-- IMAP (75.2): UIDs per folder, IMAP flags, the original message text

-- UIDVALIDITY: never changes for a folder; UIDNEXT: the next UID to give out
ALTER TABLE folders ADD COLUMN uid_validity BIGINT NOT NULL DEFAULT (EXTRACT(EPOCH FROM now())::BIGINT);
ALTER TABLE folders ADD COLUMN uid_next BIGINT NOT NULL DEFAULT 1;

-- UID inside the folder; strictly increasing — a message moved into a folder gets a new, larger UID
ALTER TABLE messages ADD COLUMN uid BIGINT;
ALTER TABLE messages ADD COLUMN is_answered BOOLEAN NOT NULL DEFAULT FALSE;
ALTER TABLE messages ADD COLUMN is_deleted BOOLEAN NOT NULL DEFAULT FALSE;

UPDATE messages m SET uid = numbered.n
FROM (SELECT id, ROW_NUMBER() OVER (PARTITION BY folder_id ORDER BY received_at, id) AS n FROM messages) numbered
WHERE m.id = numbered.id;

UPDATE folders f SET uid_next = COALESCE((SELECT MAX(uid) FROM messages WHERE folder_id = f.id), 0) + 1;

ALTER TABLE messages ALTER COLUMN uid SET NOT NULL;
CREATE UNIQUE INDEX idx_messages_folder_uid ON messages(folder_id, uid);

-- The UID is given out by the database, so every path that stores or moves a message (SMTP, web client, IMAP)
-- gets it right without knowing about IMAP
CREATE FUNCTION assign_message_uid() RETURNS trigger AS $$
BEGIN
    UPDATE folders SET uid_next = uid_next + 1 WHERE id = NEW.folder_id RETURNING uid_next - 1 INTO NEW.uid;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER messages_uid_on_insert BEFORE INSERT ON messages
    FOR EACH ROW EXECUTE FUNCTION assign_message_uid();

-- The web client saves the whole row (folder_id included) — only a real move gets a new UID
CREATE TRIGGER messages_uid_on_move BEFORE UPDATE OF folder_id ON messages
    FOR EACH ROW WHEN (NEW.folder_id IS DISTINCT FROM OLD.folder_id) EXECUTE FUNCTION assign_message_uid();

-- The message exactly as received (SMTP) or appended (IMAP APPEND); for messages without it the server builds
-- the MIME text once from the stored fields and keeps it here, so sizes and bytes never change between fetches.
-- Removed when a draft changes.
CREATE TABLE message_sources (
    message_id BIGINT PRIMARY KEY REFERENCES messages(id) ON DELETE CASCADE,
    raw BYTEA NOT NULL
);