whitespace-control.js

define(
  ["./visitor","exports"],
  function(__dependency1__, __exports__) {
    "use strict";
    var Visitor = __dependency1__["default"];

    function WhitespaceControl() {
    }
    WhitespaceControl.prototype = new Visitor();

    WhitespaceControl.prototype.Program = function(program) {
      var isRoot = !this.isRootSeen;
      this.isRootSeen = true;

      var body = program.body;
      for (var i = 0, l = body.length; i < l; i++) {
        var current = body[i],
            strip = this.accept(current);

        if (!strip) {
          continue;
        }

        var _isPrevWhitespace = isPrevWhitespace(body, i, isRoot),
            _isNextWhitespace = isNextWhitespace(body, i, isRoot),

            openStandalone = strip.openStandalone && _isPrevWhitespace,
            closeStandalone = strip.closeStandalone && _isNextWhitespace,
            inlineStandalone = strip.inlineStandalone && _isPrevWhitespace && _isNextWhitespace;

        if (strip.close) {
          omitRight(body, i, true);
        }
        if (strip.open) {
          omitLeft(body, i, true);
        }

        if (inlineStandalone) {
          omitRight(body, i);

          if (omitLeft(body, i)) {
            // If we are on a standalone node, save the indent info for partials
            if (current.type === 'PartialStatement') {
              // Pull out the whitespace from the final line
              current.indent = (/([ \t]+$)/).exec(body[i-1].original)[1];
            }
          }
        }
        if (openStandalone) {
          omitRight((current.program || current.inverse).body);

          // Strip out the previous content node if it's whitespace only
          omitLeft(body, i);
        }
        if (closeStandalone) {
          // Always strip the next node
          omitRight(body, i);

          omitLeft((current.inverse || current.program).body);
        }
      }

      return program;
    };
    WhitespaceControl.prototype.BlockStatement = function(block) {
      this.accept(block.program);
      this.accept(block.inverse);

      // Find the inverse program that is involed with whitespace stripping.
      var program = block.program || block.inverse,
          inverse = block.program && block.inverse,
          firstInverse = inverse,
          lastInverse = inverse;

      if (inverse && inverse.chained) {
        firstInverse = inverse.body[0].program;

        // Walk the inverse chain to find the last inverse that is actually in the chain.
        while (lastInverse.chained) {
          lastInverse = lastInverse.body[lastInverse.body.length-1].program;
        }
      }

      var strip = {
        open: block.openStrip.open,
        close: block.closeStrip.close,

        // Determine the standalone candiacy. Basically flag our content as being possibly standalone
        // so our parent can determine if we actually are standalone
        openStandalone: isNextWhitespace(program.body),
        closeStandalone: isPrevWhitespace((firstInverse || program).body)
      };

      if (block.openStrip.close) {
        omitRight(program.body, null, true);
      }

      if (inverse) {
        var inverseStrip = block.inverseStrip;

        if (inverseStrip.open) {
          omitLeft(program.body, null, true);
        }

        if (inverseStrip.close) {
          omitRight(firstInverse.body, null, true);
        }
        if (block.closeStrip.open) {
          omitLeft(lastInverse.body, null, true);
        }

        // Find standalone else statments
        if (isPrevWhitespace(program.body)
            && isNextWhitespace(firstInverse.body)) {

          omitLeft(program.body);
          omitRight(firstInverse.body);
        }
      } else {
        if (block.closeStrip.open) {
          omitLeft(program.body, null, true);
        }
      }

      return strip;
    };

    WhitespaceControl.prototype.MustacheStatement = function(mustache) {
      return mustache.strip;
    };

    WhitespaceControl.prototype.PartialStatement = 
        WhitespaceControl.prototype.CommentStatement = function(node) {
      /* istanbul ignore next */
      var strip = node.strip || {};
      return {
        inlineStandalone: true,
        open: strip.open,
        close: strip.close
      };
    };


    function isPrevWhitespace(body, i, isRoot) {
      if (i === undefined) {
        i = body.length;
      }

      // Nodes that end with newlines are considered whitespace (but are special
      // cased for strip operations)
      var prev = body[i-1],
          sibling = body[i-2];
      if (!prev) {
        return isRoot;
      }

      if (prev.type === 'ContentStatement') {
        return (sibling || !isRoot ? (/\r?\n\s*?$/) : (/(^|\r?\n)\s*?$/)).test(prev.original);
      }
    }
    function isNextWhitespace(body, i, isRoot) {
      if (i === undefined) {
        i = -1;
      }

      var next = body[i+1],
          sibling = body[i+2];
      if (!next) {
        return isRoot;
      }

      if (next.type === 'ContentStatement') {
        return (sibling || !isRoot ? (/^\s*?\r?\n/) : (/^\s*?(\r?\n|$)/)).test(next.original);
      }
    }

    // Marks the node to the right of the position as omitted.
    // I.e. {{foo}}' ' will mark the ' ' node as omitted.
    //
    // If i is undefined, then the first child will be marked as such.
    //
    // If mulitple is truthy then all whitespace will be stripped out until non-whitespace
    // content is met.
    function omitRight(body, i, multiple) {
      var current = body[i == null ? 0 : i + 1];
      if (!current || current.type !== 'ContentStatement' || (!multiple && current.rightStripped)) {
        return;
      }

      var original = current.value;
      current.value = current.value.replace(multiple ? (/^\s+/) : (/^[ \t]*\r?\n?/), '');
      current.rightStripped = current.value !== original;
    }

    // Marks the node to the left of the position as omitted.
    // I.e. ' '{{foo}} will mark the ' ' node as omitted.
    //
    // If i is undefined then the last child will be marked as such.
    //
    // If mulitple is truthy then all whitespace will be stripped out until non-whitespace
    // content is met.
    function omitLeft(body, i, multiple) {
      var current = body[i == null ? body.length - 1 : i - 1];
      if (!current || current.type !== 'ContentStatement' || (!multiple && current.leftStripped)) {
        return;
      }

      // We omit the last node if it's whitespace only and not preceeded by a non-content node.
      var original = current.value;
      current.value = current.value.replace(multiple ? (/\s+$/) : (/[ \t]+$/), '');
      current.leftStripped = current.value !== original;
      return current.leftStripped;
    }

    __exports__["default"] = WhitespaceControl;
  });