index.js

const { extractValue, dataTypeCheck } = require("./utils");

const validate = rules => {
  return (req, res, next) => {
    let error_messages = [];
    rules.forEach(rule => {
      let value = extractValue(req, rule);
      if (rule.is_optional && !value) {
        return;
      }
      if (!value) {
        error_messages.push(rule.message || `Invalid ${rule.key}, value not found in ${rule.from}`);
        return;
      }
      if (rule.datatype && !dataTypeCheck(rule.datatype, value)) {
        error_messages.push(
          rule.message ||
            `Invalid ${rule.key}, required a ${rule.datatype} value`
        );
        return;
      }
      if (rule.validation_function && !rule.validation_function(value)) {
        error_messages.push(rule.message || `Invalid ${rule.key}`);
      }
    });
    if (error_messages.length > 0) {
      res.status(400);
      res.send({ error_messages });
    } else {
      next();
    }
  };
};

exports.validate = validate;