feat: enable webextension builds

Currently only supports Chrome due to no `chrome` -> `browser` polyfill

src/background/background.ts

@@ -0,0 +1,111 @@
+chrome.runtime.onMessage.addListener(
+  function(request, sender, sendResponse) {
+    if (request.contentScriptQuery == "queryExchangeRates") {
+      const url = "https://open.er-api.com/v6/latest/USD";
+      fetch(url)
+          .then(response => {
+            console.log(response)
+            return response.json()
+          })
+          .then(json => {
+            sendResponse(json)
+          })
+          .catch(error => {
+            console.error("Failed to get exchange rates", error);
+          })
+      return true;
+    }
+})
+
+chrome.runtime.onMessage.addListener(
+  function(request, sender, sendResponse) {
+    if (request.contentScriptQuery == "querySchema") {
+      const url = "https://raw.githubusercontent.com/danocmx/node-tf2-static-schema/master/static/items.json";
+      fetch(url)
+          .then(response => response.json())
+          .then(json => sendResponse(json))
+          .catch(error => {
+            console.error("Failed to get schema", error);
+          })
+      return true;
+    }
+  }
+);
+
+chrome.runtime.onMessage.addListener(
+  function(request, sender, sendResponse) {
+    if (request.contentScriptQuery == "getPricesTFToken") {
+      fetch('https://api2.prices.tf/auth/access', {
+        method: 'post',
+        headers: new Headers({
+          'Accept': 'application/json'
+        })
+      })
+      .then(response => response.json())
+      .then(json => sendResponse(json['accessToken']))
+      .catch(error => {
+        console.error("Failed to get access token", error);
+      })
+      return true;
+    }
+  }
+)
+
+class PricesResponse {
+  keys: number
+  metal: number
+}
+
+async function priceUsingPricesTF(token: string, sku: string, retries: number = 3): Promise<PricesResponse> {
+  const url = `https://api2.prices.tf/prices/${encodeURIComponent(sku)}`;
+  const response = await fetch(url, {
+    method: 'get',
+    headers: {
+      'Accept': 'application/json',
+      'Authorization': `Bearer ${token}`,
+    }
+  })
+  if (response.status === 404 && sku.includes(';') && !sku.includes(';uncraftable')) {
+    const quality: number = parseInt(sku.split(';')[1], 10);
+    if(quality === 6) {
+      // Try uncraftable variant if unique weapon
+      return priceUsingPricesTF(token, sku + ';uncraftable');
+    }
+  }
+  if(response.status === 503) {
+    // Happens if we send too many requests in a short period of time
+    // Retry after a few seconds
+    if(retries >= 0) {
+      console.log(`Cloudflare rate limit exceeded, trying again after 1 second, ${retries} retries left`)
+      await new Promise(resolve => setTimeout(resolve, 1000));
+      return priceUsingPricesTF(token, sku, retries - 1);
+    } else {
+      throw new Error(`Cloudflare rate limit exceeded, stopping`)
+    }
+  }
+  const data = await response.json();
+  const prices = new PricesResponse();
+  prices.keys = data['sellKeys']
+  prices.metal = data['sellHalfScrap'] / 18.0;
+  return prices;
+}
+
+chrome.runtime.onMessage.addListener(
+  function(request, sender, sendResponse) {
+    if (request.contentScriptQuery == "priceSKU") {
+      const sku: string = request.sku
+      const service: string = request.service
+      const token: string = request.token
+      switch (service) {
+        case "prices.tf": {
+          priceUsingPricesTF(token, sku).then((response) => {
+            sendResponse(JSON.stringify(response));
+          })
+          return true;
+        }
+        default:
+          return false;
+      }
+    }
+  }
+);