feat(kernel): extension host — discovery, DAG resolve, apiVersion check, activate, HostAPI (wraps bus); 50 tests

1 files changed, 64 insertions, 0 deletions

diff --git a/packages/kernel/src/host/dag.ts b/packages/kernel/src/host/dag.ts
new file mode 100644
index 0000000..5cde2f5
--- /dev/null
+++ b/packages/kernel/src/host/dag.ts
@@ -0,0 +1,64 @@
+import type { Manifest } from "../contracts/extension.js";
+
+export function resolveActivationOrder(manifests: readonly Manifest[]): Manifest[] {
+	const byId = new Map<string, Manifest>();
+	for (const m of manifests) {
+		if (byId.has(m.id)) {
+			throw new Error(`Duplicate extension id: "${m.id}"`);
+		}
+		byId.set(m.id, m);
+	}
+
+	for (const m of manifests) {
+		for (const dep of m.dependsOn ?? []) {
+			if (!byId.has(dep)) {
+				throw new Error(`Extension "${m.id}" depends on "${dep}", which is not available.`);
+			}
+		}
+	}
+
+	const inDegree = new Map<string, number>();
+	const dependents = new Map<string, string[]>();
+
+	for (const m of manifests) {
+		inDegree.set(m.id, 0);
+		dependents.set(m.id, []);
+	}
+
+	for (const m of manifests) {
+		for (const dep of m.dependsOn ?? []) {
+			const list = dependents.get(dep);
+			if (list !== undefined) list.push(m.id);
+			inDegree.set(m.id, (inDegree.get(m.id) ?? 0) + 1);
+		}
+	}
+
+	const queue: string[] = [];
+	for (const [id, deg] of inDegree) {
+		if (deg === 0) queue.push(id);
+	}
+
+	const result: Manifest[] = [];
+	let idx = 0;
+	while (idx < queue.length) {
+		const id = queue[idx];
+		if (id === undefined) break;
+		idx++;
+		const m = byId.get(id);
+		if (m === undefined) continue;
+		result.push(m);
+		for (const dep of dependents.get(id) ?? []) {
+			const newDeg = (inDegree.get(dep) ?? 1) - 1;
+			inDegree.set(dep, newDeg);
+			if (newDeg === 0) queue.push(dep);
+		}
+	}
+
+	if (result.length !== manifests.length) {
+		const remaining = manifests.filter((m) => !result.some((r) => r.id === m.id));
+		const ids = remaining.map((m) => m.id).join(", ");
+		throw new Error(`Dependency cycle detected among extensions: ${ids}`);
+	}
+
+	return result;
+}