-- Migration 016: per-(user, channel) caption-availability memory (ADR-024).
--
-- Some channels never publish English captions (foreign-language news, music,
-- etc.). Each of their new videos still costs ONE rate-limited caption fetch
-- (ADR-014) before resolving to "none" — and on a throttled egress IP that fetch
-- may 429 and churn through the backoff machinery first. This table remembers
-- channels that repeatedly yield no captions so discovery can stop attempting
-- their videos, freeing the scarce fetch budget for channels that do have them.
--
-- consecutive_none counts no-caption outcomes in a row; a successful fetch resets
-- it to 0. Once it crosses the threshold the channel is suppressed until
-- captionless_until, after which one video is re-probed (auto-recovery for a
-- channel that starts adding captions). Per-user + RLS-scoped, consistent with
-- the rest of the user-owned schema (subscriptions are per-user; ADR-012).
CREATE TABLE channel_caption_state (
    user_id           UUID        NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    channel_id        TEXT        NOT NULL,
    consecutive_none  INT         NOT NULL DEFAULT 0,
    captionless_until TIMESTAMPTZ,
    updated_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
    PRIMARY KEY (user_id, channel_id)
);

CREATE INDEX idx_channel_caption_state_user_id ON channel_caption_state(user_id);

ALTER TABLE channel_caption_state ENABLE ROW LEVEL SECURITY;
ALTER TABLE channel_caption_state FORCE ROW LEVEL SECURITY;
CREATE POLICY channel_caption_state_isolation ON channel_caption_state
    FOR ALL
    USING (user_id = current_setting('tapir.current_user_id', true)::uuid);