chore: use @lit/task library to manage async tasks for fetching the b…

…anner from the auction (#42)

package.json

@@ -39,6 +39,7 @@
     "vite-plugin-dts": "^3.8.3"
   },
   "dependencies": {
+    "@lit/task": "^1.0.1",
     "lit": "^3.1.3",
     "skeleton-webcomponent-loader": "^2.1.4"
   }

src/index.ts

@@ -1,6 +1,8 @@
+import { Task } from "@lit/task";
 import { LitElement, type TemplateResult, css, html } from "lit";
-import { customElement, property, state } from "lit/decorators.js";
+import { customElement, property } from "lit/decorators.js";
 import { TopsortConfigurationError, TopsortRequestError } from "./errors";
+import type { Auction, Banner, BannerState } from "./types";
 
 /* Set up global environment for TS_BANNERS */
 
@@ -9,7 +11,7 @@ declare global {
     TS_BANNERS: {
       getLink(banner: Banner): string;
       getLoadingElement(): HTMLElement;
-      getErrorElement(error: Error): HTMLElement;
+      getErrorElement(error: unknown): HTMLElement;
       getNoWinnersElement(): HTMLElement;
       getBannerElement(banner: Banner): HTMLElement;
     };
@@ -44,50 +46,6 @@ const getDeviceType = (): "mobile" | "desktop" => {
   return "desktop";
 };
 
-interface Loading {
-  status: "loading";
-}
-
-interface Errored {
-  status: "errored";
-  error: Error;
-}
-
-interface NoWinners {
-  status: "nowinners";
-}
-
-interface Ready {
-  status: "ready";
-  banner: Banner;
-}
-
-interface Auction {
-  type: "banners";
-  slots: 1;
-  device: "mobile" | "desktop";
-  slotId: string;
-  category?: {
-    id?: string;
-    ids?: string[];
-    disjunctions?: string[][];
-  };
-  geoTargeting?: {
-    location: string;
-  };
-  searchQuery?: string;
-}
-
-/** The banner object returned from the auction request */
-export interface Banner {
-  type: "product" | "vendor" | "brand" | "url";
-  id: string;
-  resolvedBidId: string;
-  asset: [{ url: string }];
-}
-
-type BannerState = Loading | Errored | NoWinners | Ready;
-
 /**
  * A banner web component that runs an auction and renders the winning banner.
  */
@@ -117,10 +75,10 @@ export class TopsortBanner extends LitElement {
   @property({ attribute: "location", type: String })
   readonly location?: string;
 
-  @state()
-  private state: BannerState = {
-    status: "loading",
-  };
+  private task = new Task(this, {
+    task: this.runAuction,
+    args: () => [this.buildAuction()],
+  });
 
   private getLink(banner: Banner): string {
     if (window.TS_BANNERS.getLink) {
@@ -137,25 +95,26 @@ export class TopsortBanner extends LitElement {
       const element = window.TS_BANNERS.getLoadingElement();
       return html`${element}`;
     }
-    return html`<div class="ts-banner-${this.state.status}">Loading</div>`;
+    // By default, hide the component while loading
+    return html``;
   }
 
-  private getErrorElement(error: Error): TemplateResult {
+  private getErrorElement(error: unknown): TemplateResult {
     if (window.TS_BANNERS.getErrorElement) {
       const element = window.TS_BANNERS.getErrorElement(error);
       return html`${element}`;
     }
-    return html`<div class="ts-banner-${this.state.status}>
-      <pre>${error.message}</pre>
-    </div>`;
+    // By default, hide the component if there is an error
+    return html``;
   }
 
   private getNoWinnersElement(): TemplateResult {
     if (window.TS_BANNERS.getNoWinnersElement) {
       const element = window.TS_BANNERS.getNoWinnersElement();
       return html`${element}`;
     }
-    return html`<div class="ts-banner-${this.state.status}"></div>`;
+    // By default, hide the component if there are no winners
+    return html``;
   }
 
   private getBannerElement(banner: Banner): TemplateResult {
@@ -175,133 +134,112 @@ export class TopsortBanner extends LitElement {
         <div style="${style}"
              data-ts-clickable
              data-ts-resolved-bid=${banner.resolvedBidId}
-             class="ts-banner-${this.state.status}">
+             class="ts-banner">
           <a href="${href}">
             <img src="${src}" alt="Topsort banner"></img>
           </a>
         </div>
         `;
   }
 
-  private setState(state: BannerState) {
-    this.state = state;
+  private emitEvent(status: string) {
     const event = new CustomEvent("statechange", {
-      detail: { state, slotId: this.slotId },
+      detail: { slotId: this.slotId, status },
       bubbles: true,
       composed: true,
     });
     this.dispatchEvent(event);
   }
 
-  private async runAuction() {
+  private buildAuction(): Auction {
     const device = getDeviceType();
-    try {
-      const auction: Auction = {
-        type: "banners",
-        slots: 1,
-        device,
-        slotId: this.slotId,
+    const auction: Auction = {
+      type: "banners",
+      slots: 1,
+      device,
+      slotId: this.slotId,
+    };
+    if (this.categoryId) {
+      auction.category = {
+        id: this.categoryId,
       };
-      if (this.categoryId) {
-        auction.category = {
-          id: this.categoryId,
-        };
-      } else if (this.categoryIds) {
-        auction.category = {
-          ids: this.categoryIds.split(",").map((item) => item.trim()),
-        };
-      } else if (this.categoryDisjunctions) {
-        auction.category = {
-          disjunctions: [this.categoryDisjunctions.split(",").map((item) => item.trim())],
-        };
-      } else if (this.searchQuery) {
-        auction.searchQuery = this.searchQuery;
-      }
-      if (this.location) {
-        auction.geoTargeting = {
-          location: this.location,
-        };
-      }
-      const token = window.TS.token;
-      const url = window.TS.url || "https://api.topsort.com";
-      const res = await fetch(new URL(`${url}/v2/auctions`), {
-        method: "POST",
-        mode: "cors",
-        headers: {
-          Authorization: `Bearer ${token}`,
-          "Content-Type": "application/json",
-          "X-UA": `topsort/banners-${import.meta.env.PACKAGE_VERSION} (${device}})`,
-        },
-        body: JSON.stringify({
-          auctions: [auction],
-        }),
-      });
-      if (res.ok) {
-        const data = await res.json();
-        const result = data.results[0];
-        if (result) {
-          if (result.error) {
-            logError(result.error);
-            this.setState({
-              status: "errored",
-              error: Error("Unknown Error"),
-            });
-          } else if (result.winners[0]) {
-            const winner = result.winners[0];
-            this.setState({
-              status: "ready",
-              banner: winner,
-            });
-          } else {
-            this.setState({
-              status: "nowinners",
-            });
-          }
-        }
-      } else {
-        const error = await res.json();
-        logError(error);
-        this.setState({
-          status: "errored",
-          error: new TopsortRequestError(error.message, res.status),
-        });
-      }
-    } catch (err) {
-      logError(err);
-      if (err instanceof Error) {
-        this.setState({
-          status: "errored",
-          error: err,
-        });
-      } else {
-        this.setState({
-          status: "errored",
-          error: Error("Unknown Error"),
-        });
-      }
+    } else if (this.categoryIds) {
+      auction.category = {
+        ids: this.categoryIds.split(",").map((item) => item.trim()),
+      };
+    } else if (this.categoryDisjunctions) {
+      auction.category = {
+        disjunctions: [this.categoryDisjunctions.split(",").map((item) => item.trim())],
+      };
+    } else if (this.searchQuery) {
+      auction.searchQuery = this.searchQuery;
     }
+    if (this.location) {
+      auction.geoTargeting = {
+        location: this.location,
+      };
+    }
+    return auction;
   }
 
-  // Runs when DOM is loaded. Much like React's `getInitialProps`
-  connectedCallback() {
-    super.connectedCallback();
-    this.runAuction();
+  private async runAuction(
+    [auction]: Auction[],
+    { signal }: { signal: AbortSignal },
+  ): Promise<BannerState> {
+    const device = getDeviceType();
+    const token = window.TS.token;
+    const url = window.TS.url || "https://api.topsort.com";
+    const res = await fetch(new URL(`${url}/v2/auctions`), {
+      method: "POST",
+      mode: "cors",
+      headers: {
+        Authorization: `Bearer ${token}`,
+        "Content-Type": "application/json",
+        "X-UA": `topsort/banners-${import.meta.env.PACKAGE_VERSION} (${device}})`,
+      },
+      body: JSON.stringify({
+        auctions: [auction],
+      }),
+      signal,
+    });
+    if (!res.ok) {
+      const error = await res.json();
+      logError(error);
+      throw new Error(error.message);
+    }
+    const data = await res.json();
+    const result = data.results[0];
+    if (!result) throw new TopsortRequestError("No auction results", res.status);
+    if (result.error) {
+      logError(result.error);
+      throw new Error(result.error);
+    }
+    if (result.winners.length) {
+      return {
+        status: "ready",
+        banners: result.winners,
+      };
+    }
+    return {
+      status: "nowinners",
+    };
   }
 
   protected render() {
     if (!window.TS.token || !this.slotId) {
       return this.getErrorElement(new TopsortConfigurationError(window.TS.token, this.slotId));
     }
-    switch (this.state.status) {
-      case "ready":
-        return this.getBannerElement(this.state.banner);
-      case "nowinners":
-        return this.getNoWinnersElement();
-      case "loading":
-        return this.getLoadingElement();
-      case "errored":
-        return this.getErrorElement(this.state.error);
-    }
+    return this.task.render({
+      pending: () => this.getLoadingElement(),
+      complete: (value) => {
+        this.emitEvent(value.status);
+        if (value.status === "nowinners") {
+          return this.getNoWinnersElement();
+        }
+        return this.getBannerElement(value.banners[0]);
+      },
+      error: (error) => this.getErrorElement(error),
+    });
   }
 
   // avoid shadow dom since we cannot attach to events via analytics.js