fast-browser-with-jev
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import { BrowserOperationError } from "./contracts.ts";
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import type {
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BrowserBridge, Decision, DecisionInput, EvidenceRequest, Observation, RunResult, Step, StepTrace,
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} from "./contracts.ts";
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import { DecisionError } from "./jev.ts";
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import { CredentialError } from "./credentials.ts";
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/** Only fixed, non-sensitive messages may be used for this error type. */
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export class TextGenerationError extends Error {}
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export interface ControllerDeps {
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browser: BrowserBridge;
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decide: (input: DecisionInput, signal: AbortSignal) => Promise<Decision>;
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generateText?: (prompt: string, signal: AbortSignal) => Promise<string>;
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resolveCredential?: (name: string, signal: AbortSignal) => Promise<string>;
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/** Best-effort local failure capture; returned artifacts are never forwarded. */
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captureEvidence?: (request: EvidenceRequest, signal: AbortSignal) => Promise<unknown>;
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}
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export interface RunOptions {
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signal?: AbortSignal;
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maxSteps?: number;
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timeoutMs?: number;
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minConfidence?: number;
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/** Caller/scenario identity used only to scope local failure evidence. */
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runId?: string;
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}
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const MAX_TEXT = 8_000;
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function nonempty(value: unknown, max: number): value is string {
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return typeof value === "string" && value.trim().length > 0 && value.length <= max;
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}
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export function validateSteps(steps: Step[], maxSteps = 10): void {
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if (!Number.isInteger(maxSteps) || maxSteps < 1 || maxSteps > 10
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|| !Array.isArray(steps) || steps.length < 1 || steps.length > maxSteps) {
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throw new Error("Run requires 1–10 bounded steps");
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}
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for (const step of steps) {
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if (!step || !nonempty(step.instruction, 2_000) || !["click", "fill"].includes(step.action)) {
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throw new Error("Invalid step instruction or action");
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}
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if (step.action === "click") {
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if (step.text !== undefined || step.compose !== undefined || step.credential !== undefined || !step.postcondition) {
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throw new Error("Click requires a postcondition and no text");
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}
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} else {
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if ([step.text, step.compose, step.credential].filter((value) => value !== undefined).length !== 1) {
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throw new Error("Fill requires exactly one of text, compose, or credential");
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}
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if (step.credential !== undefined && (typeof step.credential !== "string" || !/^[A-Za-z0-9_.-]{1,100}$/.test(step.credential))) {
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throw new Error("Invalid credential reference name");
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}
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if (step.text !== undefined && (typeof step.text !== "string" || step.text.length > MAX_TEXT)) {
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throw new Error("Literal text exceeds the supported size");
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}
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if (step.compose !== undefined && !nonempty(step.compose, 2_000)) {
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throw new Error("Invalid composition instruction");
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}
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}
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if (step.postcondition) {
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const p = step.postcondition;
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if (!["url", "text"].includes(p.kind) || !nonempty(p.value, 2_000)) {
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throw new Error("Invalid postcondition");
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}
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if (p.kind === "url") {
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let url: URL;
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try { url = new URL(p.value); } catch { throw new Error("Postcondition requires an absolute URL"); }
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if (!["http:", "https:"].includes(url.protocol) || url.username || url.password) {
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throw new Error("Postcondition requires an HTTP(S) URL without credentials");
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}
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}
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}
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}
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}
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/** Validate even fake/plugin bridges: unknown IDs and malformed handles cannot reach execution. */
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export function validateObservation(value: Observation): void {
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if (!value || !nonempty(value.observationId, 200) || !nonempty(value.url, 8_000)
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|| typeof value.title !== "string" || value.title.length > 2_000
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|| !Array.isArray(value.candidates) || value.candidates.length > 60) {
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throw new Error("Invalid browser observation");
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}
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const url = new URL(value.url);
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if (!["http:", "https:"].includes(url.protocol) || url.username || url.password) {
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throw new Error("Invalid browser URL");
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}
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const ids = new Set<string>();
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for (const candidate of value.candidates) {
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if (!candidate || !nonempty(candidate.id, 200) || ids.has(candidate.id)
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|| !nonempty(candidate.role, 100) || typeof candidate.name !== "string" || candidate.name.length > 500
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|| !Array.isArray(candidate.actions) || candidate.actions.length < 1 || candidate.actions.length > 2
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|| candidate.actions.some((action) => action !== "click" && action !== "fill")) {
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throw new Error("Invalid browser candidate");
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}
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ids.add(candidate.id);
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}
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}
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/** Bound waits even if an injected adapter forgets to honor AbortSignal. */
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async function abortable<T>(signal: AbortSignal, operation: () => Promise<T>): Promise<T> {
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signal.throwIfAborted();
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return new Promise<T>((resolve, reject) => {
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let settled = false;
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const cleanup = () => signal.removeEventListener("abort", abort);
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const settleResolve = (value: T) => {
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if (settled) return;
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settled = true;
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cleanup();
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resolve(value);
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};
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const settleReject = (error: unknown) => {
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if (settled) return;
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settled = true;
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cleanup();
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reject(error);
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};
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const abort = () => settleReject(signal.reason ?? new Error("Aborted"));
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signal.addEventListener("abort", abort, { once: true });
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Promise.resolve().then(() => {
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signal.throwIfAborted();
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return operation();
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}).then(settleResolve, (error) => {
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// This handler deliberately consumes late rejection after cancellation.
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settleReject(error);
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});
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if (signal.aborted) abort();
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});
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}
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function evidenceFailureReason(error: unknown): string {
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if (error instanceof BrowserOperationError) {
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if (error.details.code === "browser_closed") return "Failure evidence unavailable: browser session is unavailable";
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if (error.details.code === "aborted") return "Failure evidence unavailable: capture was cancelled";
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if (error.details.code === "worker_failure") return "Failure evidence unavailable: browser transport is unavailable";
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}
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return "Failure evidence unavailable: browser evidence capture failed";
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}
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/** One bounded plan. Caller owns the browser lifetime and must close it in finally. */
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export async function runSteps(steps: Step[], deps: ControllerDeps, options: RunOptions = {}): Promise<RunResult> {
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validateSteps(steps, options.maxSteps ?? 10);
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const timeoutMs = options.timeoutMs ?? 60_000;
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const minConfidence = options.minConfidence ?? 0.85;
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if (!Number.isFinite(timeoutMs) || timeoutMs < 1 || timeoutMs > 120_000) throw new Error("Invalid run timeout");
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if (!Number.isFinite(minConfidence) || minConfidence < 0 || minConfidence > 1) throw new Error("Invalid confidence threshold");
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const controller = new AbortController();
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const abortParent = () => controller.abort(options.signal?.reason);
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options.signal?.addEventListener("abort", abortParent, { once: true });
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if (options.signal?.aborted) abortParent();
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let timedOut = false;
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const timer = setTimeout(() => { timedOut = true; controller.abort(new Error("Run deadline exceeded")); }, timeoutMs);
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const signal = controller.signal;
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const started = performance.now();
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const traces: StepTrace[] = [];
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const result = (status: RunResult["status"], reason: string): RunResult => ({
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status, reason, steps: traces, elapsedMs: Math.round(performance.now() - started),
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actionMayHaveExecuted: traces.some((item) => item.mutationState === "unknown"),
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});
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const captureFailure = async (operation: EvidenceRequest["operation"]): Promise<string | undefined> => {
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if (!deps.captureEvidence) return undefined;
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const controller = new AbortController();
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const timer = setTimeout(() => controller.abort(), 2_000);
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timer.unref?.();
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try {
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const evidence = await abortable(controller.signal, () => deps.captureEvidence!({
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runId: options.runId ?? `run-${Date.now()}`,
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reason: "failure",
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...(operation ? { operation } : {}),
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}, controller.signal));
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if (evidence && typeof evidence === "object" && "status" in evidence) {
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const status = (evidence as { status?: unknown }).status;
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if (status === "unavailable") return "Failure evidence unavailable: browser returned no evidence";
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if (status === "partial") return "Failure evidence partial: browser returned incomplete evidence";
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}
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return undefined;
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} catch (error) {
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return evidenceFailureReason(error);
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} finally { clearTimeout(timer); }
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};
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let phase = "observe";
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let trace: StepTrace | undefined;
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try {
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for (const [index, step] of steps.entries()) {
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trace = { step: index + 1, status: "error", timingsMs: {}, mutationState: "not_attempted" };
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traces.push(trace);
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const timed = async <T>(name: string, fn: () => Promise<T>): Promise<T> => {
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phase = name;
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const start = performance.now();
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try { return await abortable(signal, fn); }
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finally { trace!.timingsMs[name] = Math.round(performance.now() - start); }
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};
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const observation = await timed("observe", () => deps.browser.observe(signal));
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validateObservation(observation);
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const eligible = observation.candidates.filter((candidate) => candidate.actions.includes(step.action));
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if (!eligible.length) {
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trace.status = "abstained";
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return result("stopped", "No eligible controls; return to Pi for recovery");
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}
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// This shortcut is intentionally narrow: an exact, unique accessible name.
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const exact = eligible.filter((candidate) => candidate.name === step.instruction);
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const decision = exact.length === 1
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? { candidateId: exact[0].id, confidence: 1, model: "deterministic-exact-name" }
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: await timed("decide", () => deps.decide({ instruction: step.instruction, action: step.action, observation }, signal));
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signal.throwIfAborted();
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if (!decision || typeof decision.confidence !== "number" || !Number.isFinite(decision.confidence)
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|| decision.confidence < 0 || decision.confidence > 1 || !nonempty(decision.model, 100)) {
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throw new DecisionError("Malformed decision");
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}
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trace.confidence = decision.confidence;
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trace.model = decision.model;
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if (decision.candidateId === null || decision.confidence < minConfidence) {
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trace.status = "abstained";
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return result("stopped", "Decision uncertain; return to Pi for recovery");
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}
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const candidate = eligible.find((candidate) => candidate.id === decision.candidateId);
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if (!candidate) throw new DecisionError("Decision selected an unknown or ineligible candidate");
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trace.candidateId = candidate.id;
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let text = step.text;
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if (step.credential !== undefined) {
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if (!deps.resolveCredential) throw new CredentialError("No credential resolver is configured for this run");
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text = await timed("resolveCredential", () => deps.resolveCredential!(step.credential!, signal));
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if (typeof text !== "string" || text.length > MAX_TEXT) {
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throw new CredentialError("Resolved credential must be a bounded string");
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}
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}
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if (step.compose !== undefined) {
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if (!deps.generateText) return result("stopped", "Text generation model is not configured");
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text = await timed("generate", () => deps.generateText!(step.compose!, signal));
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if (!nonempty(text, MAX_TEXT)) return result("stopped", "Generated text is empty or exceeds the size limit");
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}
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const request = {
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observationId: observation.observationId,
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candidateId: candidate.id,
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action: step.action,
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...(text !== undefined ? { text } : {}),
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...(step.postcondition ? { postcondition: step.postcondition } : {}),
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};
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// The initiating caller owns authorization and supplies this bounded plan.
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// No interactive per-action permission layer is introduced here.
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signal.throwIfAborted();
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const acted = await timed("actAndVerify", async () => {
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trace!.mutationState = "unknown";
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try {
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return await deps.browser.act(request, signal);
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} catch (error) {
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// A typed pre-dispatch rejection is safe; once transport dispatch
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// began, preserve unknown and never retry the mutation.
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if (error instanceof BrowserOperationError && error.details.mutationState === "not_attempted") {
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trace!.mutationState = "not_attempted";
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}
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throw error;
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}
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});
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signal.throwIfAborted();
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if (!acted || typeof acted.verified !== "boolean" || typeof acted.evidence !== "string") {
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throw new Error("Invalid browser action result");
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}
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const safeEvidence = new Set([
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"field value verified", "field value and postcondition verified",
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"field value or postcondition could not be verified", "field value could not be verified",
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"URL postcondition verified", "visible-text postcondition verified", "click postcondition was not verified",
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]);
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trace.evidence = safeEvidence.has(acted.evidence) ? acted.evidence : (acted.verified ? "Postcondition verified" : "Postcondition not verified");
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trace.mutationState = acted.verified ? "verified" : "unknown";
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trace.status = acted.verified ? "verified" : "unverified";
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if (!acted.verified) {
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const evidenceStatus = await captureFailure("act");
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if (evidenceStatus) trace.evidence = evidenceStatus;
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return result("stopped", "Postcondition not verified; action was not retried");
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}
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}
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return result("completed", "All requested steps verified");
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} catch (error) {
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if (trace) trace.status = "error";
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if (signal.aborted) {
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const evidenceStatus = await captureFailure(phase === "actAndVerify" ? "act" : undefined);
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if (evidenceStatus && trace && !trace.evidence) trace.evidence = evidenceStatus;
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return result("stopped", timedOut
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? "Run deadline exceeded; an in-flight action may have executed, inspect before retrying"
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: "Run cancelled; an in-flight action may have executed, inspect before retrying");
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}
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const evidenceStatus = await captureFailure(phase === "actAndVerify" ? "act" : undefined);
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if (evidenceStatus && trace && !trace.evidence) trace.evidence = evidenceStatus;
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const detail = error instanceof DecisionError || error instanceof TextGenerationError || error instanceof CredentialError
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? error.message
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: error instanceof BrowserOperationError ? error.details.message : "operation failed";
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return result("stopped", `${phase}: ${detail}; no action retried`);
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} finally {
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clearTimeout(timer);
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options.signal?.removeEventListener("abort", abortParent);
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// End the lifetime of every adapter operation belonging to this run.
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controller.abort(new Error("Run finished"));
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}
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}
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