// CodeMirror, copyright (c) by Marijn Haverbeke and others
// Distributed under an MIT license: http://codemirror.net/LICENSE

module.exports = function (CodeMirror) {
  function Bar (cls, orientation, scroll) {
    this.orientation = orientation;
    this.scroll = scroll;
    this.screen = this.total = this.size = 1;
    this.pos = 0;

    this.node = document.createElement('div');
    this.node.className = cls + '-' + orientation;
    this.inner = this.node.appendChild(document.createElement('div'));

    var self = this;
    CodeMirror.on(this.inner, 'mousedown', function (e) {
      if (e.which !== 1) return;
      CodeMirror.e_preventDefault(e);
      var axis = self.orientation === 'horizontal' ? 'pageX' : 'pageY';
      var start = e[axis];
      var startpos = self.pos;
      function done () {
        CodeMirror.off(document, 'mousemove', move);
        CodeMirror.off(document, 'mouseup', done);
      }
      function move (e) {
        if (e.which !== 1) return done();
        self.moveTo(startpos + (e[axis] - start) * (self.total / self.size));
      }
      CodeMirror.on(document, 'mousemove', move);
      CodeMirror.on(document, 'mouseup', done);
    });

    CodeMirror.on(this.node, 'click', function (e) {
      CodeMirror.e_preventDefault(e);
      var innerBox = self.inner.getBoundingClientRect();
      var where;
      if (self.orientation === 'horizontal') {
        where = e.clientX < innerBox.left ? -1 : e.clientX > innerBox.right ? 1 : 0;
      } else {
        where = e.clientY < innerBox.top ? -1 : e.clientY > innerBox.bottom ? 1 : 0;
      }
      self.moveTo(self.pos + where * self.screen);
    });

    function onWheel (e) {
      var moved = CodeMirror.wheelEventPixels(e)[self.orientation === 'horizontal' ? 'x' : 'y'];
      var oldPos = self.pos;
      self.moveTo(self.pos + moved);
      if (self.pos !== oldPos) {
        CodeMirror.e_preventDefault(e);
      }
    }
    CodeMirror.on(this.node, 'mousewheel', onWheel);
    CodeMirror.on(this.node, 'DOMMouseScroll', onWheel);
  }

  Bar.prototype.setPos = function (pos, force) {
    if (pos < 0) pos = 0;
    if (pos > this.total - this.screen) pos = this.total - this.screen;
    if (!force && pos === this.pos) return false;
    this.pos = pos;
    this.inner.style[this.orientation === 'horizontal' ? 'left' : 'top'] =
      (pos * (this.size / this.total)) + 'px';
    return true;
  };

  Bar.prototype.moveTo = function (pos) {
    if (this.setPos(pos)) this.scroll(pos, this.orientation);
  };

  var minButtonSize = 10;

  Bar.prototype.update = function (scrollSize, clientSize, barSize) {
    var sizeChanged = this.screen !== clientSize || this.total !== scrollSize || this.size !== barSize;
    if (sizeChanged) {
      this.screen = clientSize;
      this.total = scrollSize;
      this.size = barSize;
    }

    var buttonSize = this.screen * (this.size / this.total);
    if (buttonSize < minButtonSize) {
      this.size -= minButtonSize - buttonSize;
      buttonSize = minButtonSize;
    }
    this.inner.style[this.orientation === 'horizontal' ? 'width' : 'height'] =
      buttonSize + 'px';
    this.setPos(this.pos, sizeChanged);
  };

  function SimpleScrollbars (cls, place, scroll) {
    this.addClass = cls;
    this.horiz = new Bar(cls, 'horizontal', scroll);
    place(this.horiz.node);
    this.vert = new Bar(cls, 'vertical', scroll);
    place(this.vert.node);
    this.width = null;
  }

  SimpleScrollbars.prototype.update = function (measure) {
    if (this.width == null) {
      var style = window.getComputedStyle ? window.getComputedStyle(this.horiz.node) : this.horiz.node.currentStyle;
      if (style) {
        this.width = parseInt(style.height, 10);
      }
    }
    var width = this.width || 0;

    var needsH = measure.scrollWidth > measure.clientWidth + 1;
    var needsV = measure.scrollHeight > measure.clientHeight + 1;
    this.vert.node.style.display = needsV ? 'block' : 'none';
    this.horiz.node.style.display = needsH ? 'block' : 'none';

    if (needsV) {
      this.vert.update(measure.scrollHeight, measure.clientHeight,
        measure.viewHeight - (needsH ? width : 0));
      this.vert.node.style.bottom = needsH ? width + 'px' : '0';
    }
    if (needsH) {
      this.horiz.update(measure.scrollWidth, measure.clientWidth,
        measure.viewWidth - (needsV ? width : 0) - measure.barLeft);
      this.horiz.node.style.right = needsV ? width + 'px' : '0';
      this.horiz.node.style.left = measure.barLeft + 'px';
    }

    return {right: needsV ? width : 0, bottom: needsH ? width : 0};
  };

  SimpleScrollbars.prototype.setScrollTop = function (pos) {
    this.vert.setPos(pos);
  };

  SimpleScrollbars.prototype.setScrollLeft = function (pos) {
    this.horiz.setPos(pos);
  };

  SimpleScrollbars.prototype.clear = function () {
    var parent = this.horiz.node.parentNode;
    parent.removeChild(this.horiz.node);
    parent.removeChild(this.vert.node);
  };

  CodeMirror.scrollbarModel.simple = function (place, scroll) {
    return new SimpleScrollbars('CodeMirror-simplescroll', place, scroll);
  };

  CodeMirror.scrollbarModel.overlay = function (place, scroll) {
    return new SimpleScrollbars('CodeMirror-overlayscroll', place, scroll);
  };
};