/**
 * Nightshift configuration: defaults + validation (pure), plus JSON file loading.
 * File location: <agentDir>/nightshift.json (agentDir from pi's getAgentDir()).
 */

import { readFileSync } from "node:fs";

export type CompletionDelivery = "wakeup" | "quiet";

export interface NightshiftConfig {
	/** Default wait for job_output when wait:true without timeout_ms. */
	waitTimeoutMs: number;
	/** Hard cap on any single wait; a larger model-supplied timeout_ms is clamped. */
	maxWaitTimeoutMs: number;
	/** Wake turns one session may open before notices degrade to steer, reset by user input. */
	maxConsecutiveWakes: number;
	/** 'quiet' never opens a turn; notices wait for the next real turn. */
	completionDelivery: CompletionDelivery;
}

export const DEFAULT_CONFIG: NightshiftConfig = {
	waitTimeoutMs: 30_000,
	maxWaitTimeoutMs: 600_000,
	maxConsecutiveWakes: 3,
	completionDelivery: "wakeup",
};

function fail(key: string, message: string): never {
	throw new Error(`nightshift config: ${key} ${message}`);
}

/** Validate + merge a raw config object (partial). Throws on any invalid value. */
export function resolveConfig(raw: unknown): NightshiftConfig {
	if (raw !== undefined && (typeof raw !== "object" || raw === null)) {
		throw new Error("nightshift config: expected a JSON object");
	}
	const input = (raw ?? {}) as Record<string, unknown>;

	const waitTimeoutMs = input.waitTimeoutMs ?? DEFAULT_CONFIG.waitTimeoutMs;
	const maxWaitTimeoutMs = input.maxWaitTimeoutMs ?? DEFAULT_CONFIG.maxWaitTimeoutMs;
	const maxConsecutiveWakes = input.maxConsecutiveWakes ?? DEFAULT_CONFIG.maxConsecutiveWakes;
	const completionDelivery = input.completionDelivery ?? DEFAULT_CONFIG.completionDelivery;

	if (typeof waitTimeoutMs !== "number" || !Number.isInteger(waitTimeoutMs) || waitTimeoutMs < 1) {
		fail("waitTimeoutMs", `must be a positive integer, got ${JSON.stringify(input.waitTimeoutMs)}`);
	}
	if (typeof maxWaitTimeoutMs !== "number" || !Number.isInteger(maxWaitTimeoutMs) || maxWaitTimeoutMs < 1) {
		fail("maxWaitTimeoutMs", `must be a positive integer, got ${JSON.stringify(input.maxWaitTimeoutMs)}`);
	}
	if (waitTimeoutMs > maxWaitTimeoutMs) {
		throw new Error(`nightshift config: waitTimeoutMs (${waitTimeoutMs}) exceeds maxWaitTimeoutMs (${maxWaitTimeoutMs})`);
	}
	// A budget is a count of turns: Infinity or a fraction cannot bound the
	// self-exciting wake chain this field exists to stop (dsh mirrors this).
	if (!Number.isSafeInteger(maxConsecutiveWakes) || maxConsecutiveWakes < 1) {
		fail("maxConsecutiveWakes", `must be a whole number of turns >= 1, got ${JSON.stringify(input.maxConsecutiveWakes)}`);
	}
	if (completionDelivery !== "wakeup" && completionDelivery !== "quiet") {
		fail("completionDelivery", `must be "wakeup" or "quiet", got ${JSON.stringify(input.completionDelivery)}`);
	}

	return { waitTimeoutMs, maxWaitTimeoutMs, maxConsecutiveWakes, completionDelivery };
}

/** Load and resolve the config file. Malformed JSON or invalid values throw at startup. */
export function loadConfigFile(path: string): NightshiftConfig {
	let text: string;
	try {
		text = readFileSync(path, "utf8");
	} catch {
		return DEFAULT_CONFIG; // no config file -> defaults
	}
	let raw: unknown;
	try {
		raw = JSON.parse(text);
	} catch (error) {
		throw new Error(`nightshift config: ${path} is not valid JSON: ${(error as Error).message}`);
	}
	return resolveConfig(raw);
}