package subsession

import (
	"context"
	"crypto/rand"
	"fmt"
	"log"
	"sync"

	"github.com/yourname/cyrene-ai/ai-core/internal/llm"
	"github.com/yourname/cyrene-ai/ai-core/internal/model"
)

// Manager 子会话管理器
// 负责注册 Provider、分派任务、并行执行、超时控制、结果收集
type Manager struct {
	mu        sync.RWMutex
	providers map[model.SubSessionType]Provider
	llmClient LLMClient
}

// NewManager 创建子会话管理器
func NewManager(llmClient LLMClient) *Manager {
	return &Manager{
		providers: make(map[model.SubSessionType]Provider),
		llmClient: llmClient,
	}
}

// Register 注册子会话提供者
func (m *Manager) Register(provider Provider) {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.providers[provider.Type()] = provider
	log.Printf("[subsession] 注册子会话提供者: %s (优先级=%d, 超时=%v)", provider.Type(), provider.Priority(), provider.Timeout())
}

// RegisterWithOverride 注册或覆盖子会话提供者
func (m *Manager) RegisterWithOverride(provider Provider) {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.providers[provider.Type()] = provider
	log.Printf("[subsession] 注册(覆盖)子会话提供者: %s (优先级=%d, 超时=%v)", provider.Type(), provider.Priority(), provider.Timeout())
}

// GetProvider 获取指定类型的 Provider
func (m *Manager) GetProvider(t model.SubSessionType) (Provider, bool) {
	m.mu.RLock()
	defer m.mu.RUnlock()
	p, ok := m.providers[t]
	return p, ok
}

// ListProviders 列出所有已注册的 Provider 类型
func (m *Manager) ListProviders() []model.SubSessionType {
	m.mu.RLock()
	defer m.mu.RUnlock()
	types := make([]model.SubSessionType, 0, len(m.providers))
	for t := range m.providers {
		types = append(types, t)
	}
	return types
}

// Dispatch 分派任务到子会话，并行执行，返回结果通道
func (m *Manager) Dispatch(
	ctx context.Context,
	intent *model.IntentResult,
	userMessage string,
	params CreateContextParams,
) <-chan model.SubSessionResult {

	m.mu.RLock()
	providers := make([]Provider, 0, len(m.providers))
	for _, p := range m.providers {
		providers = append(providers, p)
	}
	m.mu.RUnlock()

	resultCh := make(chan model.SubSessionResult, len(providers))
	var wg sync.WaitGroup

	for _, provider := range providers {
		if !provider.CanHandle(ctx, intent, userMessage) {
			log.Printf("[subsession] 跳过子会话 %s: CanHandle 返回 false", provider.Type())
			continue
		}

		wg.Add(1)
		go func(p Provider) {
			defer wg.Done()
			defer func() {
				if r := recover(); r != nil {
					log.Printf("[subsession] dispatch goroutine panic 恢复 (type=%s): %v", p.Type(), r)
				}
			}()

			result := model.SubSessionResult{Type: p.Type()}

			// 创建带超时的 context
			subCtx, cancel := context.WithTimeout(ctx, p.Timeout())
			defer cancel()

			// 构建 LLM 上下文
			llmMessages, err := p.CreateContext(subCtx, params)
			if err != nil {
				result.Error = fmt.Sprintf("创建上下文失败: %v", err)
				log.Printf("[subsession] %s 创建上下文失败: %v", p.Type(), err)
				resultCh <- result
				return
			}

			log.Printf("[subsession] %s 开始执行 (上下文 %d 条消息)", p.Type(), len(llmMessages))

			// 执行子会话
			subResult, execErr := p.Execute(subCtx, llmMessages)
			if execErr != nil {
				result.Error = fmt.Sprintf("执行失败: %v", execErr)
				log.Printf("[subsession] %s 执行失败: %v", p.Type(), execErr)
				resultCh <- result
				return
			}

			// 检查超时
			select {
			case <-subCtx.Done():
				result.Error = "子会话超时"
				log.Printf("[subsession] %s 超时 (limit=%v)", p.Type(), p.Timeout())
			default:
				if subResult != nil {
					result = *subResult
					result.Type = p.Type()
					log.Printf("[subsession] %s 完成: 摘要=%s", p.Type(), truncate(result.Summary, 50))
				}
			}

			resultCh <- result
		}(provider)
	}

	// 等待所有子会话完成，关闭通道
	go func() {
		defer func() {
			if r := recover(); r != nil {
				log.Printf("[subsession] wait goroutine panic 恢复: %v", r)
			}
		}()
		wg.Wait()
		close(resultCh)
	}()

	return resultCh
}

// generateID 生成随机 ID
func generateID() string {
	b := make([]byte, 12)
	rand.Read(b)
	return fmt.Sprintf("sub-%x", b)
}

// truncate 截断字符串
func truncate(s string, maxLen int) string {
	runes := []rune(s)
	if len(runes) <= maxLen {
		return s
	}
	return string(runes[:maxLen]) + "..."
}

// Ensure llm is used
var _ = llm.NewAdapter