-- 模型规划只落候选，来源绑定独立保存；正式规划仍由作者决定。
CREATE TABLE public.muse_model_plan_candidate (
    candidate_id uuid PRIMARY KEY REFERENCES public.muse_plan_candidate(candidate_id),
    task_id uuid NOT NULL REFERENCES public.muse_task(task_id),
    snapshot_id uuid NOT NULL REFERENCES public.muse_context_snapshot(snapshot_id),
    call_id text NOT NULL,
    model_evidence jsonb NOT NULL CHECK (jsonb_typeof(model_evidence)='object'),
    prompt_hash text NOT NULL,
    created_at timestamptz NOT NULL DEFAULT clock_timestamp(),
    UNIQUE (task_id, call_id)
);

-- 同一快照可能由不同真实调用消费；不能将后一次调用冒充前一次的幂等回执。
DO $migration$
DECLARE
    old_constraint text;
BEGIN
    SELECT conname INTO old_constraint FROM pg_constraint
    WHERE conrelid='public.muse_method_usage'::regclass AND contype='u'
      AND pg_get_constraintdef(oid)='UNIQUE (method_version_id, kind, context_ref, fragment_hash)';
    IF old_constraint IS NULL THEN
        RAISE EXCEPTION '消费键约束缺失，不能盲目替换';
    END IF;
    EXECUTE format('ALTER TABLE public.muse_method_usage DROP CONSTRAINT %I', old_constraint);
END
$migration$;
ALTER TABLE public.muse_method_usage ADD CONSTRAINT method_usage_call_key
    UNIQUE (method_version_id, kind, context_ref, fragment_hash, task_id, result_ref);
-- 历史无任务/调用回执维持原来的单键约束，不将其升级为真实模型消费。
CREATE UNIQUE INDEX method_usage_legacy_key ON public.muse_method_usage
    (method_version_id, kind, context_ref, fragment_hash)
    WHERE task_id IS NULL OR result_ref IS NULL;