-- ── Channels ──────────────────────────────────────────────────────────────────
-- Conformance: "Channels and channel membership". `community_id` immutable.
-- Channel UUIDs stay valid wire identifiers, but they are NOT globally unique:
-- the PK is `(community_id, id)`, so the same UUID may legitimately exist in two
-- communities (conformance lists "same channel UUID collision in two
-- communities" as a required isolation test). Handlers always carry `ctx`, so
-- `(ctx.community, h)` names exactly one channel; a client-supplied `h` can
-- never reach another community's channel.

CREATE TABLE channels (
    id              UUID NOT NULL DEFAULT gen_random_uuid(),
    community_id    UUID NOT NULL REFERENCES communities(id),
    name            VARCHAR(255) NOT NULL,
    channel_type    channel_type NOT NULL DEFAULT 'stream',
    visibility      channel_visibility NOT NULL DEFAULT 'open',
    description     TEXT,
    canvas          TEXT,
    created_by      BYTEA NOT NULL,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    archived_at     TIMESTAMPTZ,
    deleted_at      TIMESTAMPTZ,
    nip29_group_id  VARCHAR(255),
    topic_required  BOOLEAN NOT NULL DEFAULT FALSE,
    max_members     INT,
    topic           TEXT,
    topic_set_by    BYTEA,
    topic_set_at    TIMESTAMPTZ,
    purpose         TEXT,
    purpose_set_by  BYTEA,
    purpose_set_at  TIMESTAMPTZ,
    participant_hash BYTEA,
    ttl_seconds     INT,
    ttl_deadline    TIMESTAMPTZ,
    -- Labels, published as ["t", <label>] after the channel type tag on the
    -- relay-signed group-state events. The relay validates their shape.
    labels          TEXT[] NOT NULL DEFAULT '{}'
        CONSTRAINT channels_labels_bounded CHECK (cardinality(labels) <= 8),
    join_role       TEXT NOT NULL DEFAULT 'member'
        CHECK (join_role IN ('member', 'guest')),
    -- An unlisted open channel is readable and joinable by id but left out of
    -- channel listings for non-members. Matters only while the channel is open.
    unlisted        BOOLEAN NOT NULL DEFAULT FALSE,
    PRIMARY KEY (community_id, id),
    CONSTRAINT chk_channels_id_not_nil CHECK (id <> '00000000-0000-0000-0000-000000000000'::uuid)
);

-- nip29 group id and DM participant hash are unique WITHIN a community, not globally.
CREATE UNIQUE INDEX idx_channels_nip29_group ON channels (community_id, nip29_group_id)
    WHERE nip29_group_id IS NOT NULL;
CREATE UNIQUE INDEX idx_channels_dm_hash ON channels (community_id, participant_hash)
    WHERE participant_hash IS NOT NULL;
CREATE INDEX idx_channels_community_type ON channels (community_id, channel_type);
CREATE INDEX idx_channels_community_visibility ON channels (community_id, visibility);
CREATE INDEX idx_channels_created_by ON channels (community_id, created_by);
CREATE INDEX idx_channels_ttl_expiry ON channels (ttl_deadline)
    WHERE ttl_seconds IS NOT NULL AND archived_at IS NULL AND deleted_at IS NULL;
-- Tenant-independent channel-id → community lookups (Db::communities_of_channels,
-- Db::community_of_channel) carry no community_id predicate, so no
-- community_id-leading index can serve them. Covering + partial: index-only scan.
-- Not UNIQUE — the same channel id may exist under more than one community.
CREATE INDEX idx_channels_id_live ON channels (id) INCLUDE (community_id)
    WHERE deleted_at IS NULL;