-- ============================================================
-- 003_mailbox_billing_events.sql
-- Append-only event log for inbox billing.
--
-- Each row records that a mailbox was created or deleted at a
-- specific point in time. The aggregation per month is computed
-- on the fly from these events.
-- ============================================================

CREATE TABLE IF NOT EXISTS mailbox_billing_events (
  id           BIGSERIAL PRIMARY KEY,
  occurred_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
  domain       TEXT NOT NULL,
  email        TEXT NOT NULL,
  action       TEXT NOT NULL CHECK (action IN ('created', 'deleted')),
  actor_email  TEXT,
  notes        TEXT
);

CREATE INDEX IF NOT EXISTS idx_billing_events_domain_time
  ON mailbox_billing_events(domain, occurred_at);

CREATE INDEX IF NOT EXISTS idx_billing_events_email
  ON mailbox_billing_events(email);

-- ------------------------------------------------------------
-- Backfill: synthesize 'created' events for every mailbox that
-- already exists when this migration runs, so we have correct
-- historical data right from the first deploy.
--
-- We use the mailbox's created_at as the event timestamp.
-- For mailboxes that are already soft-deleted, also synthesize
-- the matching 'deleted' event using deleted_at.
--
-- The WHERE NOT EXISTS guards make this migration idempotent
-- in case it is re-run.
-- ------------------------------------------------------------

INSERT INTO mailbox_billing_events (occurred_at, domain, email, action, actor_email, notes)
SELECT m.created_at, m.domain, m.email_address, 'created', NULL, 'backfill from migration 003'
FROM mailboxes m
WHERE NOT EXISTS (
  SELECT 1 FROM mailbox_billing_events b
  WHERE b.email = m.email_address
    AND b.action = 'created'
    AND b.occurred_at = m.created_at
);

INSERT INTO mailbox_billing_events (occurred_at, domain, email, action, actor_email, notes)
SELECT m.deleted_at, m.domain, m.email_address, 'deleted', NULL, 'backfill from migration 003'
FROM mailboxes m
WHERE m.status = 'deleted'
  AND m.deleted_at IS NOT NULL
  AND NOT EXISTS (
    SELECT 1 FROM mailbox_billing_events b
    WHERE b.email = m.email_address
      AND b.action = 'deleted'
      AND b.occurred_at = m.deleted_at
  );