-- Migration: 007 – Enhance user_messages with status lifecycle and timestamps
-- Database: PostgreSQL
--
-- Adds: status (sent | read | deleted), received_at, deleted_at
-- Existing rows are backfilled to is_read=true → status='read', else status='sent'.

ALTER TABLE user_messages
    ADD COLUMN IF NOT EXISTS status      TEXT        NOT NULL DEFAULT 'sent',
    ADD COLUMN IF NOT EXISTS received_at TIMESTAMPTZ,
    ADD COLUMN IF NOT EXISTS deleted_at  TIMESTAMPTZ;

-- Backfill: rows already marked is_read should be 'read' with received_at = created_at.
UPDATE user_messages
   SET status      = 'read',
       received_at = created_at
 WHERE is_read = true AND status = 'sent';

CREATE INDEX IF NOT EXISTS idx_user_messages_status ON user_messages(user_id, status)
    WHERE status != 'deleted';