import SwiftUI
import AVFoundation // 用於語音合成
import Combine      // 匯入此框架才能使用 ObservableObject 與 @Published

// MARK: - 1. 資料模型與結構
struct ChatMessage: Identifiable, Equatable {
    let id = UUID()
    let content: String
    let isUser: Bool
}

struct OllamaRequest: Encodable {
    let model: String
    let messages: [OllamaMessage]
    let stream: Bool
}

struct OllamaMessage: Codable {
    let role: String
    let content: String
}

struct OllamaResponse: Decodable {
    let message: OllamaMessage
}

// MARK: - 2. 語音管理器
class SpeechManager: ObservableObject {
    private let synthesizer = AVSpeechSynthesizer()
    
    // @Published 需要 Combine 框架支援
    @Published var isMuted: Bool = false
    
    func speak(_ text: String) {
        // 如果正在說話，先停止
        if synthesizer.isSpeaking {
            synthesizer.stopSpeaking(at: .immediate)
        }
        
        if isMuted { return }
        
        let utterance = AVSpeechUtterance(string: text)
        // 設定語速 (0.0 ~ 1.0)，0.5 標準，稍微調慢一點比較自然
        utterance.rate = 0.5 
        
        // 設定語系：嘗試使用台灣繁體中文，若系統不支援會使用預設，如果希望唸英文比較標準，可以改為 "en-US"
        utterance.voice = AVSpeechSynthesisVoice(language: "zh-TW")
        
        synthesizer.speak(utterance)
    }
    
    func stop() {
        synthesizer.stopSpeaking(at: .immediate)
    }
}

// MARK: - 3. 主視圖 (ContentView)
struct ContentView: View {
    @State private var inputText: String = ""
    @State private var messages: [ChatMessage] = []
    @State private var isLoading: Bool = false
    
    // 初始化語音管理器
    @StateObject private var speechManager = SpeechManager()
    
    private let modelName = "gemma3:4b"
    
    var body: some View {
        ZStack {
            // 背景：深色風格
            Color(red: 0.1, green: 0.1, blue: 0.12)
                .ignoresSafeArea()
            
            VStack(spacing: 0) {
                // A. 頂部標題列
                HStack {
                    Text("Ollama Chat")
                        .font(.headline)
                        .foregroundColor(.gray)
                    
                    Spacer()
                    
                    // 靜音按鈕開關
                    Button(action: {
                        speechManager.isMuted.toggle()
                        if speechManager.isMuted { speechManager.stop() }
                    }) {
                        Image(systemName: speechManager.isMuted ? "speaker.slash.fill" : "speaker.wave.2.fill")
                            .foregroundColor(speechManager.isMuted ? .gray : .purple)
                            .padding(8)
                            .background(Color.black.opacity(0.3))
                            .clipShape(Circle())
                    }
                    .help(speechManager.isMuted ? "開啟語音" : "靜音")
                    
                    // 模型標籤
                    Text(modelName)
                        .font(.caption)
                        .padding(6)
                        .background(Color.purple.opacity(0.3))
                        .cornerRadius(8)
                        .foregroundColor(.purple)
                }
                .padding()
                .background(Color.black.opacity(0.5))
                
                // B. 訊息顯示區
                ScrollViewReader { proxy in
                    ScrollView {
                        LazyVStack(spacing: 12) {
                            ForEach(messages) { msg in
                                MessageBubble(message: msg)
                            }
                            if isLoading {
                                TypingIndicator()
                            }
                        }
                        .padding()
                    }
                    .onChange(of: messages) { _, _ in
                        if let lastId = messages.last?.id {
                            withAnimation {
                                proxy.scrollTo(lastId, anchor: .bottom)
                            }
                        }
                    }
                }
                
                // C. 底部輸入區
                HStack(spacing: 10) {
                    TextField("輸入訊息...", text: $inputText)
                        .padding(10)
                        .background(Color(white: 0.2))
                        .cornerRadius(20)
                        .foregroundColor(.white)
                        .overlay(
                            HStack {
                                if inputText.isEmpty {
                                    Text("Ask Gemma...")
                                        .foregroundColor(.gray)
                                        .padding(.leading, 12)
                                        .allowsHitTesting(false)
                                }
                                Spacer()
                            }
                        )
                        .onSubmit {
                            sendMessage()
                        }
                    
                    Button(action: sendMessage) {
                        Image(systemName: "paperplane.fill")
                            .font(.system(size: 20))
                            .foregroundColor(inputText.isEmpty ? .gray : .purple)
                            .padding(10)
                            .background(Color(white: 0.2))
                            .clipShape(Circle())
                    }
                    .disabled(inputText.isEmpty || isLoading)
                }
                .padding()
                .background(Color.black.opacity(0.8))
            }
        }
        .preferredColorScheme(.dark)
    }
    
    // MARK: - 4. 邏輯功能
    func sendMessage() {
        let cleanInput = inputText.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !cleanInput.isEmpty else { return }
        
        // 停止上一句語音
        speechManager.stop()
        
        let userMsg = cleanInput
        inputText = ""
        messages.append(ChatMessage(content: userMsg, isUser: true))
        isLoading = true
        
        // 準備 API 請求
        // 注意：iOS 模擬器請用 127.0.0.1，macOS App 若有開 Sandbox 也要設權限
        guard let url = URL(string: "http://127.0.0.1:11434/api/chat") else { return }
        
        let apiMessages = [OllamaMessage(role: "user", content: userMsg)]
        let requestBody = OllamaRequest(
            model: modelName,
            messages: apiMessages,
            stream: false
        )
        
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.httpBody = try? JSONEncoder().encode(requestBody)
        
        URLSession.shared.dataTask(with: request) { data, response, error in
            DispatchQueue.main.async {
                isLoading = false
                
                if let error = error {
                    let errMsg = "連線錯誤: \(error.localizedDescription)"
                    messages.append(ChatMessage(content: errMsg, isUser: false))
                    return
                }
                
                guard let data = data,
                      let result = try? JSONDecoder().decode(OllamaResponse.self, from: data) else {
                    messages.append(ChatMessage(content: "解析錯誤", isUser: false))
                    return
                }
                
                let aiResponse = result.message.content
                messages.append(ChatMessage(content: aiResponse, isUser: false))
                
                // MARK: 觸發語音朗讀
                speechManager.speak(aiResponse)
            }
        }.resume()
    }
}

// MARK: - 5. UI 元件
struct MessageBubble: View {
    let message: ChatMessage
    
    var body: some View {
        HStack {
            if message.isUser { Spacer() }
            
            Text(message.content)
                .padding(12)
                .background(message.isUser ? Color.purple : Color(white: 0.2))
                .foregroundColor(.white)
                .cornerRadius(16)
                .frame(maxWidth: 300, alignment: message.isUser ? .trailing : .leading)
                .textSelection(.enabled)
            
            if !message.isUser { Spacer() }
        }
    }
}

struct TypingIndicator: View {
    var body: some View {
        HStack {
            Text("Gemma is thinking...")
                .font(.caption)
                .italic()
                .foregroundColor(.gray)
            Spacer()
        }
        .padding(.leading)
    }
}

#Preview {
    ContentView()
}