-- Platform-mediated merchant settlement: per-shop, per-period statements
-- snapshotted from confirmed-received orders minus completed refunds minus a
-- platform commission. Amounts are integer minor units in the platform base
-- currency; the rate is integer basis points and lives in platform settings.

-- Settlement attributes an order to the period in which it became
-- confirmed-received. Refunds bump orders.updated_at, so that column cannot
-- stand in for the completion instant.
ALTER TABLE orders ADD COLUMN completed_at TIMESTAMPTZ;
UPDATE orders SET completed_at = updated_at
 WHERE status = 'completed' AND completed_at IS NULL;
CREATE INDEX orders_shop_completed_idx
    ON orders (shop_id, completed_at) WHERE status = 'completed';

CREATE TABLE platform_settings (
    key TEXT PRIMARY KEY,
    value TEXT NOT NULL,
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

INSERT INTO platform_settings (key, value)
VALUES ('settlement.commission_rate_bps', '500')
ON CONFLICT (key) DO NOTHING;

CREATE TYPE settlement_period_kind AS ENUM ('week', 'month');
CREATE TYPE settlement_status AS ENUM ('pending', 'confirmed');

CREATE TABLE settlement_statements (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    shop_id UUID NOT NULL REFERENCES shops (id) ON DELETE CASCADE,
    -- Statement totals are converted into and snapshotted in this currency.
    currency CHAR(3) NOT NULL REFERENCES currencies (code),
    period_kind settlement_period_kind NOT NULL,
    period_start DATE NOT NULL,
    period_end DATE NOT NULL,
    order_count INT NOT NULL DEFAULT 0 CHECK (order_count >= 0),
    gross_minor BIGINT NOT NULL DEFAULT 0 CHECK (gross_minor >= 0),
    refund_minor BIGINT NOT NULL DEFAULT 0 CHECK (refund_minor >= 0),
    commission_rate_bps INT NOT NULL
        CHECK (commission_rate_bps >= 0 AND commission_rate_bps <= 10000),
    commission_minor BIGINT NOT NULL DEFAULT 0 CHECK (commission_minor >= 0),
    payable_minor BIGINT NOT NULL DEFAULT 0 CHECK (payable_minor >= 0),
    status settlement_status NOT NULL DEFAULT 'pending',
    generated_by UUID REFERENCES users (id),
    confirmed_by UUID REFERENCES users (id),
    confirmed_at TIMESTAMPTZ,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT settlement_statements_period CHECK (period_end >= period_start),
    CONSTRAINT settlement_statements_confirmed_consistent CHECK (
        (status = 'pending' AND confirmed_by IS NULL AND confirmed_at IS NULL)
        OR (status = 'confirmed' AND confirmed_by IS NOT NULL AND confirmed_at IS NOT NULL)
    )
);

-- At most one statement per shop, period kind, and period start.
CREATE UNIQUE INDEX settlement_statements_period_idx
    ON settlement_statements (shop_id, period_kind, period_start);
CREATE INDEX settlement_statements_shop_idx
    ON settlement_statements (shop_id, created_at DESC);
CREATE INDEX settlement_statements_status_idx
    ON settlement_statements (status, created_at DESC);