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import Exception from '../exception';
function Visitor() {
this.parents = [];
}
Visitor.prototype = {
constructor: Visitor,
mutating: false,
// Visits a given value. If mutating, will replace the value if necessary.
acceptKey: function(node, name) {
let value = this.accept(node[name]);
if (this.mutating) {
// Hacky sanity check: This may have a few false positives for type for the helper
// methods but will generally do the right thing without a lot of overhead.
if (value && !Visitor.prototype[value.type]) {
throw new Exception('Unexpected node type "' + value.type + '" found when accepting ' + name + ' on ' + node.type);
}
node[name] = value;
}
},
// Performs an accept operation with added sanity check to ensure
// required keys are not removed.
acceptRequired: function(node, name) {
this.acceptKey(node, name);
if (!node[name]) {
throw new Exception(node.type + ' requires ' + name);
}
},
// Traverses a given array. If mutating, empty respnses will be removed
// for child elements.
acceptArray: function(array) {
for (let i = 0, l = array.length; i < l; i++) {
this.acceptKey(array, i);
if (!array[i]) {
array.splice(i, 1);
i--;
l--;
}
}
},
accept: function(object) {
if (!object) {
return;
}
/* istanbul ignore next: Sanity code */
if (!this[object.type]) {
throw new Exception('Unknown type: ' + object.type, object);
}
if (this.current) {
this.parents.unshift(this.current);
}
this.current = object;
let ret = this[object.type](object);
this.current = this.parents.shift();
if (!this.mutating || ret) {
return ret;
} else if (ret !== false) {
return object;
}
},
Program: function(program) {
this.acceptArray(program.body);
},
MustacheStatement: visitSubExpression,
BlockStatement: visitBlock,
PartialStatement: visitPartial,
PartialBlockStatement: function(partial) {
visitPartial.call(this, partial);
this.acceptKey(partial, 'program');
},
ContentStatement: function(/* content */) {},
CommentStatement: function(/* comment */) {},
SubExpression: visitSubExpression,
PathExpression: function(/* path */) {},
StringLiteral: function(/* string */) {},
NumberLiteral: function(/* number */) {},
BooleanLiteral: function(/* bool */) {},
UndefinedLiteral: function(/* literal */) {},
NullLiteral: function(/* literal */) {},
Hash: function(hash) {
this.acceptArray(hash.pairs);
},
HashPair: function(pair) {
this.acceptRequired(pair, 'value');
}
};
function visitSubExpression(mustache) {
this.acceptRequired(mustache, 'path');
this.acceptArray(mustache.params);
this.acceptKey(mustache, 'hash');
}
function visitBlock(block) {
visitSubExpression.call(this, block);
this.acceptKey(block, 'program');
this.acceptKey(block, 'inverse');
}
function visitPartial(partial) {
this.acceptRequired(partial, 'name');
this.acceptArray(partial.params);
this.acceptKey(partial, 'hash');
}
export default Visitor;
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