package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 4096,
	CheckOrigin:     func(r *http.Request) bool { return true },
}

type wsMessage struct {
	Message string `json:"message"`
}

// WSHandler handles WebSocket connections for chat.
type WSHandler struct {
	sessionMgr *ChatSessionManager
	sessionsMu sync.Mutex
}

func NewWSHandler(sessionMgr *ChatSessionManager) *WSHandler {
	return &WSHandler{
		sessionMgr: sessionMgr,
	}
}

func (wh *WSHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	project := r.URL.Query().Get("project")
	projectDir := r.URL.Query().Get("project_dir")
	if project == "" || projectDir == "" {
		http.Error(w, "missing project params", http.StatusBadRequest)
		return
	}

	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Printf("WebSocket upgrade error: %v", err)
		return
	}
	defer conn.Close()

	// Single write channel — all writes go through here to avoid concurrent writes
	writeCh := make(chan string, 100)
	writeDone := make(chan struct{})
	go func() {
		defer close(writeDone)
		for msg := range writeCh {
			if err := conn.WriteMessage(websocket.TextMessage, []byte(msg)); err != nil {
				log.Printf("WebSocket write error: %v", err)
				return
			}
		}
	}()

	// Helper to send via write channel
	send := func(text string) {
		select {
		case writeCh <- text:
		default:
			log.Printf("Write channel full, dropping message")
		}
	}

	sessionID := fmt.Sprintf("%s-%s", project, r.RemoteAddr)
	subID := fmt.Sprintf("ws-%d", time.Now().UnixNano())

	sess, isNew, err := wh.sessionMgr.GetOrCreate(sessionID, projectDir)
	if err != nil {
		log.Printf("Session create error: %v", err)
		send(FragmentSystemMessage(fmt.Sprintf("Greška pri pokretanju Claude-a: %v", err)))
		close(writeCh)
		<-writeDone
		return
	}

	// Send status
	send(FragmentStatus(true))

	if isNew {
		send(FragmentSystemMessage("Claude sesija pokrenuta. Možeš da pišeš."))
	} else {
		// Replay buffer
		buffer := sess.GetBuffer()
		for _, msg := range buffer {
			send(msg.Content)
		}
		send(FragmentSystemMessage("Ponovo povezan. Istorija učitana."))
	}

	// Subscribe to session broadcasts
	sub := sess.Subscribe(subID)
	defer sess.Unsubscribe(subID)

	// Start event listener if new session
	if isNew {
		go wh.listenEvents(sess)
	}

	// Forward broadcast messages to the write channel
	go func() {
		for fragment := range sub.Ch {
			send(fragment)
		}
	}()

	// Read pump: messages from browser
	for {
		_, raw, err := conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseNormalClosure) {
				log.Printf("WebSocket read error: %v", err)
			}
			break
		}

		var msg wsMessage
		if err := json.Unmarshal(raw, &msg); err != nil {
			log.Printf("Invalid WS message: %v", err)
			continue
		}

		text := strings.TrimSpace(msg.Message)
		if text == "" {
			continue
		}

		// Add user message to buffer (broadcasts to all subscribers including us)
		userFragment := FragmentUserMessage(text)
		sess.AddMessage(ChatMessage{
			Role:      "user",
			Content:   userFragment,
			Timestamp: time.Now(),
		})

		// Clear input and show typing
		send(FragmentCombine(FragmentClearInput(), FragmentTypingIndicator(true)))

		// Send to claude CLI
		if err := sess.Process.Send(text); err != nil {
			log.Printf("Send to CLI error: %v", err)
			send(FragmentSystemMessage("Greška pri slanju poruke"))
		}
	}

	// Cleanup
	close(writeCh)
	<-writeDone
}

// listenEvents reads events from the CLI process and broadcasts via AddMessage.
func (wh *WSHandler) listenEvents(sess *ChatSession) {
	var currentMsgID string
	var currentText strings.Builder
	msgCounter := 0

	for {
		select {
		case event, ok := <-sess.Process.Events:
			if !ok {
				sess.AddMessage(ChatMessage{
					Role:      "system",
					Content:   FragmentSystemMessage("Claude sesija završena."),
					Timestamp: time.Now(),
				})
				return
			}

			switch event.Type {
			case "system":
				if event.Subtype == "init" {
					log.Printf("CLI session started: %s", event.SessionID)
				}

			case "stream_event":
				if event.Event == nil {
					continue
				}
				wh.handleStreamEvent(sess, event.Event, &currentMsgID, &currentText, &msgCounter)

			case "assistant":
				if event.Message != nil {
					for _, c := range event.Message.Content {
						switch c.Type {
						case "tool_use":
							inputStr := ""
							if c.Input != nil {
								if b, err := json.Marshal(c.Input); err == nil {
									inputStr = string(b)
								}
							}
							fragment := FragmentToolCall(c.Name, inputStr)
							sess.AddMessage(ChatMessage{
								Role:      "tool",
								Content:   fragment,
								Timestamp: time.Now(),
							})
						case "text":
							if currentMsgID != "" && currentText.Len() > 0 {
								rendered := renderMarkdown(currentText.String())
								fragment := FragmentAssistantComplete(currentMsgID, rendered)
								sess.AddMessage(ChatMessage{
									Role:      "assistant",
									Content:   fragment,
									Timestamp: time.Now(),
								})
								currentText.Reset()
							}
						}
					}
				}

			case "result":
				fragment := FragmentTypingIndicator(false)
				sess.AddMessage(ChatMessage{
					Role:      "system",
					Content:   fragment,
					Timestamp: time.Now(),
				})
				if event.Result != nil {
					parts := []string{}
					if event.Result.Duration > 0 {
						secs := event.Result.Duration / 1000
						if secs >= 60 {
							parts = append(parts, fmt.Sprintf("%.0fm %.0fs", secs/60, float64(int(secs)%60)))
						} else {
							parts = append(parts, fmt.Sprintf("%.1fs", secs))
						}
					}
					if event.Result.CostUSD > 0 {
						parts = append(parts, fmt.Sprintf("$%.4f", event.Result.CostUSD))
					}
					if event.Result.NumTurns > 0 {
						parts = append(parts, fmt.Sprintf("%d turn(s)", event.Result.NumTurns))
					}
					if len(parts) > 0 {
						costMsg := FragmentSystemMessage(strings.Join(parts, " · "))
						sess.AddMessage(ChatMessage{
							Role:      "system",
							Content:   costMsg,
							Timestamp: time.Now(),
						})
					}
				}
			}

		case err, ok := <-sess.Process.Errors:
			if !ok {
				return
			}
			log.Printf("CLI error [%s]: %v", sess.ID, err)
		}
	}
}

func (wh *WSHandler) handleStreamEvent(sess *ChatSession, se *StreamEvent, currentMsgID *string, currentText *strings.Builder, msgCounter *int) {
	switch se.Type {
	case "content_block_start":
		*msgCounter++
		*currentMsgID = fmt.Sprintf("msg-%d-%d", time.Now().UnixMilli(), *msgCounter)
		currentText.Reset()
		fragment := FragmentAssistantStart(*currentMsgID)
		sess.AddMessage(ChatMessage{
			Role:      "assistant",
			Content:   fragment,
			Timestamp: time.Now(),
		})

	case "content_block_delta":
		if se.Delta != nil && se.Delta.Text != "" {
			currentText.WriteString(se.Delta.Text)
			fragment := FragmentAssistantChunk(*currentMsgID, se.Delta.Text)
			sess.AddMessage(ChatMessage{
				Role:      "assistant",
				Content:   fragment,
				Timestamp: time.Now(),
			})
		}
	}
}

func renderMarkdown(text string) string {
	return RenderMD(text)
}