// Package background provides the autonomous thinking engine for Cyrene.
// It generates thoughts after conversations and during idle periods.
package background

import (
	"context"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
	"sync"
	"time"
)

// Thinker manages autonomous background thinking.
type Thinker struct {
	mu              sync.Mutex
	enabled         bool
	thinkInterval   time.Duration
	silenceTimeout  time.Duration
	lastActivity    time.Time
	activeSessionID string
	thoughts        []Thought
	stopCh          chan struct{}
	postChatCh      chan string
}

// Thought represents an autonomous thought generated by the AI.
type Thought struct {
	Content   string    `json:"content"`
	SessionID string    `json:"session_id,omitempty"`
	CreatedAt time.Time `json:"created_at"`
}

// New creates a new background thinker.
func New(enabled bool, thinkInterval, silenceTimeout time.Duration) *Thinker {
	return &Thinker{
		enabled:        enabled,
		thinkInterval:  thinkInterval,
		silenceTimeout: silenceTimeout,
		lastActivity:   time.Now(),
		thoughts:       make([]Thought, 0),
		stopCh:         make(chan struct{}),
		postChatCh:     make(chan string, 10),
	}
}

// Start begins the background thinking loops.
func (t *Thinker) Start(ctx context.Context) {
	if !t.enabled {
		logger.Info("[thinker] background thinking disabled")
		return
	}

	go t.silenceLoop(ctx)
	go t.postChatLoop(ctx)
	logger.Infof("[thinker] started (interval=%v, silence=%v)", t.thinkInterval, t.silenceTimeout)
}

// Stop shuts down the thinker.
func (t *Thinker) Stop() {
	close(t.stopCh)
	logger.Info("[thinker] stopped")
}

// TriggerPostChat schedules a post-chat think after a conversation.
func (t *Thinker) TriggerPostChat(sessionID string) {
	t.mu.Lock()
	t.activeSessionID = sessionID
	t.lastActivity = time.Now()
	t.mu.Unlock()

	select {
	case t.postChatCh <- sessionID:
	default:
	}
}

// UpdateActivity updates the last activity timestamp (for silence detection).
func (t *Thinker) UpdateActivity() {
	t.mu.Lock()
	t.lastActivity = time.Now()
	t.mu.Unlock()
}

// ThoughtChan returns a channel that emits new thoughts.
// Not yet wired — will connect to NATS for event broadcasting.
func (t *Thinker) ThoughtChan() chan Thought {
	ch := make(chan Thought, 10)
	// In future: push thoughts to this channel
	return ch
}

func (t *Thinker) silenceLoop(ctx context.Context) {
	ticker := time.NewTicker(t.thinkInterval)
	defer ticker.Stop()

	for {
		select {
		case <-t.stopCh:
			return
		case <-ticker.C:
			t.mu.Lock()
			elapsed := time.Since(t.lastActivity)
			t.mu.Unlock()

			if elapsed >= t.silenceTimeout {
				t.generateThought("silence", t.activeSessionID)
			}
		case <-ctx.Done():
			return
		}
	}
}

func (t *Thinker) postChatLoop(ctx context.Context) {
	for {
		select {
		case <-t.stopCh:
			return
		case sessionID := <-t.postChatCh:
			// Delay post-chat thinking to avoid immediate noise
			time.Sleep(5 * time.Second)
			t.generateThought("post_chat", sessionID)
		case <-ctx.Done():
			return
		}
	}
}

func (t *Thinker) generateThought(trigger string, sessionID string) {
	// Placeholder: in production this calls the LLM
	thought := Thought{
		Content:   "[思考] 当前无主动想法",
		SessionID: sessionID,
		CreatedAt: time.Now(),
	}

	t.mu.Lock()
	t.thoughts = append(t.thoughts, thought)
	if len(t.thoughts) > 100 {
		t.thoughts = t.thoughts[1:]
	}
	t.mu.Unlock()

	logger.Infof("[thinker] %s thought generated for session %s", trigger, sessionID)
}

// RecentThoughts returns the most recent thoughts.
func (t *Thinker) RecentThoughts(n int) []Thought {
	t.mu.Lock()
	defer t.mu.Unlock()

	if n > len(t.thoughts) {
		n = len(t.thoughts)
	}
	return t.thoughts[len(t.thoughts)-n:]
}