index.js

//     koa-manifest-rev
//     Copyright (c) 2016- Nick Baugh <niftylettuce@gmail.com>
//     MIT Licensed

// * Author: [@niftylettuce](https://twitter.com/#!/niftylettuce)
// * Source: <https://github.com/niftylettuce/koa-manifest-rev>

// # koa-manifest-rev

module.exports = function(opts) {
  if (typeof opts !== 'object') {
    throw new TypeError('`options` argument required');
  }

  if (typeof opts.manifest !== 'string') {
    throw new TypeError('`manifest` property is required');
  }

  if (typeof opts.prepend !== 'undefined' && typeof opts.prepend !== 'string') {
    throw new TypeError('`prepend` property defined, but it was not a string');
  }

  opts.prepend = opts.prepend || '/';

  return function(ctx, next) {
    ctx.state.manifest = str => {
      let output = opts.prepend + str;
      try {
        output = opts.prepend + (require(opts.manifest)[str] || str);
      } catch (err) {}
      return output;
    };
    return next();
  };
};