import * as fs from 'fs'; // Import fs module
import { getServiceAdapter } from './adapter.js';
import { MODEL_PROVIDER } from './common.js';

/**
 * Manages a pool of API service providers, handling their health and selection.
 */
export class ProviderPoolManager {
    // 默认健康检查模型配置
    static DEFAULT_HEALTH_CHECK_MODELS = {
        'gemini-cli': 'gemini-2.5-flash',
        'openai-custom': 'gpt-3.5-turbo',
        'claude-custom': 'claude-3-7-sonnet-20250219',
        'kiro-api': 'claude-3-7-sonnet-20250219',
        'qwen-api': 'qwen3-coder-flash',
        'openai-custom-responses': 'gpt-5-low'
    };

    constructor(providerPools, options = {}) {
        this.providerPools = providerPools;
        this.globalConfig = options.globalConfig || {}; // 存储全局配置
        this.providerStatus = {}; // Tracks health and usage for each provider instance
        this.roundRobinIndex = {}; // Tracks the current index for round-robin selection for each provider type
        this.maxErrorCount = options.maxErrorCount || 3; // Default to 3 errors before marking unhealthy
        this.healthCheckInterval = options.healthCheckInterval || 10 * 60 * 1000; // Default to 10 minutes
        
        // 日志级别控制
        this.logLevel = options.logLevel || 'info'; // 'debug', 'info', 'warn', 'error'
        
        // 添加防抖机制，避免频繁的文件 I/O 操作
        this.saveDebounceTime = options.saveDebounceTime || 1000; // 默认1秒防抖
        this.saveTimer = null;
        this.pendingSaves = new Set(); // 记录待保存的 providerType
        
        this.initializeProviderStatus();
    }

    /**
     * 日志输出方法，支持日志级别控制
     * @private
     */
    _log(level, message) {
        const levels = { debug: 0, info: 1, warn: 2, error: 3 };
        if (levels[level] >= levels[this.logLevel]) {
            const logMethod = level === 'debug' ? 'log' : level;
            console[logMethod](`[ProviderPoolManager] ${message}`);
        }
    }

    /**
     * 查找指定的 provider
     * @private
     */
    _findProvider(providerType, uuid) {
        if (!providerType || !uuid) {
            this._log('error', `Invalid parameters: providerType=${providerType}, uuid=${uuid}`);
            return null;
        }
        const pool = this.providerStatus[providerType];
        return pool?.find(p => p.uuid === uuid) || null;
    }

    /**
     * Initializes the status for each provider in the pools.
     * Initially, all providers are considered healthy and have zero usage.
     */
    initializeProviderStatus() {
        for (const providerType in this.providerPools) {
            this.providerStatus[providerType] = [];
            this.roundRobinIndex[providerType] = 0; // Initialize round-robin index for each type
            this.providerPools[providerType].forEach((providerConfig) => {
                // Ensure initial health and usage stats are present in the config
                providerConfig.isHealthy = providerConfig.isHealthy !== undefined ? providerConfig.isHealthy : true;
                providerConfig.isDisabled = providerConfig.isDisabled !== undefined ? providerConfig.isDisabled : false;
                providerConfig.lastUsed = providerConfig.lastUsed !== undefined ? providerConfig.lastUsed : null;
                providerConfig.usageCount = providerConfig.usageCount !== undefined ? providerConfig.usageCount : 0;
                providerConfig.errorCount = providerConfig.errorCount !== undefined ? providerConfig.errorCount : 0;
                
                // 优化2: 简化 lastErrorTime 处理逻辑
                providerConfig.lastErrorTime = providerConfig.lastErrorTime instanceof Date
                    ? providerConfig.lastErrorTime.toISOString()
                    : (providerConfig.lastErrorTime || null);

                this.providerStatus[providerType].push({
                    config: providerConfig,
                    uuid: providerConfig.uuid, // Still keep uuid at the top level for easy access
                });
            });
        }
        this._log('info', 'Initialized provider statuses: ok');
    }

    /**
     * Selects a provider from the pool for a given provider type.
     * Currently uses a simple round-robin for healthy providers.
     * If requestedModel is provided, providers that don't support the model will be excluded.
     * @param {string} providerType - The type of provider to select (e.g., 'gemini-cli', 'openai-custom').
     * @param {string} [requestedModel] - Optional. The model name to filter providers by.
     * @returns {object|null} The selected provider's configuration, or null if no healthy provider is found.
     */
    selectProvider(providerType, requestedModel = null) {
        // 参数校验
        if (!providerType || typeof providerType !== 'string') {
            this._log('error', `Invalid providerType: ${providerType}`);
            return null;
        }

        const availableProviders = this.providerStatus[providerType] || [];
        let availableAndHealthyProviders = availableProviders.filter(p =>
            p.config.isHealthy && !p.config.isDisabled
        );

        // 如果指定了模型，则排除不支持该模型的提供商
        if (requestedModel) {
            const modelFilteredProviders = availableAndHealthyProviders.filter(p => {
                // 如果提供商没有配置 notSupportedModels，则认为它支持所有模型
                if (!p.config.notSupportedModels || !Array.isArray(p.config.notSupportedModels)) {
                    return true;
                }
                // 检查 notSupportedModels 数组中是否包含请求的模型，如果包含则排除
                return !p.config.notSupportedModels.includes(requestedModel);
            });

            if (modelFilteredProviders.length === 0) {
                this._log('warn', `No available providers for type: ${providerType} that support model: ${requestedModel}`);
                return null;
            }

            availableAndHealthyProviders = modelFilteredProviders;
            this._log('debug', `Filtered ${modelFilteredProviders.length} providers supporting model: ${requestedModel}`);
        }

        if (availableAndHealthyProviders.length === 0) {
            this._log('warn', `No available and healthy providers for type: ${providerType}`);
            return null;
        }

        // 为每个提供商类型和模型组合维护独立的轮询索引
        // 使用组合键：providerType 或 providerType:model
        const indexKey = requestedModel ? `${providerType}:${requestedModel}` : providerType;
        const currentIndex = this.roundRobinIndex[indexKey] || 0;
        
        // 使用取模确保索引始终在有效范围内，即使列表长度变化
        const providerIndex = currentIndex % availableAndHealthyProviders.length;
        const selected = availableAndHealthyProviders[providerIndex];
        
        // 更新下次轮询的索引
        this.roundRobinIndex[indexKey] = (currentIndex + 1) % availableAndHealthyProviders.length;
        
        // 更新使用信息
        selected.config.lastUsed = new Date().toISOString();
        selected.config.usageCount++;

        this._log('debug', `Selected provider for ${providerType} (round-robin): ${selected.config.uuid}${requestedModel ? ` for model: ${requestedModel}` : ''}`);
        
        // 使用防抖保存
        this._debouncedSave(providerType);
        
        return selected.config;
    }

    /**
     * Marks a provider as unhealthy (e.g., after an API error).
     * @param {string} providerType - The type of the provider.
     * @param {object} providerConfig - The configuration of the provider to mark.
     */
    markProviderUnhealthy(providerType, providerConfig) {
        if (!providerConfig?.uuid) {
            this._log('error', 'Invalid providerConfig in markProviderUnhealthy');
            return;
        }

        const provider = this._findProvider(providerType, providerConfig.uuid);
        if (provider) {
            provider.config.errorCount++;
            provider.config.lastErrorTime = new Date().toISOString();

            if (provider.config.errorCount >= this.maxErrorCount) {
                provider.config.isHealthy = false;
                this._log('warn', `Marked provider as unhealthy: ${providerConfig.uuid} for type ${providerType}. Total errors: ${provider.config.errorCount}`);
            } else {
                this._log('warn', `Provider ${providerConfig.uuid} for type ${providerType} error count: ${provider.config.errorCount}/${this.maxErrorCount}. Still healthy.`);
            }
            
            this._debouncedSave(providerType);
        }
    }

    /**
     * Marks a provider as healthy.
     * @param {string} providerType - The type of the provider.
     * @param {object} providerConfig - The configuration of the provider to mark.
     * @param {boolean} isInit - Whether to reset usage count (optional, default: false).
     */
    markProviderHealthy(providerType, providerConfig, resetUsageCount = false) {
        if (!providerConfig?.uuid) {
            this._log('error', 'Invalid providerConfig in markProviderHealthy');
            return;
        }

        const provider = this._findProvider(providerType, providerConfig.uuid);
        if (provider) {
            provider.config.isHealthy = true;
            provider.config.errorCount = 0;
            provider.config.lastErrorTime = null;
            // 只有在明确要求重置使用计数时才重置
            if (resetUsageCount) {
                provider.config.usageCount = 0;
            }
            this._log('info', `Marked provider as healthy: ${provider.config.uuid} for type ${providerType}${resetUsageCount ? ' (usage count reset)' : ''}`);
            
            this._debouncedSave(providerType);
        }
    }

    /**
     * 重置提供商的计数器（错误计数和使用计数）
     * @param {string} providerType - The type of the provider.
     * @param {object} providerConfig - The configuration of the provider to mark.
     */
    resetProviderCounters(providerType, providerConfig) {
        if (!providerConfig?.uuid) {
            this._log('error', 'Invalid providerConfig in resetProviderCounters');
            return;
        }

        const provider = this._findProvider(providerType, providerConfig.uuid);
        if (provider) {
            provider.config.errorCount = 0;
            provider.config.usageCount = 0;
            this._log('info', `Reset provider counters: ${provider.config.uuid} for type ${providerType}`);
            
            this._debouncedSave(providerType);
        }
    }

    /**
     * 禁用指定提供商
     * @param {string} providerType - 提供商类型
     * @param {object} providerConfig - 提供商配置
     */
    disableProvider(providerType, providerConfig) {
        if (!providerConfig?.uuid) {
            this._log('error', 'Invalid providerConfig in disableProvider');
            return;
        }

        const provider = this._findProvider(providerType, providerConfig.uuid);
        if (provider) {
            provider.config.isDisabled = true;
            this._log('info', `Disabled provider: ${providerConfig.uuid} for type ${providerType}`);
            this._debouncedSave(providerType);
        }
    }

    /**
     * 启用指定提供商
     * @param {string} providerType - 提供商类型
     * @param {object} providerConfig - 提供商配置
     */
    enableProvider(providerType, providerConfig) {
        if (!providerConfig?.uuid) {
            this._log('error', 'Invalid providerConfig in enableProvider');
            return;
        }

        const provider = this._findProvider(providerType, providerConfig.uuid);
        if (provider) {
            provider.config.isDisabled = false;
            this._log('info', `Enabled provider: ${providerConfig.uuid} for type ${providerType}`);
            this._debouncedSave(providerType);
        }
    }

    /**
     * Performs health checks on all providers in the pool.
     * This method would typically be called periodically (e.g., via cron job).
     */
    async performHealthChecks(isInit = false) {
        this._log('info', 'Performing health checks on all providers...');
        const now = new Date();
        
        for (const providerType in this.providerStatus) {
            for (const providerStatus of this.providerStatus[providerType]) {
                const providerConfig = providerStatus.config;

                // Only attempt to health check unhealthy providers after a certain interval
                if (!providerStatus.config.isHealthy && providerStatus.config.lastErrorTime &&
                    (now.getTime() - new Date(providerStatus.config.lastErrorTime).getTime() < this.healthCheckInterval)) {
                    this._log('debug', `Skipping health check for ${providerConfig.uuid} (${providerType}). Last error too recent.`);
                    continue;
                }

                try {
                    // Perform actual health check based on provider type
                    const isHealthy = await this._checkProviderHealth(providerType, providerConfig);
                    
                    if (isHealthy === null) {
                        this._log('debug', `Health check for ${providerConfig.uuid} (${providerType}) skipped: Check not implemented.`);
                        this.resetProviderCounters(providerType, providerConfig);
                        continue;
                    }
                    
                    if (isHealthy) {
                        if (!providerStatus.config.isHealthy) {
                            // Provider was unhealthy but is now healthy
                            // 恢复健康时不重置使用计数，保持原有值
                            this.markProviderHealthy(providerType, providerConfig, true);
                            this._log('info', `Health check for ${providerConfig.uuid} (${providerType}): Marked Healthy (actual check)`);
                        } else {
                            // Provider was already healthy and still is
                            // 只在初始化时重置使用计数
                            this.markProviderHealthy(providerType, providerConfig, true);
                            this._log('debug', `Health check for ${providerConfig.uuid} (${providerType}): Still Healthy`);
                        }
                    } else {
                        // Provider is not healthy
                        this._log('warn', `Health check for ${providerConfig.uuid} (${providerType}) failed: Provider is not responding correctly.`);
                        this.markProviderUnhealthy(providerType, providerConfig);
                    }

                } catch (error) {
                    this._log('error', `Health check for ${providerConfig.uuid} (${providerType}) failed: ${error.message}`);
                    // If a health check fails, mark it unhealthy, which will update error count and lastErrorTime
                    this.markProviderUnhealthy(providerType, providerConfig);
                }
            }
        }
    }

    /**
     * 构建健康检查请求
     * @private
     */
    _buildHealthCheckRequest(providerType, modelName) {
        const baseMessage = { role: 'user', content: 'Hello, are you ok?' };
        
        // Gemini 使用不同的请求格式
        if (providerType === 'gemini-cli') {
            return {
                contents: [{
                    role: 'user',
                    parts: [{ text: baseMessage.content }]
                }]
            };
        }
        
        // OpenAI Custom Responses 使用特殊格式
        if (providerType === 'openai-custom-responses') {
            return {
                input: [baseMessage],
                model: modelName
            };
        }
        
        // 其他提供商（OpenAI、Claude、Kiro、Qwen）使用标准格式
        return {
            messages: [baseMessage],
            model: modelName
        };
    }

    /**
     * Performs an actual health check for a specific provider.
     * @param {string} providerType - The type of the provider.
     * @param {object} providerConfig - The configuration of the provider to check.
     * @returns {Promise<boolean|null>} - True if healthy, false if unhealthy, null if check not implemented.
     */
    async _checkProviderHealth(providerType, providerConfig) {
        try {
            // 如果未启用健康检查，返回 null
            if (!providerConfig.checkHealth) {
                return null;
            }

            // 合并全局配置和 provider 配置（简化代理配置）
            const proxyKeys = ['GEMINI', 'OPENAI', 'CLAUDE', 'QWEN', 'KIRO'];
            const tempConfig = {
                ...providerConfig,
                MODEL_PROVIDER: providerType
            };
            
            // 动态添加代理配置
            proxyKeys.forEach(key => {
                const proxyKey = `USE_SYSTEM_PROXY_${key}`;
                if (this.globalConfig[proxyKey] !== undefined) {
                    tempConfig[proxyKey] = this.globalConfig[proxyKey];
                }
            });

            const serviceAdapter = getServiceAdapter(tempConfig);
            
            // 确定健康检查使用的模型名称
            const modelName = providerConfig.checkModelName ||
                            ProviderPoolManager.DEFAULT_HEALTH_CHECK_MODELS[providerType];
            
            if (!modelName) {
                this._log('warn', `Unknown provider type for health check: ${providerType}`);
                return false;
            }
            
            // 构建健康检查请求
            const healthCheckRequest = this._buildHealthCheckRequest(providerType, modelName);
            
            this._log('debug', `Health check request for ${modelName}: ${JSON.stringify(healthCheckRequest)}`);
            await serviceAdapter.generateContent(modelName, healthCheckRequest);
            return true;
        } catch (error) {
            this._log('error', `Health check failed for ${providerType}: ${error.message}`);
            return false;
        }
    }

    /**
     * 优化1: 添加防抖保存方法
     * 延迟保存操作，避免频繁的文件 I/O
     * @private
     */
    _debouncedSave(providerType) {
        // 将待保存的 providerType 添加到集合中
        this.pendingSaves.add(providerType);
        
        // 清除之前的定时器
        if (this.saveTimer) {
            clearTimeout(this.saveTimer);
        }
        
        // 设置新的定时器
        this.saveTimer = setTimeout(() => {
            this._flushPendingSaves();
        }, this.saveDebounceTime);
    }
    
    /**
     * 批量保存所有待保存的 providerType（优化为单次文件写入）
     * @private
     */
    async _flushPendingSaves() {
        const typesToSave = Array.from(this.pendingSaves);
        if (typesToSave.length === 0) return;
        
        this.pendingSaves.clear();
        this.saveTimer = null;
        
        try {
            const filePath = this.globalConfig.PROVIDER_POOLS_FILE_PATH || 'provider_pools.json';
            let currentPools = {};
            
            // 一次性读取文件
            try {
                const fileContent = await fs.promises.readFile(filePath, 'utf8');
                currentPools = JSON.parse(fileContent);
            } catch (readError) {
                if (readError.code === 'ENOENT') {
                    this._log('info', 'provider_pools.json does not exist, creating new file.');
                } else {
                    throw readError;
                }
            }

            // 更新所有待保存的 providerType
            for (const providerType of typesToSave) {
                if (this.providerStatus[providerType]) {
                    currentPools[providerType] = this.providerStatus[providerType].map(p => {
                        // Convert Date objects to ISOString if they exist
                        const config = { ...p.config };
                        if (config.lastUsed instanceof Date) {
                            config.lastUsed = config.lastUsed.toISOString();
                        }
                        if (config.lastErrorTime instanceof Date) {
                            config.lastErrorTime = config.lastErrorTime.toISOString();
                        }
                        return config;
                    });
                } else {
                    this._log('warn', `Attempted to save unknown providerType: ${providerType}`);
                }
            }
            
            // 一次性写入文件
            await fs.promises.writeFile(filePath, JSON.stringify(currentPools, null, 2), 'utf8');
            this._log('info', `provider_pools.json updated successfully for types: ${typesToSave.join(', ')}`);
        } catch (error) {
            this._log('error', `Failed to write provider_pools.json: ${error.message}`);
        }
    }

}