import express from 'express';
import cors from 'cors';
import helmet from 'helmet';
import morgan from 'morgan';
import rateLimit from 'express-rate-limit';
import { Low } from 'lowdb';
import { JSONFile } from 'lowdb/node';
import { join, dirname, isAbsolute, extname } from 'path';
import { fileURLToPath } from 'url';
import { mkdirSync, unlinkSync, existsSync, readFileSync } from 'fs';
import { randomBytes, randomUUID } from 'crypto';
import multer from 'multer';
import nodemailer from 'nodemailer';

const __dirname = dirname(fileURLToPath(import.meta.url));
const dataDir = join(__dirname, 'data');

const dbFileEnv = process.env.DB_FILE;
const dbFile = dbFileEnv ? (isAbsolute(dbFileEnv) ? dbFileEnv : join(dataDir, dbFileEnv)) : join(dataDir, 'db.json');
const legacyDbFile = join(__dirname, 'db.json');
mkdirSync(dirname(dbFile), { recursive: true });
const adapter = new JSONFile(dbFile);
const defaultData = { members: [], projects: [], tasks: [], invites: [] };
const db = new Low(adapter, defaultData);

const safeReadJson = (filePath) => {
  try {
    if (!existsSync(filePath)) return null;
    const raw = readFileSync(filePath, 'utf8').trim();
    if (!raw) return null;
    return JSON.parse(raw);
  } catch {
    return null;
  }
};

const toInitials = (name = '') =>
  String(name)
    .split(' ')
    .filter(Boolean)
    .map(w => w[0])
    .join('')
    .toUpperCase()
    .slice(0, 2);

const FEATURE_TYPES = ['idea', 'feature', 'fix', 'removal'];
const FEATURE_STATUSES = ['backlog', 'planned', 'in-progress', 'shipped', 'dropped'];

const normalizeFeatureEntry = (feature = {}, previousFeature = null) => {
  const now = new Date().toISOString();
  const title = String(feature?.title || previousFeature?.title || '').trim() || 'Untitled entry';
  const type = FEATURE_TYPES.includes(feature?.type) ? feature.type : (FEATURE_TYPES.includes(previousFeature?.type) ? previousFeature.type : 'idea');
  const status = FEATURE_STATUSES.includes(feature?.status) ? feature.status : (FEATURE_STATUSES.includes(previousFeature?.status) ? previousFeature.status : 'backlog');
  const createdAt = feature?.createdAt || previousFeature?.createdAt || now;
  const updatedAt = feature?.updatedAt || previousFeature?.updatedAt || feature?.createdAt || previousFeature?.createdAt || now;
  const updatedBy = typeof feature?.updatedBy === 'string'
    ? feature.updatedBy.trim()
    : typeof previousFeature?.updatedBy === 'string'
      ? previousFeature.updatedBy.trim()
      : '';
  const shippedAt = feature?.shippedAt || previousFeature?.shippedAt || (status === 'shipped' ? (updatedAt || createdAt || now) : '');

  return {
    id: feature?.id || previousFeature?.id || randomUUID(),
    title,
    type,
    status,
    note: feature?.note || feature?.description || previousFeature?.note || '',
    createdAt,
    updatedAt,
    updatedBy,
    shippedAt,
  };
};

const ensureProjectShape = (project) => {
  if (!Array.isArray(project.members)) project.members = [];
  if (!Array.isArray(project.tasks)) project.tasks = [];
  if (!Array.isArray(project.milestones)) project.milestones = [];
  if (!Array.isArray(project.features)) project.features = [];
  project.features = project.features.map(feature => normalizeFeatureEntry(feature));
};

try {
  await db.read();
} catch (err) {
  console.warn('Primary db file was unreadable, reinitializing with defaults.', err?.message || err);
  db.data = { ...defaultData };
  await db.write();
}
if (!db.data) db.data = defaultData;
if (!db.data.invites) db.data.invites = [];
if (!db.data.members) db.data.members = [];
if (!db.data.projects) db.data.projects = [];
if (!db.data.tasks) db.data.tasks = [];

// One-time bootstrap from legacy backend/db.json when the runtime db is empty.
const runtimeHasData = (db.data.members.length + db.data.projects.length + db.data.invites.length) > 0;
if (!runtimeHasData && dbFile !== legacyDbFile) {
  const legacy = safeReadJson(legacyDbFile);
  if (legacy && typeof legacy === 'object') {
    db.data.members = Array.isArray(legacy.members) ? legacy.members : [];
    db.data.projects = Array.isArray(legacy.projects) ? legacy.projects : [];
    db.data.invites = Array.isArray(legacy.invites) ? legacy.invites : [];
    db.data.tasks = Array.isArray(legacy.tasks) ? legacy.tasks : [];
  }
}

// Normalize projects and migrate any legacy flat tasks into nested project.tasks.
for (const project of db.data.projects) ensureProjectShape(project);
for (const task of db.data.tasks) {
  const project = db.data.projects.find(p => p.id === task.projectId);
  if (!project) continue;
  ensureProjectShape(project);
  const existing = project.tasks.find(t => t.id === task.id);
  if (existing) continue;
  project.tasks.push({
    id: task.id || randomUUID(),
    title: task.title || 'Untitled Task',
    description: task.description || '',
    status: task.status || 'todo',
    priority: task.priority || 'medium',
    dueDate: task.dueDate || '',
    startDate: task.startDate || '',
    assignedTo: task.assignedTo || task.memberId || '',
    estimatedHours: task.estimatedHours,
    actualHours: task.actualHours,
    recurrence: task.recurrence || 'none',
    subtasks: Array.isArray(task.subtasks) ? task.subtasks : [],
    attachments: Array.isArray(task.attachments) ? task.attachments : [],
  });
}
db.data.tasks = [];

for (const project of db.data.projects) {
  ensureProjectShape(project);
  project.members = project.members
    .map(member => {
      if (member && typeof member === 'object') {
        return {
          ...member,
          initials: member.initials || toInitials(member.name),
        };
      }
      const roster = db.data.members.find(m => m.id === member);
      if (!roster) return null;
      return { ...roster, initials: roster.initials || toInitials(roster.name) };
    })
    .filter(Boolean);
}
await db.write();

// ── File uploads (multer) ───────────────────────────────────────────────────
const UPLOAD_DIR = join(__dirname, 'uploads');
mkdirSync(UPLOAD_DIR, { recursive: true });

const ALLOWED_MIME = new Set([
  'image/jpeg','image/png','image/gif','image/webp','image/svg+xml',
  'application/pdf','text/plain','text/csv','text/markdown',
  'application/json',
  'application/zip','application/x-zip-compressed',
  'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',      // xlsx
  'application/vnd.openxmlformats-officedocument.wordprocessingml.document', // docx
]);

const storage = multer.diskStorage({
  destination: (req, file, cb) => cb(null, UPLOAD_DIR),
  filename:    (req, file, cb) => cb(null, randomUUID() + extname(file.originalname).toLowerCase()),
});
const upload = multer({
  storage,
  limits: { fileSize: 10 * 1024 * 1024 }, // 10 MB
  fileFilter: (req, file, cb) => {
    if (ALLOWED_MIME.has(file.mimetype)) cb(null, true);
    else cb(new Error('File type not allowed'));
  },
});

// ── Notification helper ────────────────────────────────────────────────────
async function notify({ webhookUrl, notifyEmail, subject, text, payload }) {
  if (webhookUrl) {
    try {
      await fetch(webhookUrl, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(payload || { subject, text }),
        signal: AbortSignal.timeout(5000),
      });
    } catch (err) {
      console.warn('Webhook notification failed', err?.message || err);
    }
  }
  if (notifyEmail && process.env.SMTP_HOST) {
    try {
      const transporter = nodemailer.createTransport({
        host: process.env.SMTP_HOST,
        port: Number(process.env.SMTP_PORT) || 587,
        secure: process.env.SMTP_SECURE === 'true',
        auth: process.env.SMTP_USER ? { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS } : undefined,
      });
      await transporter.sendMail({
        from: process.env.SMTP_FROM || process.env.SMTP_USER || 'noreply@projecthub.local',
        to: notifyEmail,
        subject,
        text,
      });
    } catch (err) {
      console.warn('Email notification failed', err?.message || err);
    }
  }
}

const app = express();
app.use(helmet());
app.use(morgan(process.env.MORGAN_FORMAT || 'combined'));

const configuredOrigins = (process.env.CORS_ORIGIN || '')
  .split(',')
  .map(o => o.trim())
  .filter(Boolean);
const allowedOrigins = configuredOrigins.length
  ? configuredOrigins
  : ['http://localhost:5173', 'http://localhost:4000', 'null'];

const corsOptions = {
  credentials: true,
  origin: (origin, callback) => {
    if (!origin) return callback(null, true);
    if (origin === 'null' || origin.startsWith('file://')) return callback(null, true);
    if (allowedOrigins.includes(origin)) return callback(null, true);
    return callback(new Error('Not allowed by CORS'));
  },
};
app.use(cors(corsOptions));
app.use(express.json());

const limiter = rateLimit({
  windowMs: Number(process.env.RATE_WINDOW_MS) || 15 * 60 * 1000,
  max: Number(process.env.RATE_MAX) || 200,
});

const requireApiKey = (req, res, next) => {
  const key = process.env.WRITE_API_KEY;
  if (!key) return next();
  const provided = req.get('x-api-key') || req.query.api_key;
  if (provided === key) return next();
  return res.status(401).json({ error: 'Unauthorized' });
};

// Health
app.get('/health', async (req, res) => {
  try {
    await db.read();
    return res.json({ status: 'ok', timestamp: Date.now() });
  } catch (err) {
    return res.status(500).json({ status: 'error' });
  }
});

// Member CRUD
app.get('/api/members', (req, res) => {
  res.json(db.data.members);
});

app.post('/api/members', limiter, requireApiKey, async (req, res) => {
  const member = { id: Date.now().toString(), ...req.body };
  member.initials = member.initials || toInitials(member.name);
  db.data.members.push(member);
  await db.write();
  res.status(201).json(member);
});

app.delete('/api/members/:id', limiter, requireApiKey, async (req, res) => {
  db.data.members = db.data.members.filter(m => m.id !== req.params.id);
  for (const project of db.data.projects) {
    ensureProjectShape(project);
    project.members = project.members.filter(m => m.id !== req.params.id);
  }
  await db.write();
  res.status(204).end();
});

app.put('/api/members/:id', limiter, requireApiKey, async (req, res) => {
  const idx = db.data.members.findIndex(m => m.id === req.params.id);
  if (idx === -1) return res.status(404).json({ error: 'Member not found' });
  db.data.members[idx] = { ...db.data.members[idx], ...req.body, id: req.params.id };
  await db.write();
  res.json(db.data.members[idx]);
});

// Project CRUD
app.get('/api/projects', (req, res) => {
  res.json(db.data.projects);
});

app.post('/api/projects', limiter, requireApiKey, async (req, res) => {
  const project = { id: Date.now().toString(), members: [], tasks: [], milestones: [], features: [], ...req.body };
  ensureProjectShape(project);
  db.data.projects.push(project);
  await db.write();
  res.status(201).json(project);
});

app.put('/api/projects/:id', limiter, requireApiKey, async (req, res) => {
  const idx = db.data.projects.findIndex(p => p.id === req.params.id);
  const updated = { ...req.body, id: req.params.id };
  ensureProjectShape(updated);
  if (idx === -1) db.data.projects.push(updated);
  else db.data.projects[idx] = updated;
  await db.write();
  res.json(updated);
});

app.delete('/api/projects/:id', limiter, requireApiKey, async (req, res) => {
  db.data.projects = db.data.projects.filter(p => p.id !== req.params.id);
  await db.write();
  res.status(204).end();
});

// Assign member to project
app.post('/api/projects/:projectId/members/:memberId', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  const member = db.data.members.find(m => m.id === req.params.memberId);
  if (!member) return res.status(404).json({ error: 'Member not found' });

  const alreadyAssigned = project.members.some(m => m.id === member.id);
  if (!alreadyAssigned) {
    project.members.push({ ...member, initials: member.initials || toInitials(member.name) });
    await db.write();
  }
  res.json(project);
});

// Tasks (assign to member in project)
app.post('/api/projects/:projectId/tasks', limiter, requireApiKey, async (req, res) => {
  const { title, description, memberId, assignedTo } = req.body;
  const assigneeId = assignedTo || memberId || '';
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  if (assigneeId && !project.members.some(m => m.id === assigneeId)) {
    return res.status(400).json({ error: 'Member not assigned to project' });
  }

  const task = {
    id: randomUUID(),
    title: String(title || '').trim() || 'Untitled Task',
    description: description || '',
    status: req.body.status || 'todo',
    priority: req.body.priority || 'medium',
    dueDate: req.body.dueDate || '',
    startDate: req.body.startDate || '',
    assignedTo: assigneeId,
    estimatedHours: req.body.estimatedHours,
    actualHours: req.body.actualHours,
    recurrence: req.body.recurrence || 'none',
    subtasks: Array.isArray(req.body.subtasks) ? req.body.subtasks : [],
    attachments: Array.isArray(req.body.attachments) ? req.body.attachments : [],
  };

  project.tasks.push(task);
  await db.write();
  res.status(201).json(task);
});

app.get('/api/projects/:projectId/tasks', (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  res.json(project.tasks);
});

app.put('/api/projects/:projectId/tasks/:taskId', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  const idx = project.tasks.findIndex(t => t.id === req.params.taskId);
  if (idx === -1) return res.status(404).json({ error: 'Task not found' });

  const assigneeId = req.body.assignedTo || req.body.memberId || project.tasks[idx].assignedTo || '';
  if (assigneeId && !project.members.some(m => m.id === assigneeId)) {
    return res.status(400).json({ error: 'Member not assigned to project' });
  }

  project.tasks[idx] = {
    ...project.tasks[idx],
    ...req.body,
    id: req.params.taskId,
    assignedTo: assigneeId,
  };
  await db.write();
  res.json(project.tasks[idx]);
});

app.delete('/api/projects/:projectId/tasks/:taskId', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  const idx = project.tasks.findIndex(t => t.id === req.params.taskId);
  if (idx === -1) return res.status(404).json({ error: 'Task not found' });
  project.tasks.splice(idx, 1);
  await db.write();
  res.status(204).end();
});

// Feature log CRUD
app.get('/api/projects/:projectId/features', (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  res.json(project.features);
});

app.post('/api/projects/:projectId/features', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);

  const feature = normalizeFeatureEntry(req.body);
  project.features.push(feature);
  await db.write();
  res.status(201).json(feature);
});

app.put('/api/projects/:projectId/features/:featureId', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  const idx = project.features.findIndex(feature => feature.id === req.params.featureId);
  if (idx === -1) return res.status(404).json({ error: 'Feature entry not found' });

  const current = project.features[idx];
  project.features[idx] = normalizeFeatureEntry({
    ...current,
    ...req.body,
    id: req.params.featureId,
    createdAt: current.createdAt,
    shippedAt: req.body.status === 'shipped'
      ? (req.body.shippedAt || current.shippedAt || new Date().toISOString())
      : (req.body.status && req.body.status !== 'shipped' ? '' : current.shippedAt),
  }, current);

  await db.write();
  res.json(project.features[idx]);
});

app.delete('/api/projects/:projectId/features/:featureId', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  const idx = project.features.findIndex(feature => feature.id === req.params.featureId);
  if (idx === -1) return res.status(404).json({ error: 'Feature entry not found' });
  project.features.splice(idx, 1);
  await db.write();
  res.status(204).end();
});

// ── Static uploads ──────────────────────────────────────────────────────────
app.use('/uploads', express.static(UPLOAD_DIR));

// ── File attachments ────────────────────────────────────────────────────────
// Attachments are stored inline in project.tasks[].attachments[]

app.post('/api/projects/:projectId/tasks/:taskId/attachments', limiter, requireApiKey, (req, res, next) => {
  upload.single('file')(req, res, async err => {
    if (err) return res.status(400).json({ error: err.message });
    if (!req.file) return res.status(400).json({ error: 'No file provided' });

    const project = db.data.projects.find(p => p.id === req.params.projectId);
    if (!project) return res.status(404).json({ error: 'Project not found' });
    ensureProjectShape(project);
    const task = project.tasks.find(t => t.id === req.params.taskId);
    if (!task) return res.status(404).json({ error: 'Task not found' });

    if (!task.attachments) task.attachments = [];
    const attachment = {
      id:           randomUUID(),
      filename:     req.file.filename,
      originalName: req.file.originalname,
      mimetype:     req.file.mimetype,
      size:         req.file.size,
      url:          `/uploads/${req.file.filename}`,
      uploadedAt:   new Date().toISOString(),
    };
    task.attachments.push(attachment);
    await db.write();
    res.status(201).json(attachment);
  });
});

app.delete('/api/projects/:projectId/tasks/:taskId/attachments/:attachmentId', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.projectId);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  ensureProjectShape(project);
  const task = project.tasks.find(t => t.id === req.params.taskId);
  if (!task) return res.status(404).json({ error: 'Task not found' });

  const idx = task.attachments?.findIndex(a => a.id === req.params.attachmentId);
  if (idx === undefined || idx === -1) return res.status(404).json({ error: 'Attachment not found' });

  const [removed] = task.attachments.splice(idx, 1);
  // Delete file from disk
  const filePath = join(UPLOAD_DIR, removed.filename);
  if (existsSync(filePath)) { try { unlinkSync(filePath); } catch {} }

  await db.write();
  res.status(204).end();
});

// ── Webhook/notification settings on project ────────────────────────────────
// Projects can have optional webhookUrl and notifyEmail; these are just
// stored as part of the project doc. The POST /api/projects/:id/notify endpoint
// fires a test notification.
app.post('/api/projects/:id/notify', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.id);
  if (!project) return res.status(404).json({ error: 'Project not found' });
  const { subject = 'Project Hub notification', text = `Update for project: ${project.name}` } = req.body;
  notify({ webhookUrl: project.webhookUrl, notifyEmail: project.notifyEmail, subject, text, payload: { projectId: project.id, projectName: project.name, subject, text } });
  res.json({ sent: true });
});

// ── Invite system ────────────────────────────────────────────────────────────
// Generate an invite token for a project
app.post('/api/projects/:id/invites', limiter, requireApiKey, async (req, res) => {
  const project = db.data.projects.find(p => p.id === req.params.id);
  if (!project) return res.status(404).json({ error: 'Project not found' });

  const token = randomBytes(32).toString('hex');
  const expiresAt = new Date(Date.now() + 7 * 24 * 60 * 60 * 1000); // 7 days
  const invite = {
    id:        randomUUID(),
    token,
    projectId: project.id,
    projectName: project.name,
    email:     req.body.email || null,
    createdAt: new Date().toISOString(),
    expiresAt: expiresAt.toISOString(),
    acceptedAt: null,
  };
  db.data.invites.push(invite);
  await db.write();

  // Fire email if SMTP configured and email provided
  if (req.body.email) {
    const appUrl = process.env.APP_URL || 'http://localhost:5173';
    notify({
      notifyEmail: req.body.email,
      subject: `You've been invited to "${project.name}"`,
      text: `You've been invited to join the project "${project.name}".\n\nAccept your invitation:\n${appUrl}/invite/${token}\n\nThis link expires in 7 days.`,
    });
  }

  res.status(201).json({ token, expiresAt: invite.expiresAt, inviteId: invite.id });
});

// Validate an invite token (public)
app.get('/api/invites/:token', (req, res) => {
  const invite = db.data.invites.find(i => i.token === req.params.token);
  if (!invite) return res.status(404).json({ error: 'Invite not found or expired' });
  if (new Date(invite.expiresAt) < new Date()) return res.status(410).json({ error: 'Invite has expired' });
  if (invite.acceptedAt) return res.status(409).json({ error: 'Invite already accepted' });
  res.json({ projectId: invite.projectId, projectName: invite.projectName, email: invite.email, expiresAt: invite.expiresAt });
});

// Accept an invite (attaches provided member name to project if given)
app.post('/api/invites/:token/accept', limiter, async (req, res) => {
  const invite = db.data.invites.find(i => i.token === req.params.token);
  if (!invite) return res.status(404).json({ error: 'Invite not found' });
  if (new Date(invite.expiresAt) < new Date()) return res.status(410).json({ error: 'Invite has expired' });
  if (invite.acceptedAt) return res.status(409).json({ error: 'Invite already accepted' });

  invite.acceptedAt = new Date().toISOString();

  // Optionally add the member to the project
  if (req.body.name) {
    const project = db.data.projects.find(p => p.id === invite.projectId);
    if (project) {
      ensureProjectShape(project);
      const initials = req.body.name.split(' ').map(w => w[0]).join('').toUpperCase().slice(0, 2);
      const email = (req.body.email || invite.email || '').trim();
      let rosterMember = db.data.members.find(m => email && m.email === email);
      if (!rosterMember) {
        rosterMember = {
          id: randomUUID(),
          name: req.body.name,
          role: req.body.role || 'Team Member',
          initials,
          email,
        };
        db.data.members.push(rosterMember);
      }

      if (!project.members.some(m => m.id === rosterMember.id)) {
        project.members.push({ ...rosterMember, initials: rosterMember.initials || toInitials(rosterMember.name) });
      }
    }
  }

  await db.write();
  res.json({ projectId: invite.projectId, projectName: invite.projectName });
});

const PORT = process.env.PORT || 4000;
const HOST = process.env.HOST || '0.0.0.0';
app.listen(PORT, HOST, () => console.log(`Backend running on ${HOST}:${PORT}`));