import { existsSync, lstatSync, readFileSync, readdirSync } from "node:fs";
import { join } from "node:path";
import { isCurrentSessionOwner } from "./session.ts";
import type { RawScheduleRecord, ScheduleSnapshot, ScheduleState } from "./types.ts";

/**
 * 返回项目 Schedule 存储目录.
 *
 * @param cwd 项目工作目录
 * @param configDirName Pi 配置目录名
 * @returns Schedule 根目录
 */
export function scheduleRootPath(cwd: string, configDirName: string): string {
	return join(cwd, configDirName, "subagents", "schedules");
}

/**
 * 列出真实的 Schedule 子目录.
 *
 * @param cwd 项目工作目录
 * @param configDirName Pi 配置目录名
 * @returns 可读取的 Schedule 目录路径
 */
export function listScheduleDirectories(cwd: string, configDirName: string): string[] {
	const root = scheduleRootPath(cwd, configDirName);
	try {
		if (!existsSync(root) || lstatSync(root).isSymbolicLink()) return [];
		return readdirSync(root, { withFileTypes: true })
			.filter((entry) => entry.isDirectory() && !entry.isSymbolicLink())
			.map((entry) => join(root, entry.name));
	} catch {
		return [];
	}
}

function isObject(value: unknown): value is Record<string, unknown> {
	return typeof value === "object" && value !== null && !Array.isArray(value);
}

function parseRecord(value: unknown): RawScheduleRecord | undefined {
	if (!isObject(value) || typeof value.id !== "string" || !value.id.trim()) return undefined;
	if (value.sessionOnly !== undefined && typeof value.sessionOnly !== "boolean") return undefined;
	const trigger = isObject(value.trigger)
		? {
			kind: typeof value.trigger.kind === "string" ? value.trigger.kind : undefined,
			every: typeof value.trigger.every === "string" ? value.trigger.every : undefined,
			nextRunAt: typeof value.trigger.nextRunAt === "string" ? value.trigger.nextRunAt : undefined,
			at: typeof value.trigger.at === "string" ? value.trigger.at : undefined,
		}
		: undefined;
	return {
		id: value.id.trim(),
		name: typeof value.name === "string" ? value.name : undefined,
		paused: value.paused === true,
		activeRunId: typeof value.activeRunId === "string" && value.activeRunId.trim() ? value.activeRunId : undefined,
		sessionOnly: value.sessionOnly === true ? true : undefined,
		ownerSessionFile: typeof value.ownerSessionFile === "string" ? value.ownerSessionFile : undefined,
		trigger,
	};
}

function readJson(file: string): unknown {
	try {
		return JSON.parse(readFileSync(file, "utf8")) as unknown;
	} catch {
		return undefined;
	}
}

function readStartedAt(directory: string, activeRunId: string | undefined): number | undefined {
	if (!activeRunId) return undefined;
	const history = readJson(join(directory, "history.json"));
	if (!isObject(history) || !Array.isArray(history.runs)) return undefined;
	const run = history.runs.find((item) => isObject(item) && item.id === activeRunId);
	if (!isObject(run) || typeof run.startedAt !== "string") return undefined;
	const parsed = Date.parse(run.startedAt);
	return Number.isFinite(parsed) ? parsed : undefined;
}

function stateFor(record: RawScheduleRecord, nextRunAt: number | undefined, now: number): ScheduleState | undefined {
	if (record.paused) return nextRunAt === undefined ? undefined : "paused";
	if (record.activeRunId) return "running";
	if (nextRunAt === undefined) return undefined;
	return nextRunAt <= now ? "overdue" : "scheduled";
}

/**
 * 读取并筛选当前会话可见的 Schedule.
 *
 * session-only 任务只返回 owner 匹配当前会话的记录, 项目共享任务在所有会话返回.
 *
 * @param cwd 项目工作目录
 * @param currentSessionFile 当前会话文件
 * @param now 当前时间戳
 * @param configDirName Pi 配置目录名
 * @returns 当前会话可见的 Schedule 快照
 */
export function readScheduleSnapshots(
	cwd: string,
	currentSessionFile: string | undefined,
	now: number,
	configDirName: string,
): ScheduleSnapshot[] {
	const snapshots: ScheduleSnapshot[] = [];
	for (const directory of listScheduleDirectories(cwd, configDirName)) {
		const value = parseRecord(readJson(join(directory, "schedule.json")));
		if (!value) continue;
		if (value.sessionOnly !== undefined && typeof value.sessionOnly !== "boolean") continue;
		if (value.sessionOnly === true && !isCurrentSessionOwner(value.ownerSessionFile, currentSessionFile)) continue;
		const nextRunAt = typeof value.trigger?.nextRunAt === "string" ? Date.parse(value.trigger.nextRunAt) : undefined;
		const validNextRunAt = nextRunAt !== undefined && Number.isFinite(nextRunAt) ? nextRunAt : undefined;
		const state = stateFor(value, validNextRunAt, now);
		if (!state) continue;
		const triggerKind = value.trigger?.kind === "interval" ? "interval" : value.trigger?.kind === "once" ? "once" : undefined;
		if (!triggerKind) continue;
		snapshots.push({
			id: value.id,
			name: value.name?.trim() || value.id,
			scope: value.sessionOnly === true ? "current" : "shared",
			state,
			triggerKind,
			...(value.activeRunId ? { activeRunId: value.activeRunId } : {}),
			...(value.trigger?.every ? { every: value.trigger.every } : {}),
			...(validNextRunAt === undefined ? {} : { nextRunAt: validNextRunAt }),
			...(value.activeRunId ? { startedAt: readStartedAt(directory, value.activeRunId) } : {}),
		});
	}
	return snapshots.sort((left, right) => {
		const leftTime = left.nextRunAt ?? Number.POSITIVE_INFINITY;
		const rightTime = right.nextRunAt ?? Number.POSITIVE_INFINITY;
		return leftTime - rightTime || left.name.localeCompare(right.name);
	});
}