-- ============================================================
-- migrations_add_purchase_stockbuy_link.sql
-- 打通「采购申请」与「采购入库」的按单入库链路
--
-- 变更内容:
--   1. purchase_request 表新增 base_id 列（FK → material_base.id）
--   2. stock_buy 表新增 request_id 列（FK → purchase_request.id）
--
-- 执行方式（任选一种）:
--   psql -h <host> -U postgres -d inventory_system -f migrations_add_purchase_stockbuy_link.sql
--   或在 pgAdmin / Navicat / DBeaver 中打开执行
-- ============================================================

BEGIN;

-- ============================================================
-- 1. purchase_request 新增 base_id
--    硬关联基础物料表，使采购申请能精确锁定物料
-- ============================================================
ALTER TABLE purchase_request
    ADD COLUMN IF NOT EXISTS base_id INTEGER;

-- 添加外键约束（如果列已存在但无约束，会补充）
DO $$
BEGIN
    IF NOT EXISTS (
        SELECT 1 FROM information_schema.table_constraints
        WHERE constraint_name = 'fk_purchase_request_base_id'
          AND table_name = 'purchase_request'
    ) THEN
        ALTER TABLE purchase_request
            ADD CONSTRAINT fk_purchase_request_base_id
            FOREIGN KEY (base_id) REFERENCES material_base(id)
            ON DELETE SET NULL;
    END IF;
END;
$$;

-- 为 base_id 添加索引（支持按物料筛选采购申请）
CREATE INDEX IF NOT EXISTS ix_purchase_request_base_id
    ON purchase_request (base_id);

COMMENT ON COLUMN purchase_request.base_id IS '关联基础物料ID';


-- ============================================================
-- 2. stock_buy 新增 request_id
--    关联采购申请单，使入库记录可追溯到来源采购单
-- ============================================================
ALTER TABLE stock_buy
    ADD COLUMN IF NOT EXISTS request_id INTEGER;

-- 添加外键约束
DO $$
BEGIN
    IF NOT EXISTS (
        SELECT 1 FROM information_schema.table_constraints
        WHERE constraint_name = 'fk_stock_buy_request_id'
          AND table_name = 'stock_buy'
    ) THEN
        ALTER TABLE stock_buy
            ADD CONSTRAINT fk_stock_buy_request_id
            FOREIGN KEY (request_id) REFERENCES purchase_request(id)
            ON DELETE SET NULL;
    END IF;
END;
$$;

-- 为 request_id 添加索引（支持"按单查入库"的追溯查询）
CREATE INDEX IF NOT EXISTS ix_stock_buy_request_id
    ON stock_buy (request_id);

COMMENT ON COLUMN stock_buy.request_id IS '关联采购申请单ID';


-- ============================================================
-- 3. 验证结果
-- ============================================================
SELECT
    column_name,
    data_type,
    is_nullable,
    pg_catalog.col_description(
        (SELECT c.oid FROM pg_catalog.pg_class c
         WHERE c.relname = table_name),
        ordinal_position
    ) AS comment
FROM information_schema.columns
WHERE table_name IN ('purchase_request', 'stock_buy')
  AND column_name IN ('base_id', 'request_id')
ORDER BY table_name, column_name;

COMMIT;