learnharness/app/api/chats/[id]/route.ts

import { deleteChatSession, getChat, isTurnRunning, sessionCoverage, stores, type ChatDeleteMode } from "@/src/server";
import { projectNative } from "@/src/core";

export async function GET(_req: Request, { params }: { params: Promise<{ id: string }> }) {
	const { id } = await params;
	const chat = getChat(id);
	if (!chat) return Response.json({ error: "Not found" }, { status: 404 });
	// turnInFlight lets a returning client re-attach to a running turn
	// (chat-handler write-ahead + registry — see src/server/turn-liveness.ts).
	// coverage (extraction-UX redesign, 2026-09-24): the chat view's ring
	// meter + sidebar block — THE coverage surface (the all-sessions GET
	// route died with the redesign; the Extract POST stays). getChat
	// already 404'd, so the block exists.
	// Wave B (owner-approved 2026-09-26): the record's messages are native
	// agent history — clients receive the one-way projection (the AI-SDK
	// UIMessage view) until Wave D. turnInFlight lets a returning client
	// re-attach to a running turn; coverage is the chat view's ring meter.
	return Response.json({
		...chat,
		messages: projectNative(chat.messages),
		turnInFlight: isTurnRunning(id),
		coverage: sessionCoverage(id),
	});
}

/**
 * Rename (2026-09-17): the header's click-to-edit title commits here.
 * Validation is a single rule — a non-empty string after trim (the store's
 * "Untitled session" floor is never reached from this route). updatedAt is
 * deliberately NOT bumped: a rename must not reorder the sidebar (same
 * rule as the settings PUT).
 */
export async function PUT(req: Request, { params }: { params: Promise<{ id: string }> }) {
	const { id } = await params;
	if (!getChat(id)) return Response.json({ error: "Not found" }, { status: 404 });
	const body = (await req.json().catch(() => null)) as { title?: unknown } | null;
	if (typeof body?.title !== "string" || body.title.trim() === "") {
		return Response.json({ error: "title must be a non-empty string" }, { status: 400 });
	}
	const title = body.title.trim();
	const record = stores.chatStore.renameChat(id, title);
	return Response.json({ title: record.title });
}

/**
 * DELETE /api/chats/[id]?mode=preserve-graph|delete-nodes — session deletion
 * (wave 6, owner rulings 2026-09-22/23). The mode is REQUIRED and explicit:
 * no default, because the two differ in destructiveness —
 *
 *   preserve-graph  the session record, its jobs, and its extraction
 *                   bookkeeping (coverage/checkpoint rows) die; the graph
 *                   keeps every contribution the session merged.
 *   delete-nodes    "this session never happened": every ledger trace of
 *                   the session goes too — provenance, link lines,
 *                   events, mappings — and orphaned nodes die entirely
 *                   (shared nodes survive automatically, their other
 *                   sessions' content intact).
 *
 * Gates are the server orchestration's (server/chats.ts deleteChatSession):
 * 409 while a turn or background job is running, 503 while the session's
 * extraction is winding down after its abort — both retryable. The
 * response carries what was removed plus the new graphRevision (the
 * version stamp the UI polls to refetch clusters/layout).
 */
export async function DELETE(req: Request, { params }: { params: Promise<{ id: string }> }) {
	const { id } = await params;
	const mode = new URL(req.url).searchParams.get("mode");
	if (mode !== "preserve-graph" && mode !== "delete-nodes") {
		return Response.json(
			{
				error: 'mode is required and must be "preserve-graph" or "delete-nodes"',
				code: "bad_mode",
			},
			{ status: 400 },
		);
	}
	const outcome = await deleteChatSession(id, mode as ChatDeleteMode);
	if (!outcome.ok) {
		return Response.json(
			{
				error: outcome.error,
				code: outcome.code,
				...("jobIds" in outcome ? { jobIds: outcome.jobIds } : {}),
		},
			{ status: outcome.status },
		);
	}
	return Response.json({
		ok: true,
		mode: outcome.mode,
		stats: outcome.stats,
		jobsRemoved: outcome.jobsRemoved,
		graphRevision: outcome.graphRevision,
	});
}