'use strict'

/* Element Helpers */
/*
  While you can write HTML elements by hand, those helpers make it easier to
  place anchors (especially with special purpose) and spans.

  They define a monadic interface:

  a.id('my-link').content('link').writer('my-ref')
    -> <a id="my-link" href="./_writer_my-ref">link</a>

  span -> <span></span>

  The object supplies a toString() method that outputs the tag. Element
  helpers are immutable, so theoretically this should be safe from side
  effects. This interface allows the safe definition of templates which
  can be used and modified at will, for instance:

  let mySpanClass = span.class('myclass'); // -> <span class="myclass"></span>
  mySpanClass.content("Hello!"); // -> <span class="myclass">Hello!</span>

  Methods on an elementHelper return a new elementHelper that inherits from
  itself. Since those objects (should be) immutable by being frozen when they
  are created, this is semantically equivalent to returning a copy but more
  efficient in terms

  Methods:
    class :: String -> elementHelper
      Returns a new elementHelper with the given class added.

    classes :: [String] -> elementHelper
      Returns a new elementHelper with the given classes.

    id :: String -> elementHelper
      Returns a new elementHelper with the given id.


*/

var md = require('markdown-it');

var markdown = new md({
  typographer: true,
  html: true
});

var elementHelper = function (element) {
  this.element = element;
  this._classes = [];
};

var elementSetterGen = function (prop) {
  return function (value) {
    return Object.freeze(Object.create(this, {
      [prop]: {value}
    }));
  };
};

elementHelper.prototype.classes = function (newClasses) {
  return Object.freeze(Object.create(this, {
    _classes: {
      value: newClasses
    }
  }));
};

elementHelper.prototype.class = function (newClass) {
  return this.classes(this._classes.concat(newClass));
};

elementHelper.prototype.id = elementSetterGen("_id");
elementHelper.prototype.type = elementSetterGen("_linkType");
elementHelper.prototype.content = elementSetterGen("_content");
elementHelper.prototype.ref = elementSetterGen("_ref");
elementHelper.prototype.src = elementSetterGen("_src");
elementHelper.prototype.alt = elementSetterGen("_alt");

elementHelper.prototype.url = elementHelper.prototype.ref;
elementHelper.prototype.situation = elementHelper.prototype.ref;

elementHelper.prototype.once = function () {
  return this.class('once');
};

var linkTypeGen = function (type) {
  return function (ref) {
    return this.type(type).ref(ref);
  }
};

elementHelper.prototype.writer = linkTypeGen("writer");
elementHelper.prototype.replacer = linkTypeGen("replacer");
elementHelper.prototype.inserter = linkTypeGen("inserter");
elementHelper.prototype.action = linkTypeGen("action");

elementHelper.prototype.toString = function () {
  var classes = "",
      classString = "",
      idString = "",
      hrefString= "",
      contentString = "",
      srcString = "",
      altString = "";

  if (this._classes) {
    classes += this._classes.join(' ');
  }

  if (this._linkType) {
    if (classes) {
      classes += (' ' + this._linkType);
    } else {
      classes = this._linkType;
    }
  }

  if (classes) {
    classString = ` class="${classes}"`;
  }

  if (this._id) {
    idString = ` id="${this._id}"`;
  }

  if (this.element === "a") {
    if (this._linkType) {
      if (this._linkType === "action") {
        hrefString = ` href="./${this._ref}"`;
      } else {
        hrefString = ` href="./_${this._linkType}_${this._ref}"`;
      }
    } else {
      hrefString = ` href="${this._ref}"`;
    }
  }

  if (this._src) {
    srcString = ` src="${this._src}"`;
  }

  if (this._alt) {
    altString = ` alt="${this._alt}"`;
  }

  if (this._content) {
    contentString = markdown.renderInline(this._content);
  }

  return `<${this.element}${classString}${idString}${hrefString}${srcString}${altString}>${contentString}</${this.element}>`;
};

var a_proto = Object.freeze(new elementHelper("a"));
var span_proto = Object.freeze(new elementHelper("span"));
var img_proto = Object.freeze(new elementHelper("img"));

var a = function (content) {
  if (content) return a_proto.content(content);
  return a_proto;
};

var span = function (content) {
  if (content) return span_proto.content(content);
  return span_proto;
};

var img = function (alt) {
  if (alt) return img_proto.alt(alt);
  return img_proto;
};

var element = function (tag) {
  return Object.freeze(new elementHelper(tag));
};

module.exports.a = a;
module.exports.span = span;
module.exports.img = img;
module.exports.element = element;