--- /dev/null
+var Traverse = require('traverse');
+var EventEmitter = require('events').EventEmitter;
+
+module.exports = Chainsaw;
+function Chainsaw (builder) {
+ var saw = Chainsaw.saw(builder, {});
+ var r = builder.call(saw.handlers, saw);
+ if (r !== undefined) saw.handlers = r;
+ saw.record();
+ return saw.chain();
+};
+
+Chainsaw.light = function ChainsawLight (builder) {
+ var saw = Chainsaw.saw(builder, {});
+ var r = builder.call(saw.handlers, saw);
+ if (r !== undefined) saw.handlers = r;
+ return saw.chain();
+};
+
+Chainsaw.saw = function (builder, handlers) {
+ var saw = new EventEmitter;
+ saw.handlers = handlers;
+ saw.actions = [];
+
+ saw.chain = function () {
+ var ch = Traverse(saw.handlers).map(function (node) {
+ if (this.isRoot) return node;
+ var ps = this.path;
+
+ if (typeof node === 'function') {
+ this.update(function () {
+ saw.actions.push({
+ path : ps,
+ args : [].slice.call(arguments)
+ });
+ return ch;
+ });
+ }
+ });
+
+ process.nextTick(function () {
+ saw.emit('begin');
+ saw.next();
+ });
+
+ return ch;
+ };
+
+ saw.pop = function () {
+ return saw.actions.shift();
+ };
+
+ saw.next = function () {
+ var action = saw.pop();
+
+ if (!action) {
+ saw.emit('end');
+ }
+ else if (!action.trap) {
+ var node = saw.handlers;
+ action.path.forEach(function (key) { node = node[key] });
+ node.apply(saw.handlers, action.args);
+ }
+ };
+
+ saw.nest = function (cb) {
+ var args = [].slice.call(arguments, 1);
+ var autonext = true;
+
+ if (typeof cb === 'boolean') {
+ var autonext = cb;
+ cb = args.shift();
+ }
+
+ var s = Chainsaw.saw(builder, {});
+ var r = builder.call(s.handlers, s);
+
+ if (r !== undefined) s.handlers = r;
+
+ // If we are recording...
+ if ("undefined" !== typeof saw.step) {
+ // ... our children should, too
+ s.record();
+ }
+
+ cb.apply(s.chain(), args);
+ if (autonext !== false) s.on('end', saw.next);
+ };
+
+ saw.record = function () {
+ upgradeChainsaw(saw);
+ };
+
+ ['trap', 'down', 'jump'].forEach(function (method) {
+ saw[method] = function () {
+ throw new Error("To use the trap, down and jump features, please "+
+ "call record() first to start recording actions.");
+ };
+ });
+
+ return saw;
+};
+
+function upgradeChainsaw(saw) {
+ saw.step = 0;
+
+ // override pop
+ saw.pop = function () {
+ return saw.actions[saw.step++];
+ };
+
+ saw.trap = function (name, cb) {
+ var ps = Array.isArray(name) ? name : [name];
+ saw.actions.push({
+ path : ps,
+ step : saw.step,
+ cb : cb,
+ trap : true
+ });
+ };
+
+ saw.down = function (name) {
+ var ps = (Array.isArray(name) ? name : [name]).join('/');
+ var i = saw.actions.slice(saw.step).map(function (x) {
+ if (x.trap && x.step <= saw.step) return false;
+ return x.path.join('/') == ps;
+ }).indexOf(true);
+
+ if (i >= 0) saw.step += i;
+ else saw.step = saw.actions.length;
+
+ var act = saw.actions[saw.step - 1];
+ if (act && act.trap) {
+ // It's a trap!
+ saw.step = act.step;
+ act.cb();
+ }
+ else saw.next();
+ };
+
+ saw.jump = function (step) {
+ saw.step = step;
+ saw.next();
+ };
+};