Implement db.project.delete().

Removes a project from the database, but only if the project is
empty, i.e., it has no preplots, no lines and no events in its
log (except deleted).

lib/www/server/lib/db/project/delete.js

@@ -0,0 +1,56 @@
+const { setSurvey, pid2schema, pool } = require('../connection');
+const event = require('../event');
+const getSummary = require('./summary').get;
+
+// Returns true if the project has no
+// preplots, sequences or log entries,
+// or if the project ID is not found
+// in the database.
+async function isDeletable (projectId) {
+	let summary;
+
+	try {
+		summary = await getSummary(projectId);
+	} catch (err) {
+		if (err.code == "42P01") {
+			// Project does not exist
+			return true;
+		} else {
+			throw err;
+		}
+	}
+
+	if (!summary) {
+		// projectId does not exist in the database
+		return true;
+	}
+
+	if (summary.total == 0 && summary.seq_raw == 0 && summary.seq_final == 0 && !summary.prod_duration) {
+		// Check for existing events (excluding deleted)
+		const events = await event.list(projectId, {limit: 1});
+		return events.length == 0;
+	}
+	return false;
+};
+
+async function del (projectId, opts = {}) {
+	if (await isDeletable(projectId)) {
+		const schema = await pid2schema(projectId);
+		if (schema) {
+			// NOTE: Should be reasonably safe as `schema` is not
+			// under user control.
+			const sql = `
+				DROP SCHEMA ${schema} CASCADE;
+				DELETE FROM public.projects WHERE schema = '${schema}';
+
+			`;
+			console.log(sql);
+			await pool.query(sql);
+		}
+		// We don't care if schema does not exist
+	} else {
+		throw { status: 405, message: "Project is not empty" }
+	}
+}
+
+module.exports = del;