-- Migration 002: who is allowed to ask, and what a fresh PC is told.
--
-- 001 built the data. Nothing could read it: the only writer was the MQTT
-- consumer, authenticated by the broker. This adds the request/response half —
-- staff logging in from the desktop app, and a newly installed store PC
-- collecting its own broker credentials.

BEGIN;

-- ============================================================ sessions =====

-- Opaque tokens in a table, not JWTs.
--
-- A JWT cannot be revoked without a blocklist, which is a session table with
-- extra steps and worse failure modes. This system holds biometric data on
-- shop-floor PCs that get lost, resold and shared between staff, so "log that
-- device out, now" has to actually work. At this volume the lookup is one
-- indexed read.
--
-- Only the SHA-256 of each token is stored. A database dump then contains no
-- usable session — and SHA-256 rather than bcrypt because the token is 256
-- bits from crypto/rand, so there is no dictionary to slow an attacker down
-- through, only a per-request cost to pay.
CREATE TABLE sessions (
    id                 uuid PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id            uuid NOT NULL REFERENCES app_users(id) ON DELETE CASCADE,
    -- Denormalised from app_users so the auth lookup is one row, and so a
    -- session cannot outlive a user being moved between clients.
    client_id          uuid REFERENCES clients(id) ON DELETE CASCADE,
    access_hash        bytea NOT NULL UNIQUE,
    refresh_hash       bytea NOT NULL UNIQUE,
    access_expires_at  timestamptz NOT NULL,
    refresh_expires_at timestamptz NOT NULL,
    revoked_at         timestamptz,
    -- Enough to tell one device from another in a session list. Not an
    -- identifier, and deliberately not an IP address: a shop's IP tells us
    -- where a customer's staff live, which we have no reason to keep.
    device             text NOT NULL DEFAULT '',
    created_at         timestamptz NOT NULL DEFAULT now(),
    last_used_at       timestamptz
);
CREATE INDEX sessions_user_idx    ON sessions (user_id) WHERE revoked_at IS NULL;
CREATE INDEX sessions_expiry_idx  ON sessions (refresh_expires_at);

-- ============================================================ enrolment ====

-- A one-shot token that turns an anonymous install into a known site.
--
-- The installer ships with no credentials at all, so a leaked build hands out
-- nothing. The operator types this code once; the server answers with the
-- broker credentials for exactly one site and marks the token spent.
CREATE TABLE site_enrolment_tokens (
    id          uuid PRIMARY KEY DEFAULT gen_random_uuid(),
    client_id   uuid NOT NULL REFERENCES clients(id) ON DELETE CASCADE,
    site_id     uuid NOT NULL REFERENCES sites(id) ON DELETE CASCADE,
    token_hash  bytea NOT NULL UNIQUE,
    label       text NOT NULL DEFAULT '',
    expires_at  timestamptz NOT NULL,
    used_at     timestamptz,
    created_by  uuid,
    created_at  timestamptz NOT NULL DEFAULT now()
);
CREATE INDEX site_enrolment_site_idx ON site_enrolment_tokens (site_id);

-- The broker password this site publishes with, encrypted with the server's
-- own key (AES-GCM, BEHAVISION_SECRET_KEY).
--
-- It has to be recoverable, not hashed: enrolment HANDS IT OUT. Encrypting it
-- means a stolen database dump is not a set of live broker logins, which a
-- plaintext column would be. Mosquitto keeps its own hashed copy in its passwd
-- file; this is the second half of a pair that must be provisioned together.
ALTER TABLE agents ADD COLUMN mqtt_password_enc bytea;

-- ============================================================ health =======

-- Reported by the heartbeat, kept on the agent row because they describe the
-- site right now, not a history worth querying.
--
-- fraction_below_gate is the one that matters: the share of faces this site's
-- cameras saw that fell under the enrolment gate. A footfall number from a
-- badly placed camera is wrong in a way nobody can see from the number itself,
-- so the figure has to travel with its own confidence. Measured on the Office1
-- camera it was 0.727 — 73% of visitors seen and discarded, while the report
-- said what looked like a quiet week.
ALTER TABLE agents ADD COLUMN fraction_below_gate real;
ALTER TABLE agents ADD COLUMN cameras_total  integer NOT NULL DEFAULT 0;
ALTER TABLE agents ADD COLUMN cameras_up     integer NOT NULL DEFAULT 0;
ALTER TABLE agents ADD COLUMN spool_queued   integer NOT NULL DEFAULT 0;
-- Events a site lost because it was offline long enough to overflow its own
-- queue. Cumulative and never reset: a footfall figure with known-lost events
-- behind it must say so.
ALTER TABLE agents ADD COLUMN spool_dropped  bigint  NOT NULL DEFAULT 0;

COMMIT;