import fs from 'fs';
import path from 'path';
import fetch from 'node-fetch';
import { logInfo, logDebug, logError } from './logger.js';
import { getNextProxyAgent } from './proxy-manager.js';

/**
 * Account Manager - 管理多个 OAuth 账号的选择、刷新和统计
 * 
 * 设计思路：
 * 1. 支持多个 refresh_token 账号池
 * 2. 基于健康度加权轮询选择账号
 * 3. 自动刷新 access_token
 * 4. 401/402 时自动禁用异常账号
 */

const REFRESH_URL = 'https://api.workos.com/user_management/authenticate';
const REFRESH_INTERVAL_HOURS = 6;
const CLIENT_ID = 'client_01HNM792M5G5G1A2THWPXKFMXB';

class AccountManager {
    constructor() {
        this.accounts = [];
        this.settings = {
            algorithm: 'weighted', // 'weighted' or 'simple'
            refresh_interval_hours: REFRESH_INTERVAL_HOURS,
            disable_on_401: true,
            disable_on_402: true
        };
        this.simpleIndex = 0;
        this.configPath = null;
        this.endpointStats = {}; // 端点统计
    }

    /**
     * 从配置文件加载账号
     */
    async loadAccounts(configPath = null) {
        // 优先检查环境变量中的多账号配置
        const envAccounts = process.env.OAUTH_ACCOUNTS;
        if (envAccounts) {
            try {
                const parsed = JSON.parse(envAccounts);
                this.accounts = this._normalizeAccounts(parsed);
                logInfo(`AccountManager: 从环境变量加载了 ${this.accounts.length} 个账号`);
                return true;
            } catch (e) {
                logError('AccountManager: 解析 OAUTH_ACCOUNTS 环境变量失败', e);
            }
        }

        // 检查配置文件
        const possiblePaths = [
            configPath,
            path.join(process.cwd(), 'accounts.json'),
            path.join(process.cwd(), 'oauth_accounts.json')
        ].filter(Boolean);

        for (const p of possiblePaths) {
            if (fs.existsSync(p)) {
                try {
                    const content = fs.readFileSync(p, 'utf-8');
                    const data = JSON.parse(content);

                    this.accounts = this._normalizeAccounts(data.accounts || data);
                    if (data.settings) {
                        this.settings = { ...this.settings, ...data.settings };
                    }
                    this.configPath = p;

                    logInfo(`AccountManager: 从 ${p} 加载了 ${this.accounts.length} 个账号`);
                    return true;
                } catch (e) {
                    logError(`AccountManager: 读取配置文件 ${p} 失败`, e);
                }
            }
        }

        logInfo('AccountManager: 未找到多账号配置，将回退到单账号模式');
        return false;
    }

    /**
     * 标准化账号数据结构
     */
    _normalizeAccounts(accounts) {
        if (!Array.isArray(accounts)) {
            accounts = [accounts];
        }

        return accounts.map((acc, index) => ({
            id: acc.id || `account_${index + 1}`,
            name: acc.name || `账号${index + 1}`,
            refresh_token: acc.refresh_token,
            access_token: acc.access_token || null,
            last_refresh: acc.last_refresh ? new Date(acc.last_refresh).getTime() : null,
            status: acc.status || 'active', // 'active', 'disabled', 'rate_limited'
            disable_reason: acc.disable_reason || null,
            stats: acc.stats || { success: 0, fail: 0 }
        }));
    }

    /**
     * 获取活跃账号列表
     */
    getActiveAccounts() {
        return this.accounts.filter(acc => acc.status === 'active');
    }

    /**
     * 选择一个账号（基于配置的算法）
     */
    selectAccount() {
        const activeAccounts = this.getActiveAccounts();

        if (activeAccounts.length === 0) {
            throw new Error('AccountManager: 没有可用账号 - 所有账号已被禁用');
        }

        if (activeAccounts.length === 1) {
            return activeAccounts[0];
        }

        if (this.settings.algorithm === 'simple') {
            return this._simpleSelect(activeAccounts);
        } else {
            return this._weightedSelect(activeAccounts);
        }
    }

    /**
     * 简单轮询算法
     */
    _simpleSelect(accounts) {
        const account = accounts[this.simpleIndex % accounts.length];
        this.simpleIndex = (this.simpleIndex + 1) % accounts.length;
        logDebug(`AccountManager: 简单轮询选择账号 ${account.id}`);
        return account;
    }

    /**
     * 基于健康度的加权选择算法
     */
    _weightedSelect(accounts) {
        const weights = accounts.map(acc => {
            const total = acc.stats.success + acc.stats.fail;
            if (total === 0) {
                return 1; // 新账号默认权重
            }
            // 成功率 + 0.1（确保失败账号也有机会恢复）
            return (acc.stats.success / total) + 0.1;
        });

        const totalWeight = weights.reduce((sum, w) => sum + w, 0);
        let random = Math.random() * totalWeight;

        for (let i = 0; i < weights.length; i++) {
            random -= weights[i];
            if (random <= 0) {
                const acc = accounts[i];
                logDebug(`AccountManager: 加权选择账号 ${acc.id}, 健康度: ${((weights[i] - 0.1) * 100).toFixed(1)}%`);
                return acc;
            }
        }

        return accounts[accounts.length - 1];
    }

    /**
     * 获取账号的 access_token（自动刷新）
     */
    async getAccessToken(account) {
        // 检查是否需要刷新
        const needsRefresh = !account.access_token || this._shouldRefresh(account);

        if (needsRefresh) {
            await this._refreshToken(account);
        }

        return account.access_token;
    }

    /**
     * 检查是否需要刷新 token
     */
    _shouldRefresh(account) {
        if (!account.last_refresh) {
            return true;
        }
        const hoursSinceRefresh = (Date.now() - account.last_refresh) / (1000 * 60 * 60);
        return hoursSinceRefresh >= this.settings.refresh_interval_hours;
    }

    /**
     * 刷新账号的 access_token
     */
    async _refreshToken(account) {
        logInfo(`AccountManager: 刷新账号 ${account.id} 的 token...`);

        try {
            const formData = new URLSearchParams();
            formData.append('grant_type', 'refresh_token');
            formData.append('refresh_token', account.refresh_token);
            formData.append('client_id', CLIENT_ID);

            const proxyAgentInfo = getNextProxyAgent(REFRESH_URL);
            const fetchOptions = {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/x-www-form-urlencoded'
                },
                body: formData.toString()
            };

            if (proxyAgentInfo?.agent) {
                fetchOptions.agent = proxyAgentInfo.agent;
            }

            const response = await fetch(REFRESH_URL, fetchOptions);

            if (!response.ok) {
                const errorText = await response.text();
                throw new Error(`刷新失败: ${response.status} ${errorText}`);
            }

            const data = await response.json();

            // 更新账号信息
            account.access_token = data.access_token;
            account.refresh_token = data.refresh_token; // 更新 refresh_token
            account.last_refresh = Date.now();

            // 记录用户信息
            if (data.user) {
                account.email = data.user.email;
                logInfo(`AccountManager: 账号 ${account.id} 刷新成功 - ${data.user.email}`);
            }

            // 保存配置
            this._saveConfig();

            return data.access_token;

        } catch (error) {
            logError(`AccountManager: 账号 ${account.id} 刷新失败`, error);

            // 刷新失败可能是 refresh_token 失效，禁用账号
            if (error.message.includes('401') || error.message.includes('invalid')) {
                this.disableAccount(account.id, 'refresh_token_invalid');
            }

            throw error;
        }
    }

    /**
     * 记录请求结果
     */
    recordResult(accountId, endpoint, success, statusCode) {
        const account = this.accounts.find(acc => acc.id === accountId);
        if (!account) return;

        if (success) {
            account.stats.success++;
        } else {
            account.stats.fail++;

            // 检查是否需要禁用账号
            if (statusCode === 401 && this.settings.disable_on_401) {
                this.disableAccount(accountId, '401_unauthorized');
            } else if (statusCode === 402 && this.settings.disable_on_402) {
                this.disableAccount(accountId, '402_payment_required');
            }
        }

        // 更新端点统计
        if (!this.endpointStats[endpoint]) {
            this.endpointStats[endpoint] = { success: 0, fail: 0 };
        }
        if (success) {
            this.endpointStats[endpoint].success++;
        } else {
            this.endpointStats[endpoint].fail++;
        }
    }

    /**
     * 禁用账号
     */
    disableAccount(accountId, reason) {
        const account = this.accounts.find(acc => acc.id === accountId);
        if (!account) return;

        account.status = 'disabled';
        account.disable_reason = reason;
        account.disabled_at = new Date().toISOString();

        logError(`AccountManager: 账号 ${accountId} 已禁用，原因: ${reason}`);

        // 保存配置
        this._saveConfig();

        // 记录到废弃账号文件
        this._logDeprecatedAccount(account);
    }

    /**
     * 记录废弃账号到文件
     */
    _logDeprecatedAccount(account) {
        try {
            const logPath = path.join(process.cwd(), 'deprecated_accounts.txt');
            const logEntry = `[${new Date().toISOString()}] ${account.id} (${account.email || 'unknown'}) - ${account.disable_reason}\n`;
            fs.appendFileSync(logPath, logEntry, 'utf-8');
        } catch (e) {
            logError('AccountManager: 记录废弃账号失败', e);
        }
    }

    /**
     * 保存配置到文件
     */
    _saveConfig() {
        if (!this.configPath) return;

        try {
            const data = {
                accounts: this.accounts.map(acc => ({
                    id: acc.id,
                    name: acc.name,
                    refresh_token: acc.refresh_token,
                    access_token: acc.access_token,
                    last_refresh: acc.last_refresh ? new Date(acc.last_refresh).toISOString() : null,
                    status: acc.status,
                    disable_reason: acc.disable_reason,
                    email: acc.email,
                    stats: acc.stats
                })),
                settings: this.settings,
                last_updated: new Date().toISOString()
            };

            fs.writeFileSync(this.configPath, JSON.stringify(data, null, 2), 'utf-8');
            logDebug(`AccountManager: 配置已保存到 ${this.configPath}`);
        } catch (e) {
            logError('AccountManager: 保存配置失败', e);
        }
    }

    /**
     * 获取状态信息（用于 /status 页面）
     */
    getStatus() {
        return {
            total_accounts: this.accounts.length,
            active_accounts: this.getActiveAccounts().length,
            algorithm: this.settings.algorithm,
            accounts: this.accounts.map(acc => ({
                id: acc.id,
                name: acc.name,
                email: acc.email || 'unknown',
                status: acc.status,
                disable_reason: acc.disable_reason,
                stats: acc.stats,
                health: this._calculateHealth(acc),
                last_refresh: acc.last_refresh ? new Date(acc.last_refresh).toISOString() : null
            })),
            endpoint_stats: this.endpointStats
        };
    }

    /**
     * 计算账号健康度
     */
    _calculateHealth(account) {
        const total = account.stats.success + account.stats.fail;
        if (total === 0) return 100;
        return Math.round((account.stats.success / total) * 100);
    }

    /**
     * 检查是否有多账号配置
     */
    hasMultipleAccounts() {
        return this.accounts.length > 1;
    }

    /**
     * 获取账号数量
     */
    getAccountCount() {
        return this.accounts.length;
    }
}

// 单例实例
let accountManagerInstance = null;

/**
 * 获取 AccountManager 实例
 */
export function getAccountManager() {
    if (!accountManagerInstance) {
        accountManagerInstance = new AccountManager();
    }
    return accountManagerInstance;
}

/**
 * 初始化 AccountManager
 */
export async function initializeAccountManager() {
    const manager = getAccountManager();
    const loaded = await manager.loadAccounts();
    return loaded;
}

export default AccountManager;