feat: add user centric features

migrations/0008_create_collections.up.sql

@@ -0,0 +1,54 @@
+-- Collections group posts/quotes. They carry their own visibility flag —
+-- a private collection holds posts that are themselves public on the user's
+-- feed, but the collection page is only visible to the owner.
+--
+-- `item_count` is denormalized so listing pages don't need a join+count.
+-- It's kept in sync by collection_items triggers below.
+CREATE TABLE IF NOT EXISTS collections (
+    id           UUID         PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id      UUID         NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    title        VARCHAR(120) NOT NULL,
+    description  TEXT,
+    cover_url    TEXT,
+    is_public    BOOLEAN      NOT NULL DEFAULT FALSE,
+    item_count   INT          NOT NULL DEFAULT 0,
+    created_at   TIMESTAMPTZ  NOT NULL DEFAULT now(),
+    updated_at   TIMESTAMPTZ  NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS collections_user_created_idx
+    ON collections (user_id, created_at DESC);
+
+-- Public-collection lookups by owner+visibility (for /u/<handle> page).
+CREATE INDEX IF NOT EXISTS collections_user_public_idx
+    ON collections (user_id, is_public) WHERE is_public = TRUE;
+
+CREATE TABLE IF NOT EXISTS collection_items (
+    collection_id  UUID         NOT NULL REFERENCES collections(id) ON DELETE CASCADE,
+    post_id        UUID         NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
+    position       INT          NOT NULL DEFAULT 0,
+    added_at       TIMESTAMPTZ  NOT NULL DEFAULT now(),
+    PRIMARY KEY (collection_id, post_id)
+);
+
+CREATE INDEX IF NOT EXISTS collection_items_position_idx
+    ON collection_items (collection_id, position);
+
+-- Keep item_count in sync.
+CREATE OR REPLACE FUNCTION sync_collection_item_count() RETURNS TRIGGER AS $$
+BEGIN
+    IF TG_OP = 'INSERT' THEN
+        UPDATE collections SET item_count = item_count + 1, updated_at = now()
+            WHERE id = NEW.collection_id;
+    ELSIF TG_OP = 'DELETE' THEN
+        UPDATE collections SET item_count = GREATEST(item_count - 1, 0), updated_at = now()
+            WHERE id = OLD.collection_id;
+    END IF;
+    RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS collection_items_count_trg ON collection_items;
+CREATE TRIGGER collection_items_count_trg
+    AFTER INSERT OR DELETE ON collection_items
+    FOR EACH ROW EXECUTE FUNCTION sync_collection_item_count();