Implement endpoint for QC deletion.

Closes #217.

lib/www/server/lib/db/qc/results/delete.js

@@ -0,0 +1,69 @@
+const { setSurvey, transaction } = require('../../connection');
+
+async function del (projectId, sequenceId, opts = {}) {
+	const client = await setSurvey(projectId);
+
+	await transaction.begin(client);
+
+	if (sequenceId) {
+
+		const queries = [
+			`
+				UPDATE raw_lines
+				SET meta = meta - 'lastQCHash'
+				WHERE sequence = $1;
+			`,
+			`
+				DELETE
+				FROM event_log_full
+				WHERE
+					sequence = $1 AND meta ? 'qc_id';
+			`,
+			`
+				UPDATE info
+				SET value = value - 'hash'
+				WHERE key = 'qc'
+				-- Consume the parameter that we are passing
+				AND $1 = $1;
+			`
+		];
+
+		const values = [ sequenceId ];
+
+		for (const text of queries) {
+			await client.query(text, values);
+		}
+
+	} else {
+
+		const queries = [
+			`
+				UPDATE raw_lines
+				SET meta = meta - 'lastQCHash';
+			`,
+			`
+				DELETE
+				FROM event_log_full
+				WHERE
+					meta ? 'qc_id';
+			`,
+			`
+				UPDATE info
+				SET value = value - 'hash'
+				WHERE key = 'qc';
+			`
+		];
+
+		for (const text of queries) {
+			await client.query(text);
+		}
+
+	}
+
+	await transaction.commit(client);
+	client.release();
+
+	return;
+}
+
+module.exports = del;