-- Internal credit ledger foundation; no public payment or credit-grant route.
CREATE TABLE IF NOT EXISTS opt_credit_accounts (
  tenant_id text PRIMARY KEY CHECK (length(tenant_id) > 0),
  available bigint NOT NULL DEFAULT 0 CHECK (available >= 0 AND available <= 9007199254740991),
  reserved bigint NOT NULL DEFAULT 0 CHECK (reserved >= 0 AND reserved <= 9007199254740991)
);

CREATE TABLE IF NOT EXISTS opt_credit_reservations (
  tenant_id text NOT NULL REFERENCES opt_credit_accounts(tenant_id),
  reservation_id text NOT NULL CHECK (length(reservation_id) > 0),
  amount bigint NOT NULL CHECK (amount > 0 AND amount <= 9007199254740991),
  status text NOT NULL CHECK (status IN ('reserved', 'settled', 'released')),
  settled_amount bigint CHECK (settled_amount >= 0 AND settled_amount <= amount),
  PRIMARY KEY (tenant_id, reservation_id)
);

CREATE TABLE IF NOT EXISTS opt_credit_events (
  event_id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  tenant_id text NOT NULL REFERENCES opt_credit_accounts(tenant_id),
  idempotency_key text NOT NULL CHECK (length(idempotency_key) > 0),
  kind text NOT NULL CHECK (kind IN ('verified_payment', 'reserve', 'settle', 'release')),
  amount bigint NOT NULL CHECK (amount >= 0 AND amount <= 9007199254740991),
  reference text NOT NULL CHECK (length(reference) > 0),
  created_at timestamptz NOT NULL DEFAULT now(),
  UNIQUE (tenant_id, idempotency_key)
);
-- A single external payment cannot fund multiple tenants or grants.
CREATE UNIQUE INDEX IF NOT EXISTS opt_credit_verified_payment_reference
  ON opt_credit_events(reference) WHERE kind = 'verified_payment';

-- Server-owned price snapshot. Never read price or credits from PAY0 metadata.
CREATE TABLE IF NOT EXISTS opt_credit_purchases (
  tenant_id text NOT NULL CHECK (length(tenant_id) > 0),
  purchase_id text NOT NULL CHECK (length(purchase_id) > 0),
  checkout_session_id text NOT NULL UNIQUE CHECK (length(checkout_session_id) > 0),
  amount_minor bigint NOT NULL CHECK (amount_minor > 0 AND amount_minor <= 9007199254740991),
  currency text NOT NULL CHECK (currency ~ '^[A-Z]{3}$'),
  credits bigint NOT NULL CHECK (credits > 0 AND credits <= 9007199254740991),
  created_at timestamptz NOT NULL DEFAULT now(),
  PRIMARY KEY (tenant_id, purchase_id)
);