initial commit

.gitignore

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+node_modules
+dist
+.vscode

eslint.config.js

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+import js from "@eslint/js";
+import eslintPluginPrettierRecommended from "eslint-plugin-prettier/recommended";
+import globals from "globals";
+
+export default [
+  {    
+    ignores: ["dist"]  
+  },
+  {
+    ...js.configs.recommended,
+    ...eslintPluginPrettierRecommended,
+    rules: {
+      "no-unused-vars": "warn",
+      "no-undef": "warn",
+    },
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        l: "readonly",
+      },
+    },
+  },
+];

lib/countries.js

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+export const COUNTRIES = [
+  { countryCode: "ww", currencyCode: "usd" },
+  { countryCode: "ca", currencyCode: "cad" },
+  // { countryCode: "us", currencyCode: "usd" },
+  { countryCode: "in", currencyCode: "inr" },
+  // { countryCode: "za", currencyCode: "zar" },
+  // { countryCode: "au", currencyCode: "aud" },
+  // { countryCode: "hk", currencyCode: "hkd" },
+  // { countryCode: "jp", currencyCode: "EUR" },
+  // { countryCode: "my", currencyCode: "EUR" },
+  // { countryCode: "nz", currencyCode: "EUR" },
+  // { countryCode: "ph", currencyCode: "EUR" },
+  // { countryCode: "sg", currencyCode: "EUR" },
+  // { countryCode: "tw", currencyCode: "EUR" },
+  // { countryCode: "th", currencyCode: "EUR" },
+  // { countryCode: "at", currencyCode: "EUR" },
+  // { countryCode: "be", currencyCode: "EUR" },
+  // { countryCode: "cy", currencyCode: "EUR" },
+  // { countryCode: "cz", currencyCode: "EUR" },
+  // { countryCode: "dk", currencyCode: "EUR" },
+  // { countryCode: "ee", currencyCode: "EUR" },
+  // { countryCode: "fi", currencyCode: "EUR" },
+  // { countryCode: "fr", currencyCode: "EUR" },
+  // { countryCode: "de", currencyCode: "EUR" },
+  // { countryCode: "gr", currencyCode: "EUR" },
+  // { countryCode: "ie", currencyCode: "EUR" },
+  // { countryCode: "it", currencyCode: "EUR" },
+  // { countryCode: "lt", currencyCode: "EUR" },
+  // { countryCode: "lu", currencyCode: "EUR" },
+  // { countryCode: "mt", currencyCode: "EUR" },
+  // { countryCode: "nl", currencyCode: "EUR" },
+  // { countryCode: "no", currencyCode: "EUR" },
+  // { countryCode: "pl", currencyCode: "EUR" },
+  // { countryCode: "pt", currencyCode: "EUR" },
+  // { countryCode: "ro", currencyCode: "EUR" },
+  // { countryCode: "sk", currencyCode: "EUR" },
+  // { countryCode: "si", currencyCode: "EUR" },
+  // { countryCode: "es", currencyCode: "EUR" },
+  // { countryCode: "se", currencyCode: "EUR" },
+  // { countryCode: "ch", currencyCode: "EUR" },
+  // { countryCode: "tr", currencyCode: "EUR" },
+  // { countryCode: "gb", currencyCode: "EUR" },
+  // { countryCode: "ar", currencyCode: "EUR" },
+  // { countryCode: "br", currencyCode: "EUR" },
+  // { countryCode: "cl", currencyCode: "EUR" },
+  // { countryCode: "co", currencyCode: "EUR" },
+  // { countryCode: "mx", currencyCode: "EUR" },
+  // { countryCode: "pe", currencyCode: "EUR" },
+];

lib/currency.js

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+import currency from "currency.js";
+
+export const baseCurrency = "usd";
+
+export const convertCurrency = async (price, outCurrency, rates) => {
+  return currency(price).divide(rates[baseCurrency][outCurrency]);
+};
+
+export const loadCurrencyRates = async () => {
+  l("loading currency rates");
+  try {
+    const res = await fetch(
+      `https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest/v1/currencies/${baseCurrency}.json`,
+    );
+    return await res.json();
+  } catch (e) {
+    l("error", e);
+    return null;
+  }
+};

lib/getPriceForCountry.js

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+const timeout = (duration) => new Promise((r) => setTimeout(r, duration));
+
+const observePriceOnPage = (page) =>
+  new Promise((res, rej) => {
+    timeout(10000).then(() => rej(""));
+
+    var observer = new MutationObserver(() => {
+      const price = page
+        .querySelector(".active-price")
+        .querySelector("span").textContent;
+      if (price) {
+        observer.disconnect();
+        res(price);
+      }
+    });
+
+    observer.observe(page, {
+      attributes: true,
+      childList: true,
+      characterData: true,
+      subtree: true,
+    });
+  });
+
+const bookUrlForCountry = (country) => {
+  const urlPattern = /^https:\/\/www\.kobo\.com\/../;
+  const newPath = `https://www.kobo.com/${country}`;
+
+  return window.location.href.replace(urlPattern, newPath);
+};
+
+export const getPriceForCountry = (country) =>
+  new Promise((res) => {
+    const url = bookUrlForCountry(country);
+
+    l("going to", url);
+
+    const iframe = document.createElement("iframe");
+
+    iframe.src = url;
+
+    iframe.hidden = true;
+
+    document.body.append(iframe);
+
+    iframe.contentWindow.onload = () => {
+      l("starting observing price on", url);
+      observePriceOnPage(iframe.contentDocument.body, url)
+        .then(res)
+        .catch(() => {
+          l(`failed to find price for ${url}`);
+          res("");
+        })
+        .finally(() => document.body.removeChild(iframe));
+    };
+  });

lib/index.js

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+import './logger'
+import { COUNTRIES } from "./countries";
+import { getPriceForCountry } from "./getPriceForCountry";
+import { loadCurrencyRates, convertCurrency } from "./currency";
+
+async function main() {
+  try {
+    const rates = await loadCurrencyRates();
+
+    l('currency rates', rates)
+
+    const prices = await Promise.all(
+      COUNTRIES.map(async (c) => {
+        l("looking price for", c.countryCode);
+        const originalPrice = await getPriceForCountry(c.countryCode);
+        const convertedPrice = await convertCurrency(
+          originalPrice,
+          c.currencyCode,
+          rates,
+        );
+
+        return { ...c, originalPrice, convertedPrice };
+      }),
+    );
+
+    l(prices);
+  } catch (e) {
+    l("error", e);
+  } finally {
+    l("done");
+  }
+}
+
+l("starting...");
+
+window.onload = () => {
+  l("page is fully loaded");
+  void main();
+};

lib/logger.js

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+globalThis.l = (...m) => console.log("KOBOPRICE", ...m);

manifest.json

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+{
+  "name": "Kobo Price",
+  "description": "Lowest book price finder",
+  "version": "1.0",
+  "manifest_version": 3,
+  "permissions": ["activeTab"],
+  "content_scripts": [
+    {
+      "js": ["dist/index.js"],
+      "run_at": "document_end",
+      "matches": [
+        "https://www.kobo.com/*/*/ebook/*",
+        "https://www.kobo.com/*/*/audiobook/*"
+      ]
+    }
+  ]
+}

package.json

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+{
+  "type": "module",
+  "name": "koboprice",
+  "version": "1.0.0",
+  "description": "find lowest price on Kobo",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "lint": "eslint --fix",
+    "build": "esbuild lib/index.js --bundle --minify --sourcemap --target=chrome58,firefox57,safari11,edge16 --outfile=dist/index.js",
+    "watch-build": "npm run build -- --watch",
+    "watch-ext": "web-ext run",
+    "watch": "concurrently npm:watch-build npm:watch-ext"
+  },
+  "author": "",
+  "license": "ISC",
+  "devDependencies": {
+    "@eslint/js": "^9.6.0",
+    "concurrently": "^8.2.2",
+    "esbuild": "0.23.0",
+    "eslint": "^9.6.0",
+    "eslint-config-prettier": "^9.1.0",
+    "eslint-plugin-prettier": "^5.1.3",
+    "globals": "^15.8.0",
+    "prettier": "3.3.2",
+    "web-ext": "^8.2.0"
+  },
+  "dependencies": {
+    "currency.js": "^2.0.4"
+  }
+}

prettierrc.json

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+{
+    "trailingComma": "es5",
+    "tabWidth": 4,
+    "semi": false,
+    "singleQuote": true
+  }