chore: add pos to db with trigger

Author: seaerchin

apps/studio/prisma/migrations/20250422134621_add_pos_to_db/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "Resource" ADD COLUMN     "pos" DECIMAL(1000,95);

apps/studio/prisma/migrations/20250422175330_add_db_trigger_for_pos/migration.sql

@@ -0,0 +1,30 @@
+-- NOTE: this is a custo migration to add a db trigger on
+-- insertion of any `null` values into the `Resource`.`pos` row
+CREATE OR REPLACE FUNCTION set_default_pos()
+RETURNS TRIGGER AS $$
+BEGIN
+    -- Check if the parent resource is of type 'Folder'
+    IF EXISTS (
+        SELECT 1
+        FROM "Resource"
+        WHERE "id" = NEW."parentId"
+        AND "type" = 'Folder'
+    ) THEN
+        -- If the pos is NULL, calculate the next available pos for this parentId
+        IF NEW."pos" IS NULL THEN
+            SELECT COALESCE(MAX("pos"), 0) + 1
+            INTO NEW."pos"
+            FROM "Resource"
+            WHERE "parentId" = NEW."parentId";
+        END IF;
+    END IF;
+    
+    -- Return the modified row
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER set_pos_default
+BEFORE INSERT ON "Resource"
+FOR EACH ROW
+EXECUTE FUNCTION set_default_pos();

apps/studio/prisma/schema.prisma

@@ -68,6 +68,13 @@ model Resource {
   state ResourceState? @default(Draft)
   type  ResourceType
 
+  // NOTE: refer to the postgres docs here 
+  // https://www.postgresql.org/docs/current/datatype-numeric.html#DATATYPE-NUMERIC-TABLE
+  // this creates a numeric type that has a scale of 1000 (can store up to 1000 digits)
+  // of which 96 are after the decimal point.
+  // This means that our users can create up to 10e5 pages (probably way more than required)
+  pos Decimal? @db.Decimal(1000, 95)
+
   createdAt          DateTime             @default(now())
   updatedAt          DateTime             @default(now()) @updatedAt
   ResourcePermission ResourcePermission[]