todo/backend/src/todo.js

const express = require('express');
const paginate = require('express-paginate');
const Database = require('./db_interface.js');
const User = require('./user.js');
const { Op } = require('sequelize');

let router = express.Router();

router.use(express.json());

function map_todo(result) {
  return {
    id: result.id,
    content: result.content,
    tags: result.tags
  };
}

function parse_tags(tags) {
  result = {
    complete: undefined,
    required: [],
    excluded: []
  };
  tags.map((tag) => {
    if (tag === 'complete') {
      complete = true;
    } else if (tag === '~complete') {
      complete = false;
    } else if (tag.startsWith('~')) {
      excluded.push(tag);
    } else {
      required.push(tag);
    }
  });
  return result;
}

const todo_fields = ['currentPage', 'limit'];

router.use(paginate.middleware(10, 50));
router.use('/todos', User.enforce_session_login);
router.get('/todos', async (req, res) => {
  if (!req.query) {
    return res.status(400).json({
      error: `query must include the fields: ${todo_fields.join(', ')}}`
    });
  } else {
    let error = [];
    for (let field of todo_fields) {
      if (!req.query[field]) {
        error.push(field);
      }
    }
    if (error.length > 0) {
      return res.status(400).json({
        error: `query must include the fields: ${error.join(', ')}}`
      });
    }
  }
  let tag_options = {};
  if (req.query.tags) {
    let parsed = parse_tags(req.query.tags.split(','));
    tag_options['tags'] = {
      [Op.and]: parsed.required,
      [Op.not]: parsed.excluded
    };
    if (parsed.complete !== undefined) {
      tag_options['complete'] = {
        [Op.is]: parsed.complete
      };
    }
  }
  console.log(tag_options);
  let all_todos = await Database.schemas.todo.findAndCountAll({
    where: {
      user: req.get('id'),
      ...tag_options
    },
    limit: req.query.limit,
    offset: req.skip
  });
  const item_count = all_todos.count;
  const page_count = Math.ceil(item_count / req.query.limit);
  res.json({
    result: all_todos.map(map_todo),
    currentPage: req.query.currentPage,
    pageCount: page_count,
    itemCount: item_count,
    pages: paginate.getArrayPages(req)(5, page_count, req.query.currentPage)
  });
});

router.use('/todo', User.enforce_session_login);
router.get('/todo/:id([a-f0-9-]+)', async (req, res) => {
  let userid = req.get('id');
  let id = req.params?.id;

  let match = await Database.schemas.todo.findOne({
    where: {
      user: userid,
      id: id
    }
  });
  if (!match) {
    return res.sendStatus(404);
  }

  return res.json({
    result: map_todo(match),
    tags: get_tags(match.id)
  });
});

router.use('/todo', User.enforce_session_login);
router.post('/todo/:id([a-f0-9-]+)', async (req, res) => {
  let userid = req.get('id');
  let id = req.params?.id;

  let body = req.body;

  if (!body) {
    return res.sendStatus(400);
  }

  let match = await Database.schemas.todo.findOne({
    where: {
      user: userid,
      id: id
    }
  });
  if (!match) {
    return res.sendStatus(404);
  }

  //

  return res.json({
    result: map_todo(match),
    tags: get_tags(match.id)
  });
});

module.exports = {
  router: router
};