-- ==========================================
-- Chat Switchboard — 006 Multi-User: DMs + Channels
-- ==========================================
-- Extends channels with 'dm' and 'channel' types, ai_mode, and topic.
-- Adds presence tracking table.
-- ICD §3 (Channels & Conversations) — v0.23.1
-- ==========================================

-- ── Channel type extension ───────────────────────────────────────────
-- Add 'dm' (human-to-human, AI silent unless @mentioned)
-- Add 'channel' (named persistent space, configurable ai_mode)
-- Existing 'direct', 'group', 'workflow' are unchanged.
ALTER TABLE channels DROP CONSTRAINT IF EXISTS channels_type_check;
ALTER TABLE channels ADD CONSTRAINT channels_type_check
    CHECK (type IN ('direct', 'dm', 'group', 'channel', 'workflow'));

-- ── ai_mode ──────────────────────────────────────────────────────────
-- auto          : AI responds to every message (existing behavior for 'direct')
-- mention_only  : AI silent unless @mentioned (default for 'dm')
-- off           : AI disabled entirely
ALTER TABLE channels
    ADD COLUMN IF NOT EXISTS ai_mode VARCHAR(20) NOT NULL DEFAULT 'auto'
        CHECK (ai_mode IN ('auto', 'mention_only', 'off'));

-- Back-fill: DM channels should be mention_only
-- (No existing rows should have type='dm' yet, but be safe)
UPDATE channels SET ai_mode = 'mention_only' WHERE type = 'dm' AND ai_mode = 'auto';

-- ── topic ─────────────────────────────────────────────────────────────
ALTER TABLE channels
    ADD COLUMN IF NOT EXISTS topic TEXT;

-- ── Presence (in-memory heartbeat, DB stores last_seen for persistence) ──
-- Not queried at high frequency — updated by heartbeat (30s), read on load.
CREATE TABLE IF NOT EXISTS user_presence (
    user_id     UUID PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
    last_seen   TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    status      VARCHAR(20) NOT NULL DEFAULT 'online'
                CHECK (status IN ('online', 'away', 'offline'))
);

CREATE INDEX IF NOT EXISTS idx_user_presence_last_seen ON user_presence(last_seen DESC);

COMMENT ON TABLE user_presence IS 'Heartbeat-driven presence. Rows upserted every 30s by active clients.';
COMMENT ON COLUMN channels.ai_mode IS 'auto=respond always, mention_only=@mention required, off=AI disabled';
COMMENT ON COLUMN channels.topic IS 'Short channel description shown in header';