Add: fetchDelay option (#339)

README.md

@@ -117,6 +117,20 @@ pbs.twimg.com/media/$1:orig
 * Lines starting with `#` are ignored.
 * Empty lines are ignored.
 
+Fetch delay
+------------
+
+You can set a delay between each download:
+
+```
+https://i.imgur.com 5
+http://example.com 10
+```
+
+* Each line includes
+  - The origin of the image.
+  - The delay (in seconds).
+
 Retry on failure
 ----------------
 

src/background.js

@@ -31,7 +31,25 @@ let INC = 0;
 const batches = new Map;
 const batchDownloadLock = createLock({maxActiveReader: 5});
 
-browser.runtime.onMessage.addListener((message, sender) => {
+// this is used to log error raised by onMessage handler,
+// otherwise the stack trace will be removed after passing the error to the content script.
+function logError(fn) {
+  return (...args) => {
+    try {
+      const result = fn(...args);
+      if (!result || !result.catch) return result;
+      return result.catch(err => {
+        console.error(err);
+        throw err;
+      });
+    } catch (err) {
+      console.error(err);
+      throw err;
+    }
+  };
+}
+
+browser.runtime.onMessage.addListener(logError((message, sender) => {
 	switch (message.method) {
 		case "singleDownload":
 			message.tabId = sender.tab.id;
@@ -76,7 +94,7 @@ browser.runtime.onMessage.addListener((message, sender) => {
       return imageCache.get(message.url)
         .then(blob => URL.createObjectURL(blob));
 	}
-});
+}));
 
 browser.browserAction.onClicked.addListener(tab => {
 	MENU_ACTIONS[pref.get("browserAction")].handler(tab);

src/lib/fetch-delay.js

@@ -0,0 +1,49 @@
+import {createLockPool} from "@eight04/read-write-lock";
+
+import {pref} from "./pref.js";
+import {parseText} from "./readline.js";
+
+pref.ready().then(() => {
+  update();
+  pref.on("change", change => {
+    if (change.fetchDelay != null) {
+      update();
+    }
+  });
+});
+
+const lock = createLockPool({maxActiveReader: 3});
+let meta = new Map;
+
+function update() {
+  const newMeta = new Map;
+  for (const lines of parseText(pref.get('fetchDelay'))) {
+    const [origin, delay] = lines[0].trim().split(/\s+/);
+    const delayMs = Number(delay) * 1000;
+    newMeta.set(origin, {
+      ...meta.get(origin),
+      delayMs
+    });
+  }
+  meta = newMeta;
+}
+
+export async function fetchDelay(url, cb) {
+  const origin = new URL(url).origin;
+  if (meta.has(origin)) {
+    return await lock.write([origin], async () => {
+      const t = (meta.get(origin).lastFetch || 0) + meta.get(origin).delayMs - Date.now();
+      await delay(t > 0 ? t : 0);
+      try {
+        return await cb();
+      } finally {
+        meta.get(origin).lastFetch = Date.now();
+      }
+    });
+  }
+  return await lock.read([origin], cb);
+}
+
+function delay(ms) {
+  return new Promise(resolve => setTimeout(resolve, ms));
+}

src/lib/image-cache.js

@@ -5,6 +5,7 @@ import {IS_CHROME} from "./env.js";
 import {fetchImage} from "./fetch-image.js";
 import {fetchXHR} from "./fetch.js";
 import {retry} from "./retry.js";
+import {fetchDelay} from "./fetch-delay.js";
 
 export const imageCache = createImageCache();
 
@@ -27,11 +28,13 @@ function createImageCache() {
 
   function add({url, tabId, frameId, referrer}) {
     return cache.set(url, async () => {
-      const data = await retry(() => _fetchImage(url, tabId, frameId, referrer), url);
-      const resource = data.blob;
-      delete data.blob;
-      const meta = Object.assign(data, await detectDimension(resource));
-      return {resource, meta};
+      return await fetchDelay(url, async () => {
+        const data = await retry(() => _fetchImage(url, tabId, frameId, referrer), url);
+        const resource = data.blob;
+        delete data.blob;
+        const meta = Object.assign(data, await detectDimension(resource));
+        return {resource, meta};
+      });
     });
   }
 

src/lib/pref.js

@@ -45,6 +45,7 @@ const DEFAULT = {
   urlMap: "",
   useCache: true,
   useExpression: false,
+  fetchDelay: "",
   variableMaxLength: 128,
   filePattern: "Image Picka/${pageTitle}/${name}${ext}",
   filePatternHistory: [],

src/options.js

@@ -324,6 +324,13 @@ const root = createUI({
           learnMore: "https://github.com/eight04/image-picka#transform-url-with-regexp",
           className: "form-monospace"
         },
+        {
+          type: "textarea",
+          key: "fetchDelay",
+          label: _("optionFetchDelayLabel"),
+          learnMore: "https://github.com/eight04/image-picka#fetch-delay",
+          className: "form-monospace"
+        },
         {
           type: "textarea",
           key: "retryOnFailure",

src/static/_locales/en/messages.json

@@ -92,9 +92,13 @@
     "message": "Detect image URLs from links.",
     "description": "Label of detectLink option"
   },
-	"optionDblClickLabel": {
-		"message": "Download with double click",
-		"description": "Label of dblClick option"
+  "optionDblClickLabel": {
+    "message": "Download with double click",
+    "description": "Label of dblClick option"
+  },
+	"optionFetchDelayLabel": {
+		"message": "Delay between each image fetch",
+		"description": "Label of fetchDelay option"
 	},
 	"optionPreviewMaxHeightUpperBoundLabel": {
 		"message": "The maximum value of the thumbnail size slider",