bem-xjst/lib/bemxjst/match.js

Declarative Template Engine for the browser and server

var tree = require('./tree');
var PropertyMatch = tree.PropertyMatch;
var AddMatch = tree.AddMatch;
var WrapMatch = tree.WrapMatch;
var ExtendMatch = tree.ExtendMatch;
var CustomMatch = tree.CustomMatch;

function MatchNested(template, pred) {
  this.template = template;
  this.keys = pred.key;
  this.value = pred.value;
}

MatchNested.prototype.exec = function(context) {
  var val = context;
  var keys = this.keys;

  for (var i = 0; i < keys.length - 1; i++) {
    val = val[keys[i]];
    if (!val)
      return false;
  }

  val = val[keys[i]];

  if (this.value === true)
    return val !== undefined && val !== '' && val !== false && val !== null;

  return String(val) === this.value;
};

function MatchCustom(template, pred) {
  this.template = template;
  this.body = pred.body;
}

MatchCustom.prototype.exec = function(context) {
  return this.body.call(context, context, context.ctx);
};

function MatchWrap(template) {
  this.template = template;
  this.wrap = null;
}

MatchWrap.prototype.exec = function(context) {
  var res = this.wrap !== context.ctx;
  this.wrap = context.ctx;
  return res;
};

function MatchExtend(template) {
  this.template = template;
  this.wrap = null;
}

MatchExtend.prototype.exec = function(context) {
  var res = this.ext !== context.ctx;
  this.ext = context.ctx;
  return res;
};

function AddWrap(template, pred) {
  this.template = template;
  this.key = pred.key;
  this.value = pred.value;
}

AddWrap.prototype.exec = function(context) {
  return context[this.key] === this.value;
};

function MatchTemplate(mode, template) {
  this.mode = mode;
  this.predicates = new Array(template.predicates.length);
  this.body = template.body;

  var postpone = [];

  for (var i = 0, j = 0; i < this.predicates.length; i++, j++) {
    var pred = template.predicates[i];
    if (pred instanceof PropertyMatch) {
      this.predicates[j] = new MatchNested(this, pred);
    } else if (pred instanceof ExtendMatch) {
      j--;
      postpone.push(new MatchExtend(this));
    } else if (pred instanceof AddMatch) {
      this.predicates[j] = new AddWrap(this, pred);
    } else if (pred instanceof CustomMatch) {
      this.predicates[j] = new MatchCustom(this, pred);

      // Push MatchWrap later, they should not be executed first.
      // Otherwise they will set flag too early, and body might not be executed
    } else if (pred instanceof WrapMatch) {
      j--;
      postpone.push(new MatchWrap(this));
    } else {
      // Skip
      j--;
    }
  }

  // Insert late predicates
  for (var i = 0; i < postpone.length; i++, j++)
    this.predicates[j] = postpone[i];

  if (this.predicates.length !== j)
    this.predicates.length = j;
}
exports.MatchTemplate = MatchTemplate;

function Match(entity, modeName) {
  this.entity = entity;
  this.modeName = modeName;
  this.bemxjst = this.entity.bemxjst;
  this.templates = [];

  // applyNext mask
  this.mask = [ 0 ];

  // We are going to create copies of mask for nested `applyNext()`
  this.maskSize = 0;
  this.maskOffset = 0;

  this.count = 0;
  this.depth = -1;

  this.thrownError = null;
}
exports.Match = Match;

Match.prototype.prepend = function(other) {
  this.templates = other.templates.concat(this.templates);
  this.count += other.count;

  while (Math.ceil(this.count / 31) > this.mask.length)
    this.mask.push(0);

  this.maskSize = this.mask.length;
};

Match.prototype.push = function(template) {
  this.templates.push(new MatchTemplate(this, template));
  this.count++;

  if (Math.ceil(this.count / 31) > this.mask.length)
    this.mask.push(0);

  this.maskSize = this.mask.length;
};

Match.prototype.tryCatch = function(fn, ctx) {
  try {
    return fn.call(ctx, ctx, ctx.ctx);
  } catch (e) {
    this.thrownError = e;
    if (this.modeName) {
      this.thrownError.ctx = ctx;
      this.thrownError.name = 'BEMXJST ERROR';
      var classBuilder = this.entity.bemxjst.classBuilder;

      var cause = e.stack.split('\n')[1];
      this.thrownError.message = 'Template error in mode ' +
            this.modeName + ' in block ' +
            classBuilder.build(ctx.ctx.block, ctx.ctx.elem) +
            '\n    ' + e.message + '\n';
      this.thrownError.stack = this.thrownError.name + ': ' +
            this.thrownError.message + ' ' + cause + '\n' + e.stack;
    }
  }
};

Match.prototype.exec = function(context) {
  var save = this.checkDepth();

  var template;
  var bitIndex = this.maskOffset;
  var mask = this.mask[bitIndex];
  var bit = 1;
  for (var i = 0; i < this.count; i++) {
    if ((mask & bit) === 0) {
      template = this.templates[i];
      for (var j = 0; j < template.predicates.length; j++) {
        var pred = template.predicates[j];

        /* jshint maxdepth : false */
        if (!pred.exec(context))
          break;
      }

      // All predicates matched!
      if (j === template.predicates.length)
        break;
    }

    if (bit === 0x40000000) {
      bitIndex++;
      mask = this.mask[bitIndex];
      bit = 1;
    } else {
      bit <<= 1;
    }
  }

  if (i === this.count) {
    this.restoreDepth(save);

    if (this.modeName === 'mods')
      return context.mods;

    if (this.modeName === 'elemMods')
      return context.elemMods;

    return context.ctx[this.modeName];
  }

  var oldMask = mask;
  var oldMatch = this.bemxjst.match;
  this.mask[bitIndex] |= bit;
  this.bemxjst.match = this;

  this.thrownError = null;

  var out;
  if (typeof template.body === 'function')
    out = this.tryCatch(template.body, context);
  else
    out = template.body;

  this.mask[bitIndex] = oldMask;
  this.bemxjst.match = oldMatch;
  this.restoreDepth(save);

  var e = this.thrownError;
  if (e !== null) {
    this.thrownError = null;
    throw e;
  }

  return out;
};

Match.prototype.checkDepth = function() {
  if (this.depth === -1) {
    this.depth = this.bemxjst.depth;
    return -1;
  }

  if (this.bemxjst.depth === this.depth)
    return this.depth;

  var depth = this.depth;
  this.depth = this.bemxjst.depth;

  this.maskOffset += this.maskSize;

  while (this.mask.length < this.maskOffset + this.maskSize)
    this.mask.push(0);

  return depth;
};

Match.prototype.restoreDepth = function(depth) {
  if (depth !== -1 && depth !== this.depth)
    this.maskOffset -= this.maskSize;
  this.depth = depth;
};