-- The latest still frame from each camera, held by the server itself.
--
-- Camera snapshots already worked, through the same presigned-URL path face
-- images use: the agent asks for a URL, PUTs the JPEG to object storage, and
-- the server presigns a short-lived link when somebody looks. That is the right
-- design for face images - one per visit, unbounded, and they must never touch
-- a shop PC's disk or the server's.
--
-- It is the wrong design for the ONE case where a deployment has no object
-- storage at all. Head office then reports "This system is not storing images"
-- for every camera, forever, on a screen whose whole point is to SHOW the
-- camera. A self-hosted customer who does not want an S3 bucket, and every
-- local install, got a wall of empty tiles.
--
-- What makes this safe to put in the database, when face images are not:
--
--   * ONE ROW PER CAMERA. The primary key is the camera, so a snapshot
--     replaces its predecessor. An estate's storage is (cameras x ~100 KB)
--     and does not grow with time or with footfall. Face images grow with
--     every visitor who ever walks in, which is why they stay in a bucket.
--   * It is a picture of a shop floor, not a face crop attached to an
--     identity. It carries no template and is not tied to a person.
--   * ON DELETE CASCADE from the camera. Removing a camera removes its
--     picture, with no second place to remember to clean up.
--
-- When object storage IS configured nothing changes: the bucket path stays
-- primary and this table is not written.

BEGIN;

CREATE TABLE IF NOT EXISTS camera_snapshots (
    camera_id   uuid PRIMARY KEY REFERENCES site_cameras(id) ON DELETE CASCADE,
    -- Denormalised deliberately, like every other table here: a cross-tenant
    -- read should require a wrong WHERE clause rather than a forgotten join.
    client_id   uuid        NOT NULL REFERENCES clients(id) ON DELETE CASCADE,
    site_id     uuid        NOT NULL REFERENCES sites(id)   ON DELETE CASCADE,
    image       bytea       NOT NULL,
    bytes       integer     NOT NULL,
    captured_at timestamptz NOT NULL DEFAULT now()
);

CREATE INDEX IF NOT EXISTS camera_snapshots_client_idx
    ON camera_snapshots (client_id);

COMMIT;