/**
 * DC-108: Multi-host fleet management — deploy across multiple servers
 *
 * Foundation API for registering remote DashCaddy instances and coordinating
 * deployments across them. Each host runs its own DashCaddy container; this
 * module tracks the fleet state and can forward commands.
 *
 * GET    /api/v1/fleet/hosts           — list all registered hosts
 * POST   /api/v1/fleet/hosts           — register a new host
 * DELETE /api/v1/fleet/hosts/:hostId   — deregister a host
 * GET    /api/v1/fleet/status          — fleet-wide status overview
 * POST   /api/v1/fleet/deploy          — deploy to multiple hosts
 *
 * Host state is persisted in {dataDir}/fleet-hosts.json
 */
const express = require('express');
const fs = require('fs');
const fsp = require('fs').promises;
const path = require('path');
const crypto = require('crypto');
const { ok, errorResponse } = require('../src/utils/responses');
const { ErrorCodes } = require('../src/utilities/error-codes');

const HOSTS_FILE = process.env.FLEET_HOSTS_FILE || path.join(process.cwd(), 'data', 'fleet-hosts.json');

module.exports = function({ log, asyncHandler }) {
  const wrap = asyncHandler || ((fn) => (req, res, next) => Promise.resolve(fn(req, res, next)).catch(next));
  const router = express.Router();

  async function loadHosts() {
    const hostsFile = process.env.FLEET_HOSTS_FILE || HOSTS_FILE;
    try {
      const data = await fsp.readFile(hostsFile, 'utf8');
      return JSON.parse(data);
    } catch {
      return [];
    }
  }

  async function saveHosts(hosts) {
    const hostsFile = process.env.FLEET_HOSTS_FILE || HOSTS_FILE;
    await fsp.mkdir(path.dirname(hostsFile), { recursive: true });
    await fsp.writeFile(hostsFile, JSON.stringify(hosts, null, 2));
  }

  // GET /api/v1/fleet/hosts
  router.get('/fleet/hosts', wrap(async (req, res) => {
    const hosts = await loadHosts();
    ok(res, { total: hosts.length, hosts });
  }));

  // POST /api/v1/fleet/hosts — register a new host
  router.post('/fleet/hosts', wrap(async (req, res) => {
    const { name, hostname, apiKey, port = 3001, tags = [] } = req.body || {};

    if (!name || !hostname) {
      return errorResponse(res, 400, 'name and hostname are required', {
        code: ErrorCodes.GENERAL.INVALID_INPUT,
      });
    }

    const hosts = await loadHosts();

    // Check for duplicate
    if (hosts.some(h => h.hostname === hostname)) {
      return errorResponse(res, 409, `Host ${hostname} already registered`, {
        code: ErrorCodes.GENERAL.CONFLICT,
      });
    }

    const host = {
      id: crypto.randomUUID(),
      name,
      hostname,
      port,
      apiKey: apiKey ? '***' : null, // Never store the actual key
      apiKeyHash: apiKey ? crypto.createHash('sha256').update(apiKey).digest('hex') : null,
      tags,
      status: 'unknown',
      registeredAt: new Date().toISOString(),
      lastSeen: null,
      containerCount: null,
    };

    hosts.push(host);
    await saveHosts(hosts);

    if (log) log.info('fleet', 'Host registered', { name, hostname });

    ok(res, { host }, 201);
  }));

  // DELETE /api/v1/fleet/hosts/:hostId
  router.delete('/fleet/hosts/:hostId', wrap(async (req, res) => {
    const { hostId } = req.params;
    const hosts = await loadHosts();
    const filtered = hosts.filter(h => h.id !== hostId);

    if (filtered.length === hosts.length) {
      return errorResponse(res, 404, `Host ${hostId} not found`);
    }

    await saveHosts(filtered);
    ok(res, { message: 'Host deregistered' });
  }));

  // GET /api/v1/fleet/status — aggregate fleet status
  router.get('/fleet/status', wrap(async (req, res) => {
    const hosts = await loadHosts();

    // Try to reach each host and get its health
    const statusPromises = hosts.map(async (host) => {
      try {
        const url = `http://${host.hostname}:${host.port}/api/v1/system/health`;
        const controller = new AbortController();
        const timeout = setTimeout(() => controller.abort(), 3000);
        const response = await fetch(url, {
          signal: controller.signal,
          headers: host.apiKeyHash ? { 'x-api-key': host.apiKeyHash } : {},
        }).finally(() => clearTimeout(timeout));

        if (response.ok) {
          const data = await response.json();
          host.status = data.status || 'healthy';
          host.lastSeen = new Date().toISOString();
          host.containerCount = data.checks?.services?.total || null;
        } else {
          host.status = 'unreachable';
        }
      } catch {
        host.status = 'offline';
      }
      return host;
    });

    const updatedHosts = await Promise.all(statusPromises);
    await saveHosts(updatedHosts);

    const summary = {
      total: updatedHosts.length,
      healthy: updatedHosts.filter(h => h.status === 'healthy').length,
      degraded: updatedHosts.filter(h => h.status === 'degraded').length,
      unhealthy: updatedHosts.filter(h => h.status === 'unhealthy').length,
      offline: updatedHosts.filter(h => h.status === 'offline' || h.status === 'unreachable').length,
    };

    ok(res, { summary, hosts: updatedHosts });
  }));

  // POST /api/v1/fleet/deploy — deploy a template to multiple hosts
  router.post('/fleet/deploy', wrap(async (req, res) => {
    const { templateId, hostIds = [], config = {} } = req.body || {};

    if (!templateId) {
      return errorResponse(res, 400, 'templateId is required');
    }

    const hosts = await loadHosts();
    const targetHosts = hostIds.length > 0
      ? hosts.filter(h => hostIds.includes(h.id))
      : hosts;

    if (targetHosts.length === 0) {
      return errorResponse(res, 400, 'No valid hosts to deploy to');
    }

    // Generate deployment plan
    const plan = targetHosts.map(host => ({
      hostId: host.id,
      hostname: host.hostname,
      templateId,
      config,
      status: 'pending',
      deployUrl: `http://${host.hostname}:${host.port}/api/v1/apps/deploy`,
    }));

    ok(res, {
      templateId,
      totalHosts: plan.length,
      plan,
      message: 'Deployment plan generated. Forward each step to the host API.',
    });
  }));

  return router;
};