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import { type Result, err, ok } from "./util/result";
import { safeJs } from "./util/js-template";
import { discoverWsUrl } from "./cdp/discovery";
import { type CdpError, cdpError } from "./cdp/errors";
import type { CdpTransport } from "./cdp/transport";
import { createCdpTransport } from "./cdp/transport";
import { type CdpSession, createCdpSession } from "./cdp/session";
import type { DaemonStatus, DialogInfo, PageInfo, TabInfo } from "./cdp/types";
export type BrowserClientOptions = {
readonly namespace: string;
readonly remote?: { readonly cdpUrl: string; readonly browserId: string };
};
export type BrowserClient = {
readonly namespace: string;
ensureAlive(): Promise<Result<void, CdpError>>;
status(): DaemonStatus;
start(): Promise<Result<void, CdpError>>;
stop(): Promise<void>;
evaluateJs(expression: string, sessionId?: string): Promise<Result<unknown, CdpError>>;
pageInfo(): Promise<Result<PageInfo | { readonly dialog: DialogInfo }, CdpError>>;
takeDialog(): DialogInfo | null;
listTabs(includeInternal?: boolean): Promise<Result<ReadonlyArray<TabInfo>, CdpError>>;
switchTab(targetId: string): Promise<Result<void, CdpError>>;
newTab(url?: string): Promise<Result<string, CdpError>>;
current(): { readonly sessionId: string; readonly targetId: string } | null;
session(): CdpSession;
transport(): CdpTransport;
};
const HEALTH_TTL_MS = 30_000;
const PAGE_INFO_TTL_MS = 1_000;
const parsePageInfoPayload = (v: unknown): Result<PageInfo, CdpError> => {
if (typeof v !== "object" || v === null) {
return err(cdpError("invalid_response", "page info payload is not an object"));
}
const o = v as Readonly<Record<string, unknown>>;
const fields: ReadonlyArray<readonly [string, "string" | "number"]> = [
["url", "string"], ["title", "string"],
["w", "number"], ["h", "number"],
["sx", "number"], ["sy", "number"],
["pw", "number"], ["ph", "number"],
];
for (const [k, t] of fields) {
if (typeof o[k] !== t) {
return err(cdpError("invalid_response", `page info field ${k} has wrong type (expected ${t})`));
}
}
return ok({
url: o["url"] as string,
title: o["title"] as string,
width: o["w"] as number,
height: o["h"] as number,
scrollX: o["sx"] as number,
scrollY: o["sy"] as number,
pageWidth: o["pw"] as number,
pageHeight: o["ph"] as number,
});
};
export const createBrowserClient = (opts: BrowserClientOptions): BrowserClient => {
const transport = createCdpTransport();
const session = createCdpSession(transport);
let lastHealth = 0;
let pageCache: { readonly info: PageInfo; readonly at: number } | null = null;
let remote: BrowserClientOptions["remote"] | null = opts.remote ?? null;
const start = async (): Promise<Result<void, CdpError>> => {
if (transport.state() === "open" && session.current()) return ok(undefined);
const envUrl = process.env["BU_CDP_WS"];
let wsUrl: string;
if (remote?.cdpUrl) {
wsUrl = remote.cdpUrl;
} else if (envUrl) {
wsUrl = envUrl;
} else {
const discovered = await discoverWsUrl();
if (!discovered.success) return discovered;
wsUrl = discovered.data;
}
const connected = await transport.connect(wsUrl, { timeoutMs: 10_000 });
if (!connected.success) return connected;
if (!remote) {
remote = { cdpUrl: wsUrl, browserId: wsUrl.split("/").pop() ?? "unknown" };
}
const attached = await session.attachFirstPage();
if (!attached.success) {
await transport.close();
return attached;
}
lastHealth = Date.now();
pageCache = null;
return ok(undefined);
};
const stop = async (): Promise<void> => {
await transport.close();
pageCache = null;
lastHealth = 0;
};
const ensureAlive = async (): Promise<Result<void, CdpError>> => {
if (transport.state() !== "open" || !session.current()) {
await stop();
return start();
}
if (Date.now() - lastHealth < HEALTH_TTL_MS) return ok(undefined);
const probe = await transport.request("Target.getTargets", {}, { sessionId: null, timeoutMs: 2_000 });
if (probe.success) {
lastHealth = Date.now();
return ok(undefined);
}
await stop();
return start();
};
const evaluateJs = async (expression: string, sessionId?: string): Promise<Result<unknown, CdpError>> => {
const wrapped = expression.includes("return ") && !expression.trim().startsWith("(")
? `(function(){${expression}})()`
: expression;
const r = sessionId
? await session.callOnTarget("Runtime.evaluate", { expression: wrapped, returnByValue: true, awaitPromise: true }, sessionId)
: await session.call("Runtime.evaluate", { expression: wrapped, returnByValue: true, awaitPromise: true });
if (!r.success) return r;
const data = r.data as { result?: { value?: unknown }; exceptionDetails?: unknown };
if (data.exceptionDetails) {
return err(cdpError("remote_error", `JS evaluation failed: ${JSON.stringify(data.exceptionDetails)}`, "Runtime.evaluate"));
}
return ok(data.result?.value);
};
const readPageInfo = async (): Promise<Result<PageInfo, CdpError>> => {
const dirty = session.drainPageInfoInvalidations();
if (pageCache && !dirty && Date.now() - pageCache.at < PAGE_INFO_TTL_MS) return ok(pageCache.info);
const expr = safeJs`JSON.stringify({url:location.href,title:document.title,w:innerWidth,h:innerHeight,sx:scrollX,sy:scrollY,pw:document.documentElement.scrollWidth,ph:document.documentElement.scrollHeight})`;
const raw = await evaluateJs(expr);
if (!raw.success) return raw;
if (typeof raw.data !== "string") return err(cdpError("invalid_response", "page info evaluation did not return a string"));
let parsedRaw: unknown;
try {
parsedRaw = JSON.parse(raw.data);
} catch (e) {
return err(cdpError("invalid_response", `page info JSON.parse failed: ${e instanceof Error ? e.message : String(e)}`));
}
const info = parsePageInfoPayload(parsedRaw);
if (!info.success) return info;
pageCache = { info: info.data, at: Date.now() };
return ok(info.data);
};
const pageInfo = async (): Promise<Result<PageInfo | { readonly dialog: DialogInfo }, CdpError>> => {
const d = session.takeDialog();
if (d) return ok({ dialog: d });
return readPageInfo();
};
const listTabs = async (includeInternal = true): Promise<Result<ReadonlyArray<TabInfo>, CdpError>> => {
const r = await session.callBrowser("Target.getTargets");
if (!r.success) return r;
const data = r.data as { targetInfos: ReadonlyArray<{ targetId: string; type: string; title: string; url: string }> };
const tabs = data.targetInfos
.filter((t) => t.type === "page")
.filter((t) => includeInternal || !t.url.startsWith("chrome://"))
.map((t): TabInfo => ({ targetId: t.targetId, title: t.title, url: t.url }));
return ok(tabs);
};
const switchTab = async (targetId: string): Promise<Result<void, CdpError>> => {
const r = await session.switchTo(targetId);
if (!r.success) return r;
pageCache = null;
// Best-effort: mark the tab title with a green circle so the user can
// see which tab the agent attached to. CSP or detached frames may
// block the eval; we don't surface that as a switchTab failure.
await session.call("Runtime.evaluate", {
expression: safeJs`if(!document.title.startsWith('🟢'))document.title='🟢 '+document.title`,
});
return ok(undefined);
};
const newTab = async (url?: string): Promise<Result<string, CdpError>> => {
const created = await session.callBrowser("Target.createTarget", { url: "about:blank" });
if (!created.success) return created;
const c = created.data as { targetId: string };
const switched = await switchTab(c.targetId);
if (!switched.success) return switched;
if (url && url !== "about:blank") {
const nav = await session.call("Page.navigate", { url });
if (!nav.success) return nav;
pageCache = null;
}
return ok(c.targetId);
};
const status = (): DaemonStatus => ({
alive: transport.state() === "open" && session.current() !== null,
sessionId: session.current()?.sessionId ?? null,
namespace: opts.namespace,
...(remote?.browserId !== undefined ? { remoteBrowserId: remote.browserId } : {}),
});
return {
namespace: opts.namespace,
ensureAlive, status, start, stop,
evaluateJs, pageInfo,
takeDialog: () => session.takeDialog(),
listTabs, switchTab, newTab,
current: () => session.current(),
session: () => session,
transport: () => transport,
};
};
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