-- §5.5 (v1.2 Hierarchies): extension-point markers — opt-in module polymorphism.
--
-- An extension point marks a module NAME at a node (app or group) as one
-- descendants are *expected* to provide or override. Imports of an EP name
-- resolve DYNAMICALLY against the inheriting app's view (the app can supply
-- its own module), instead of the Phase 4b lexical default (sealed to the
-- importing script's defining node). See docs §5.5.
--
-- This table holds only the MARKER (owner, name) — it is pure declaration,
-- structurally identical to a `secrets` name. The optional DEFAULT BODY is
-- just a co-located `kind = 'module'` script of the same name at this node
-- (Phase 4b already stores/resolves/caches those); there is no body column
-- here. So a marker is config, not code → ON DELETE CASCADE (unlike the
-- module body's RESTRICT in 0050).
--
-- Ownership is polymorphic (mirrors vars/secrets/scripts): exactly one of
-- (app_id, group_id) is set, with per-owner partial-unique LOWER(name)
-- indexes for case-insensitive uniqueness.

CREATE TABLE extension_points (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    group_id    UUID REFERENCES groups(id) ON DELETE CASCADE,
    app_id      UUID REFERENCES apps(id) ON DELETE CASCADE,
    CONSTRAINT extension_points_owner_exactly_one
        CHECK ((group_id IS NULL) <> (app_id IS NULL)),
    name        TEXT NOT NULL,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- One marker per (owner, name), case-insensitive. Partial because the owner
-- is split across two nullable columns.
CREATE UNIQUE INDEX extension_points_group_uidx
    ON extension_points (group_id, LOWER(name)) WHERE group_id IS NOT NULL;
CREATE UNIQUE INDEX extension_points_app_uidx
    ON extension_points (app_id, LOWER(name)) WHERE app_id IS NOT NULL;

-- Lookup indexes for the resolver's chain join + list-by-owner.
CREATE INDEX extension_points_group_id_idx ON extension_points (group_id) WHERE group_id IS NOT NULL;
CREATE INDEX extension_points_app_id_idx ON extension_points (app_id) WHERE app_id IS NOT NULL;