/*
 * Copyright (C) 2020-2022, IrineSistiana
 *
 * This file is part of mosdns.
 *
 * mosdns is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * mosdns is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package coremain

import (
	"fmt"
	"io"
	"sync"

	"go.uber.org/zap"
)

// HotReloadManager 热加载管理器
type HotReloadManager struct {
	mosdns      *Mosdns
	mu          sync.RWMutex
	isReloading bool
	configPath  string
}

// NewHotReloadManager 创建热加载管理器
func NewHotReloadManager(m *Mosdns, configPath string) *HotReloadManager {
	return &HotReloadManager{
		mosdns:     m,
		configPath: configPath,
	}
}

// Reload 执行热加载
// 返回值：成功加载的插件数，错误信息
func (hrm *HotReloadManager) Reload() (int, error) {
	hrm.mu.Lock()
	if hrm.isReloading {
		hrm.mu.Unlock()
		return 0, fmt.Errorf("reload is already in progress")
	}
	hrm.isReloading = true
	hrm.mu.Unlock()

	defer func() {
		hrm.mu.Lock()
		hrm.isReloading = false
		hrm.mu.Unlock()
	}()

	hrm.mosdns.logger.Info("🔄 开始热加载配置...")

	// 1. 加载新配置
	newCfg, actualPath, err := loadConfig(hrm.configPath)
	if err != nil {
		hrm.mosdns.logger.Error("failed to load config", zap.Error(err))
		return 0, fmt.Errorf("配置文件加载失败: %w", err)
	}
	hrm.mosdns.logger.Info("✅ 配置文件加载成功", zap.String("path", actualPath))

	// 2. 验证新配置
	validator := NewConfigValidator(newCfg, hrm.mosdns.logger)
	if err := validator.Validate(); err != nil {
		hrm.mosdns.logger.Error("config validation failed", zap.Error(err))
		return 0, fmt.Errorf("配置验证失败: %w", err)
	}
	hrm.mosdns.logger.Info("✅ 配置验证通过")

	// 3. 备份旧插件
	oldPlugins := hrm.mosdns.plugins
	hrm.mosdns.logger.Info("📦 备份旧插件", zap.Int("count", len(oldPlugins)))

	// 4. 创建新插件映射
	hrm.mosdns.plugins = make(map[string]any)

	// 5. 加载预设插件
	if err := hrm.mosdns.loadPresetPlugins(); err != nil {
		// 恢复旧插件
		hrm.mosdns.plugins = oldPlugins
		hrm.mosdns.logger.Error("failed to load preset plugins", zap.Error(err))
		return 0, fmt.Errorf("预设插件加载失败: %w", err)
	}

	// 6. 加载新配置的插件
	if err := hrm.mosdns.loadPluginsFromCfg(newCfg, 0); err != nil {
		// 恢复旧插件
		hrm.mosdns.plugins = oldPlugins
		hrm.mosdns.logger.Error("failed to load plugins from new config", zap.Error(err))
		return 0, fmt.Errorf("新插件加载失败: %w", err)
	}

	newPluginCount := len(hrm.mosdns.plugins)
	hrm.mosdns.logger.Info("✅ 新插件加载成功", zap.Int("count", newPluginCount))

	// 7. 关闭旧插件（在新插件成功加载后）
	hrm.closeOldPlugins(oldPlugins)

	// 8. 更新配置引用
	hrm.mosdns.config = newCfg

	hrm.mosdns.logger.Info("🎉 热加载完成！",
		zap.Int("old_plugin_count", len(oldPlugins)),
		zap.Int("new_plugin_count", newPluginCount))

	return newPluginCount, nil
}

// closeOldPlugins 关闭旧插件
func (hrm *HotReloadManager) closeOldPlugins(oldPlugins map[string]any) {
	hrm.mosdns.logger.Info("🔒 开始关闭旧插件", zap.Int("count", len(oldPlugins)))
	closedCount := 0

	for tag, p := range oldPlugins {
		if closer, ok := p.(io.Closer); ok {
			hrm.mosdns.logger.Debug("closing old plugin", zap.String("tag", tag))
			if err := closer.Close(); err != nil {
				hrm.mosdns.logger.Warn("failed to close old plugin",
					zap.String("tag", tag),
					zap.Error(err))
			} else {
				closedCount++
			}
		}
	}

	hrm.mosdns.logger.Info("✅ 旧插件关闭完成",
		zap.Int("total", len(oldPlugins)),
		zap.Int("closed", closedCount))
}

// IsReloading 检查是否正在重载
func (hrm *HotReloadManager) IsReloading() bool {
	hrm.mu.RLock()
	defer hrm.mu.RUnlock()
	return hrm.isReloading
}

// GetConfigPath 获取配置文件路径
func (hrm *HotReloadManager) GetConfigPath() string {
	return hrm.configPath
}

// SetConfigPath 设置配置文件路径
func (hrm *HotReloadManager) SetConfigPath(path string) {
	hrm.mu.Lock()
	defer hrm.mu.Unlock()
	hrm.configPath = path
}