-- Migration 008: Direct Message tables.
-- Adds dm_participants and dm_open_state tables for DM channel support.
-- The channels.type column is TEXT with no CHECK constraint, so 'dm' is
-- already a valid value — no schema alteration needed.

CREATE TABLE IF NOT EXISTS dm_participants (
    channel_id INTEGER NOT NULL REFERENCES channels(id) ON DELETE CASCADE,
    user_id    INTEGER NOT NULL REFERENCES users(id)    ON DELETE CASCADE,
    PRIMARY KEY (channel_id, user_id)
);

CREATE INDEX IF NOT EXISTS idx_dm_participants_user ON dm_participants(user_id);

CREATE TABLE IF NOT EXISTS dm_open_state (
    user_id    INTEGER NOT NULL REFERENCES users(id)    ON DELETE CASCADE,
    channel_id INTEGER NOT NULL REFERENCES channels(id) ON DELETE CASCADE,
    opened_at  TEXT    NOT NULL DEFAULT (datetime('now')),
    PRIMARY KEY (user_id, channel_id)
);