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Rework hooks structure to be a linkedlist
Allows for safe removal of hooks whilst they are being invoked
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250005ad16
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@ -20,7 +20,16 @@ const VALID_HOOKS = [
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// Flags for what hooks have handlers registered
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let states = { }
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// Hooks by id
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// Doubly-LinkedList of hooks by id.
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// - hooks[id] points to head of list
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// - each list item looks like:
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// {
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// cb: the callback function
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// location: filename/line of code that added the hook
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// previousHook: reference to previous hook in list
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// nextHook: reference to next hook in list
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// removed: a flag that is set if the item was removed
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// }
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let hooks = { }
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// Hooks by label
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@ -54,20 +63,33 @@ function add(hookId, callback) {
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if (VALID_HOOKS.indexOf(id) === -1) {
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throw new Error(`Invalid hook '${id}'`);
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}
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if (label) {
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if (labelledHooks[label] && labelledHooks[label][id]) {
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if (label && labelledHooks[label] && labelledHooks[label][id]) {
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throw new Error("Hook "+hookId+" already registered")
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}
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labelledHooks[label] = labelledHooks[label]||{};
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labelledHooks[label][id] = callback;
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}
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// Get location of calling code
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const stack = new Error().stack;
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const callModule = stack.split("\n")[2].split("(")[1].slice(0,-1);
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Log.debug(`Adding hook '${hookId}' from ${callModule}`);
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hooks[id] = hooks[id] || [];
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hooks[id].push({cb:callback,location:callModule});
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const hookItem = {cb:callback, location: callModule, previousHook: null, nextHook: null }
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let tailItem = hooks[id];
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if (tailItem === undefined) {
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hooks[id] = hookItem;
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} else {
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while(tailItem.nextHook !== null) {
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tailItem = tailItem.nextHook
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}
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tailItem.nextHook = hookItem;
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hookItem.previousHook = tailItem;
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}
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if (label) {
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labelledHooks[label] = labelledHooks[label]||{};
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labelledHooks[label][id] = hookItem;
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}
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// TODO: get rid of this;
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states[id] = true;
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}
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@ -100,21 +122,29 @@ function remove(hookId) {
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}
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}
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function removeHook(id,callback) {
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let i = hooks[id].findIndex(hook => hook.cb === callback);
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if (i !== -1) {
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hooks[id].splice(i,1);
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if (hooks[id].length === 0) {
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function removeHook(id,hookItem) {
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let previousHook = hookItem.previousHook;
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let nextHook = hookItem.nextHook;
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if (previousHook) {
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previousHook.nextHook = nextHook;
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} else {
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hooks[id] = nextHook;
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}
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if (nextHook) {
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nextHook.previousHook = previousHook;
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}
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hookItem.removed = true;
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if (!previousHook && !nextHook) {
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delete hooks[id];
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delete states[id];
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}
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}
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}
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function trigger(hookId, payload, done) {
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const hookStack = hooks[hookId];
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if (!hookStack || hookStack.length === 0) {
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let hookItem = hooks[hookId];
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if (!hookItem) {
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if (done) {
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done();
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return;
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@ -124,7 +154,7 @@ function trigger(hookId, payload, done) {
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}
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if (!done) {
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return new Promise((resolve,reject) => {
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invokeStack(hookStack,payload,function(err) {
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invokeStack(hookItem,payload,function(err) {
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if (err !== undefined && err !== false) {
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if (!(err instanceof Error)) {
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err = new Error(err);
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@ -137,18 +167,21 @@ function trigger(hookId, payload, done) {
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})
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});
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} else {
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invokeStack(hookStack,payload,done)
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invokeStack(hookItem,payload,done)
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}
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}
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function invokeStack(hookStack,payload,done) {
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let i = 0;
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function invokeStack(hookItem,payload,done) {
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function callNextHook(err) {
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if (i === hookStack.length || err) {
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if (!hookItem || err) {
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done(err);
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return;
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}
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const hook = hookStack[i++];
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const callback = hook.cb;
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if (hookItem.removed) {
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hookItem = hookItem.nextHook;
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callNextHook();
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return;
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}
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const callback = hookItem.cb;
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if (callback.length === 1) {
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try {
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let result = callback(payload);
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@ -161,6 +194,7 @@ function invokeStack(hookStack,payload,done) {
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result.then(handleResolve, callNextHook)
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return;
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}
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hookItem = hookItem.nextHook;
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callNextHook();
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} catch(err) {
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done(err);
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@ -177,6 +211,7 @@ function invokeStack(hookStack,payload,done) {
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}
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function handleResolve(result) {
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if (result === undefined) {
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hookItem = hookItem.nextHook;
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callNextHook();
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} else {
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done(result);
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@ -121,7 +121,46 @@ describe("util/hooks", function() {
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})
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})
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})
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it("allows a hook to remove itself whilst being called", function(done) {
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let data = { order: [] }
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hooks.add("onSend.A", function(payload) { payload.order.push("A") } )
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hooks.add("onSend.B", function(payload) {
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hooks.remove("*.B");
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})
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hooks.add("onSend.C", function(payload) { payload.order.push("C") } )
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hooks.add("onSend.D", function(payload) { payload.order.push("D") } )
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hooks.trigger("onSend", data, err => {
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try {
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should.not.exist(err);
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data.order.should.eql(["A","C","D"])
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done();
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} catch(e) {
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done(e);
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}
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})
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});
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it("allows a hook to remove itself and others whilst being called", function(done) {
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let data = { order: [] }
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hooks.add("onSend.A", function(payload) { payload.order.push("A") } )
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hooks.add("onSend.B", function(payload) {
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hooks.remove("*.B");
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hooks.remove("*.C");
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})
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hooks.add("onSend.C", function(payload) { payload.order.push("C") } )
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hooks.add("onSend.D", function(payload) { payload.order.push("D") } )
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hooks.trigger("onSend", data, err => {
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try {
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should.not.exist(err);
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data.order.should.eql(["A","D"])
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done();
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} catch(e) {
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done(e);
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}
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})
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});
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it("halts execution on return false", function(done) {
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hooks.add("onSend.A", function(payload) { payload.order.push("A"); return false } )
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