/**
 * =============================================================================
 *            动态版 - 姿态识别与模型管理脚本 (v2.0)
 * =============================================================================
 * 功能列表:
 * - 实时姿态检测 (MoveNet)
 * - KNN 分类器训练
 * - 实时姿态预测
 * - 坐标完美对齐 (Canvas与Video重叠)
 * - ✅ 动态添加/删除/重命名姿态类别
 * - ✅ 模型导出为包含类别信息的 JSON 文件
 * - ✅ 从 JSON 文件导入模型并恢复类别状态
 * =============================================================================
 */

'use strict';

// --- 全局变量和常量 ---
const videoElement = document.getElementById('video');
const canvasElement = document.getElementById('canvas');
const canvasCtx = canvasElement.getContext('2d');
const statusElement = document.getElementById('status');
const resultElement = document.getElementById('result-text');

// UI元素
const poseClassesContainer = document.getElementById('pose-classes-container');
const addClassButton = document.getElementById('btn-add-class');
const predictButton = document.getElementById('btn-predict');
const exportButton = document.getElementById('btn-export');
const importButton = document.getElementById('btn-import');
const fileImporter = document.getElementById('file-importer');

let detector, classifier, animationFrameId;
let isPredicting = false;

// 📌 核心状态管理: 使用一个对象来管理所有动态状态
const appState = {
    classMap: {},      // 存储 classId -> className 的映射, e.g., {0: '姿态 A', 1: '姿态 B'}
    nextClassId: 0     // 用于生成唯一的 classId
};

// --- 主应用逻辑 ---

/**
 * 初始化应用，加载模型并设置摄像头
 */
async function init() {
    try {
        classifier = knnClassifier.create();
        const detectorConfig = { modelType: poseDetection.movenet.modelType.SINGLEPOSE_LIGHTNING };
        detector = await poseDetection.createDetector(poseDetection.SupportedModels.MoveNet, detectorConfig);

        await setupCamera();
        setupEventListeners();
        mainLoop();

        statusElement.innerText = "模型和摄像头已就绪!";
        enableControls();
        addNewClass(); // 默认创建第一个类别

    } catch (error) {
        console.error("初始化失败:", error);
        statusElement.innerText = "初始化失败，请检查摄像头权限或刷新。";
        statusElement.style.backgroundColor = '#fce8e6';
        statusElement.style.color = '#d93025';
    }
}

/**
 * 设置和启动用户摄像头
 */
async function setupCamera() {
    const stream = await navigator.mediaDevices.getUserMedia({ video: true });
    videoElement.srcObject = stream;
    return new Promise((resolve) => {
        videoElement.onloadedmetadata = () => {
            videoElement.play();
            canvasElement.width = videoElement.videoWidth;
            canvasElement.height = videoElement.videoHeight;
            resolve();
        };
    });
}

/**
 * 为所有交互式元素绑定事件监听器
 */
function setupEventListeners() {
    addClassButton.addEventListener('click', addNewClass);
    predictButton.addEventListener('click', togglePrediction);
    exportButton.addEventListener('click', exportModel);
    importButton.addEventListener('click', () => fileImporter.click());
    fileImporter.addEventListener('change', importModel);
}

// --- 动态类别管理 ---

/**
 * 动态创建一个新类别的UI元素并添加到页面
 * @param {number} classId - 类别的唯一ID
 * @param {string} className - 类别的名称
 */
function createClassUI(classId, className) {
    const poseClassDiv = document.createElement('div');
    poseClassDiv.className = 'pose-class';
    poseClassDiv.dataset.classId = classId;

    poseClassDiv.innerHTML = `
        <div class="class-info">
            <input type="text" class="class-name-input" value="${className}" data-class-id="${classId}">
            <span class="sample-count">(0 样本)</span>
        </div>
        <div class="class-actions">
            <button class="btn-sample" data-class-id="${classId}">采集样本</button>
            <button class="btn-delete-class" title="删除类别" data-class-id="${classId}">×</button>
        </div>
    `;

    poseClassesContainer.appendChild(poseClassDiv);

    // 为新创建的元素绑定事件
    const nameInput = poseClassDiv.querySelector('.class-name-input');
    nameInput.addEventListener('change', (e) => {
        appState.classMap[classId] = e.target.value;
    });

    const sampleButton = poseClassDiv.querySelector('.btn-sample');
    sampleButton.addEventListener('click', () => addExample(classId));
    
    if (isPredicting) sampleButton.disabled = true; // 如果在预测中，禁用新按钮

    const deleteButton = poseClassDiv.querySelector('.btn-delete-class');
    deleteButton.addEventListener('click', () => deleteClass(classId));
}

/**
 * 添加一个新的姿态类别
 */
function addNewClass() {
    const classId = appState.nextClassId;
    const className = `Class ${classId + 1}`;
    appState.classMap[classId] = className;
    appState.nextClassId++;
    createClassUI(classId, className);
}

/**
 * 删除一个指定的姿态类别
 * @param {number} classId - 要删除的类别的ID
 */
function deleteClass(classId) {
    if (confirm(`确定要删除类别 "${appState.classMap[classId]}" 吗？所有样本都将丢失。`)) {
        // 从UI中移除
        const elementToRemove = poseClassesContainer.querySelector(`[data-class-id="${classId}"]`);
        if (elementToRemove) elementToRemove.remove();

        // 从状态和分类器中移除
        delete appState.classMap[classId];
        classifier.clearClass(classId);

        updateSampleCounts();
        updatePredictionUI(); // 检查是否还有类别可以预测
        checkExportAbility();
    }
}

/**
 * 采集一个姿态样本并添加到KNN分类器
 * @param {number} classId 类别的ID
 */
async function addExample(classId) {
    const poses = await detector.estimatePoses(videoElement, { flipHorizontal: true });
    if (poses && poses.length > 0) {
        const poseTensor = flattenPose(poses[0]);
        classifier.addExample(poseTensor, classId);
        poseTensor.dispose();
        
        updateSampleCounts();
        checkExportAbility();
    } else {
        console.warn(`为类别 ${appState.classMap[classId]} 采集样本失败，未检测到姿态。`);
    }
}

// --- 模型与预测逻辑 ---

/**
 * 开始或停止姿态预测
 */
function togglePrediction() {
    if (classifier.getNumClasses() === 0) {
        alert("请先为至少一个姿态采集样本后再开始预测！");
        return;
    }
    isPredicting = !isPredicting;
    updatePredictionUI();
}

/**
 * 应用的主循环
 */
async function mainLoop() {
    const poses = await detector.estimatePoses(videoElement, { flipHorizontal: true });
    canvasCtx.clearRect(0, 0, canvasElement.width, canvasElement.height);

    if (poses && poses.length > 0) {
        drawPose(poses[0]);
        if (isPredicting && classifier.getNumClasses() > 0) {
            const poseTensor = flattenPose(poses[0]);
            const result = await classifier.predictClass(poseTensor, 3);
            poseTensor.dispose();
            
            const confidence = Math.round(result.confidences[result.label] * 100);
            // 📌 动态获取类别名称
            const predictedClassName = appState.classMap[result.label] || '未知类别';
            resultElement.innerText = `姿态: ${predictedClassName} (${confidence}%)`;
        }
    }
    animationFrameId = requestAnimationFrame(mainLoop);
}

// --- 模型管理函数 (已更新以支持动态类别) ---

/**
 * 导出KNN模型为包含类别信息的JSON文件
 */
function exportModel() {
    if (classifier.getNumClasses() === 0) {
        alert('模型中还没有任何样本，无法导出！');
        return;
    }

    const dataset = classifier.getClassifierDataset();
    const datasetObj = {};
    Object.keys(dataset).forEach((key) => {
        const data = dataset[key];
        datasetObj[key] = data.arraySync();
    });

    // 📌 导出格式大更新: 同时保存 classMap 和 dataset
    const modelData = {
        classMap: appState.classMap,
        dataset: datasetObj
    };

    const jsonStr = JSON.stringify(modelData);
    const blob = new Blob([jsonStr], { type: "application/json" });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `pose-knn-model.json`;
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    URL.revokeObjectURL(url);
}

/**
 * 从JSON文件导入KNN模型并恢复类别状态
 * @param {Event} event
 */
function importModel(event) {
    const file = event.target.files[0];
    if (!file) return;

    const reader = new FileReader();
    reader.onload = (e) => {
        try {
            const modelData = JSON.parse(e.target.result);
            
            // 📌 导入格式验证
            if (!modelData.classMap || !modelData.dataset) {
                throw new Error("无效的模型文件格式。");
            }
            
            // 1. 清理现有状态
            classifier.clearAllClasses();
            poseClassesContainer.innerHTML = '';
            appState.classMap = {};

            // 2. 加载新状态
            appState.classMap = modelData.classMap;
            const classIds = Object.keys(appState.classMap).map(Number);
            appState.nextClassId = classIds.length > 0 ? Math.max(...classIds) + 1 : 0;
            
            // 3. 恢复UI
            classIds.forEach(id => {
                createClassUI(id, appState.classMap[id]);
            });

            // 4. 加载模型数据
            const newDataset = {};
            Object.keys(modelData.dataset).forEach((key) => {
                newDataset[key] = tf.tensor(modelData.dataset[key]);
            });
            classifier.setClassifierDataset(newDataset);
            
            updateSampleCounts();
            checkExportAbility();
            alert('模型导入成功！');

        } catch (error) {
            console.error("导入模型失败:", error);
            alert(`导入失败！请确保文件是正确的模型JSON文件。\n错误: ${error.message}`);
        } finally {
            fileImporter.value = '';
        }
    };
    reader.readAsText(file);
}


// --- 辅助和UI更新函数 ---

function flattenPose(pose) {
    const keypoints = pose.keypoints.map(p => [p.x / videoElement.videoWidth, p.y / videoElement.videoHeight]).flat();
    return tf.tensor(keypoints);
}

function drawPose(pose) {
    // 绘制关键点和骨骼...
    if (pose.keypoints) {
        // 绘制关键点
        for (const keypoint of pose.keypoints) {
            if (keypoint.score > 0.3) {
                canvasCtx.beginPath();
                canvasCtx.arc(keypoint.x, keypoint.y, 5, 0, 2 * Math.PI);
                canvasCtx.fillStyle = '#1a73e8'; 
                canvasCtx.fill();
            }
        }
        // 绘制骨骼连接线
        const adjacentPairs = poseDetection.util.getAdjacentPairs(poseDetection.SupportedModels.MoveNet);
        adjacentPairs.forEach(([i, j]) => {
            const kp1 = pose.keypoints[i];
            const kp2 = pose.keypoints[j];
            if (kp1.score > 0.3 && kp2.score > 0.3) {
                canvasCtx.beginPath();
                canvasCtx.moveTo(kp1.x, kp1.y);
                canvasCtx.lineTo(kp2.x, kp2.y);
                canvasCtx.strokeStyle = 'blue';
                canvasCtx.lineWidth = 2;
                canvasCtx.stroke();
            }
        });
    }
}

/**
 * 更新所有类别UI上的样本数量
 */
function updateSampleCounts() {
    const dataset = classifier.getClassifierDataset();
    const allClassElements = document.querySelectorAll('.pose-class');
    allClassElements.forEach(el => {
        const classId = parseInt(el.dataset.classId, 10);
        const classInfo = dataset[classId];
        const count = classInfo ? classInfo.shape[0] : 0;
        el.querySelector('.sample-count').innerText = `(${count} 样本)`;
    });
}

/**
 * 根据状态更新UI
 */
function updatePredictionUI() {
    const allActionButtons = document.querySelectorAll('.btn-sample, .btn-delete-class, .btn-add-class, #btn-import');
    if (isPredicting) {
        predictButton.innerText = "停止预测";
        predictButton.classList.add('stop');
        resultElement.innerText = "正在分析...";
        allActionButtons.forEach(btn => btn.disabled = true);
        document.querySelectorAll('.class-name-input').forEach(input => input.disabled = true);
        checkExportAbility();
    } else {
        predictButton.innerText = "开始预测";
        predictButton.classList.remove('stop');
        resultElement.innerText = "已停止";
        allActionButtons.forEach(btn => btn.disabled = false);
        document.querySelectorAll('.class-name-input').forEach(input => input.disabled = false);
        checkExportAbility();
    }
    // 只有在有类别且有样本时才能预测
    predictButton.disabled = isPredicting ? false : classifier.getNumClasses() === 0;
}

function enableControls() {
    [predictButton, importButton, exportButton, addClassButton].forEach(btn => btn.disabled = false);
    checkExportAbility();
}

/** 检查是否可以导出模型并更新按钮状态 */
function checkExportAbility() {
    exportButton.disabled = isPredicting || classifier.getNumClasses() === 0;
}

function cleanup() {
    if (detector) detector.dispose();
    if (classifier) classifier.clearAllClasses();
    if (animationFrameId) cancelAnimationFrame(animationFrameId);
}

// --- 启动应用 ---
window.onbeforeunload = cleanup;
init();