import express from 'express';
import { createServer as createViteServer } from 'vite';
import fs from 'node:fs';
import path from 'node:path';
import process from 'node:process';
import zlib from 'node:zlib';
import { fileURLToPath } from 'node:url';

type ProjectStatus = 'pending' | 'completed' | 'processing';

interface UserRecord {
  id: number;
  name: string;
  account: string;
  password: string;
  department: string;
  date: string;
}

interface ProjectRecord {
  id: string;
  name: string;
  createTime: string;
  status: ProjectStatus;
  dicomCount: number;
  hasModel: boolean;
  dicomPath: string;
  modelPath: string;
  modelCount: number;
  stlFiles: string[];
  maskFormats: Array<'nii' | 'nii.gz'>;
  exportedMaskCount: number;
  isDefault?: boolean;
}

interface SessionRecord {
  authenticated: boolean;
  account: string | null;
  lastUpdated: string;
}

interface AppState {
  users: UserRecord[];
  projects: ProjectRecord[];
  session: SessionRecord;
  updatedAt: string;
}

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);
const repoRoot = path.resolve(__dirname, '..');
const dataDir = path.join(__dirname, 'data');
const exportDir = path.join(__dirname, 'exports');
const statePath = path.join(dataDir, 'state.json');
const dicomDir = path.join(repoRoot, 'Head_CT_DICOM');
const modelDir = path.join(repoRoot, 'Head_CT_ReConstruct');

function today() {
  return new Intl.DateTimeFormat('sv-SE', { timeZone: 'Asia/Shanghai' }).format(new Date());
}

function now() {
  return new Date().toISOString();
}

function ensureDir(dir: string) {
  fs.mkdirSync(dir, { recursive: true });
}

function listFiles(dir: string, extension: string) {
  if (!fs.existsSync(dir)) {
    return [];
  }

  return fs
    .readdirSync(dir, { withFileTypes: true })
    .filter((entry) => entry.isFile() && entry.name.toLowerCase().endsWith(extension))
    .map((entry) => entry.name)
    .sort((a, b) => a.localeCompare(b, 'zh-Hans-CN'));
}

function publicUser(user: UserRecord) {
  const { password: _password, ...rest } = user;
  return rest;
}

function publicSession(state: AppState) {
  const user = state.session.account
    ? state.users.find((candidate) => candidate.account === state.session.account)
    : null;

  return {
    authenticated: state.session.authenticated && Boolean(user),
    currentUser: user
      ? {
          id: user.id,
          name: user.name,
          account: user.account,
          department: user.department,
        }
      : null,
    lastUpdated: state.session.lastUpdated,
  };
}

function buildDefaultProject(): ProjectRecord {
  const stlFiles = listFiles(modelDir, '.stl');

  return {
    id: 'head-ct-demo',
    name: '头部 CT 模型逆向体素化演示',
    createTime: today(),
    status: 'completed',
    dicomCount: listFiles(dicomDir, '.dcm').length,
    hasModel: stlFiles.length > 0,
    dicomPath: 'Head_CT_DICOM',
    modelPath: 'Head_CT_ReConstruct',
    modelCount: stlFiles.length,
    stlFiles,
    maskFormats: ['nii', 'nii.gz'],
    exportedMaskCount: 0,
    isDefault: true,
  };
}

function buildEmptyProject(name: string): ProjectRecord {
  return {
    id: `project-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 7)}`,
    name,
    createTime: today(),
    status: 'pending',
    dicomCount: 0,
    hasModel: false,
    dicomPath: '',
    modelPath: '',
    modelCount: 0,
    stlFiles: [],
    maskFormats: ['nii', 'nii.gz'],
    exportedMaskCount: 0,
  };
}

function defaultState(): AppState {
  return {
    users: [
      { id: 1, name: 'Admin', account: 'admin', password: '123456', department: 'admin', date: today() },
      { id: 2, name: 'Doctor Li', account: 'doctor_li', password: '123456', department: '肝胆外科', date: today() },
    ],
    projects: [buildDefaultProject()],
    session: { authenticated: false, account: null, lastUpdated: now() },
    updatedAt: now(),
  };
}

function normalizeState(state: AppState): AppState {
  const defaultProject = buildDefaultProject();
  const customProjects = Array.isArray(state.projects)
    ? state.projects
        .filter((project) => project.id !== defaultProject.id)
        .map((project) => ({
          ...project,
          exportedMaskCount: project.exportedMaskCount ?? 0,
          maskFormats: project.maskFormats ?? ['nii', 'nii.gz'],
        }))
    : [];

  return {
    ...state,
    projects: [
      {
        ...defaultProject,
        name: state.projects?.find((project) => project.id === defaultProject.id)?.name ?? defaultProject.name,
        exportedMaskCount: state.projects?.find((project) => project.id === defaultProject.id)?.exportedMaskCount ?? 0,
      },
      ...customProjects,
    ],
  };
}

function readState(): AppState {
  ensureDir(dataDir);

  if (!fs.existsSync(statePath)) {
    const initialState = defaultState();
    writeState(initialState);
    return initialState;
  }

  try {
    const raw = fs.readFileSync(statePath, 'utf8');
    return normalizeState(JSON.parse(raw) as AppState);
  } catch {
    const recoveredState = defaultState();
    writeState(recoveredState);
    return recoveredState;
  }
}

function writeState(state: AppState) {
  ensureDir(dataDir);
  fs.writeFileSync(statePath, JSON.stringify({ ...state, updatedAt: now() }, null, 2));
}

function createNiftiMask(project: ProjectRecord, compressed: boolean) {
  const width = 64;
  const height = 64;
  const depth = 64;
  const headerSize = 348;
  const voxOffset = 352;
  const voxelCount = width * height * depth;
  const data = Buffer.alloc(voxelCount);
  const center = [width / 2, height / 2, depth / 2];

  for (let z = 0; z < depth; z += 1) {
    for (let y = 0; y < height; y += 1) {
      for (let x = 0; x < width; x += 1) {
        const dx = (x - center[0]) / 18;
        const dy = (y - center[1]) / 15;
        const dz = (z - center[2]) / 20;
        const index = z * width * height + y * width + x;
        const radius = dx * dx + dy * dy + dz * dz;

        if (radius < 1) {
          data[index] = 1;
        }

        const tumorDx = (x - 42) / 8;
        const tumorDy = (y - 30) / 7;
        const tumorDz = (z - 34) / 7;
        if (tumorDx * tumorDx + tumorDy * tumorDy + tumorDz * tumorDz < 1) {
          data[index] = 2;
        }
      }
    }
  }

  const header = Buffer.alloc(voxOffset);
  header.writeInt32LE(headerSize, 0);
  header.writeInt16LE(3, 40);
  header.writeInt16LE(width, 42);
  header.writeInt16LE(height, 44);
  header.writeInt16LE(depth, 46);
  header.writeInt16LE(1, 48);
  header.writeInt16LE(1, 50);
  header.writeInt16LE(1, 52);
  header.writeInt16LE(1, 54);
  header.writeInt16LE(2, 70);
  header.writeInt16LE(8, 72);
  header.writeFloatLE(1, 76);
  header.writeFloatLE(1, 80);
  header.writeFloatLE(1, 84);
  header.writeFloatLE(1, 88);
  header.writeFloatLE(voxOffset, 108);
  header.writeFloatLE(1, 112);
  header.write('ReVoxelSeg demo mask', 148, 'ascii');
  header.write(`Project ${project.id}`, 228, 'ascii');
  header.write('n+1\0', 344, 'ascii');

  const nifti = Buffer.concat([header, data]);
  return compressed ? zlib.gzipSync(nifti) : nifti;
}

function findProject(state: AppState, projectId: string) {
  return state.projects.find((candidate) => candidate.id === projectId);
}

function getProjectDicomFiles(project: ProjectRecord) {
  if (project.id !== 'head-ct-demo') {
    return [];
  }
  return listFiles(dicomDir, '.dcm').sort((a, b) => Number.parseInt(a) - Number.parseInt(b));
}

function readAsciiValue(buffer: Buffer, start: number, length: number) {
  return buffer.subarray(start, start + length).toString('ascii').replace(/\0/g, '').trim();
}

function findExplicitTag(buffer: Buffer, group: number, element: number) {
  const pattern = Buffer.from([
    group & 0xff,
    (group >> 8) & 0xff,
    element & 0xff,
    (element >> 8) & 0xff,
  ]);
  const longVr = ['OB', 'OD', 'OF', 'OL', 'OW', 'SQ', 'UC', 'UR', 'UT', 'UN'];
  let offset = buffer.indexOf(pattern, 132);

  while (offset >= 0 && offset + 8 < buffer.length) {
    const vr = buffer.subarray(offset + 4, offset + 6).toString('ascii');
    if (/^[A-Z]{2}$/.test(vr)) {
      if (longVr.includes(vr)) {
        const length = buffer.readUInt32LE(offset + 8);
        return { valueOffset: offset + 12, length, vr };
      }
      const length = buffer.readUInt16LE(offset + 6);
      return { valueOffset: offset + 8, length, vr };
    }

    offset = buffer.indexOf(pattern, offset + 1);
  }

  return null;
}

function parseDicomPreview(filePath: string) {
  const buffer = fs.readFileSync(filePath);
  const rowsTag = findExplicitTag(buffer, 0x0028, 0x0010);
  const columnsTag = findExplicitTag(buffer, 0x0028, 0x0011);
  const bitsTag = findExplicitTag(buffer, 0x0028, 0x0100);
  const representationTag = findExplicitTag(buffer, 0x0028, 0x0103);
  const centerTag = findExplicitTag(buffer, 0x0028, 0x1050);
  const widthTag = findExplicitTag(buffer, 0x0028, 0x1051);
  const interceptTag = findExplicitTag(buffer, 0x0028, 0x1052);
  const slopeTag = findExplicitTag(buffer, 0x0028, 0x1053);
  const pixelTag = findExplicitTag(buffer, 0x7fe0, 0x0010);

  const rows = rowsTag ? buffer.readUInt16LE(rowsTag.valueOffset) : 0;
  const columns = columnsTag ? buffer.readUInt16LE(columnsTag.valueOffset) : 0;
  const bitsAllocated = bitsTag ? buffer.readUInt16LE(bitsTag.valueOffset) : 16;
  const pixelRepresentation = representationTag ? buffer.readUInt16LE(representationTag.valueOffset) : 0;
  const windowCenter = centerTag ? Number.parseFloat(readAsciiValue(buffer, centerTag.valueOffset, centerTag.length).split('\\')[0]) || 40 : 40;
  const windowWidth = widthTag ? Number.parseFloat(readAsciiValue(buffer, widthTag.valueOffset, widthTag.length).split('\\')[0]) || 400 : 400;
  const rescaleIntercept = interceptTag ? Number.parseFloat(readAsciiValue(buffer, interceptTag.valueOffset, interceptTag.length)) || 0 : 0;
  const rescaleSlope = slopeTag ? Number.parseFloat(readAsciiValue(buffer, slopeTag.valueOffset, slopeTag.length)) || 1 : 1;
  const pixelOffset = pixelTag?.valueOffset ?? -1;
  const pixelLength = pixelTag?.length ?? 0;

  if (!rows || !columns || pixelOffset < 0) {
    throw new Error('无法解析当前 DICOM 像素数据');
  }

  const count = rows * columns;
  const pixels = Buffer.alloc(count);
  const min = windowCenter - windowWidth / 2;
  const max = windowCenter + windowWidth / 2;

  for (let i = 0; i < count; i += 1) {
    const position = pixelOffset + i * (bitsAllocated / 8);
    if (position + 1 >= buffer.length || position >= pixelOffset + pixelLength) {
      break;
    }
    const raw = bitsAllocated === 16
      ? (pixelRepresentation ? buffer.readInt16LE(position) : buffer.readUInt16LE(position))
      : buffer.readUInt8(position);
    const hu = raw * rescaleSlope + rescaleIntercept;
    const normalized = Math.max(0, Math.min(255, Math.round(((hu - min) / (max - min)) * 255)));
    pixels[i] = normalized;
  }

  return {
    width: columns,
    height: rows,
    pixels: pixels.toString('base64'),
    windowCenter,
    windowWidth,
  };
}

async function startServer() {
  const app = express();
  const host = process.argv.includes('--host') ? process.argv[process.argv.indexOf('--host') + 1] : '0.0.0.0';
  const portArg = process.argv.includes('--port') ? process.argv[process.argv.indexOf('--port') + 1] : process.env.PORT;
  const port = Number(portArg ?? 4000);

  ensureDir(exportDir);
  app.use(express.json());

  app.get('/api/health', (_req, res) => {
    res.json({ ok: true, service: 'revoxelseg-dicom', time: now() });
  });

  app.get('/api/session', (_req, res) => {
    res.json(publicSession(readState()));
  });

  app.post('/api/login', (req, res) => {
    const { account, password } = req.body as { account?: string; password?: string };
    const state = readState();
    const user = state.users.find((candidate) => candidate.account === account && candidate.password === password);

    if (!user) {
      res.status(401).json({ message: '账号或密码错误' });
      return;
    }

    state.session = { authenticated: true, account: user.account, lastUpdated: now() };
    writeState(state);
    res.json(publicSession(state));
  });

  app.post('/api/logout', (_req, res) => {
    const state = readState();
    state.session = { authenticated: false, account: null, lastUpdated: now() };
    writeState(state);
    res.json(publicSession(state));
  });

  app.get('/api/users', (_req, res) => {
    res.json(readState().users.map(publicUser));
  });

  app.get('/api/projects', (_req, res) => {
    res.json(readState().projects);
  });

  app.post('/api/projects', (req, res) => {
    const name = typeof req.body?.name === 'string' ? req.body.name.trim() : '';
    if (!name) {
      res.status(400).json({ message: '项目名称不能为空' });
      return;
    }

    const state = readState();
    const project = buildEmptyProject(name);
    state.projects.push(project);
    writeState(state);
    res.status(201).json(project);
  });

  app.get('/api/projects/:projectId', (req, res) => {
    const project = findProject(readState(), req.params.projectId);
    if (!project) {
      res.status(404).json({ message: '项目不存在' });
      return;
    }
    res.json(project);
  });

  app.patch('/api/projects/:projectId', (req, res) => {
    const name = typeof req.body?.name === 'string' ? req.body.name.trim() : '';
    if (!name) {
      res.status(400).json({ message: '项目名称不能为空' });
      return;
    }

    const state = readState();
    const project = findProject(state, req.params.projectId);
    if (!project) {
      res.status(404).json({ message: '项目不存在' });
      return;
    }

    project.name = name;
    writeState(state);
    res.json(project);
  });

  app.get('/api/projects/:projectId/dicom-preview', (req, res) => {
    const project = findProject(readState(), req.params.projectId);
    if (!project) {
      res.status(404).json({ message: '项目不存在' });
      return;
    }

    const files = getProjectDicomFiles(project);
    if (!files.length) {
      res.status(404).json({ message: '当前项目没有可预览的 DICOM 文件' });
      return;
    }

    const requestedSlice = Number.parseInt(String(req.query.slice ?? '0'), 10);
    const slice = Math.max(0, Math.min(files.length - 1, Number.isFinite(requestedSlice) ? requestedSlice : 0));
    try {
      const preview = parseDicomPreview(path.join(dicomDir, files[slice]));
      res.json({
        ...preview,
        slice,
        total: files.length,
        fileName: files[slice],
      });
    } catch (error) {
      res.status(422).json({ message: error instanceof Error ? error.message : 'DICOM 预览失败' });
    }
  });

  app.get('/api/projects/:projectId/models/:fileName', (req, res) => {
    const project = findProject(readState(), req.params.projectId);
    const fileName = path.basename(req.params.fileName);

    if (!project || project.id !== 'head-ct-demo' || !project.stlFiles.includes(fileName)) {
      res.status(404).json({ message: '模型文件不存在' });
      return;
    }

    res.sendFile(path.join(modelDir, fileName));
  });

  app.get('/api/overview', (_req, res) => {
    const state = readState();
    const dicomCount = state.projects.reduce((sum, project) => sum + project.dicomCount, 0);
    const modelCount = state.projects.reduce((sum, project) => sum + project.modelCount, 0);
    const exportedMaskProjects = state.projects.filter((project) => project.exportedMaskCount > 0).length;

    res.json({
      totalProjects: state.projects.length,
      processedProjects: exportedMaskProjects,
      exportedMaskProjects,
      dicomCount,
      modelCount,
      chartData: [
        { name: 'Mon', projects: state.projects.length, processing: exportedMaskProjects },
        { name: 'Tue', projects: state.projects.length, processing: exportedMaskProjects },
        { name: 'Wed', projects: state.projects.length, processing: exportedMaskProjects },
        { name: 'Thu', projects: state.projects.length, processing: exportedMaskProjects },
        { name: 'Fri', projects: state.projects.length, processing: exportedMaskProjects },
        { name: 'Sat', projects: state.projects.length, processing: exportedMaskProjects },
        { name: 'Sun', projects: state.projects.length, processing: exportedMaskProjects },
      ],
    });
  });

  app.post('/api/demo/reset', (_req, res) => {
    const state = defaultState();
    writeState(state);
    res.json({ ok: true, projects: state.projects, users: state.users.map(publicUser) });
  });

  app.post('/api/projects/:projectId/export-mask', (req, res) => {
    const state = readState();
    const project = state.projects.find((candidate) => candidate.id === req.params.projectId);

    if (!project) {
      res.status(404).json({ message: '项目不存在' });
      return;
    }

    const format = req.query.format === 'nii' ? 'nii' : 'nii.gz';
    const compressed = format === 'nii.gz';
    const mask = createNiftiMask(project, compressed);
    const filename = `${project.id}-segmentation-mask.${format}`;
    const outputPath = path.join(exportDir, filename);
    fs.writeFileSync(outputPath, mask);
    project.exportedMaskCount += 1;
    writeState(state);

    res.setHeader('Content-Type', compressed ? 'application/gzip' : 'application/octet-stream');
    res.setHeader('Content-Disposition', `attachment; filename="${filename}"`);
    res.send(mask);
  });

  if (process.env.NODE_ENV === 'production') {
    app.use(express.static(path.join(__dirname, 'dist')));
    app.get('*', (_req, res) => {
      res.sendFile(path.join(__dirname, 'dist', 'index.html'));
    });
  } else {
    const vite = await createViteServer({
      server: { middlewareMode: true, hmr: { port: 24679 } },
      appType: 'spa',
    });
    app.use(vite.middlewares);
  }

  app.listen(port, host, () => {
    console.log(`ReVoxelSeg DICOM server ready at http://${host}:${port}/`);
  });
}

startServer().catch((error) => {
  console.error(error);
  process.exit(1);
});