Added log like function

sql/nft/website/functions/log_like.sql

@@ -0,0 +1,37 @@
+CREATE OR REPLACE FUNCTION log_like
+(
+  _account                                address,
+  _token_id                               uint256
+)
+RETURNS uint256
+AS
+$$
+  DECLARE _previous                       boolean;
+  DECLARE _token_likes                    uint256;
+BEGIN
+  IF NOT EXISTS(SELECT 1 FROM nfts WHERE token_id = _token_id) THEN
+    RAISE EXCEPTION 'Invalid token id';
+  END IF;
+
+  SELECT likes.liked                      INTO _previous
+  WHERE likes.liked_by                    = _account
+  AND likes.token_id                      = _token_id
+  LIMIT 1;
+
+  UPDATE likes
+  SET
+    last_unliked_at                       = CASE WHEN liked = true  THEN NOW() ELSE last_unliked_at END,
+    last_liked_at                         = CASE WHEN liked = false THEN NOW() ELSE last_liked_at   END,
+    liked                                 = !liked
+  WHERE likes.liked_by                    = _account
+  AND likes.token_id                      = _token_id;
+
+  UPDATE nfts
+  SET likes                               = likes + (CASE WHEN _previous = true THEN -1 ELSE 1 END)
+  WHERE token_id                          = _token_id
+  RETURNING nfts.likes                    INTO _token_likes;
+
+  RETURN _token_likes;
+END
+$$
+LANGUAGE plpgsql;