first commit

exchange/trigger.js

@@ -0,0 +1,80 @@
+// wraps around a low level trigger and feeds
+// it live market data.
+
+const _ = require('lodash');
+
+const exchangeUtils = require('./exchangeUtils');
+const bindAll = exchangeUtils.bindAll;
+
+const triggers = require('./triggers');
+
+// @param api: a gekko broker wrapper instance
+// @param type: type of trigger to wrap
+// @param props: properties to feed to trigger
+class Trigger {
+  constructor({api, type, props, onTrigger}) {
+    this.onTrigger = onTrigger;
+    this.api = api;
+
+    this.isLive = true;
+
+    // note: we stay on the safe side and trigger
+    // as soon as the bid goes below trail.
+    this.tickerProp = 'bid';
+
+    if(!_.has(triggers, type)) {
+      throw new Error('Gekko Broker does not know trigger ' + type);
+    }
+
+    this.CHECK_INTERVAL = this.api.interval * 10;
+
+    bindAll(this);
+    this.trigger = new triggers[type]({
+      onTrigger: this.propogateTrigger,
+      ...props
+    })
+
+    this.scheduleFetch();
+  }
+
+  scheduleFetch() {
+    this.timout = setTimeout(this.fetch, this.CHECK_INTERVAL);
+  }
+
+  fetch() {
+    if(!this.isLive) {
+      return;
+    }
+    this.api.getTicker(this.processTicker)
+  }
+
+  processTicker(err, ticker) {
+    if(!this.isLive) {
+      return;
+    }
+    
+    if(err) {
+      return console.log('[GB/trigger] failed to fetch ticker:', err);
+    }
+
+    this.price = ticker[this.tickerProp];
+
+    this.trigger.updatePrice(this.price);
+    this.scheduleFetch();
+  }
+
+  cancel() {
+    this.isLive = false;
+    clearTimeout(this.timout);
+  }
+
+  propogateTrigger(payload) {
+    if(!this.isLive) {
+      return;
+    }
+    this.isLive = false;
+    this.onTrigger(payload);
+  }
+}
+
+module.exports = Trigger;