From 6f8c5bd14126de37b357109795475b27e0c45a94 Mon Sep 17 00:00:00 2001
From: Brandon Cheng <github.uconn.brandon@mailhero.io>
Date: Tue, 30 Aug 2016 17:38:55 -0400
Subject: [PATCH] Initial commit

---
 README.md    |  36 ++++++++++++++++
 index.js     | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++
 package.json |  20 +++++++++
 3 files changed, 173 insertions(+)
 create mode 100644 README.md
 create mode 100644 index.js
 create mode 100644 package.json

diff --git a/README.md b/README.md
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index 0000000..2f273c2
--- /dev/null
+++ b/README.md
@@ -0,0 +1,36 @@
+# Back Forward History
+
+This is an addon to the history JavaScript
+[history](https://github.com/mjackson/history) library. It enables tracking of
+back and forward locations.
+
+# Setup
+
+```js
+import React from 'react'
+import { render } from 'react-dom'
+import { Router, Route, browserHistory } from 'react-router'
+
+import HistoryTracker from './back-forward-history'
+
+HistoryTracker.listenTo(browserHistory)
+```
+
+# API
+
+### listenTo(browserHistory)
+Call this method to initialize this addon. Calling it more than once will result
+in unexpected behavior
+
+### canGoBack(n = 1)
+Check if you can go back n pages. Defaults to 1.
+
+### canGoForward(n = 1)
+Check if you can go forward n pages. Defaults to 1.
+
+### setTagForKey(key, tag)
+Set a tag for a location you may want to return to. Get a key with
+`currentLocationKey`.
+
+### goToLocationWithTag(tag)
+Goes backward or forward to reach a tag.
diff --git a/index.js b/index.js
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+++ b/index.js
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+const SESSIONSTORAGE_PREFIX = 'BackForwardHistory_';
+
+class BackForwardHistory {
+  browserHistory
+  historyStack
+  currentIndex
+  titles
+  tags
+
+  get firstLocationKey() {
+    return this.historyStack[0];
+  }
+
+  get currentLocationKey() {
+    return this.historyStack[this.currentIndex];
+  }
+
+  canGoBack(n = 1) {
+    return this.currentIndex >= n;
+  }
+
+  canGoForward(n = 1) {
+    return this.currentIndex < (this.historyStack.length - n)
+  }
+
+  get currentlyOnFirstPage() {
+    return this.currentLocationKey == this.firstLocationKey;
+  }
+
+  get currentlyOnLastPage() {
+    return !this.canGoForward()
+  }
+
+  constructor() {
+    this.loadStateFromSession();
+  }
+
+  listenTo(browserHistory) {
+    this.browserHistory = browserHistory
+    browserHistory.listen(this.onHistoryEvent.bind(this));
+  }
+
+  loadStateFromSession() {
+    this.historyStack = JSON.parse(sessionStorage.getItem(SESSIONSTORAGE_PREFIX + 'historyStack')) || [];
+    this.currentIndex = sessionStorage.getItem(SESSIONSTORAGE_PREFIX + 'currentIndex') || 0;
+    this.titles = JSON.parse(sessionStorage.getItem(SESSIONSTORAGE_PREFIX + 'titles')) || {};
+    this.tags = JSON.parse(sessionStorage.getItem(SESSIONSTORAGE_PREFIX + 'tags')) || {};
+  }
+
+  saveStateToSession() {
+    sessionStorage.setItem(SESSIONSTORAGE_PREFIX + 'historyStack', JSON.stringify(this.historyStack));
+    sessionStorage.setItem(SESSIONSTORAGE_PREFIX + 'currentIndex', this.currentIndex);
+    sessionStorage.setItem(SESSIONSTORAGE_PREFIX + 'titles', JSON.stringify(this.titles));
+    sessionStorage.setItem(SESSIONSTORAGE_PREFIX + 'tags', JSON.stringify(this.tags));
+  }
+
+  resetState() {
+    this.historyStack = [];
+    this.currentIndex = 0;
+    this.titles = new Map();
+    this.tags = new Map();
+    saveStateToSession();
+  }
+
+  onHistoryEvent({ pathname, key, action }) {
+    if (this.historyStack.length === 0) {
+      this.historyStack.push(key);
+    }
+
+    if (action === 'PUSH') {
+      if (!this.currentlyOnLastPage) {
+        this.historyStack = this.historyStack.splice(0, this.currentIndex+1)
+      }
+
+      this.historyStack.push(key);
+      this.currentIndex++;
+    } else if (action === 'POP') {
+      const potentialIndex = this.historyStack.indexOf(key);
+
+      if (potentialIndex === -1) {
+        // User hit go on url bar. Reset history stack.
+        this.historyStack = [key]
+      }
+
+      this.currentIndex = this.historyStack.indexOf(key);
+    }
+
+    this.saveStateToSession()
+  }
+
+  getLastLocationTitle() {
+    return this.titles[this.historyStack[this.currentIndex-1]]
+  }
+
+  getTitleForKey(key) {
+    return this.titles[key]
+  }
+
+  setTitleForKey(key, title) {
+    this.titles[key] = title
+  }
+
+  setTagForKey(key, tag) {
+    this.tags[tag] = key
+  }
+
+  goToLocationWithTag(tag) {
+    const indexOfTag = this.historyStack.indexOf(this.tags[tag]);
+    if (indexOfTag === -1) {
+      throw new Error('No index found for key')
+    }
+
+    this.browserHistory.go(indexOfTag - this.currentIndex)
+  }
+}
+
+export default new BackForwardHistory()
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..58f219d
--- /dev/null
+++ b/package.json
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+{
+  "name": "back-forward-history",
+  "version": "1.0.0",
+  "description": "This is an addon to the history JavaScript library. It enables tracking of back and forward locations.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "UConn Center for Open Research, Resrouces, and Equipment",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git@github.uconn.edu:Brandon/BackForwardHistory.git"
+  },
+  "keywords": [
+    "history",
+    "react",
+    "react-router"
+  ]
+}