CREATE TYPE freight_pricing_method AS ENUM ('by_piece', 'by_weight');

CREATE TABLE freight_templates (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    shop_id UUID NOT NULL REFERENCES shops (id) ON DELETE CASCADE,
    name TEXT NOT NULL,
    is_default BOOLEAN NOT NULL DEFAULT false,
    always_free BOOLEAN NOT NULL DEFAULT false,
    pricing_method freight_pricing_method NOT NULL DEFAULT 'by_piece',
    first_fee_minor BIGINT NOT NULL DEFAULT 0 CHECK (first_fee_minor >= 0),
    first_unit INT NOT NULL DEFAULT 1 CHECK (first_unit > 0),
    additional_fee_minor BIGINT NOT NULL DEFAULT 0 CHECK (additional_fee_minor >= 0),
    additional_unit INT NOT NULL DEFAULT 1 CHECK (additional_unit > 0),
    free_threshold_minor BIGINT CHECK (free_threshold_minor > 0),
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

-- At most one default template per shop.
CREATE UNIQUE INDEX freight_templates_one_default
    ON freight_templates (shop_id) WHERE is_default;
CREATE INDEX idx_freight_templates_shop ON freight_templates (shop_id);

CREATE TABLE freight_region_rules (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    template_id UUID NOT NULL REFERENCES freight_templates (id) ON DELETE CASCADE,
    regions TEXT[] NOT NULL,
    first_fee_minor BIGINT NOT NULL CHECK (first_fee_minor >= 0),
    first_unit INT NOT NULL CHECK (first_unit > 0),
    additional_fee_minor BIGINT NOT NULL CHECK (additional_fee_minor >= 0),
    additional_unit INT NOT NULL CHECK (additional_unit > 0)
);

CREATE INDEX idx_freight_region_rules_template ON freight_region_rules (template_id);

CREATE TABLE shipping_companies (
    code TEXT PRIMARY KEY,
    name JSONB NOT NULL,
    active BOOLEAN NOT NULL DEFAULT true
);

INSERT INTO shipping_companies (code, name) VALUES
    ('sf-express', '{"en": "SF Express", "zh": "顺丰速运"}'),
    ('zto', '{"en": "ZTO Express", "zh": "中通快递"}'),
    ('yto', '{"en": "YTO Express", "zh": "圆通速递"}'),
    ('ems', '{"en": "EMS", "zh": "中国邮政 EMS"}'),
    ('ups', '{"en": "UPS", "zh": "联合包裹"}'),
    ('fedex', '{"en": "FedEx", "zh": "联邦快递"}');

ALTER TABLE products
    ADD COLUMN freight_template_id UUID REFERENCES freight_templates (id) ON DELETE SET NULL;

ALTER TABLE skus
    ADD COLUMN weight_grams INT CHECK (weight_grams > 0);

ALTER TABLE orders
    ADD COLUMN shipping_fee_minor BIGINT NOT NULL DEFAULT 0 CHECK (shipping_fee_minor >= 0);

-- Checkout snapshots so later template edits never touch history.
ALTER TABLE order_items
    ADD COLUMN freight_template_id UUID,
    ADD COLUMN freight_pricing_method freight_pricing_method;

ALTER TABLE shipments
    ADD COLUMN shipping_company_code TEXT REFERENCES shipping_companies (code);