketResolution",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True, primary_key=True, serialize=False, verbose_name="ID"
+                    ),
+                ),
+                ("resolution_type", models.CharField(default="resolved", max_length=80)),
+                ("root_cause", models.TextField(blank=True)),
+                ("solution_text", models.TextField()),
+                ("created_at", models.DateTimeField(auto_now_add=True)),
+                ("updated_at", models.DateTimeField(auto_now=True)),
+                (
+                    "confirmed_by",
+                    models.ForeignKey(
+                        blank=True,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
+                        to=settings.AUTH_USER_MODEL,
+                    ),
+                ),
+                (
+                    "linked_solution",
+                    models.ForeignKey(
+                        blank=True,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
+                        to="solutions.solution",
+                    ),
+                ),
+                (
+                    "ticket",
+                    models.OneToOneField(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="resolution",
+                        to="tickets.ticket",
+                    ),
+                ),
+            ],
+        ),
+        migrations.CreateModel(
+            name="TicketSolutionLink",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True, primary_key=True, serialize=False, verbose_name="ID"
+                    ),
+                ),
+                ("link_type", models.CharField(default="referenced", max_length=40)),
+                ("agent_run_id", models.BigIntegerField(blank=True, null=True)),
+                ("created_at", models.DateTimeField(auto_now_add=True)),
+                (
+                    "created_by",
+                    models.ForeignKey(
+                        blank=True,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
+                        to=settings.AUTH_USER_MODEL,
+                    ),
+                ),
+                (
+                    "solution",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="ticket_links",
+                        to="solutions.solution",
+                    ),
+                ),
+                (
+                    "ticket",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="solution_links",
+                        to="tickets.ticket",
+                    ),
+                ),
+            ],
+            options={
+                "unique_together": {("ticket", "solution", "link_type")},
+            },
+        ),
+    ]

backend/apps/solutions/migrations/__init__.py

@@ -0,0 +1 @@
+

backend/apps/solutions/models.py

@@ -0,0 +1,64 @@
+from django.conf import settings
+from django.db import models
+
+from apps.tickets.models import Ticket, TicketCategory
+
+
+class Solution(models.Model):
+    title = models.CharField(max_length=200)
+    problem_signature = models.TextField()
+    related_system = models.CharField(max_length=120, blank=True)
+    environment_scope = models.CharField(max_length=120, blank=True)
+    category = models.ForeignKey(TicketCategory, null=True, blank=True, on_delete=models.SET_NULL)
+    root_cause = models.TextField()
+    solution = models.TextField()
+    risk_note = models.TextField(blank=True)
+    status = models.CharField(max_length=40, default="draft")
+    usage_count = models.PositiveIntegerField(default=0)
+    created_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        ordering = ["-updated_at"]
+
+    def __str__(self) -> str:
+        return self.title
+
+
+class TicketResolution(models.Model):
+    ticket = models.OneToOneField(Ticket, on_delete=models.CASCADE, related_name="resolution")
+    resolution_type = models.CharField(max_length=80, default="resolved")
+    root_cause = models.TextField(blank=True)
+    solution_text = models.TextField()
+    linked_solution = models.ForeignKey(Solution, null=True, blank=True, on_delete=models.SET_NULL)
+    confirmed_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+
+class TicketSolutionLink(models.Model):
+    ticket = models.ForeignKey(Ticket, on_delete=models.CASCADE, related_name="solution_links")
+    solution = models.ForeignKey(Solution, on_delete=models.CASCADE, related_name="ticket_links")
+    link_type = models.CharField(max_length=40, default="referenced")
+    agent_run_id = models.BigIntegerField(null=True, blank=True)
+    created_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        unique_together = [("ticket", "solution", "link_type")]

backend/apps/solutions/schemas.py

@@ -0,0 +1,44 @@
+from datetime import datetime
+
+from ninja import Schema
+
+
+class SolutionIn(Schema):
+    title: str
+    problem_signature: str
+    related_system: str = ""
+    environment_scope: str = ""
+    root_cause: str
+    solution: str
+    risk_note: str = ""
+    status: str = "draft"
+
+
+class SolutionOut(Schema):
+    id: int
+    title: str
+    problem_signature: str
+    related_system: str
+    environment_scope: str
+    root_cause: str
+    solution: str
+    risk_note: str
+    status: str
+    usage_count: int
+    created_at: datetime
+    updated_at: datetime
+
+
+class TicketSolutionLinkIn(Schema):
+    ticket_id: int
+    link_type: str = "referenced"
+    agent_run_id: int | None = None
+
+
+class TicketSolutionLinkOut(Schema):
+    id: int
+    ticket_id: int
+    solution_id: int
+    link_type: str
+    solution_usage_count: int
+    created_at: datetime

backend/apps/solutions/tests/__init__.py

@@ -0,0 +1 @@
+

backend/apps/solutions/tests/test_solution_api.py

@@ -0,0 +1,41 @@
+from apps.tickets.models import Ticket
+
+
+def test_create_and_list_solution(client, db):
+    response = client.post(
+        "/api/solutions",
+        data={
+            "title": "Restart callback worker",
+            "problem_signature": "HTTP 500 from callback",
+            "root_cause": "Worker connection pool stale",
+            "solution": "Restart callback worker and verify queue depth.",
+            "status": "published",
+        },
+        content_type="application/json",
+    )
+
+    assert response.status_code == 200
+    solution_id = response.json()["id"]
+
+    response = client.get("/api/solutions")
+    assert response.status_code == 200
+    assert response.json()[0]["id"] == solution_id
+
+
+def test_link_solution_to_ticket_increments_usage(client, db):
+    ticket = Ticket.objects.create(ticket_no="TK202606300020", title="A", description="A")
+    solution = client.post(
+        "/api/solutions",
+        data={"title": "S", "problem_signature": "P", "root_cause": "R", "solution": "Do S"},
+        content_type="application/json",
+    ).json()
+
+    response = client.post(
+        f"/api/solutions/{solution['id']}/link-ticket",
+        data={"ticket_id": ticket.id, "link_type": "adopted"},
+        content_type="application/json",
+    )
+
+    assert response.status_code == 200
+    assert response.json()["link_type"] == "adopted"
+    assert response.json()["solution_usage_count"] == 1

backend/config/settings/base.py

@@ -19,6 +19,7 @@ INSTALLED_APPS = [
     "apps.audit",
     "apps.system",
     "apps.tickets",
+    "apps.solutions",
 ]
 
 MIDDLEWARE = [

backend/config/urls.py

@@ -3,6 +3,7 @@ from django.urls import path
 from ninja import NinjaAPI
 
 from apps.audit.api import router as audit_router
+from apps.solutions.api import router as solutions_router
 from apps.system.api import router as system_router
 from apps.tickets.api import router as tickets_router
 
@@ -10,6 +11,7 @@ api = NinjaAPI(title="AI Ticket Platform API", version="0.1.0")
 api.add_router("/system", system_router)
 api.add_router("/audit", audit_router)
 api.add_router("/tickets", tickets_router)
+api.add_router("/solutions", solutions_router)
 
 urlpatterns = [
     path("admin/", admin.site.urls),