-- B03：场景切片派生缓存与向量代次索引——参考书原文的确定性切窗。
-- 原文以 muse_source_version 为权威；切片与索引是可全量重建的派生数据，禁原地改写。
DO $migration$
BEGIN
    -- 切片台账：来源版本的定位窗；窗计划哈希锁定切窗方案，同版本只认一个窗计划。
    CREATE TABLE public.muse_source_slice (
        slice_id uuid PRIMARY KEY,
        source_id uuid NOT NULL REFERENCES public.muse_source(source_id),
        revision bigint NOT NULL CHECK (revision > 0),
        起点 int NOT NULL CHECK (起点 >= 0),
        终点 int NOT NULL CHECK (终点 > 起点),
        窗计划哈希 text NOT NULL,
        检索文本 text NOT NULL,
        检索文本哈希 text NOT NULL CHECK (检索文本哈希 ~ '^[0-9a-f]{64}$'),
        built_at timestamptz NOT NULL DEFAULT clock_timestamp()
    );
    -- 同版本同窗计划内起点唯一；不同窗计划可并存，重建时整计划替换。
    CREATE UNIQUE INDEX muse_source_slice_window
        ON public.muse_source_slice (source_id, revision, 窗计划哈希, 起点);
    CREATE INDEX muse_source_slice_by_source ON public.muse_source_slice (source_id, revision);

    -- 派生数据禁原地改写；删除仅允许全量重建事务成批进行。
    CREATE FUNCTION public.muse_guard_source_slice() RETURNS trigger LANGUAGE plpgsql AS $guard$
    BEGIN
        RAISE EXCEPTION '场景切片是派生数据，禁止原地改写；重建请整批删除后重算';
    END;
    $guard$;
    CREATE TRIGGER muse_source_slice_guard BEFORE UPDATE ON public.muse_source_slice
        FOR EACH ROW EXECUTE FUNCTION public.muse_guard_source_slice();

    -- 切片向量索引：与 muse_method_index 同构（哈希 bigram，内存余弦）。
    CREATE TABLE public.muse_source_slice_index (
        slice_id uuid PRIMARY KEY REFERENCES public.muse_source_slice(slice_id) ON DELETE CASCADE,
        检索文本 text NOT NULL,
        检索文本哈希 text NOT NULL,
        vector double precision[] NOT NULL CHECK (array_length(vector, 1) > 0),
        embedder text NOT NULL,
        built_at timestamptz NOT NULL DEFAULT clock_timestamp()
    );

    -- 代次台账：当前有效索引身份；检索时对不上即拒绝为陈旧。
    CREATE TABLE public.muse_source_slice_index_version (
        ledger_id bigint PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
        索引身份 text NOT NULL,
        embedder text NOT NULL,
        slice_count int NOT NULL CHECK (slice_count >= 0),
        built_at timestamptz NOT NULL DEFAULT clock_timestamp(),
        active boolean NOT NULL DEFAULT false
    );
    CREATE UNIQUE INDEX muse_source_slice_index_active
        ON public.muse_source_slice_index_version (active) WHERE active;

    -- 代次守卫：切片与索引的事务变更递增代次，检索按代次判新鲜（仿 V0059）。
    CREATE TABLE public.muse_source_slice_guard (
        singleton boolean PRIMARY KEY DEFAULT true CHECK (singleton),
        generation bigint NOT NULL DEFAULT 0 CHECK (generation >= 0)
    );
    INSERT INTO public.muse_source_slice_guard (singleton, generation) VALUES (true, 0);

    CREATE FUNCTION public.muse_source_slice_changed() RETURNS trigger
    LANGUAGE plpgsql SECURITY DEFINER SET search_path = pg_catalog AS $guard$
    BEGIN
        UPDATE public.muse_source_slice_guard
           SET generation = generation + 1
         WHERE singleton;
        IF NOT FOUND THEN
            RAISE EXCEPTION 'source slice mutation guard is missing';
        END IF;
        RETURN NULL;
    END;
    $guard$;

    CREATE TRIGGER muse_source_slice_changed
        AFTER INSERT OR UPDATE OR DELETE OR TRUNCATE ON public.muse_source_slice
        FOR EACH STATEMENT EXECUTE FUNCTION public.muse_source_slice_changed();
    CREATE TRIGGER muse_source_slice_index_changed
        AFTER INSERT OR UPDATE OR DELETE OR TRUNCATE ON public.muse_source_slice_index
        FOR EACH STATEMENT EXECUTE FUNCTION public.muse_source_slice_changed();
    CREATE TRIGGER muse_source_slice_head_changed
        AFTER INSERT OR UPDATE OR DELETE OR TRUNCATE ON public.muse_source_slice_index_version
        FOR EACH STATEMENT EXECUTE FUNCTION public.muse_source_slice_changed();

    REVOKE ALL ON public.muse_source_slice_guard FROM PUBLIC, muse_app, muse_eval;
    GRANT SELECT ON public.muse_source_slice_guard TO muse_app, muse_eval;
    REVOKE ALL ON FUNCTION public.muse_source_slice_changed() FROM PUBLIC;
END
$migration$;