import 'dotenv/config';

import { watch } from 'node:fs';
import { mkdir, writeFile } from 'node:fs/promises';
import { createServer } from 'node:http';
import { createRequire } from 'node:module';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

import { Server } from 'socket.io';

import contentStore from './contentStore.cjs';

const repositoryRoot = fileURLToPath(new URL('..', import.meta.url));
const require = createRequire(import.meta.url);
const packageJson = require('../package.json');
const defaultWebOrigin = 'http://127.0.0.1:5173';
const host = process.env.TOOLKIT_SOCKET_HOST ?? '127.0.0.1';
const port = Number.parseInt(process.env.TOOLKIT_SOCKET_PORT ?? '5175', 10);
const allowedOrigins = (
  process.env.TOOLKIT_SOCKET_CORS_ORIGIN ?? defaultWebOrigin
)
  .split(',')
  .map(origin => origin.trim())
  .filter(Boolean);

if (Number.isNaN(port)) {
  throw new Error('TOOLKIT_SOCKET_PORT must be a valid number.');
}

const socketHealthStartedAt = Date.now();
const socketHealthStartedAtIso = new Date(socketHealthStartedAt).toISOString();

function createSocketHealthPayload() {
  return {
    ok: true,
    service: 'blb-toolkit-socket',
    version: packageJson.version,
    startedAt: socketHealthStartedAtIso,
    timestamp: new Date().toISOString(),
    uptimeSeconds: Math.max(
      0,
      Math.round((Date.now() - socketHealthStartedAt) / 1000),
    ),
  };
}

function writeJsonResponse(response, statusCode, body) {
  response.writeHead(statusCode, {
    'Access-Control-Allow-Headers': 'Content-Type',
    'Access-Control-Allow-Methods': 'GET, HEAD, OPTIONS',
    'Access-Control-Allow-Origin': '*',
    'Cache-Control': 'no-store',
    'Content-Type': 'application/json',
  });
  response.end(`${JSON.stringify(body)}\n`);
}

const httpServer = createServer((request, response) => {
  const pathname = request.url?.split('?')[0];

  if (pathname === '/health') {
    writeJsonResponse(response, 200, createSocketHealthPayload());
    return;
  }

  writeJsonResponse(response, 404, {
    ok: false,
    service: 'blb-toolkit-socket',
  });
});

const io = new Server(httpServer, {
  cors: {
    methods: ['GET', 'POST'],
    origin: allowedOrigins,
  },
  maxHttpBufferSize: 100 * 1024 * 1024,
});

const contentWatchDebounceMs = 100;
let contentWatchTimer = null;

const assetUploadConfig = {
  audio: {
    directory: path.join(repositoryRoot, 'src', 'assets', 'music', 'uploads'),
    publicPrefix: '/src/assets/music/uploads',
  },
  image: {
    directory: path.join(repositoryRoot, 'src', 'assets', 'images', 'uploads'),
    publicPrefix: '/src/assets/images/uploads',
  },
};

function getErrorMessage(error) {
  return error instanceof Error
    ? error.message
    : 'Unknown toolkit content error.';
}

function createContentError(resource, error) {
  return {
    error: getErrorMessage(error),
    resource,
  };
}

async function readContent(resource) {
  return contentStore.readJsonResource(resource);
}

async function saveContent(resource, content) {
  return contentStore.writeJsonResource(resource, content);
}

async function createContentRecord(resource, record) {
  return contentStore.createJsonRecord(resource, record);
}

async function updateContentRecord(resource, record) {
  return contentStore.updateJsonRecord(resource, record);
}

async function deleteContentRecord(resource, id) {
  return contentStore.deleteJsonRecord(resource, id);
}

function sanitizeAssetFileName(fileName) {
  const baseName = path.basename(String(fileName ?? 'asset'));
  const sanitizedName = baseName.replace(/[^a-zA-Z0-9._-]+/g, '-');

  return sanitizedName.length > 0 ? sanitizedName : 'asset';
}

function parseDataUrl(dataUrl) {
  if (typeof dataUrl !== 'string') {
    throw new Error('Asset upload requires a data URL.');
  }

  const dataUrlMatch = /^data:([^;]+);base64,(.+)$/u.exec(dataUrl);

  if (dataUrlMatch == null) {
    throw new Error('Asset upload data URL was invalid.');
  }

  return {
    buffer: Buffer.from(dataUrlMatch[2], 'base64'),
    mimeType: dataUrlMatch[1],
  };
}

async function uploadAsset(payload) {
  const kind = payload?.kind;
  const uploadConfig = assetUploadConfig[kind];

  if (uploadConfig == null) {
    throw new Error(`Unsupported asset upload kind: ${String(kind)}`);
  }

  const { buffer, mimeType } = parseDataUrl(payload?.dataUrl);

  if (!mimeType.startsWith(`${kind}/`)) {
    throw new Error(`Selected file was not a valid ${kind} asset.`);
  }

  const fileName = `${Date.now()}-${sanitizeAssetFileName(payload?.fileName)}`;
  const assetPath = path.join(uploadConfig.directory, fileName);

  await mkdir(uploadConfig.directory, { recursive: true });
  await writeFile(assetPath, buffer);

  return {
    assetPath: path.relative(repositoryRoot, assetPath),
    fileName,
    kind,
    mimeType,
    publicPath: `${uploadConfig.publicPrefix}/${fileName}`,
  };
}

async function broadcastChangedContent(resource) {
  try {
    io.emit('toolkit:content:changed', await readContent(resource));
  } catch (error) {
    io.emit('toolkit:content:error', createContentError(resource, error));
  }
}

function scheduleContentBroadcast(resource) {
  if (contentWatchTimer != null) {
    clearTimeout(contentWatchTimer);
  }

  contentWatchTimer = setTimeout(() => {
    contentWatchTimer = null;
    broadcastChangedContent(resource);
  }, contentWatchDebounceMs);
}

const contentWatchers = Object.entries(contentStore.defaultResourcePaths).map(
  ([resource, resourcePath]) =>
    watch(resourcePath, { persistent: false }, () => {
      scheduleContentBroadcast(resource);
    }),
);

io.on('connection', socket => {
  socket.emit('toolkit:ready', {
    connectedAt: new Date().toISOString(),
    socketId: socket.id,
  });

  socket.on('toolkit:event', payload => {
    socket.broadcast.emit('toolkit:event', payload);
  });

  socket.on('toolkit:content:read', async (payload, respond) => {
    const resource = payload?.resource;

    try {
      respond?.({
        ok: true,
        ...(await readContent(resource)),
      });
    } catch (error) {
      const contentError = createContentError(resource, error);

      respond?.({
        ok: false,
        ...contentError,
      });
      socket.emit('toolkit:content:error', contentError);
    }
  });

  socket.on('toolkit:content:save', async (payload, respond) => {
    const resource = payload?.resource;

    try {
      const changedContent = await saveContent(resource, payload?.content);

      respond?.({
        ok: true,
        ...changedContent,
      });
      io.emit('toolkit:content:changed', changedContent);
    } catch (error) {
      const contentError = createContentError(resource, error);

      respond?.({
        ok: false,
        ...contentError,
      });
      socket.emit('toolkit:content:error', contentError);
    }
  });

  socket.on('toolkit:content:create', async (payload, respond) => {
    const resource = payload?.resource;

    try {
      const changedContent = await createContentRecord(
        resource,
        payload?.record,
      );

      respond?.({
        ok: true,
        ...changedContent,
      });
      io.emit('toolkit:content:changed', changedContent);
    } catch (error) {
      const contentError = createContentError(resource, error);

      respond?.({
        ok: false,
        ...contentError,
      });
      socket.emit('toolkit:content:error', contentError);
    }
  });

  socket.on('toolkit:content:update', async (payload, respond) => {
    const resource = payload?.resource;

    try {
      const changedContent = await updateContentRecord(
        resource,
        payload?.record,
      );

      respond?.({
        ok: true,
        ...changedContent,
      });
      io.emit('toolkit:content:changed', changedContent);
    } catch (error) {
      const contentError = createContentError(resource, error);

      respond?.({
        ok: false,
        ...contentError,
      });
      socket.emit('toolkit:content:error', contentError);
    }
  });

  socket.on('toolkit:content:delete', async (payload, respond) => {
    const resource = payload?.resource;

    try {
      const changedContent = await deleteContentRecord(resource, payload?.id);

      respond?.({
        ok: true,
        ...changedContent,
      });
      io.emit('toolkit:content:changed', changedContent);
    } catch (error) {
      const contentError = createContentError(resource, error);

      respond?.({
        ok: false,
        ...contentError,
      });
      socket.emit('toolkit:content:error', contentError);
    }
  });

  socket.on('toolkit:asset:upload', async (payload, respond) => {
    try {
      respond?.({
        ok: true,
        ...(await uploadAsset(payload)),
      });
    } catch (error) {
      respond?.({
        error: getErrorMessage(error),
        ok: false,
      });
    }
  });
});

function closeServer(signal) {
  console.log(`[toolkit-socket] received ${signal}; shutting down`);

  for (const contentWatcher of contentWatchers) {
    contentWatcher.close();
  }

  io.close(() => {
    httpServer.close(() => {
      process.exit(0);
    });
  });
}

process.on('SIGINT', () => closeServer('SIGINT'));
process.on('SIGTERM', () => closeServer('SIGTERM'));

httpServer.listen(port, host, () => {
  console.log(
    `[toolkit-socket] listening at http://${host}:${port} with CORS ${allowedOrigins.join(
      ', ',
    )}`,
  );
});