| 1 | /** |
| 2 | * JSON-RPC 2.0 peer over the `CWX1` channel. |
| 3 | * |
| 4 | * Every inbound request gets an `AbortController`; `$/cancel {id}` from the |
| 5 | * core aborts it. The core resolves a cancelled call on its own side after a |
| 6 | * 500 ms grace, so a late answer here is harmless (the core drops it). |
| 7 | */ |
| 8 | import { ErrorCode, MAX_INFLIGHT, validateMessage, type HostTier, type Message, type RpcErrorWire } from './protocol.ts' |
| 9 | |
| 10 | export class RpcError extends Error { |
| 11 | constructor( |
| 12 | readonly code: number, |
| 13 | message: string, |
| 14 | readonly data?: unknown, |
| 15 | ) { |
| 16 | super(message) |
| 17 | this.name = 'RpcError' |
| 18 | } |
| 19 | |
| 20 | toWire(): RpcErrorWire { |
| 21 | return this.data === undefined |
| 22 | ? { code: this.code, message: this.message } |
| 23 | : { code: this.code, message: this.message, data: this.data as never } |
| 24 | } |
| 25 | } |
| 26 | |
| 27 | export interface RequestContext { |
| 28 | id: number |
| 29 | signal: AbortSignal |
| 30 | } |
| 31 | |
| 32 | type RequestHandler = (params: any, cx: RequestContext) => Promise<unknown> | unknown |
| 33 | type NotificationHandler = (params: any) => void |
| 34 | |
| 35 | export class RpcPeer { |
| 36 | private nextId = 1 |
| 37 | private readonly pending = new Map<number, { resolve: (v: any) => void; reject: (e: Error) => void }>() |
| 38 | private readonly inbound = new Map<number, AbortController>() |
| 39 | private readonly requestHandlers = new Map<string, RequestHandler>() |
| 40 | private readonly notificationHandlers = new Map<string, NotificationHandler>() |
| 41 | private closed = false |
| 42 | |
| 43 | constructor( |
| 44 | private readonly send: (message: Message) => void, |
| 45 | /** The trust tier this host serves: methods reserved for the other tier are neither sent nor accepted. */ |
| 46 | private readonly tier: HostTier, |
| 47 | ) {} |
| 48 | |
| 49 | onRequest(method: string, handler: RequestHandler) { |
| 50 | this.requestHandlers.set(method, handler) |
| 51 | } |
| 52 | |
| 53 | onNotification(method: string, handler: NotificationHandler) { |
| 54 | this.notificationHandlers.set(method, handler) |
| 55 | } |
| 56 | |
| 57 | /** |
| 58 | * Send a host→core request. Outbound messages are validated strictly first. |
| 59 | * When `signal` aborts before the answer, the core is sent `$/cancel` for it |
| 60 | * and the promise rejects as cancelled at once; an answer that still arrives |
| 61 | * is dropped (the core drops its own after a cancel as well). |
| 62 | */ |
| 63 | request<T = any>(method: string, params: unknown, signal?: AbortSignal): Promise<T> { |
| 64 | if (this.closed) return Promise.reject(new RpcError(ErrorCode.NotAvailable, 'channel closed')) |
| 65 | if (signal?.aborted) return Promise.reject(new RpcError(ErrorCode.Cancelled, 'cancelled')) |
| 66 | // The core's per-direction limit. |
| 67 | if (this.pending.size >= MAX_INFLIGHT) { |
| 68 | return Promise.reject(new RpcError(ErrorCode.Internal, `more than ${MAX_INFLIGHT} requests in flight`)) |
| 69 | } |
| 70 | const id = this.nextId++ |
| 71 | const message = { jsonrpc: '2.0' as const, id, method, params } |
| 72 | validateMessage(message, 'host_to_core', this.tier) |
| 73 | return new Promise<T>((resolve, reject) => { |
| 74 | const onAbort = () => { |
| 75 | if (!this.pending.delete(id)) return |
| 76 | this.notify('$/cancel', { id }) |
| 77 | reject(new RpcError(ErrorCode.Cancelled, 'cancelled')) |
| 78 | } |
| 79 | this.pending.set(id, { |
| 80 | resolve: (value) => { |
| 81 | signal?.removeEventListener('abort', onAbort) |
| 82 | resolve(value) |
| 83 | }, |
| 84 | reject: (error) => { |
| 85 | signal?.removeEventListener('abort', onAbort) |
| 86 | reject(error) |
| 87 | }, |
| 88 | }) |
| 89 | signal?.addEventListener('abort', onAbort, { once: true }) |
| 90 | this.send(message) |
| 91 | }) |
| 92 | } |
| 93 | |
| 94 | notify(method: string, params: unknown) { |
| 95 | if (this.closed) return |
| 96 | const message = { jsonrpc: '2.0' as const, method, params } |
| 97 | validateMessage(message, 'host_to_core', this.tier) |
| 98 | this.send(message) |
| 99 | } |
| 100 | |
| 101 | /** Dispatch one decoded core→host message. Throws `ProtocolError` for malformed input. */ |
| 102 | handle(raw: unknown) { |
| 103 | const message = validateMessage(raw, 'core_to_host', this.tier) as any |
| 104 | if ('method' in message) { |
| 105 | if (message.method === '$/cancel') { |
| 106 | this.inbound.get(message.params.id)?.abort() |
| 107 | return |
| 108 | } |
| 109 | if ('id' in message) { |
| 110 | void this.dispatchRequest(message.id, message.method, message.params ?? {}) |
| 111 | return |
| 112 | } |
| 113 | this.notificationHandlers.get(message.method)?.(message.params ?? {}) |
| 114 | return |
| 115 | } |
| 116 | const waiter = this.pending.get(message.id) |
| 117 | if (!waiter) return |
| 118 | this.pending.delete(message.id) |
| 119 | if ('error' in message) { |
| 120 | waiter.reject(new RpcError(message.error.code, message.error.message, message.error.data)) |
| 121 | } else { |
| 122 | waiter.resolve(message.result) |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | /** Fail every outbound request; used when the channel closes. */ |
| 127 | close(reason: string) { |
| 128 | this.closed = true |
| 129 | for (const [, waiter] of this.pending) waiter.reject(new RpcError(ErrorCode.NotAvailable, reason)) |
| 130 | this.pending.clear() |
| 131 | for (const [, controller] of this.inbound) controller.abort() |
| 132 | } |
| 133 | |
| 134 | private async dispatchRequest(id: number, method: string, params: unknown) { |
| 135 | const handler = this.requestHandlers.get(method) |
| 136 | if (!handler) { |
| 137 | this.reply(id, undefined, new RpcError(ErrorCode.MethodNotFound, `no handler for \`${method}\``)) |
| 138 | return |
| 139 | } |
| 140 | const controller = new AbortController() |
| 141 | this.inbound.set(id, controller) |
| 142 | try { |
| 143 | const result = await handler(params, { id, signal: controller.signal }) |
| 144 | this.reply(id, result ?? {}) |
| 145 | } catch (error) { |
| 146 | this.reply(id, undefined, toRpcError(error, controller.signal)) |
| 147 | } finally { |
| 148 | this.inbound.delete(id) |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | private reply(id: number, result: unknown, error?: RpcError) { |
| 153 | if (this.closed) return |
| 154 | this.send(error ? { jsonrpc: '2.0', id, error: error.toWire() } : { jsonrpc: '2.0', id, result }) |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | export function toRpcError(error: unknown, signal?: AbortSignal): RpcError { |
| 159 | if (error instanceof RpcError) return error |
| 160 | if (signal?.aborted) return new RpcError(ErrorCode.Cancelled, 'cancelled') |
| 161 | const message = error instanceof Error ? `${error.name}: ${error.message}` : String(error) |
| 162 | return new RpcError(ErrorCode.ExecutionFailed, message.slice(0, 4096)) |
| 163 | } |
| 164 |