package main

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

	"github.com/gorilla/websocket"
	"github.com/yuin/goldmark"
)

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()

	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)
		writeWSText(conn, FragmentSystemMessage(fmt.Sprintf("Greška pri pokretanju Claude-a: %v", err)))
		return
	}

	// Send status
	writeWSText(conn, FragmentStatus(true))

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

	// Write pump: forward broadcast messages to this WebSocket
	wsDone := make(chan struct{})
	go func() {
		defer close(wsDone)
		for fragment := range sub.Ch {
			if err := conn.WriteMessage(websocket.TextMessage, []byte(fragment)); err != nil {
				return
			}
		}
	}()

	// 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 directly to this connection only
		writeWSText(conn, FragmentCombine(FragmentClearInput(), FragmentTypingIndicator(true)))

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

	// Don't close session — it stays alive for reconnect
}

// 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 "assistant":
				if event.Message != nil {
					for _, c := range event.Message.Content {
						if c.Type == "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 "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 event.Delta != nil && event.Delta.Text != "" {
					currentText.WriteString(event.Delta.Text)
					fragment := FragmentAssistantChunk(currentMsgID, event.Delta.Text)
					sess.AddMessage(ChatMessage{
						Role:      "assistant",
						Content:   fragment,
						Timestamp: time.Now(),
					})
				}

			case "content_block_stop":
				if currentText.Len() > 0 && currentMsgID != "" {
					rendered := renderMarkdown(currentText.String())
					fragment := FragmentAssistantComplete(currentMsgID, rendered)
					sess.AddMessage(ChatMessage{
						Role:      "assistant",
						Content:   fragment,
						Timestamp: time.Now(),
					})
				}

			case "result":
				fragment := FragmentTypingIndicator(false)
				sess.AddMessage(ChatMessage{
					Role:      "system",
					Content:   fragment,
					Timestamp: time.Now(),
				})
				if event.Result != nil && event.Result.CostUSD > 0 {
					costMsg := FragmentSystemMessage(fmt.Sprintf("Gotovo (%.4f USD)", event.Result.CostUSD))
					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 renderMarkdown(text string) string {
	var buf bytes.Buffer
	if err := goldmark.Convert([]byte(text), &buf); err != nil {
		return text
	}
	return buf.String()
}

func writeWSText(conn *websocket.Conn, text string) {
	conn.WriteMessage(websocket.TextMessage, []byte(text))
}