Display history refactor (#691)

* Create DisplayHistory

* Change arguments for _setContentTermsOrKanji

* Set up history-driven content updates

* Use new history only

* Load definitions if missing

* Refactor definitions getting

* Add support for wildcards

* Move definitions setup

* Add events

* Allow state change even if there is no history state

* Update search page to use history

* Fix history overwriting

* Fix search page not seeing state chang events during prepare

* Update state if necessary

* Don't reassign query text if the same

* Remove DisplayContext

* Initialize with real history state

* Track URL

* Update DisplayHistory to support pseudo-history

* Configure history settings on search page

* Fix state

* Use full URL

* Change data format of setContent

* Rename details to content

* Update event arguments

* Fix animation

* Remove old state changes

* Clear content properly

* Remove set/clear content overrides

* Fix setting up event listeners for content clear

* Make clearContent private

* Make focus opt-in

* Validate source

* Add unloaded type

* Generalize content params

* Update how extension unload content is assigned

* Restore query blurring

8 files changed, 472 insertions, 219 deletions

diff --git a/ext/bg/js/search.js b/ext/bg/js/search.js
index c29abbaa..c5051fa9 100644
--- a/ext/bg/js/search.js
+++ b/ext/bg/js/search.js
@@ -33,6 +33,7 @@ class DisplaySearch extends Display {
         this._intro = document.querySelector('#intro');
         this._clipboardMonitorEnable = document.querySelector('#clipboard-monitor-enable');
         this._wanakanaEnable = document.querySelector('#wanakana-enable');
+        this._queryText = '';
         this._introVisible = true;
         this._introAnimationTimer = null;
         this._clipboardMonitor = new ClipboardMonitor({
@@ -68,6 +69,9 @@ class DisplaySearch extends Display {
         await this._queryParser.prepare();
 
         this._queryParser.on('searched', this._onQueryParserSearch.bind(this));
+        this.on('contentUpdating', this._onContentUpdating.bind(this));
+
+        this.setHistorySettings({useBrowserHistory: true});
 
         const options = this.getOptions();
 
@@ -83,7 +87,6 @@ class DisplaySearch extends Display {
         }
 
         this._setQuery(query);
-        this._onSearchQueryUpdated(this._query.value, false);
 
         if (mode !== 'popup') {
             if (options.general.enableClipboardMonitor === true) {
@@ -100,7 +103,6 @@ class DisplaySearch extends Display {
         this._search.addEventListener('click', this._onSearch.bind(this), false);
         this._query.addEventListener('input', this._onSearchInput.bind(this), false);
         this._wanakanaEnable.addEventListener('change', this._onWanakanaEnableChange.bind(this));
-        window.addEventListener('popstate', this._onPopState.bind(this));
         window.addEventListener('copy', this._onCopy.bind(this));
         this._clipboardMonitor.on('change', this._onExternalSearchUpdate.bind(this));
 
@@ -108,6 +110,8 @@ class DisplaySearch extends Display {
 
         await this._prepareNestedPopups();
 
+        this.initializeState();
+
         this._isPrepared = true;
     }
 
@@ -158,29 +162,47 @@ class DisplaySearch extends Display {
         }
     }
 
-    async setContent(...args) {
-        this._query.blur();
-        this._closePopups();
-        return await super.setContent(...args);
-    }
+    // Private
 
-    clearContent() {
+    _onContentUpdating({type, source, content}) {
+        let animate = false;
+        let valid = false;
+        switch (type) {
+            case 'terms':
+            case 'kanji':
+                animate = content.animate;
+                valid = content.definitions.length > 0;
+                this._query.blur();
+                break;
+            case 'clear':
+                valid = false;
+                animate = true;
+                source = '';
+                break;
+        }
+        if (typeof source !== 'string') { source = ''; }
         this._closePopups();
-        return super.clearContent();
+        this._setQuery(source);
+        this._setIntroVisible(!valid, animate);
+        this._setTitleText(source);
+        this._updateSearchButton();
     }
 
-    // Private
-
     _onQueryParserSearch({type, definitions, sentence, cause, textSource}) {
         this.setContent({
             focus: false,
             history: cause !== 'mouse',
-            type,
-            source: textSource.text(),
-            definitions,
-            context: {
+            params: {
+                type,
+                query: textSource.text(),
+                wildcards: 'off'
+            },
+            state: {
                 sentence,
                 url: window.location.href
+            },
+            content: {
+                definitions
             }
         });
     }
@@ -202,22 +224,9 @@ class DisplaySearch extends Display {
         e.preventDefault();
 
         const query = this._query.value;
-
-        this._queryParser.setText(query);
-
-        const url = new URL(window.location.href);
-        url.searchParams.set('query', query);
-        window.history.pushState(null, '', url.toString());
-
         this._onSearchQueryUpdated(query, true);
     }
 
-    _onPopState() {
-        const {queryParams: {query=''}} = parseUrl(window.location.href);
-        this._setQuery(query);
-        this._onSearchQueryUpdated(this._query.value, false);
-    }
-
     _onRuntimeMessage({action, params}, sender, callback) {
         const messageHandler = this._runtimeMessageHandlers.get(action);
         if (typeof messageHandler === 'undefined') { return false; }
@@ -230,49 +239,25 @@ class DisplaySearch extends Display {
     }
 
     _onExternalSearchUpdate({text, animate=true}) {
-        this._setQuery(text);
-        const url = new URL(window.location.href);
-        url.searchParams.set('query', text);
-        window.history.pushState(null, '', url.toString());
-        this._onSearchQueryUpdated(this._query.value, animate);
+        this._onSearchQueryUpdated(text, animate);
     }
 
-    async _onSearchQueryUpdated(query, animate) {
-        try {
-            const details = {};
-            const match = /^([*\uff0a]*)([\w\W]*?)([*\uff0a]*)$/.exec(query);
-            if (match !== null) {
-                if (match[1]) {
-                    details.wildcard = 'prefix';
-                } else if (match[3]) {
-                    details.wildcard = 'suffix';
-                }
-                query = match[2];
-            }
-
-            const valid = (query.length > 0);
-            this._setIntroVisible(!valid, animate);
-            this._updateSearchButton();
-            if (valid) {
-                const {definitions} = await api.termsFind(query, details, this.getOptionsContext());
-                this.setContent({
-                    focus: false,
-                    history: false,
-                    definitions,
-                    source: query,
-                    type: 'terms',
-                    context: {
-                        sentence: {text: query, offset: 0},
-                        url: window.location.href
-                    }
-                });
-            } else {
-                this.clearContent();
+    _onSearchQueryUpdated(query, animate) {
+        this.setContent({
+            focus: false,
+            history: false,
+            params: {
+                query
+            },
+            state: {
+                sentence: {text: query, offset: 0},
+                url: window.location.href
+            },
+            content: {
+                definitions: null,
+                animate
             }
-            this._setTitleText(query);
-        } catch (e) {
-            this.onError(e);
-        }
+        });
     }
 
     _onWanakanaEnableChange(e) {
@@ -335,6 +320,8 @@ class DisplaySearch extends Display {
                 // NOP
             }
         }
+        if (this._queryText === interpretedQuery) { return; }
+        this._queryText = interpretedQuery;
         this._query.value = interpretedQuery;
         this._queryParser.setText(interpretedQuery);
     }
diff --git a/ext/bg/search.html b/ext/bg/search.html
index 8f7c1d4c..dd44b376 100644
--- a/ext/bg/search.html
+++ b/ext/bg/search.html
@@ -83,9 +83,9 @@
         <script src="/fg/js/dom-text-scanner.js"></script>
         <script src="/fg/js/source.js"></script>
         <script src="/mixed/js/audio-system.js"></script>
-        <script src="/mixed/js/display-context.js"></script>
         <script src="/mixed/js/display.js"></script>
         <script src="/mixed/js/display-generator.js"></script>
+        <script src="/mixed/js/display-history.js"></script>
         <script src="/mixed/js/dynamic-loader.js"></script>
         <script src="/mixed/js/media-loader.js"></script>
         <script src="/mixed/js/scroll.js"></script>
diff --git a/ext/fg/float.html b/ext/fg/float.html
index 9e0e9ff4..f5a85f8e 100644
--- a/ext/fg/float.html
+++ b/ext/fg/float.html
@@ -50,9 +50,9 @@
         <script src="/fg/js/dom-text-scanner.js"></script>
         <script src="/fg/js/source.js"></script>
         <script src="/mixed/js/audio-system.js"></script>
-        <script src="/mixed/js/display-context.js"></script>
         <script src="/mixed/js/display.js"></script>
         <script src="/mixed/js/display-generator.js"></script>
+        <script src="/mixed/js/display-history.js"></script>
         <script src="/mixed/js/dynamic-loader.js"></script>
         <script src="/mixed/js/frame-endpoint.js"></script>
         <script src="/mixed/js/media-loader.js"></script>
diff --git a/ext/fg/js/float.js b/ext/fg/js/float.js
index f23a9b93..513ee178 100644
--- a/ext/fg/js/float.js
+++ b/ext/fg/js/float.js
@@ -50,6 +50,8 @@ class DisplayFloat extends Display {
         ]);
         window.addEventListener('message', this._onWindowMessage.bind(this), false);
 
+        this.initializeState();
+
         this._frameEndpoint.signal();
     }
 
diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index 73cea841..09928cd4 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -429,12 +429,17 @@ class Frontend {
             {
                 focus,
                 history: false,
-                type,
-                source: textSource.text(),
-                definitions,
-                context: {
+                params: {
+                    type,
+                    query: textSource.text(),
+                    wildcards: 'off'
+                },
+                state: {
                     sentence,
                     url
+                },
+                content: {
+                    definitions
                 }
             }
         );
diff --git a/ext/mixed/js/display-context.js b/ext/mixed/js/display-context.js
deleted file mode 100644
index 2322974a..00000000
--- a/ext/mixed/js/display-context.js
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * Copyright (C) 2019-2020  Yomichan Authors
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-
-class DisplayContext {
-    constructor(type, source, definitions, context) {
-        this.type = type;
-        this.source = source;
-        this.definitions = definitions;
-        this.context = context;
-    }
-
-    get(key) {
-        return this.context[key];
-    }
-
-    set(key, value) {
-        this.context[key] = value;
-    }
-
-    update(data) {
-        Object.assign(this.context, data);
-    }
-
-    get previous() {
-        return this.context.previous;
-    }
-
-    get next() {
-        return this.context.next;
-    }
-
-    static push(self, type, source, definitions, context) {
-        const newContext = new DisplayContext(type, source, definitions, context);
-        if (self !== null) {
-            newContext.update({previous: self});
-            self.update({next: newContext});
-        }
-        return newContext;
-    }
-}
diff --git a/ext/mixed/js/display-history.js b/ext/mixed/js/display-history.js
new file mode 100644
index 00000000..cf2db8d5
--- /dev/null
+++ b/ext/mixed/js/display-history.js
@@ -0,0 +1,178 @@
+/*
+ * Copyright (C) 2020  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+class DisplayHistory extends EventDispatcher {
+    constructor({clearable=true, useBrowserHistory=false}) {
+        super();
+        this._clearable = clearable;
+        this._useBrowserHistory = useBrowserHistory;
+        this._historyMap = new Map();
+
+        const historyState = history.state;
+        const {id, state} = isObject(historyState) ? historyState : {id: null, state: null};
+        this._current = this._createHistoryEntry(id, location.href, state, null, null);
+    }
+
+    get state() {
+        return this._current.state;
+    }
+
+    get content() {
+        return this._current.content;
+    }
+
+    get useBrowserHistory() {
+        return this._useBrowserHistory;
+    }
+
+    set useBrowserHistory(value) {
+        this._useBrowserHistory = value;
+    }
+
+    prepare() {
+        window.addEventListener('popstate', this._onPopState.bind(this), false);
+    }
+
+    hasNext() {
+        return this._current.next !== null;
+    }
+
+    hasPrevious() {
+        return this._current.previous !== null;
+    }
+
+    clear() {
+        if (!this._clearable) { return; }
+        this._clear();
+    }
+
+    back() {
+        return this._go(false);
+    }
+
+    forward() {
+        return this._go(true);
+    }
+
+    pushState(state, content, url) {
+        if (typeof url === 'undefined') { url = location.href; }
+
+        const entry = this._createHistoryEntry(null, url, state, content, this._current);
+        this._current.next = entry;
+        this._current = entry;
+        this._updateHistoryFromCurrent(!this._useBrowserHistory);
+    }
+
+    replaceState(state, content, url) {
+        if (typeof url === 'undefined') { url = location.href; }
+
+        this._current.url = url;
+        this._current.state = state;
+        this._current.content = content;
+        this._updateHistoryFromCurrent(true);
+    }
+
+    _onPopState() {
+        this._updateStateFromHistory();
+        this._triggerStateChanged(false);
+    }
+
+    _go(forward) {
+        const target = forward ? this._current.next : this._current.previous;
+        if (target === null) {
+            return false;
+        }
+
+        if (this._useBrowserHistory) {
+            if (forward) {
+                history.forward();
+            } else {
+                history.back();
+            }
+        } else {
+            this._current = target;
+            this._updateHistoryFromCurrent(true);
+        }
+
+        return true;
+    }
+
+    _triggerStateChanged(synthetic) {
+        this.trigger('stateChanged', {history: this, synthetic});
+    }
+
+    _updateHistoryFromCurrent(replace) {
+        const {id, state, url} = this._current;
+        if (replace) {
+            history.replaceState({id, state}, '', url);
+        } else {
+            history.pushState({id, state}, '', url);
+        }
+        this._triggerStateChanged(true);
+    }
+
+    _updateStateFromHistory() {
+        let state = history.state;
+        let id = null;
+        if (isObject(state)) {
+            id = state.id;
+            if (typeof id === 'string') {
+                const entry = this._historyMap.get(id);
+                if (typeof entry !== 'undefined') {
+                    // Valid
+                    this._current = entry;
+                    return;
+                }
+            }
+            // Partial state recovery
+            state = state.state;
+        } else {
+            state = null;
+        }
+
+        // Fallback
+        this._current.id = (typeof id === 'string' ? id : this._generateId());
+        this._current.state = state;
+        this._current.content = null;
+        this._clear();
+    }
+
+    _createHistoryEntry(id, url, state, content, previous) {
+        if (typeof id !== 'string') { id = this._generateId(); }
+        const entry = {
+            id,
+            url,
+            next: null,
+            previous,
+            state,
+            content
+        };
+        this._historyMap.set(id, entry);
+        return entry;
+    }
+
+    _generateId() {
+        return yomichan.generateId(16);
+    }
+
+    _clear() {
+        this._historyMap.clear();
+        this._historyMap.set(this._current.id, this._current);
+        this._current.next = null;
+        this._current.previous = null;
+    }
+}
diff --git a/ext/mixed/js/display.js b/ext/mixed/js/display.js
index b2d7d54d..e78b9765 100644
--- a/ext/mixed/js/display.js
+++ b/ext/mixed/js/display.js
@@ -18,8 +18,8 @@
 /* global
  * AudioSystem
  * DOM
- * DisplayContext
  * DisplayGenerator
+ * DisplayHistory
  * Frontend
  * MediaLoader
  * PopupFactory
@@ -30,14 +30,14 @@
  * dynamicLoader
  */
 
-class Display {
+class Display extends EventDispatcher {
     constructor(spinner, container) {
+        super();
         this._spinner = spinner;
         this._container = container;
         this._definitions = [];
         this._optionsContext = {depth: 0, url: window.location.href};
         this._options = null;
-        this._context = null;
         this._index = 0;
         this._audioPlaying = null;
         this._audioFallback = null;
@@ -64,6 +64,9 @@ class Display {
         this._hotkeys = new Map();
         this._actions = new Map();
         this._messageHandlers = new Map();
+        this._history = new DisplayHistory({clearable: true, useBrowserHistory: false});
+        this._historyChangeIgnore = false;
+        this._historyHasChanged = false;
 
         this.registerActions([
             ['close',               () => { this.onEscape(); }],
@@ -116,12 +119,27 @@ class Display {
     async prepare() {
         this._setInteractive(true);
         await this._displayGenerator.prepare();
+        this._history.prepare();
+        this._history.on('stateChanged', this._onStateChanged.bind(this));
         yomichan.on('extensionUnloaded', this._onExtensionUnloaded.bind(this));
         api.crossFrame.registerHandlers([
             ['popupMessage', {async: 'dynamic', handler: this._onMessage.bind(this)}]
         ]);
     }
 
+    initializeState() {
+        this._onStateChanged();
+    }
+
+    setHistorySettings({clearable, useBrowserHistory}) {
+        if (typeof clearable !== 'undefined') {
+            this._history.clearable = clearable;
+        }
+        if (typeof useBrowserHistory !== 'undefined') {
+            this._history.useBrowserHistory = useBrowserHistory;
+        }
+    }
+
     onError(error) {
         if (yomichan.isExtensionUnloaded) { return; }
         yomichan.logError(error);
@@ -202,46 +220,25 @@ class Display {
         }
     }
 
-    async setContent(details) {
-        const token = {}; // Unique identifier token
-        this._setContentToken = token;
-        try {
-            this._mediaLoader.unloadAll();
-
-            const {focus, history, type, source, definitions, context} = details;
-
-            if (!history) {
-                this._context = new DisplayContext(type, source, definitions, context);
-            } else {
-                this._context = DisplayContext.push(this._context, type, source, definitions, context);
-            }
+    setContent(details) {
+        const {focus, history, params, state, content} = details;
 
-            if (focus !== false) {
-                window.focus();
-            }
+        if (focus) {
+            window.focus();
+        }
 
-            switch (type) {
-                case 'terms':
-                case 'kanji':
-                    {
-                        const {sentence, url, index=0, scroll=null} = context;
-                        await this._setContentTermsOrKanji((type === 'terms'), definitions, sentence, url, index, scroll, token);
-                    }
-                    break;
-            }
-        } catch (e) {
-            this.onError(e);
-        } finally {
-            if (this._setContentToken === token) {
-                this._setContentToken = null;
-            }
+        const urlSearchParams = new URLSearchParams();
+        for (const [key, value] of Object.entries(params)) {
+            urlSearchParams.append(key, value);
         }
-    }
+        const url = `${location.protocol}//${location.host}${location.pathname}?${urlSearchParams.toString()}`;
 
-    clearContent() {
-        this._setEventListenersActive(false);
-        this._container.textContent = '';
-        this._setEventListenersActive(true);
+        if (history && this._historyHasChanged) {
+            this._history.pushState(state, content, url);
+        } else {
+            this._history.clear();
+            this._history.replaceState(state, content, url);
+        }
     }
 
     setCustomCss(css) {
@@ -348,8 +345,95 @@ class Display {
 
     // Private
 
+    async _onStateChanged() {
+        if (this._historyChangeIgnore) { return; }
+
+        const token = {}; // Unique identifier token
+        this._setContentToken = token;
+        try {
+            const urlSearchParams = new URLSearchParams(location.search);
+            let type = urlSearchParams.get('type');
+            if (type === null) { type = 'terms'; }
+
+            let asigned = false;
+            const eventArgs = {type, urlSearchParams, token};
+            this._historyHasChanged = true;
+            this._mediaLoader.unloadAll();
+            switch (type) {
+                case 'terms':
+                case 'kanji':
+                    {
+                        const source = urlSearchParams.get('query');
+                        if (!source) { break; }
+
+                        const isTerms = (type === 'terms');
+                        let {state, content} = this._history;
+                        let changeHistory = false;
+                        if (!isObject(content)) {
+                            content = {};
+                            changeHistory = true;
+                        }
+                        if (!isObject(state)) {
+                            state = {};
+                            changeHistory = true;
+                        }
+
+                        let {definitions} = content;
+                        if (!Array.isArray(definitions)) {
+                            definitions = await this._findDefinitions(isTerms, source, urlSearchParams);
+                            if (this._setContentToken !== token) { return; }
+                            content.definitions = definitions;
+                            changeHistory = true;
+                        }
+
+                        if (changeHistory) {
+                            this._historyStateUpdate(state, content);
+                        }
+
+                        asigned = true;
+                        eventArgs.source = source;
+                        eventArgs.content = content;
+                        this.trigger('contentUpdating', eventArgs);
+                        await this._setContentTermsOrKanji(token, isTerms, definitions, state);
+                    }
+                    break;
+                case 'unloaded':
+                    {
+                        const {content} = this._history;
+                        eventArgs.content = content;
+                        this.trigger('contentUpdating', eventArgs);
+                        this._setContentExtensionUnloaded();
+                    }
+                    break;
+            }
+
+            if (!asigned) {
+                const {content} = this._history;
+                eventArgs.type = 'clear';
+                eventArgs.content = content;
+                this.trigger('contentUpdating', eventArgs);
+                this._clearContent();
+            }
+
+            eventArgs.stale = (this._setContentToken !== token);
+            this.trigger('contentUpdated', eventArgs);
+        } catch (e) {
+            this.onError(e);
+        } finally {
+            if (this._setContentToken === token) {
+                this._setContentToken = null;
+            }
+        }
+    }
+
     _onExtensionUnloaded() {
-        this._setContentExtensionUnloaded();
+        this.setContent({
+            focus: false,
+            history: false,
+            params: {type: 'unloaded'},
+            state: {},
+            content: {}
+        });
     }
 
     _onSourceTermView(e) {
@@ -365,27 +449,32 @@ class Display {
     async _onKanjiLookup(e) {
         try {
             e.preventDefault();
-            if (!this._context) { return; }
+            if (!this._historyHasState()) { return; }
 
             const link = e.target;
-            this._context.update({
-                index: this._entryIndexFind(link),
-                scroll: this._windowScroll.y
-            });
-            const context = {
-                sentence: this._context.get('sentence'),
-                url: this._context.get('url')
-            };
+            const {state} = this._history;
+
+            state.index = this._entryIndexFind(link);
+            state.scroll = this._windowScroll.y;
+            this._historyStateUpdate(state);
 
-            const source = link.textContent;
-            const definitions = await api.kanjiFind(source, this.getOptionsContext());
+            const query = link.textContent;
+            const definitions = await api.kanjiFind(query, this.getOptionsContext());
             this.setContent({
                 focus: false,
                 history: true,
-                type: 'kanji',
-                source,
-                definitions,
-                context
+                params: {
+                    type: 'kanji',
+                    query,
+                    wildcards: 'off'
+                },
+                state: {
+                    sentence: state.sentence,
+                    url: state.url
+                },
+                content: {
+                    definitions
+                }
             });
         } catch (error) {
             this.onError(error);
@@ -410,10 +499,12 @@ class Display {
 
     async _onTermLookup(e) {
         try {
-            if (!this._context) { return; }
+            if (!this._historyHasState()) { return; }
 
             const termLookupResults = await this._termLookup(e);
-            if (!termLookupResults) { return; }
+            if (!termLookupResults || !this._historyHasState()) { return; }
+
+            const {state} = this._history;
             const {textSource, definitions} = termLookupResults;
 
             const scannedElement = e.target;
@@ -421,22 +512,25 @@ class Display {
             const layoutAwareScan = this._options.scanning.layoutAwareScan;
             const sentence = docSentenceExtract(textSource, sentenceExtent, layoutAwareScan);
 
-            this._context.update({
-                index: this._entryIndexFind(scannedElement),
-                scroll: this._windowScroll.y
-            });
-            const context = {
-                sentence,
-                url: this._context.get('url')
-            };
+            state.index = this._entryIndexFind(scannedElement);
+            state.scroll = this._windowScroll.y;
+            this._historyStateUpdate(state);
 
             this.setContent({
                 focus: false,
                 history: true,
-                type: 'terms',
-                source: textSource.text(),
-                definitions,
-                context
+                params: {
+                    type: 'terms',
+                    query: textSource.text(),
+                    wildcards: 'off'
+                },
+                state: {
+                    sentence,
+                    url: state.url
+                },
+                content: {
+                    definitions
+                }
             });
         } catch (error) {
             this.onError(error);
@@ -583,7 +677,7 @@ class Display {
             this.addMultipleEventListeners('.action-view-note', 'click', this._onNoteView.bind(this));
             this.addMultipleEventListeners('.action-play-audio', 'click', this._onAudioPlay.bind(this));
             this.addMultipleEventListeners('.kanji-link', 'click', this._onKanjiLookup.bind(this));
-            if (this._options.scanning.enablePopupSearch) {
+            if (this._options !== null && this._options.scanning.enablePopupSearch) {
                 this.addMultipleEventListeners('.term-glossary-item, .tag', 'mouseup', this._onGlossaryMouseUp.bind(this));
                 this.addMultipleEventListeners('.term-glossary-item, .tag', 'mousedown', this._onGlossaryMouseDown.bind(this));
                 this.addMultipleEventListeners('.term-glossary-item, .tag', 'mousemove', this._onGlossaryMouseMove.bind(this));
@@ -593,7 +687,34 @@ class Display {
         }
     }
 
-    async _setContentTermsOrKanji(isTerms, definitions, sentence, url, index, scroll, token) {
+    async _findDefinitions(isTerms, source, urlSearchParams) {
+        const optionsContext = this.getOptionsContext();
+        if (isTerms) {
+            const findDetails = {};
+            if (urlSearchParams.get('wildcards') !== 'off') {
+                const match = /^([*\uff0a]*)([\w\W]*?)([*\uff0a]*)$/.exec(source);
+                if (match !== null) {
+                    if (match[1]) {
+                        findDetails.wildcard = 'prefix';
+                    } else if (match[3]) {
+                        findDetails.wildcard = 'suffix';
+                    }
+                    source = match[2];
+                }
+            }
+
+            const {definitions} = await api.termsFind(source, findDetails, optionsContext);
+            return definitions;
+        } else {
+            const definitions = await api.kanjiFind(source, optionsContext);
+            return definitions;
+        }
+    }
+
+    async _setContentTermsOrKanji(token, isTerms, definitions, {sentence=null, url=null, index=0, scroll=null}) {
+        if (typeof url !== 'string') { url = window.location.href; }
+        sentence = this._getValidSentenceData(sentence);
+
         this._setEventListenersActive(false);
 
         this._definitions = definitions;
@@ -603,7 +724,7 @@ class Display {
             definition.url = url;
         }
 
-        this._updateNavigation(this._context.previous, this._context.next);
+        this._updateNavigation(this._history.hasPrevious(), this._history.hasNext());
         this._setNoContentVisible(definitions.length === 0);
 
         const container = this._container;
@@ -657,6 +778,11 @@ class Display {
         this._setNoContentVisible(false);
     }
 
+    _clearContent() {
+        this._setEventListenersActive(false);
+        this._container.textContent = '';
+    }
+
     _setNoContentVisible(visible) {
         const noResults = document.querySelector('#no-results');
 
@@ -746,24 +872,11 @@ class Display {
     }
 
     _relativeTermView(next) {
-        if (this._context === null) { return false; }
-
-        const relative = next ? this._context.next : this._context.previous;
-        if (!relative) { return false; }
-
-        this._context.update({
-            index: this._index,
-            scroll: this._windowScroll.y
-        });
-        this.setContent({
-            focus: false,
-            history: false,
-            type: relative.type,
-            source: relative.source,
-            definitions: relative.definitions,
-            context: relative.context
-        });
-        return true;
+        if (next) {
+            return this._history.hasNext() && this._history.forward();
+        } else {
+            return this._history.hasPrevious() && this._history.back();
+        }
     }
 
     _noteTryAdd(mode) {
@@ -913,6 +1026,13 @@ class Display {
         return index >= 0 && index < entries.length ? entries[index] : null;
     }
 
+    _getValidSentenceData(sentence) {
+        let {text, offset} = (isObject(sentence) ? sentence : {});
+        if (typeof text !== 'string') { text = ''; }
+        if (typeof offset !== 'number') { offset = 0; }
+        return {text, offset};
+    }
+
     _clozeBuild({text, offset}, source) {
         return {
             sentence: text.trim(),
@@ -1000,4 +1120,20 @@ class Display {
             this._audioPlay(this._definitions[index], this._getFirstExpressionIndex(), index);
         }
     }
+
+    _historyHasState() {
+        return isObject(this._history.state);
+    }
+
+    _historyStateUpdate(state, content) {
+        const historyChangeIgnorePre = this._historyChangeIgnore;
+        try {
+            this._historyChangeIgnore = true;
+            if (typeof state === 'undefined') { state = this._history.state; }
+            if (typeof content === 'undefined') { content = this._history.content; }
+            this._history.replaceState(state, content);
+        } finally {
+            this._historyChangeIgnore = historyChangeIgnorePre;
+        }
+    }
 }