Can URI templates be used to match URIs to routes?

Question

Frameworks like ASP.NET or Nancy provide a syntax that can be used for specifying routes, such as:

MapRoute(\"/customers/{id}/invoices/{invoiceId}\", ...)


        

Answer 1

I suspect it would be very difficult. Certainly things like the prefix syntax would make it impossible to regenerate the original parameters.

For things like path segment expansion

 {/list*}           /red/green/blue

How would you know which parts of the path were literals and which parts were part of the parameter? There are lots of fairly freaky behavior in the URITemplate spec, I suspect even if it is possible to match, it would be fairly expensive.

Are you interested in doing this for the purposes of routing?

Answer 2

It is simple regarding match but regarding resolve you need to replace the ASP.net part by the RFC 6570.

Unfortunately I am doing this in node with express js and this might not be helpful, but I am sure something like https://github.com/geraintluff/uri-templates (for resolving) is also available in ASP.

Here is some .js code to illustrate the rewriting of a hyperschema USING RFC 6570 to use with express js (the advantage of the use within schema is that you could also define regexes for your uri templates):

  var deref = require('json-schema-deref');
  var tv4 = require('tv4');
  var url = require('url');
  var rql = require('rql/parser');
  var hyperschema = {
  "$schema": "http://json-schema.org/draft-04/hyper-schema",
  "links": [
    {
      "href": "{/id}{/ooo*}{#q}",
      "method": "GET",
      "rel": "self",
      "schema": {
        "type": "object",
        "properties": {
          "params": {
            "type": "object",
            "properties": {
              "id": {"$ref": "#/definitions/id"}
            },
            "additionalProperties": false
          }
        },
        "additionalProperties": true
      }
    }
  ],
  "definitions": {
    "id": {
      "type": "string",
      "pattern": "[a-z]{0,3}"
    }
  }
}

// DOJO lang AND _
function getDottedProperty(object, parts, create) {
    var key;
    var i = 0;

    while (object && (key = parts[i++])) {
        if (typeof object !== 'object') {
            return undefined;
        }
        object = key in object ? object[key] : (create ? object[key] = {} : undefined);
    }

    return object;
}
function getProperty(object, propertyName, create) {
    return getDottedProperty(object, propertyName.split('.'), create);
}
function _rEscape(str) {
  return str.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
}

function getPattern(k, ldo, customCat) {
  // ...* = explode = array
  // ...: = maxLength
  var key = ((k.slice(-1) === '*') ? k.slice(0,-1) : k).split(':')[0];
  var cat = (customCat) ? customCat : 'params'; // becomes default of customCat in TS
  var pattern = '';
  if (typeof ldo === 'object' && ldo.hasOwnProperty('schema')) {
    var res = getProperty(ldo.schema, ['properties',cat,'properties',key,'pattern'].join('.'));
    if (res) {
      console.log(['properties',cat,'properties',key,'pattern'].join('.'),res);
      return ['(',res,')'].join('');
    }
  }
  return pattern;
}
function ldoToRouter(ldo) {
  var expression = ldo.href.replace(/(\{\+)/g, '{') // encoding
    .replace(/(\{\?.*\})/g, '') // query
    .replace(/\{[#]([^}]*)\}/g, function(_, arg) {
      // crosshatch
      //console.log(arg);
      return ['(?:[/]*)?#:',arg,getPattern(arg,ldo,'anchor')].join('');
    })
    .replace(/\{([./])?([^}]*)\}/g, function(_, op, arg) {
      // path seperator
      //console.log(op, '::', arg, '::', ldo.schema);
      return [op,':',arg,getPattern(arg,ldo)].join('');
    });
    return {method: ldo.method.toLowerCase(), args:[expression]};
}

deref(hyperschema, function(err, fullSchema) {
  console.log('deref hyperschema:',JSON.stringify(fullSchema));
  var router = fullSchema.links.map(ldoToRouter);

  console.log('router:',JSON.stringify(router));
});