added trade-hub role and files

roles/trade_hub/files/trade-hub/backend/app/available.py

@@ -0,0 +1,69 @@
+"""Public listing of inventory items owners marked as `available`.
+
+Read-only and unauthenticated, like the catalog. Notes are never included: the
+listing only reveals the owner's username, quantity and catalog details.
+"""
+import math
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy import select
+from sqlalchemy.orm import Session as DbSession
+
+from app.db import get_db
+from app.inventory import SORT_KEYS, enrich_entry
+from app.models import InventoryEntry, User
+from app.schemas import AvailablePage
+
+router = APIRouter(prefix="/api/v1/available", tags=["available"])
+
+MAX_PAGE_SIZE = 100
+
+
+@router.get("", response_model=AvailablePage)
+def list_available(
+    category: str | None = None,
+    search: str | None = None,
+    sort: str = Query(default="updated", pattern="^(name|category|quantity|updated)$"),
+    page: int = Query(default=1, ge=1),
+    page_size: int = Query(default=25, ge=1),
+    db: DbSession = Depends(get_db),
+):
+    page_size = min(page_size, MAX_PAGE_SIZE)
+    rows = db.execute(
+        select(InventoryEntry, User.username)
+        .join(User, User.id == InventoryEntry.user_id)
+        .where(InventoryEntry.visibility == "available")
+    ).all()
+
+    items = []
+    for entry, username in rows:
+        enriched = enrich_entry(entry)
+        if not enriched["available"]:
+            continue
+        enriched["username"] = username
+        items.append(enriched)
+
+    if category is not None and category.strip():
+        wanted = category.strip()
+        items = [i for i in items if i["category"] == wanted]
+    if search is not None and search.strip():
+        needle = search.strip().lower()
+        items = [
+            i
+            for i in items
+            if needle in i["name"].lower()
+            or needle in i["class_name"].lower()
+            or needle in i["username"].lower()
+        ]
+
+    items.sort(key=SORT_KEYS[sort])
+    total = len(items)
+    total_pages = max(1, math.ceil(total / page_size))
+    start = (page - 1) * page_size
+    return {
+        "total": total,
+        "page": page,
+        "page_size": page_size,
+        "total_pages": total_pages,
+        "items": items[start : start + page_size],
+    }