'use strict';

var serialize = require('./util').serialize

module.exports = function(env) {

  function display(s, k, a, x) {
    return k(s, console.log(x));
  }

  // Caching for a wppl function f.
  //
  // Caution: if f isn't deterministic weird stuff can happen, since
  // caching is across all uses of f, even in different execuation
  // paths.
  function cache(s, k, a, f) {
    var c = {};
    var cf = function(s, k, a) {
      var args = Array.prototype.slice.call(arguments, 3);
      var stringedArgs = serialize(args);
      if (stringedArgs in c) {
        return k(s, c[stringedArgs]);
      } else {
        var newk = function(s, r) {
          if (stringedArgs in c) {
            // This can happen when cache is used on recursive functions
            console.log('Already in cache:', stringedArgs);
            if (serialize(c[stringedArgs]) !== serialize(r)) {
              console.log('OLD AND NEW CACHE VALUE DIFFER!');
              console.log('Old value:', c[stringedArgs]);
              console.log('New value:', r);
            }
          }
          c[stringedArgs] = r;
          return k(s, r);
        };
        return f.apply(this, [s, newk, a].concat(args));
      }
    };
    return k(s, cf);
  }

  function apply(s, k, a, wpplFn, args) {
    return wpplFn.apply(global, [s, k, a].concat(args));
  }

  // Annotating a function object with its lexical id and
  //    a list of its free variable values.
  var __uniqueid = 0;
  var _Fn = {
    tag: function(fn, lexid, freevarvals) {
      fn.__lexid = lexid;
      fn.__uniqueid = __uniqueid++;
      fn.__freeVarVals = freevarvals;
      return fn;
    }
  };

  return {
    display: display,
    cache: cache,
    apply: apply,
    _Fn: _Fn
  };

};