import * as path from "node:path";
import { parseExternalCliJsonlEvent, type ExternalCliParser, type ExternalCliParserProgress, type ExternalCliParserTerminal } from "./external-cli-runner.ts";
import type { ExternalCliPreflightSpec } from "./external-cli-preflight.ts";

const MAX_EVENT_TYPE_LENGTH = 128;
const MAX_ERROR_LENGTH = 4_096;
const MAX_OVERSIZED_TOOL_CALL_BYTES = 1024 * 1024;

export const CURSOR_AGENT_ADAPTER_ID = "cursor-agent" as const;
export const CURSOR_AGENT_WRITER_ADAPTER_ID = "cursor-agent-writer" as const;
export const CURSOR_AGENT_ENV_ALLOWLIST = [
	"PATH",
	"HOME",
	"USERPROFILE",
	"CURSOR_API_KEY",
	"HTTP_PROXY",
	"HTTPS_PROXY",
	"NO_PROXY",
	"http_proxy",
	"https_proxy",
	"no_proxy",
	"SSL_CERT_FILE",
	"SSL_CERT_DIR",
] as const;

function terminalError(event: Record<string, unknown>): string {
	for (const value of [event.result, event.error, event.message]) {
		if (typeof value === "string" && value.trim()) return value.trim().slice(0, MAX_ERROR_LENGTH);
	}
	const subtype = typeof event.subtype === "string" && event.subtype ? event.subtype : "unknown";
	return `Cursor Agent reported terminal result ${subtype}.`;
}

export function createCursorAgentJsonlParser(): ExternalCliParser {
	let eventCount = 0;
	let terminal: ExternalCliParserTerminal | undefined;
	return {
		parseLine(line): ExternalCliParserProgress {
			const event = parseExternalCliJsonlEvent(line, "Cursor Agent", MAX_EVENT_TYPE_LENGTH);
			if (terminal) throw new Error("Cursor Agent emitted an event after its terminal state.");
			eventCount += 1;
			if (event.type === "error") terminal = { state: "failed", error: terminalError(event) };
			else if (event.type === "result") {
				if (event.subtype === "success" && event.is_error === false && typeof event.result === "string" && event.result.trim()) {
					terminal = { state: "completed", output: event.result.trim() };
				} else terminal = { state: "failed", error: terminalError(event) };
			}
			return { phase: terminal ? terminal.state : "streaming", eventCount };
		},
		skipOversizedLine(prefix, byteLength): ExternalCliParserProgress | undefined {
			if (terminal || byteLength > MAX_OVERSIZED_TOOL_CALL_BYTES || !/^\s*\{\s*"type"\s*:\s*"tool_call"\s*,/.test(prefix)) return undefined;
			eventCount += 1;
			return { phase: "streaming", eventCount };
		},
		finish(): ExternalCliParserTerminal | undefined {
			return terminal;
		},
	};
}

export function resolveCursorAgentLaunch(input: {
	adapter: typeof CURSOR_AGENT_ADAPTER_ID | typeof CURSOR_AGENT_WRITER_ADAPTER_ID;
	command: string;
	cwd: string;
	asyncDir: string;
	stepIndex: number;
	/** Test-only executable prefix for a fake Cursor Agent process. */
	commandPrefixArgs?: readonly string[];
}): {
	command: string;
	args: string[];
	finalOutputPath?: undefined;
	promptFilePath: string;
	temporaryDirectories: string[];
	environment: { allowlist: readonly string[] };
	preflight: ExternalCliPreflightSpec;
	parser: ExternalCliParser;
} {
	const writer = input.adapter === CURSOR_AGENT_WRITER_ADAPTER_ID;
	const promptDirectory = path.join(input.asyncDir, `external-${input.stepIndex}.cursor-prompt`);
	const promptFilePath = path.join(promptDirectory, "handoff.txt");
	const promptRelative = path.relative(input.cwd, promptDirectory);
	const promptOutsideWorkspace = promptRelative.startsWith("..") || path.isAbsolute(promptRelative);
	const prefix = [...(input.commandPrefixArgs ?? [])];
	const args = [
		...prefix,
		"-p",
		"--output-format", "stream-json",
		...(writer ? [] : ["--mode", "ask"]),
		"--sandbox", "enabled",
		"--workspace", input.cwd,
		...(promptOutsideWorkspace ? ["--add-dir", promptDirectory] : []),
		`Read the complete handoff from the private file at ${promptFilePath}. Follow it and return only the final answer.`,
	];
	return {
		command: input.command,
		args,
		promptFilePath,
		temporaryDirectories: [promptDirectory],
		environment: { allowlist: CURSOR_AGENT_ENV_ALLOWLIST },
		preflight: {
			id: input.adapter,
			versionArgs: [...prefix, "--version"],
			helpArgs: [...prefix, "--help"],
			validate(result) {
				if (!/^\d{4}\.\d{2}\.\d{2}-[0-9a-f]+$/.test(result.version)) throw new Error(`Unsupported Cursor Agent version response: ${JSON.stringify(result.version)}.`);
				for (const required of ["Start the Cursor Agent", "--print", "stream-json", "--sandbox <mode>", "enabled", "--workspace <path-or-name>", "--add-dir <path>", ...(writer ? ["all tools", "including write and shell"] : ["--mode <mode>", "ask:", "read-only"])]) {
					if (!result.help.includes(required)) throw new Error(`Cursor Agent help does not document required option ${JSON.stringify(required)}.`);
				}
			},
		},
		parser: createCursorAgentJsonlParser(),
	};
}