import {lstat, opendir} from 'node:fs/promises';
import path from 'node:path';
import {performance} from 'node:perf_hooks';
import type {Bot} from '@wp2508/mineflayer';
import {get_project_root_path} from '../../../utils/path_utils.ts';
import type {InfoContext} from '../types.ts';
import {metadata, ResourceInfo} from '../resource_metrics.ts';

export interface StorageInfo {
    available: boolean;
    total_bytes: number | null;
    file_count: number;
    partial: boolean;
}

/** lstat and streamed directory enumeration never intentionally follow symlinks. Live mutation can race a scan. */
export async function scan_storage(directory: string, cancelled = () => false,
    limits = {entries: 20000, depth: 32, milliseconds: 2000}): Promise<StorageInfo> {
    const info: StorageInfo = {available: false, total_bytes: null, file_count: 0, partial: false};
    const start = performance.now();
    let entries = 0;
    const pending: [string, number][] = [[directory, 0]];
    while (pending.length) {
        if (cancelled() || entries >= limits.entries || performance.now() - start >= limits.milliseconds) {
            info.partial = true; break;
        }
        const [current, depth] = pending.pop()!;
        entries++;
        try {
            const stat = await lstat(current);
            if (current === directory) {
                if (!stat.isDirectory() || stat.isSymbolicLink()) { info.partial = true; break; }
                info.available = true;
                info.total_bytes = 0;
            }
            if (stat.isSymbolicLink()) continue;
            if (stat.isFile()) {
                info.total_bytes! += stat.size;
                info.file_count++;
            } else if (stat.isDirectory()) {
                if (depth >= limits.depth) { info.partial = true; continue; }
                const dir = await opendir(current);
                for await (const entry of dir) {
                    if (cancelled() || entries + pending.length >= limits.entries
                        || performance.now() - start >= limits.milliseconds) { info.partial = true; break; }
                    if (!entry.isSymbolicLink()) pending.push([path.join(current, entry.name), depth + 1]);
                }
            }
        } catch (error) {
            if (current === directory && (error as NodeJS.ErrnoException).code === 'ENOENT') {
                info.available = true;
                info.total_bytes = 0;
            } else info.partial = true;
        }
    }
    return info;
}

export class init extends ResourceInfo<StorageInfo> {
    readonly name = 'used_storage';
    readonly i18n = metadata('机器人数据存储', '统计 data/bot/<bot_id> 下文件的逻辑大小，跳过符号链接。'
        + '每 30 秒尽力扫描一次，不重叠执行；上限为 20000 个条目、32 层深度和 2 秒。'
        + '扫描期间的并发文件变动可能影响结果；该指标不代表实际分配的磁盘空间。', {
        available: ['存储统计是否可用', '目录可访问或不存在时为 true，不存在按 0 统计；缺少有效机器人编号或根目录不可访问时为 false'],
        total_bytes: ['文件总大小', '已观察到的普通文件逻辑大小之和，单位为字节；不可用时为 null'],
        file_count: ['文件数量', '已观察到的普通文件数量'],
        partial: ['结果是否不完整', '因扫描上限、取消或错误而未完成扫描；保留已读取文件的统计小计'],
    });
    constructor(_bot: Bot, options?: InfoContext) {
        super({available: false, total_bytes: null, file_count: 0, partial: true});
        if (!Number.isSafeInteger(options?.bot_id) || options!.bot_id! <= 0) return;
        const directory = path.join(get_project_root_path(), 'data', 'bot', String(options!.bot_id));
        this.start(30000, async () => { this.publish(await scan_storage(directory, () => this.disposed)); }, true);
    }
}