Return an HTTP response to the caller

CREATE TABLE orders AS SELECT * FROM (VALUES
  (1,  'Alice Ng',      'north', DATE '2026-01-03', 120.00, 'widget', 'a|b',   '{"channel":"web","items":[1,2]}'),
  (2,  'alice ng',      'north', DATE '2026-01-05',  80.50, 'gadget', 'b',     '{"channel":"shop","items":[3]}'),
  (3,  'Bob  Okafor',   'south', DATE '2026-01-05', 300.00, 'widget', 'a|c',   '{"channel":"web","items":[4,5,6]}'),
  (4,  'Carla Díaz',    'east',  DATE '2026-01-09',  NULL,  'gizmo',  NULL,    '{"channel":"web","items":[]}'),
  (5,  'Bob Okafor',    'south', DATE '2026-01-12',  45.25, 'gadget', 'c',     '{"channel":"phone","items":[7]}'),
  (6,  'Dev Patel',     'west',  DATE '2026-01-12', 510.00, 'widget', 'a',     '{"channel":"web","items":[8,9]}'),
  (7,  'Carla Diaz',    'east',  DATE '2026-01-20',  99.99, 'gizmo',  'b|c',   '{"channel":"shop","items":[10]}'),
  (8,  'Dev Patel',     'west',  DATE '2026-02-02', 510.00, 'widget', 'a',     '{"channel":"web","items":[8,9]}'),
  (9,  'Eve Larsen',    NULL,    DATE '2026-02-03',  15.00, 'gadget', NULL,    '{"channel":"web","items":[11]}'),
  (10, 'Alice Ng',      'north', DATE '2026-02-10', 220.00, 'gizmo',  'a|b|c', '{"channel":"phone","items":[12,13]}')
) t(order_id, customer, region, order_date, amount, product, tags, meta);

CREATE TEMP TABLE requests AS SELECT * FROM (VALUES (1, 6), (2, 4), (3, 99)) t(request_id, order_id);
-- a found order is a 200 with its JSON; one that is not found is a 404 with an error body
CREATE TEMP TABLE responses AS
SELECT r.request_id,
       CASE WHEN o.order_id IS NULL THEN 404 ELSE 200 END AS status,
       CASE WHEN o.order_id IS NULL THEN to_json({'error': 'order ' || r.order_id || ' not found'})::VARCHAR
            ELSE to_json({'order_id': o.order_id, 'customer': o.customer, 'amount': o.amount})::VARCHAR END AS body
FROM requests r LEFT JOIN orders o USING (order_id);
CREATE TEMP TABLE result AS
SELECT request_id, status,
       MAP {'Content-Type': 'application/json; charset=utf-8', 'Content-Length': octet_length(encode(body))::VARCHAR} AS headers, body,
       'HTTP/1.1 ' || status || ' ' || CASE status WHEN 200 THEN 'OK' WHEN 404 THEN 'Not Found' END || chr(13) || chr(10)
         || 'Content-Type: application/json; charset=utf-8' || chr(13) || chr(10)
         || 'Content-Length: ' || octet_length(encode(body)) || chr(13) || chr(10) || chr(13) || chr(10) || body AS wire
FROM responses;
SELECT request_id, status, headers, body FROM result ORDER BY request_id;
SELECT CASE WHEN ((SELECT list(status ORDER BY request_id) FROM result) = [200, 200, 404] AND (SELECT headers['Content-Length'] FROM result WHERE request_id = 2) = '53' AND (SELECT wire FROM result WHERE request_id = 3) = 'HTTP/1.1 404 Not Found' || chr(13) || chr(10) || 'Content-Type: application/json; charset=utf-8' || chr(13) || chr(10) || 'Content-Length: 30' || chr(13) || chr(10) || chr(13) || chr(10) || '{"error":"order 99 not found"}' AND (SELECT body FROM result WHERE request_id = 2) = '{"order_id":4,"customer":"Carla Díaz","amount":null}') THEN 'as expected' ELSE error('the requests did not get a 200, a 200 and a 404 with a Content-Length counted in bytes and the response laid out as HTTP') END AS verdict;