class Channel { constructor() { this.init(); this.deleteOnUnload(); // a way to handle channel errors // // this.onChannelError = (err) => { console.error('event source error: ', err); }; } init() { // unique identifier: current time and random number // this.uid = new Date().getTime().toString() + "-" + Math.random().toString(16).slice(-6); this.requestId = 1; // the currently connected EventSource // this.eventSource = null; // the id of the last EventSource event we received // this.lastEventId = 0; // this last event id acknowledgment sent to the server // this.lastAcknowledgedEventId = 0; // a registry of requestId to successFunc/failureFunc // // These functions are registered during a +poke and are executed // in the onServerEvent()/onServerError() callbacks. Only one of // the functions will be called, and the outstanding poke will be // removed after calling the success or failure function. // this.outstandingPokes = new Map(); // a registry of requestId to subscription functions. // // These functions are registered during a +subscribe and are // executed in the onServerEvent()/onServerError() callbacks. The // event function will be called whenever a new piece of data on this // subscription is available, which may be 0, 1, or many times. The // disconnect function may be called exactly once. // this.outstandingSubscriptions = new Map(); } setOnChannelError(onError = (err) => {}) { this.onChannelError = onError; } deleteOnUnload() { window.addEventListener("unload", (event) => { this.delete(); }); } // sends a poke to an app on an urbit ship // poke(ship, app, mark, json, successFunc, failureFunc) { let id = this.nextId(); this.outstandingPokes.set( id, { success: successFunc, fail: failureFunc } ); this.sendJSONToChannel({ id, action: "poke", ship, app, mark, json }); } // subscribes to a path on an specific app and ship. // // Returns a subscription id, which is the same as the same internal id // passed to your Urbit. subscribe( ship, app, path, connectionErrFunc = () => {}, eventFunc = () => {}, quitFunc = () => {}) { let id = this.nextId(); this.outstandingSubscriptions.set( id, { err: connectionErrFunc, event: eventFunc, quit: quitFunc } ); this.sendJSONToChannel({ id, action: "subscribe", ship, app, path }); return id; } // quit the channel // delete() { let id = this.nextId(); navigator.sendBeacon(this.channelURL(), JSON.stringify([{ id, action: "delete" }])); if (this.eventSource) { this.eventSource.close(); } } // unsubscribe to a specific subscription // unsubscribe(subscription) { let id = this.nextId(); this.sendJSONToChannel({ id, action: "unsubscribe", subscription }); } // sends a JSON command command to the server. // sendJSONToChannel(j) { let req = new XMLHttpRequest(); req.open("PUT", this.channelURL()); req.setRequestHeader("Content-Type", "application/json"); if (this.lastEventId == this.lastAcknowledgedEventId) { let x = JSON.stringify([j]); req.send(x); } else { // we add an acknowledgment to clear the server side queue // // The server side puts messages it sends us in a queue until we // acknowledge that we received it. // let x = JSON.stringify( [{action: "ack", "event-id": parseInt(this.lastEventId)}, j] ); req.send(x); this.lastEventId = this.lastAcknowledgedEventId; } this.connectIfDisconnected(); } // connects to the EventSource if we are not currently connected // connectIfDisconnected() { if (this.eventSource) { return; } this.eventSource = new EventSource(this.channelURL(), {withCredentials:true}); this.eventSource.onmessage = e => { this.lastEventId = e.lastEventId; let obj = JSON.parse(e.data); let pokeFuncs = this.outstandingPokes.get(obj.id); let subFuncs = this.outstandingSubscriptions.get(obj.id); if (obj.response == "poke" && !!pokeFuncs) { let funcs = pokeFuncs; if (obj.hasOwnProperty("ok")) { funcs["success"](); } else if (obj.hasOwnProperty("err")) { funcs["fail"](obj.err); } else { console.error("Invalid poke response: ", obj); } this.outstandingPokes.delete(obj.id); } else if (obj.response == "subscribe" || (obj.response == "poke" && !!subFuncs)) { let funcs = subFuncs; // on a response to a subscribe, we only notify the caller on err // if (obj.hasOwnProperty("err")) { funcs["err"](obj.err); this.outstandingSubscriptions.delete(obj.id); } } else if (obj.response == "diff") { let funcs = subFuncs; funcs["event"](obj.json); } else if (obj.response == "quit") { let funcs = subFuncs; funcs["quit"](obj); this.outstandingSubscriptions.delete(obj.id); } else { console.log("Unrecognized response: ", e); } } this.eventSource.onerror = e => { this.delete(); this.init(); this.onChannelError(e); } } channelURL() { return "/~/channel/" + this.uid; } nextId() { return this.requestId++; } } window.channel = Channel;