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';
type DicomPlane = 'axial' | 'sagittal' | 'coronal';
type DicomDisplayMode = 'default' | 'bone' | 'soft' | 'contrast';

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');
const dicomPreviewCache = new Map<string, unknown>();
const dicomVolumeCache = new Map<DicomDisplayMode, {
  frames: Buffer[];
  width: number;
  height: number;
  windowCenter: number;
  windowWidth: number;
  rowSpacing: number;
  columnSpacing: number;
  sliceSpacing: number;
  sliceThickness: number | null;
  spacingBetweenSlices: number | null;
}>();
const modelPreviewCache = new Map<string, unknown>();

interface DicomAttributes {
  patientName: string;
  patientId: string;
  studyDate: string;
  studyDescription: string;
  seriesDescription: string;
  modality: string;
  manufacturer: string;
  rows: number;
  columns: number;
  bitsAllocated: number;
  pixelRepresentation: number;
  windowCenter: number;
  windowWidth: number;
  rescaleIntercept: number;
  rescaleSlope: number;
  rowSpacing: number;
  columnSpacing: number;
  sliceThickness: number | null;
  spacingBetweenSlices: number | null;
  imagePosition: number[] | null;
}

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(naturalFileCompare);
}

function naturalFileCompare(a: string, b: string) {
  return a.localeCompare(b, 'zh-Hans-CN', { numeric: true, sensitivity: 'base' });
}

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');
}

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

function readTagString(buffer: Buffer, group: number, element: number) {
  const tag = findExplicitTag(buffer, group, element);
  return tag ? readAsciiValue(buffer, tag.valueOffset, tag.length) : '';
}

function readTagUInt16(buffer: Buffer, group: number, element: number, fallback = 0) {
  const tag = findExplicitTag(buffer, group, element);
  return tag && tag.valueOffset + 1 < buffer.length ? buffer.readUInt16LE(tag.valueOffset) : fallback;
}

function parseNumberList(value: string) {
  return value
    .split('\\')
    .map((item) => Number.parseFloat(item.trim()))
    .filter((item) => Number.isFinite(item));
}

function median(values: number[]) {
  if (!values.length) {
    return null;
  }
  const sorted = [...values].sort((a, b) => a - b);
  return sorted[Math.floor(sorted.length / 2)];
}

function parseDicomAttributes(buffer: Buffer, mode: DicomDisplayMode): DicomAttributes {
  const fallbackCenter = Number.parseFloat(readTagString(buffer, 0x0028, 0x1050).split('\\')[0]) || 40;
  const fallbackWidth = Number.parseFloat(readTagString(buffer, 0x0028, 0x1051).split('\\')[0]) || 400;
  const { windowCenter, windowWidth } = resolveDisplayWindow(mode, fallbackCenter, fallbackWidth);
  const pixelSpacing = parseNumberList(readTagString(buffer, 0x0028, 0x0030));
  const imagePosition = parseNumberList(readTagString(buffer, 0x0020, 0x0032));
  const sliceThickness = Number.parseFloat(readTagString(buffer, 0x0018, 0x0050));
  const spacingBetweenSlices = Number.parseFloat(readTagString(buffer, 0x0018, 0x0088));

  return {
    patientName: readTagString(buffer, 0x0010, 0x0010) || '未知',
    patientId: readTagString(buffer, 0x0010, 0x0020) || '未知',
    studyDate: readTagString(buffer, 0x0008, 0x0020) || '未知',
    studyDescription: readTagString(buffer, 0x0008, 0x1030) || '未知',
    seriesDescription: readTagString(buffer, 0x0008, 0x103e) || '未知',
    modality: readTagString(buffer, 0x0008, 0x0060) || '未知',
    manufacturer: readTagString(buffer, 0x0008, 0x0070) || '未知',
    rows: readTagUInt16(buffer, 0x0028, 0x0010),
    columns: readTagUInt16(buffer, 0x0028, 0x0011),
    bitsAllocated: readTagUInt16(buffer, 0x0028, 0x0100, 16),
    pixelRepresentation: readTagUInt16(buffer, 0x0028, 0x0103),
    windowCenter,
    windowWidth,
    rescaleIntercept: Number.parseFloat(readTagString(buffer, 0x0028, 0x1052)) || 0,
    rescaleSlope: Number.parseFloat(readTagString(buffer, 0x0028, 0x1053)) || 1,
    rowSpacing: pixelSpacing[0] || 1,
    columnSpacing: pixelSpacing[1] || pixelSpacing[0] || 1,
    sliceThickness: Number.isFinite(sliceThickness) ? Math.abs(sliceThickness) : null,
    spacingBetweenSlices: Number.isFinite(spacingBetweenSlices) ? Math.abs(spacingBetweenSlices) : null,
    imagePosition: imagePosition.length >= 3 ? imagePosition.slice(0, 3) : null,
  };
}

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 resolveDisplayWindow(mode: DicomDisplayMode, fallbackCenter: number, fallbackWidth: number) {
  if (mode === 'bone') {
    return { windowCenter: 500, windowWidth: 2000 };
  }
  if (mode === 'soft') {
    return { windowCenter: 40, windowWidth: 400 };
  }
  if (mode === 'contrast') {
    return { windowCenter: 80, windowWidth: 180 };
  }
  return { windowCenter: fallbackCenter, windowWidth: fallbackWidth };
}

function parseDicomPreview(filePath: string, mode: DicomDisplayMode = 'default') {
  const buffer = fs.readFileSync(filePath);
  const attrs = parseDicomAttributes(buffer, mode);
  const pixelTag = findExplicitTag(buffer, 0x7fe0, 0x0010);
  const pixelOffset = pixelTag?.valueOffset ?? -1;
  const pixelLength = pixelTag?.length ?? 0;

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

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

  for (let i = 0; i < count; i += 1) {
    const position = pixelOffset + i * (attrs.bitsAllocated / 8);
    if (position + 1 >= buffer.length || position >= pixelOffset + pixelLength) {
      break;
    }
    const raw = attrs.bitsAllocated === 16
      ? (attrs.pixelRepresentation ? buffer.readInt16LE(position) : buffer.readUInt16LE(position))
      : buffer.readUInt8(position);
    const hu = raw * attrs.rescaleSlope + attrs.rescaleIntercept;
    let normalized = Math.max(0, Math.min(255, Math.round(((hu - min) / (max - min)) * 255)));
    if (mode === 'contrast') {
      normalized = Math.max(0, Math.min(255, Math.round((normalized - 128) * 1.35 + 128)));
    }
    pixels[i] = normalized;
  }

  const enhancedPixels = enhanceDicomEdges(pixels, attrs.columns, attrs.rows);

  return {
    width: attrs.columns,
    height: attrs.rows,
    pixels: enhancedPixels.toString('base64'),
    windowCenter: attrs.windowCenter,
    windowWidth: attrs.windowWidth,
    mode,
    spacing: {
      row: attrs.rowSpacing,
      column: attrs.columnSpacing,
      slice: attrs.sliceThickness ?? attrs.spacingBetweenSlices ?? 1,
    },
    physicalSize: {
      width: attrs.columns * attrs.columnSpacing,
      height: attrs.rows * attrs.rowSpacing,
    },
    attributes: attrs,
  };
}

function parseDicomPixels(filePath: string, mode: DicomDisplayMode = 'default') {
  const preview = parseDicomPreview(filePath, mode);
  return {
    ...preview,
    pixelBuffer: Buffer.from(preview.pixels, 'base64'),
  };
}

function estimateSliceSpacing(parsed: ReturnType<typeof parseDicomPixels>[]) {
  const positionDiffs: number[] = [];
  for (let index = 1; index < parsed.length; index += 1) {
    const previous = parsed[index - 1].attributes.imagePosition;
    const current = parsed[index].attributes.imagePosition;
    if (previous && current) {
      const dx = current[0] - previous[0];
      const dy = current[1] - previous[1];
      const dz = current[2] - previous[2];
      const distance = Math.sqrt(dx * dx + dy * dy + dz * dz);
      if (distance > 0.0001) {
        positionDiffs.push(distance);
      }
    }
  }

  return median(positionDiffs)
    ?? parsed[0]?.attributes.spacingBetweenSlices
    ?? parsed[0]?.attributes.sliceThickness
    ?? 1;
}

function getDicomVolume(files: string[], mode: DicomDisplayMode) {
  const cached = dicomVolumeCache.get(mode);
  if (cached) {
    return cached;
  }

  const parsed = files.map((fileName) => parseDicomPixels(path.join(dicomDir, fileName), mode));
  const sliceSpacing = estimateSliceSpacing(parsed);
  const volume = {
    frames: parsed.map((frame) => frame.pixelBuffer),
    width: parsed[0]?.width ?? 0,
    height: parsed[0]?.height ?? 0,
    windowCenter: parsed[0]?.windowCenter ?? 40,
    windowWidth: parsed[0]?.windowWidth ?? 400,
    rowSpacing: parsed[0]?.attributes.rowSpacing ?? 1,
    columnSpacing: parsed[0]?.attributes.columnSpacing ?? 1,
    sliceSpacing,
    sliceThickness: parsed[0]?.attributes.sliceThickness ?? null,
    spacingBetweenSlices: parsed[0]?.attributes.spacingBetweenSlices ?? null,
  };
  dicomVolumeCache.set(mode, volume);
  return volume;
}

function resampleNearest(pixels: Buffer, width: number, height: number, targetWidth: number, targetHeight: number) {
  if (width === targetWidth && height === targetHeight) {
    return pixels;
  }

  const output = Buffer.alloc(targetWidth * targetHeight);
  for (let y = 0; y < targetHeight; y += 1) {
    const sourceY = Math.min(height - 1, Math.floor((y / targetHeight) * height));
    for (let x = 0; x < targetWidth; x += 1) {
      const sourceX = Math.min(width - 1, Math.floor((x / targetWidth) * width));
      output[y * targetWidth + x] = pixels[sourceY * width + sourceX];
    }
  }
  return output;
}

function resampleToPhysicalAspect(pixels: Buffer, width: number, height: number, xSpacing: number, ySpacing: number) {
  const physicalWidth = width * xSpacing;
  const physicalHeight = height * ySpacing;
  const unit = Math.max(0.001, Math.min(xSpacing, ySpacing));
  let targetWidth = Math.max(1, Math.round(physicalWidth / unit));
  let targetHeight = Math.max(1, Math.round(physicalHeight / unit));
  const maxDimension = 960;
  const scale = Math.min(1, maxDimension / Math.max(targetWidth, targetHeight));
  targetWidth = Math.max(1, Math.round(targetWidth * scale));
  targetHeight = Math.max(1, Math.round(targetHeight * scale));

  return {
    width: targetWidth,
    height: targetHeight,
    pixels: resampleNearest(pixels, width, height, targetWidth, targetHeight),
    physicalWidth,
    physicalHeight,
  };
}

function warmDicomVolumeCache(files: string[]) {
  setTimeout(() => {
    try {
      getDicomVolume(files, 'default');
      getDicomVolume(files, 'soft');
    } catch (error) {
      console.warn('DICOM volume warmup failed:', error);
    }
  }, 300);
}

function createReformattedPreview(files: string[], plane: Exclude<DicomPlane, 'axial'>, slice: number, mode: DicomDisplayMode) {
  const volume = getDicomVolume(files, mode);
  const maxSlice = plane === 'sagittal' ? volume.width - 1 : volume.height - 1;
  const clampedSlice = Math.max(0, Math.min(maxSlice, slice));
  const outputWidth = files.length;
  const outputHeight = plane === 'sagittal' ? volume.height : volume.width;
  const pixels = Buffer.alloc(outputWidth * outputHeight);

  volume.frames.forEach((frame, z) => {
    for (let row = 0; row < outputHeight; row += 1) {
      const sourceIndex = plane === 'sagittal'
        ? row * volume.width + clampedSlice
        : clampedSlice * volume.width + row;
      const targetIndex = row * outputWidth + z;
      pixels[targetIndex] = frame[sourceIndex] ?? 0;
    }
  });

  const cropped = cropDicomContent(pixels, outputWidth, outputHeight);
  const ySpacing = plane === 'sagittal' ? volume.rowSpacing : volume.columnSpacing;
  const physical = resampleToPhysicalAspect(cropped.pixels, cropped.width, cropped.height, volume.sliceSpacing, ySpacing);
  const enhancedPixels = enhanceDicomEdges(physical.pixels, physical.width, physical.height);

  return {
    width: physical.width,
    height: physical.height,
    pixels: enhancedPixels.toString('base64'),
    windowCenter: volume.windowCenter,
    windowWidth: volume.windowWidth,
    slice: clampedSlice,
    total: maxSlice + 1,
    fileName: `${plane}-${clampedSlice}`,
    mode,
    spacing: {
      row: volume.rowSpacing,
      column: volume.columnSpacing,
      slice: volume.sliceSpacing,
      displayX: volume.sliceSpacing,
      displayY: ySpacing,
    },
    physicalSize: {
      width: physical.physicalWidth,
      height: physical.physicalHeight,
    },
  };
}

function createDicomFusionVolume(files: string[], start: number, end: number, mode: DicomDisplayMode) {
  const volume = getDicomVolume(files, mode);
  const total = volume.frames.length;
  const safeStart = Math.max(0, Math.min(total - 1, Number.isFinite(start) ? start : 0));
  const safeEnd = Math.max(safeStart, Math.min(total - 1, Number.isFinite(end) ? end : safeStart + 49));
  const maxFrames = 64;
  const rangeLength = safeEnd - safeStart + 1;
  const step = Math.max(1, Math.ceil(rangeLength / maxFrames));
  const indices: number[] = [];
  for (let index = safeStart; index <= safeEnd; index += step) {
    indices.push(index);
  }
  if (indices[indices.length - 1] !== safeEnd) {
    indices.push(safeEnd);
  }

  const maxTextureDimension = 256;
  const textureScale = Math.min(1, maxTextureDimension / Math.max(volume.width, volume.height));
  const targetWidth = Math.max(1, Math.round(volume.width * textureScale));
  const targetHeight = Math.max(1, Math.round(volume.height * textureScale));
  const frames = indices.map((index) => (
    resampleNearest(volume.frames[index], volume.width, volume.height, targetWidth, targetHeight).toString('base64')
  ));

  return {
    width: targetWidth,
    height: targetHeight,
    start: safeStart,
    end: safeEnd,
    total,
    indices,
    frames,
    mode,
    spacing: {
      row: volume.rowSpacing,
      column: volume.columnSpacing,
      slice: volume.sliceSpacing,
    },
    physicalSize: {
      width: volume.width * volume.columnSpacing,
      height: volume.height * volume.rowSpacing,
      depth: Math.max(1, rangeLength) * volume.sliceSpacing,
      unit: 'mm',
    },
  };
}

function enhanceDicomEdges(pixels: Buffer, width: number, height: number) {
  if (width < 3 || height < 3) {
    return pixels;
  }

  const output = Buffer.from(pixels);
  for (let y = 1; y < height - 1; y += 1) {
    for (let x = 1; x < width - 1; x += 1) {
      const index = y * width + x;
      const center = pixels[index];
      const neighborAverage = (
        pixels[index - 1] +
        pixels[index + 1] +
        pixels[index - width] +
        pixels[index + width]
      ) / 4;
      const sharpened = Math.round(center * 1.08 + (center - neighborAverage) * 0.55);
      output[index] = Math.max(0, Math.min(255, sharpened));
    }
  }
  return output;
}

function cropDicomContent(pixels: Buffer, width: number, height: number) {
  const threshold = 12;
  const columnHits = Array.from({ length: width }, () => 0);
  const rowHits = Array.from({ length: height }, () => 0);

  for (let y = 0; y < height; y += 1) {
    for (let x = 0; x < width; x += 1) {
      if (pixels[y * width + x] > threshold) {
        columnHits[x] += 1;
        rowHits[y] += 1;
      }
    }
  }

  const minColumnHits = Math.max(4, Math.floor(height * 0.012));
  const minRowHits = Math.max(4, Math.floor(width * 0.012));
  let minX = columnHits.findIndex((hits) => hits >= minColumnHits);
  let maxX = width - 1 - [...columnHits].reverse().findIndex((hits) => hits >= minColumnHits);
  let minY = rowHits.findIndex((hits) => hits >= minRowHits);
  let maxY = height - 1 - [...rowHits].reverse().findIndex((hits) => hits >= minRowHits);

  if (maxX < minX || maxY < minY) {
    return { pixels, width, height };
  }

  const padding = 18;
  minX = Math.max(0, minX - padding);
  minY = Math.max(0, minY - padding);
  maxX = Math.min(width - 1, maxX + padding);
  maxY = Math.min(height - 1, maxY + padding);

  const croppedWidth = maxX - minX + 1;
  const croppedHeight = maxY - minY + 1;
  const croppedPixels = Buffer.alloc(croppedWidth * croppedHeight);
  for (let row = 0; row < croppedHeight; row += 1) {
    const sourceStart = (minY + row) * width + minX;
    pixels.copy(croppedPixels, row * croppedWidth, sourceStart, sourceStart + croppedWidth);
  }

  return { pixels: croppedPixels, width: croppedWidth, height: croppedHeight };
}

function createStlPreview(filePath: string, fileName: string, limit: number) {
  const cacheKey = `${fileName}:${limit}`;
  const cached = modelPreviewCache.get(cacheKey);
  if (cached) {
    return cached;
  }

  const buffer = fs.readFileSync(filePath);
  if (buffer.length < 84) {
    throw new Error('STL 文件内容为空或不完整');
  }

  const triangleCount = buffer.readUInt32LE(80);
  const expectedLength = 84 + triangleCount * 50;
  if (triangleCount <= 0 || expectedLength > buffer.length + 1024) {
    throw new Error('当前仅支持二进制 STL 预览');
  }

  const sampleLimit = Math.max(100, Math.min(limit, 200000));
  const step = Math.max(1, Math.ceil(triangleCount / sampleLimit));
  const vertices: number[] = [];
  let sampledTriangles = 0;
  const bounds = {
    min: { x: Infinity, y: Infinity, z: Infinity },
    max: { x: -Infinity, y: -Infinity, z: -Infinity },
  };

  for (let triangleIndex = 0; triangleIndex < triangleCount; triangleIndex += 1) {
    const offset = 84 + triangleIndex * 50;
    if (offset + 50 > buffer.length) {
      break;
    }

    const shouldSample = triangleIndex % step === 0;
    for (let vertex = 0; vertex < 3; vertex += 1) {
      const vertexOffset = offset + 12 + vertex * 12;
      const x = buffer.readFloatLE(vertexOffset);
      const y = buffer.readFloatLE(vertexOffset + 4);
      const z = buffer.readFloatLE(vertexOffset + 8);
      bounds.min.x = Math.min(bounds.min.x, x);
      bounds.min.y = Math.min(bounds.min.y, y);
      bounds.min.z = Math.min(bounds.min.z, z);
      bounds.max.x = Math.max(bounds.max.x, x);
      bounds.max.y = Math.max(bounds.max.y, y);
      bounds.max.z = Math.max(bounds.max.z, z);
      if (shouldSample) {
        vertices.push(
          Number(x.toFixed(3)),
          Number(y.toFixed(3)),
          Number(z.toFixed(3)),
        );
      }
    }
    if (shouldSample) {
      sampledTriangles += 1;
    }
  }

  const payload = {
    fileName,
    triangleCount,
    sampledTriangles,
    vertices,
    bounds: {
      min: {
        x: Number(bounds.min.x.toFixed(3)),
        y: Number(bounds.min.y.toFixed(3)),
        z: Number(bounds.min.z.toFixed(3)),
      },
      max: {
        x: Number(bounds.max.x.toFixed(3)),
        y: Number(bounds.max.y.toFixed(3)),
        z: Number(bounds.max.z.toFixed(3)),
      },
    },
  };
  modelPreviewCache.set(cacheKey, payload);
  return payload;
}

function writeOctal(buffer: Buffer, value: number, offset: number, length: number) {
  const text = value.toString(8).padStart(length - 1, '0').slice(-(length - 1));
  buffer.write(`${text}\0`, offset, length, 'ascii');
}

function createTarEntryHeader(name: string, size: number, mtime: number) {
  const header = Buffer.alloc(512);
  const safeName = name.slice(0, 100);
  header.write(safeName, 0, 100, 'utf8');
  writeOctal(header, 0o644, 100, 8);
  writeOctal(header, 0, 108, 8);
  writeOctal(header, 0, 116, 8);
  writeOctal(header, size, 124, 12);
  writeOctal(header, Math.floor(mtime), 136, 12);
  header.fill(' ', 148, 156);
  header.write('0', 156, 1, 'ascii');
  header.write('ustar', 257, 6, 'ascii');
  header.write('00', 263, 2, 'ascii');

  let checksum = 0;
  for (const byte of header) {
    checksum += byte;
  }
  writeOctal(header, checksum, 148, 8);
  return header;
}

function createDicomTarGz(files: string[]) {
  const chunks: Buffer[] = [];

  files.forEach((fileName) => {
    const filePath = path.join(dicomDir, fileName);
    const stat = fs.statSync(filePath);
    const data = fs.readFileSync(filePath);
    chunks.push(createTarEntryHeader(`Head_CT_DICOM/${fileName}`, data.length, stat.mtimeMs / 1000));
    chunks.push(data);
    const remainder = data.length % 512;
    if (remainder > 0) {
      chunks.push(Buffer.alloc(512 - remainder));
    }
  });

  chunks.push(Buffer.alloc(1024));
  return zlib.gzipSync(Buffer.concat(chunks));
}

function estimateSliceSpacingFromAttributes(attributes: DicomAttributes[]) {
  const diffs: number[] = [];
  for (let index = 1; index < attributes.length; index += 1) {
    const previous = attributes[index - 1].imagePosition;
    const current = attributes[index].imagePosition;
    if (previous && current) {
      const dx = current[0] - previous[0];
      const dy = current[1] - previous[1];
      const dz = current[2] - previous[2];
      const distance = Math.sqrt(dx * dx + dy * dy + dz * dz);
      if (distance > 0.0001) {
        diffs.push(distance);
      }
    }
  }

  return {
    value: median(diffs)
      ?? attributes[0]?.spacingBetweenSlices
      ?? attributes[0]?.sliceThickness
      ?? 1,
    source: diffs.length ? 'ImagePositionPatient' : attributes[0]?.spacingBetweenSlices ? 'SpacingBetweenSlices' : attributes[0]?.sliceThickness ? 'SliceThickness' : '默认 1mm',
  };
}

function formatNumber(value: number | null | undefined, digits = 3) {
  return typeof value === 'number' && Number.isFinite(value) ? Number(value.toFixed(digits)) : null;
}

function createDicomInfo(project: ProjectRecord, files: string[]) {
  const attributes = files.map((fileName) => {
    const buffer = fs.readFileSync(path.join(dicomDir, fileName));
    return parseDicomAttributes(buffer, 'default');
  });
  const first = attributes[0];
  const last = attributes[attributes.length - 1];
  const sliceSpacing = estimateSliceSpacingFromAttributes(attributes);
  const physicalWidth = first.columns * first.columnSpacing;
  const physicalHeight = first.rows * first.rowSpacing;
  const physicalDepth = Math.max(files.length - 1, 0) * sliceSpacing.value;

  return {
    project: {
      id: project.id,
      name: project.name,
      dicomPath: project.dicomPath,
    },
    patient: {
      name: first.patientName,
      id: first.patientId,
    },
    study: {
      date: first.studyDate,
      description: first.studyDescription,
      modality: first.modality,
      manufacturer: first.manufacturer,
    },
    series: {
      description: first.seriesDescription,
      files: files.length,
      firstFile: files[0] ?? '',
      lastFile: files[files.length - 1] ?? '',
    },
    image: {
      rows: first.rows,
      columns: first.columns,
      bitsAllocated: first.bitsAllocated,
      pixelRepresentation: first.pixelRepresentation,
      windowCenter: first.windowCenter,
      windowWidth: first.windowWidth,
      rescaleIntercept: first.rescaleIntercept,
      rescaleSlope: first.rescaleSlope,
    },
    spacing: {
      row: formatNumber(first.rowSpacing),
      column: formatNumber(first.columnSpacing),
      slice: formatNumber(sliceSpacing.value),
      sliceSource: sliceSpacing.source,
      sliceThickness: formatNumber(first.sliceThickness),
      spacingBetweenSlices: formatNumber(first.spacingBetweenSlices),
    },
    physicalSize: {
      width: formatNumber(physicalWidth),
      height: formatNumber(physicalHeight),
      depth: formatNumber(physicalDepth),
      unit: 'mm',
    },
    position: {
      firstImagePosition: first.imagePosition,
      lastImagePosition: last?.imagePosition ?? null,
    },
  };
}

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.delete('/api/projects/:projectId', (req, res) => {
    const state = readState();
    const index = state.projects.findIndex((project) => project.id === req.params.projectId);
    if (index < 0) {
      res.status(404).json({ message: '项目不存在' });
      return;
    }

    const [deleted] = state.projects.splice(index, 1);
    writeState(state);
    res.json({ ok: true, deletedId: deleted.id });
  });

  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 requestedPlane = String(req.query.plane ?? 'axial');
    const plane: DicomPlane = requestedPlane === 'sagittal' || requestedPlane === 'coronal' ? requestedPlane : 'axial';
    const requestedMode = String(req.query.mode ?? 'default');
    const mode: DicomDisplayMode = requestedMode === 'bone' || requestedMode === 'soft' || requestedMode === 'contrast' ? requestedMode : 'default';
    const requestedSlice = Number.parseInt(String(req.query.slice ?? '0'), 10);
    const cacheKey = `${project.id}:${plane}:${mode}:${Number.isFinite(requestedSlice) ? requestedSlice : 0}`;
    if (dicomPreviewCache.has(cacheKey)) {
      res.json(dicomPreviewCache.get(cacheKey));
      return;
    }

    try {
      let payload: unknown;
      if (plane === 'axial') {
        const slice = Math.max(0, Math.min(files.length - 1, Number.isFinite(requestedSlice) ? requestedSlice : 0));
        const preview = parseDicomPreview(path.join(dicomDir, files[slice]), mode);
        payload = {
          ...preview,
          plane,
          slice,
          total: files.length,
          fileName: files[slice],
        };
      } else {
        payload = {
          ...createReformattedPreview(files, plane, Number.isFinite(requestedSlice) ? requestedSlice : 0, mode),
          plane,
        };
      }

      dicomPreviewCache.set(cacheKey, payload);
      res.json(payload);
    } catch (error) {
      res.status(422).json({ message: error instanceof Error ? error.message : 'DICOM 预览失败' });
    }
  });

  app.get('/api/projects/:projectId/dicom-fusion-volume', (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: '当前项目没有可融合的 DICOM 文件' });
      return;
    }

    const requestedMode = String(req.query.mode ?? 'soft');
    const mode: DicomDisplayMode = requestedMode === 'bone' || requestedMode === 'soft' || requestedMode === 'contrast' ? requestedMode : 'soft';
    const start = Number.parseInt(String(req.query.start ?? '0'), 10);
    const end = Number.parseInt(String(req.query.end ?? '49'), 10);

    try {
      res.json(createDicomFusionVolume(files, start, end, mode));
    } catch (error) {
      res.status(422).json({ message: error instanceof Error ? error.message : 'DICOM 三维融合体生成失败' });
    }
  });

  app.get('/api/projects/:projectId/dicom-archive', (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: '当前项目没有可下载的 DICOM 文件' });
      return;
    }

    try {
      const archive = createDicomTarGz(files);
      const filename = `${project.id}-${project.dicomPath || 'DICOM'}-${files.length}-files.tar.gz`;
      res.setHeader('Content-Type', 'application/gzip');
      res.setHeader('Content-Disposition', `attachment; filename="${filename}"`);
      res.send(archive);
    } catch (error) {
      res.status(500).json({ message: error instanceof Error ? error.message : 'DICOM 压缩包生成失败' });
    }
  });

  app.get('/api/projects/:projectId/dicom-info', (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: '当前项目没有可查询的 DICOM 文件' });
      return;
    }

    try {
      res.json(createDicomInfo(project, files));
    } catch (error) {
      res.status(422).json({ message: error instanceof Error ? error.message : 'DICOM 信息解析失败' });
    }
  });

  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/projects/:projectId/models/:fileName/preview', (req, res) => {
    const project = findProject(readState(), req.params.projectId);
    const fileName = path.basename(req.params.fileName);
    const limit = Number.parseInt(String(req.query.limit ?? '5000'), 10);

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

    try {
      res.json(createStlPreview(path.join(modelDir, fileName), fileName, Number.isFinite(limit) ? limit : 5000));
    } catch (error) {
      res.status(422).json({ message: error instanceof Error ? error.message : 'STL 预览失败' });
    }
  });

  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}/`);
    warmDicomVolumeCache(getProjectDicomFiles(buildDefaultProject()));
  });
}

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