import parser to support nested tags

template.js

@@ -0,0 +1,81 @@
+const lexical = require('./lexical.js');
+const error = require('./error.js');
+
+module.exports = function(Tag) {
+
+    var stream = {
+        init: function(tokens) {
+            this.tokens = tokens;
+            this.handlers = {};
+            return this;
+        },
+        on: function(name, cb) {
+            this.handlers[name] = cb;
+            return this;
+        },
+        trigger: function(event, arg) {
+            var h = this.handlers[event];
+            if (typeof h === 'function') {
+                h(arg);
+                return true;
+            }
+        },
+        start: function() {
+            this.trigger('start');
+            while (!this.stopRequested && (token = this.tokens.shift())) {
+                var template;
+                if (token.type == 'tag') {
+                    if (this.trigger(`tag:${token.name}`, token)) continue;
+                    template = parseTag(token, this.tokens);
+                } else {
+                    template = token;
+                }
+                this.trigger('template', template);
+            }
+            if (!this.stopRequested) this.trigger('end');
+            return this;
+        },
+        stop: function() {
+            this.stopRequested = true;
+            return this;
+        },
+        onStart: function(cb) {
+            return this.on('start', cb);
+        },
+        onEnd: function(cb) {
+            return this.on('end', cb);
+        },
+        onTag: function(name, cb) {
+            return this.on(`tag:${name}`, cb);
+        },
+        onTemplate: function(cb) {
+            return this.on('template', cb);
+        }
+    };
+
+    function parse(tokens) {
+        var templates = [];
+        var token;
+        while (token = tokens.shift()) {
+            if (token.type === 'tag') {
+                var tagInstance = parseTag(token, tokens);
+                templates.push(tagInstance);
+            } else templates.push(token);
+        }
+        return templates;
+    }
+
+    function parseTag(token, tokens) {
+        return Tag.construct(token).parse(tokens);
+    }
+
+
+    function parseStream(tokens) {
+        var s = Object.create(stream);
+        return s.init(tokens);
+    }
+
+    return {
+        parse, parseTag, parseStream
+    };
+};