feat: Oracle Canvas, Revision History and Canvas Sharing (#33)

Co-authored-by: Sagnik <sagnik7896@gmail.com>
Reviewed-on: #33

backend/oracle/collaboration_service.py

@@ -11,6 +11,8 @@ import uuid
 from datetime import datetime, timezone
 from typing import Any
 
+from .canvas_service import canvas_service
+
 logger = logging.getLogger(__name__)
 
 # ── In-memory store (demo mode) ───────────────────────────────────────────────
@@ -23,6 +25,32 @@ def _now() -> str:
     return datetime.now(timezone.utc).isoformat()
 
 
+def _clone_components_for_fork(
+    components: list[dict[str, Any]],
+    *,
+    actor_id: str,
+    source_page_id: str,
+    source_branch_id: str,
+    source_revision: int,
+) -> list[dict[str, Any]]:
+    cloned: list[dict[str, Any]] = []
+    for component in components:
+        forked = copy.deepcopy(component)
+        original_component_id = str(forked.get("componentId") or "")
+        forked["componentId"] = str(uuid.uuid4())
+        provenance = dict(forked.get("provenance") or {})
+        provenance["forkedAt"] = _now()
+        provenance["forkedBy"] = actor_id
+        provenance["sourcePageId"] = source_page_id
+        provenance["sourceBranchId"] = source_branch_id
+        provenance["sourceRevision"] = source_revision
+        if original_component_id:
+            provenance["sourceComponentId"] = original_component_id
+        forked["provenance"] = provenance
+        cloned.append(forked)
+    return cloned
+
+
 # ── Three-way diff engine ─────────────────────────────────────────────────────
 
 def _three_way_diff(
@@ -228,17 +256,50 @@ class CollaborationService:
         Creates a fork from the source_page snapshot at its current headRevision.
         Returns ForkRecord.
         """
+        if recipient_user_id == created_by:
+            raise ValueError("You cannot share a canvas with your own account.")
+
         fork_id = str(uuid.uuid4())
-        fork_page_id = str(uuid.uuid4())
-        fork_branch_id = str(uuid.uuid4())
+        fork_page = await canvas_service.create_page(
+            tenant_id=source_page["tenantId"],
+            owner_id=recipient_user_id,
+            title=f"{source_page['title']} Fork",
+            page_type="fork",
+            branch_name=f"fork-{str(fork_id)[:8]}",
+            sharing_policy={
+                "shareMode": "direct_fork_only",
+                "allowReshare": visibility == "team",
+                "defaultForkVisibility": visibility,
+            },
+        )
+
+        fork_components = _clone_components_for_fork(
+            source_page.get("components", []),
+            actor_id=created_by,
+            source_page_id=source_page["pageId"],
+            source_branch_id=source_page["branchId"],
+            source_revision=source_page["headRevision"],
+        )
+
+        await canvas_service.commit_revision(
+            page_id=fork_page["pageId"],
+            tenant_id=source_page["tenantId"],
+            actor_id=created_by,
+            commit_kind="merge",
+            commit_summary=f"Forked from {source_page['title']} at rev.{source_page['headRevision']}",
+            components=fork_components,
+            execution_id=None,
+            merge_request_id=None,
+            idempotency_key=f"fork_{fork_id}",
+        )
 
         fork = {
             "forkId": fork_id,
             "sourcePageId": source_page["pageId"],
             "sourceBranchId": source_page["branchId"],
             "sourceRevision": source_page["headRevision"],
-            "forkPageId": fork_page_id,
-            "forkBranchId": fork_branch_id,
+            "forkPageId": fork_page["pageId"],
+            "forkBranchId": fork_page["branchId"],
             "recipientUserId": recipient_user_id,
             "createdBy": created_by,
             "visibility": visibility,