Improve autocomplete behaviour

Fixes vector-im/vector-web#1761

.eslintrc

@@ -78,18 +78,26 @@
     /** react **/
 
     // bind or arrow function in props causes performance issues
-    "react/jsx-no-bind": ["error"],
+    "react/jsx-no-bind": ["error", {
+      "ignoreRefs": true
+    }],
     "react/jsx-key": ["error"],
     "react/prefer-stateless-function": ["warn"],
-    "react/sort-comp": ["warn"],
 
     /** flowtype **/
-    "flowtype/require-parameter-type": 1,
+    "flowtype/require-parameter-type": [
+      1,
+      {
+        "excludeArrowFunctions": true
+      }
+    ],
+    "flowtype/define-flow-type": 1,
     "flowtype/require-return-type": [
       1,
       "always",
       {
-        "annotateUndefined": "never"
+        "annotateUndefined": "never",
+        "excludeArrowFunctions": true
       }
     ],
     "flowtype/space-after-type-colon": [

code_style.md

@@ -158,5 +158,11 @@ React
   <Foo onClick={this.doStuff}> // Better
   <Foo onClick={this.onFooClick}> // Best, if onFooClick would do anything other than directly calling doStuff
   ```
+  
+  Not doing so is acceptable in a single case; in function-refs:
+  
+  ```jsx
+  <Foo ref={(self) => this.component = self}>
+  ```
 - Think about whether your component really needs state: are you duplicating
   information in component state that could be derived from the model?

package.json

@@ -62,8 +62,8 @@
     "babel-loader": "^5.4.0",
     "babel-polyfill": "^6.5.0",
     "eslint": "^2.13.1",
-    "eslint-plugin-flowtype": "^2.3.0",
-    "eslint-plugin-react": "^5.2.2",
+    "eslint-plugin-flowtype": "^2.17.0",
+    "eslint-plugin-react": "^6.2.1",
     "expect": "^1.16.0",
     "json-loader": "^0.5.3",
     "karma": "^0.13.22",

src/RichText.js

@@ -15,6 +15,7 @@ import {
 import * as sdk from  './index';
 import * as emojione from 'emojione';
 import {stateToHTML} from 'draft-js-export-html';
+import {SelectionRange} from "./autocomplete/Autocompleter";
 
 const MARKDOWN_REGEX = {
     LINK: /(?:\[([^\]]+)\]\(([^\)]+)\))|\<(\w+:\/\/[^\>]+)\>/g,
@@ -203,7 +204,7 @@ export function selectionStateToTextOffsets(selectionState: SelectionState,
     };
 }
 
-export function textOffsetsToSelectionState({start, end}: {start: number, end: number},
+export function textOffsetsToSelectionState({start, end}: SelectionRange,
                                             contentBlocks: Array<ContentBlock>): SelectionState {
     let selectionState = SelectionState.createEmpty();
 

src/SlashCommands.js

@@ -17,6 +17,8 @@ limitations under the License.
 var MatrixClientPeg = require("./MatrixClientPeg");
 var dis = require("./dispatcher");
 var Tinter = require("./Tinter");
+import sdk from './index';
+import Modal from './Modal';
 
 
 class Command {
@@ -56,6 +58,16 @@ var success = function(promise) {
 };
 
 var commands = {
+    ddg: new Command("ddg", "<query>", function(roomId, args) {
+        const ErrorDialog = sdk.getComponent('dialogs.ErrorDialog');
+        // TODO Don't explain this away, actually show a search UI here.
+        Modal.createDialog(ErrorDialog, {
+            title: "/ddg is not a command",
+            description: "To use it, just wait for autocomplete results to load and tab through them.",
+        });
+        return success();
+    }),
+
     // Change your nickname
     nick: new Command("nick", "<display_name>", function(room_id, args) {
         if (args) {

src/autocomplete/AutocompleteProvider.js

@@ -1,10 +1,10 @@
-import Q from 'q';
 import React from 'react';
+import type {Completion, SelectionRange} from './Autocompleter';
 
 export default class AutocompleteProvider {
     constructor(commandRegex?: RegExp, fuseOpts?: any) {
-        if(commandRegex) {
-            if(!commandRegex.global) {
+        if (commandRegex) {
+            if (!commandRegex.global) {
                 throw new Error('commandRegex must have global flag set');
             }
             this.commandRegex = commandRegex;
@@ -14,18 +14,24 @@ export default class AutocompleteProvider {
     /**
      * Of the matched commands in the query, returns the first that contains or is contained by the selection, or null.
      */
-    getCurrentCommand(query: string, selection: {start: number, end: number}): ?Array<string> {
-        if (this.commandRegex == null) {
+    getCurrentCommand(query: string, selection: {start: number, end: number}, force: boolean = false): ?string {
+        let commandRegex = this.commandRegex;
+
+        if (force && this.shouldForceComplete()) {
+            console.log('forcing complete');
+            commandRegex = /[^\W]+/g;
+        }
+
+        if (commandRegex == null) {
             return null;
         }
 
-        this.commandRegex.lastIndex = 0;
+        commandRegex.lastIndex = 0;
         
         let match;
-        while ((match = this.commandRegex.exec(query)) != null) {
+        while ((match = commandRegex.exec(query)) != null) {
             let matchStart = match.index,
                 matchEnd = matchStart + match[0].length;
-            
             if (selection.start <= matchEnd && selection.end >= matchStart) {
                 return {
                     command: match,
@@ -45,8 +51,8 @@ export default class AutocompleteProvider {
         };
     }
 
-    getCompletions(query: string, selection: {start: number, end: number}) {
-        return Q.when([]);
+    async getCompletions(query: string, selection: SelectionRange, force: boolean = false): Array<Completion> {
+        return [];
     }
 
     getName(): string {
@@ -57,4 +63,9 @@ export default class AutocompleteProvider {
         console.error('stub; should be implemented in subclasses');
         return null;
     }
+
+    // Whether we should provide completions even if triggered forcefully, without a sigil.
+    shouldForceComplete(): boolean {
+        return false;
+    }
 }

src/autocomplete/Autocompleter.js

@@ -1,22 +1,63 @@
+// @flow
+
+import type {Component} from 'react';
 import CommandProvider from './CommandProvider';
 import DuckDuckGoProvider from './DuckDuckGoProvider';
 import RoomProvider from './RoomProvider';
 import UserProvider from './UserProvider';
 import EmojiProvider from './EmojiProvider';
+import Q from 'q';
+
+export type SelectionRange = {
+    start: number,
+    end: number
+};
+
+export type Completion = {
+    completion: string,
+    component: ?Component,
+    range: SelectionRange,
+    command: ?string,
+};
 
 const PROVIDERS = [
     UserProvider,
-    CommandProvider,
-    DuckDuckGoProvider,
     RoomProvider,
     EmojiProvider,
+    CommandProvider,
+    DuckDuckGoProvider,
 ].map(completer => completer.getInstance());
 
-export function getCompletions(query: string, selection: {start: number, end: number}) {
-    return PROVIDERS.map(provider => {
-        return {
-            completions: provider.getCompletions(query, selection),
-            provider,
-        };
-    });
+// Providers will get rejected if they take longer than this.
+const PROVIDER_COMPLETION_TIMEOUT = 3000;
+
+export async function getCompletions(query: string, selection: SelectionRange, force: boolean = false): Array<Completion> {
+    /* Note: That this waits for all providers to return is *intentional*
+     otherwise, we run into a condition where new completions are displayed
+     while the user is interacting with the list, which makes it difficult
+     to predict whether an action will actually do what is intended
+
+     It ends up containing a list of Q promise states, which are objects with
+     state (== "fulfilled" || "rejected") and value. */
+    const completionsList = await Q.allSettled(
+        PROVIDERS.map(provider => {
+            return Q(provider.getCompletions(query, selection, force))
+                .timeout(PROVIDER_COMPLETION_TIMEOUT);
+        })
+    );
+
+    return completionsList
+        .filter(completion => completion.state === "fulfilled")
+        .map((completionsState, i) => {
+            return {
+                completions: completionsState.value,
+                provider: PROVIDERS[i],
+
+                /* the currently matched "command" the completer tried to complete
+                 * we pass this through so that Autocomplete can figure out when to
+                 * re-show itself once hidden.
+                 */
+                command: PROVIDERS[i].getCurrentCommand(query, selection, force),
+            };
+        });
 }

src/autocomplete/CommandProvider.js

@@ -1,6 +1,5 @@
 import React from 'react';
 import AutocompleteProvider from './AutocompleteProvider';
-import Q from 'q';
 import Fuse from 'fuse.js';
 import {TextualCompletion} from './Components';
 
@@ -23,7 +22,7 @@ const COMMANDS = [
     {
         command: '/invite',
         args: '<user-id>',
-        description: 'Invites user with given id to current room'
+        description: 'Invites user with given id to current room',
     },
     {
         command: '/join',
@@ -40,6 +39,11 @@ const COMMANDS = [
         args: '<display-name>',
         description: 'Changes your display nickname',
     },
+    {
+        command: '/ddg',
+        args: '<query>',
+        description: 'Searches DuckDuckGo for results',
+    }
 ];
 
 let COMMAND_RE = /(^\/\w*)/g;
@@ -54,7 +58,7 @@ export default class CommandProvider extends AutocompleteProvider {
         });
     }
 
-    getCompletions(query: string, selection: {start: number, end: number}) {
+    async getCompletions(query: string, selection: {start: number, end: number}) {
         let completions = [];
         let {command, range} = this.getCurrentCommand(query, selection);
         if (command) {
@@ -70,7 +74,7 @@ export default class CommandProvider extends AutocompleteProvider {
                 };
             });
         }
-        return Q.when(completions);
+        return completions;
     }
 
     getName() {

src/autocomplete/DuckDuckGoProvider.js

@@ -1,6 +1,5 @@
 import React from 'react';
 import AutocompleteProvider from './AutocompleteProvider';
-import Q from 'q';
 import 'whatwg-fetch';
 
 import {TextualCompletion} from './Components';
@@ -20,61 +19,59 @@ export default class DuckDuckGoProvider extends AutocompleteProvider {
          + `&format=json&no_redirect=1&no_html=1&t=${encodeURIComponent(REFERRER)}`;
     }
 
-    getCompletions(query: string, selection: {start: number, end: number}) {
+    async getCompletions(query: string, selection: {start: number, end: number}) {
         let {command, range} = this.getCurrentCommand(query, selection);
         if (!query || !command) {
-            return Q.when([]);
+            return [];
         }
 
-        return fetch(DuckDuckGoProvider.getQueryUri(command[1]), {
+        const response = await fetch(DuckDuckGoProvider.getQueryUri(command[1]), {
             method: 'GET',
-        })
-            .then(response => response.json())
-            .then(json => {
-                let results = json.Results.map(result => {
-                    return {
-                        completion: result.Text,
-                        component: (
-                            <TextualCompletion
-                                title={result.Text}
-                                description={result.Result} />
-                        ),
-                        range,
-                    };
-                });
-                if (json.Answer) {
-                    results.unshift({
-                        completion: json.Answer,
-                        component: (
-                            <TextualCompletion
-                                title={json.Answer}
-                                description={json.AnswerType} />
-                        ),
-                        range,
-                    });
-                }
-                if (json.RelatedTopics && json.RelatedTopics.length > 0) {
-                    results.unshift({
-                        completion: json.RelatedTopics[0].Text,
-                        component: (
-                            <TextualCompletion
-                                title={json.RelatedTopics[0].Text} />
-                        ),
-                        range,
-                    });
-                }
-                if (json.AbstractText) {
-                    results.unshift({
-                        completion: json.AbstractText,
-                        component: (
-                            <TextualCompletion
-                                title={json.AbstractText} />
-                        ),
-                        range,
-                    });
-                }
-                return results;
+        });
+        const json = await response.json();
+        let results = json.Results.map(result => {
+            return {
+                completion: result.Text,
+                component: (
+                    <TextualCompletion
+                        title={result.Text}
+                        description={result.Result} />
+                ),
+                range,
+            };
+        });
+        if (json.Answer) {
+            results.unshift({
+                completion: json.Answer,
+                component: (
+                    <TextualCompletion
+                        title={json.Answer}
+                        description={json.AnswerType} />
+                ),
+                range,
             });
+        }
+        if (json.RelatedTopics && json.RelatedTopics.length > 0) {
+            results.unshift({
+                completion: json.RelatedTopics[0].Text,
+                component: (
+                    <TextualCompletion
+                        title={json.RelatedTopics[0].Text} />
+                ),
+                range,
+            });
+        }
+        if (json.AbstractText) {
+            results.unshift({
+                completion: json.AbstractText,
+                component: (
+                    <TextualCompletion
+                        title={json.AbstractText} />
+                ),
+                range,
+            });
+        }
+        return results;
     }
 
     getName() {

src/autocomplete/EmojiProvider.js

@@ -1,10 +1,10 @@
 import React from 'react';
 import AutocompleteProvider from './AutocompleteProvider';
-import Q from 'q';
 import {emojioneList, shortnameToImage, shortnameToUnicode} from 'emojione';
 import Fuse from 'fuse.js';
 import sdk from '../index';
 import {PillCompletion} from './Components';
+import type {SelectionRange, Completion} from './Autocompleter';
 
 const EMOJI_REGEX = /:\w*:?/g;
 const EMOJI_SHORTNAMES = Object.keys(emojioneList);
@@ -17,7 +17,7 @@ export default class EmojiProvider extends AutocompleteProvider {
         this.fuse = new Fuse(EMOJI_SHORTNAMES);
     }
 
-    getCompletions(query: string, selection: {start: number, end: number}) {
+    async getCompletions(query: string, selection: SelectionRange) {
         const EmojiText = sdk.getComponent('views.elements.EmojiText');
 
         let completions = [];
@@ -35,7 +35,7 @@ export default class EmojiProvider extends AutocompleteProvider {
                 };
             }).slice(0, 8);
         }
-        return Q.when(completions);
+        return completions;
     }
 
     getName() {

src/autocomplete/RoomProvider.js

@@ -1,6 +1,5 @@
 import React from 'react';
 import AutocompleteProvider from './AutocompleteProvider';
-import Q from 'q';
 import MatrixClientPeg from '../MatrixClientPeg';
 import Fuse from 'fuse.js';
 import {PillCompletion} from './Components';
@@ -21,12 +20,12 @@ export default class RoomProvider extends AutocompleteProvider {
         });
     }
 
-    getCompletions(query: string, selection: {start: number, end: number}) {
+    async getCompletions(query: string, selection: {start: number, end: number}, force = false) {
         const RoomAvatar = sdk.getComponent('views.avatars.RoomAvatar');
 
         let client = MatrixClientPeg.get();
         let completions = [];
-        const {command, range} = this.getCurrentCommand(query, selection);
+        const {command, range} = this.getCurrentCommand(query, selection, force);
         if (command) {
             // the only reason we need to do this is because Fuse only matches on properties
             this.fuse.set(client.getRooms().filter(room => !!room).map(room => {
@@ -48,7 +47,7 @@ export default class RoomProvider extends AutocompleteProvider {
                 };
             }).slice(0, 4);
         }
-        return Q.when(completions);
+        return completions;
     }
 
     getName() {
@@ -68,4 +67,8 @@ export default class RoomProvider extends AutocompleteProvider {
             {completions}
         </div>;
     }
+
+    shouldForceComplete(): boolean {
+        return true;
+    }
 }

src/autocomplete/UserProvider.js

@@ -20,11 +20,11 @@ export default class UserProvider extends AutocompleteProvider {
         });
     }
 
-    getCompletions(query: string, selection: {start: number, end: number}) {
+    async getCompletions(query: string, selection: {start: number, end: number}, force = false) {
         const MemberAvatar = sdk.getComponent('views.avatars.MemberAvatar');
 
         let completions = [];
-        let {command, range} = this.getCurrentCommand(query, selection);
+        let {command, range} = this.getCurrentCommand(query, selection, force);
         if (command) {
             this.fuse.set(this.users);
             completions = this.fuse.search(command[0]).map(user => {
@@ -37,11 +37,11 @@ export default class UserProvider extends AutocompleteProvider {
                             title={displayName}
                             description={user.userId} />
                     ),
-                    range
+                    range,
                 };
             }).slice(0, 4);
         }
-        return Q.when(completions);
+        return completions;
     }
 
     getName() {
@@ -64,4 +64,8 @@ export default class UserProvider extends AutocompleteProvider {
             {completions}
         </div>;
     }
+
+    shouldForceComplete(): boolean {
+        return true;
+    }
 }

src/components/views/rooms/Autocomplete.js

@@ -2,11 +2,17 @@ import React from 'react';
 import ReactDOM from 'react-dom';
 import classNames from 'classnames';
 import flatMap from 'lodash/flatMap';
+import isEqual from 'lodash/isEqual';
 import sdk from '../../../index';
+import type {Completion, SelectionRange} from '../../../autocomplete/Autocompleter';
 
 import {getCompletions} from '../../../autocomplete/Autocompleter';
 
+const COMPOSER_SELECTED = 0;
+
 export default class Autocomplete extends React.Component {
+    completionPromise: Promise = null;
+
     constructor(props) {
         super(props);
 
@@ -19,79 +25,137 @@ export default class Autocomplete extends React.Component {
             // array of completions, so we can look up current selection by offset quickly
             completionList: [],
 
-            // how far down the completion list we are
-            selectionOffset: 0,
+            // how far down the completion list we are (THIS IS 1-INDEXED!)
+            selectionOffset: COMPOSER_SELECTED,
+
+            // whether we should show completions if they're available
+            shouldShowCompletions: true,
+
+            hide: false,
+
+            forceComplete: false,
         };
     }
 
-    componentWillReceiveProps(props, state) {
+    async componentWillReceiveProps(props, state) {
         if (props.query === this.props.query) {
+            return null;
+        }
+
+        return await this.complete(props.query, props.selection);
+    }
+
+    async complete(query, selection) {
+        let forceComplete = this.state.forceComplete;
+        const completionPromise = getCompletions(query, selection, forceComplete);
+        this.completionPromise = completionPromise;
+        const completions = await this.completionPromise;
+
+        // There's a newer completion request, so ignore results.
+        if (completionPromise !== this.completionPromise) {
             return;
         }
 
-        getCompletions(props.query, props.selection).forEach(completionResult => {
-            try {
-                completionResult.completions.then(completions => {
-                    let i = this.state.completions.findIndex(
-                        completion => completion.provider === completionResult.provider
-                    );
+        const completionList = flatMap(completions, provider => provider.completions);
 
-                    i = i === -1 ? this.state.completions.length : i;
-                    let newCompletions = Object.assign([], this.state.completions);
-                    completionResult.completions = completions;
-                    newCompletions[i] = completionResult;
-
-                    this.setState({
-                        completions: newCompletions,
-                        completionList: flatMap(newCompletions, provider => provider.completions),
-                    });
-                }, err => {
-                    console.error(err);
-                });
-            } catch (e) {
-                // An error in one provider shouldn't mess up the rest.
-                console.error(e);
+        // Reset selection when completion list becomes empty.
+        let selectionOffset = COMPOSER_SELECTED;
+        if (completionList.length > 0) {
+            /* If the currently selected completion is still in the completion list,
+             try to find it and jump to it. If not, select composer.
+             */
+            const currentSelection = this.state.selectionOffset === 0 ? null :
+                this.state.completionList[this.state.selectionOffset - 1].completion;
+            selectionOffset = completionList.findIndex(
+                completion => completion.completion === currentSelection);
+            if (selectionOffset === -1) {
+                selectionOffset = COMPOSER_SELECTED;
+            } else {
+                selectionOffset++; // selectionOffset is 1-indexed!
             }
+        } else {
+            // If no completions were returned, we should turn off force completion.
+            forceComplete = false;
+        }
+
+        let hide = this.state.hide;
+        // These are lists of booleans that indicate whether whether the corresponding provider had a matching pattern
+        const oldMatches = this.state.completions.map(completion => !!completion.command.command),
+            newMatches = completions.map(completion => !!completion.command.command);
+
+        // So, essentially, we re-show autocomplete if any provider finds a new pattern or stops finding an old one
+        if (!isEqual(oldMatches, newMatches)) {
+            hide = false;
+        }
+
+        this.setState({
+            completions,
+            completionList,
+            selectionOffset,
+            hide,
+            forceComplete,
         });
     }
 
     countCompletions(): number {
-        return this.state.completions.map(completionResult => {
-            return completionResult.completions.length;
-        }).reduce((l, r) => l + r);
+        return this.state.completionList.length;
     }
 
     // called from MessageComposerInput
-    onUpArrow(): boolean {
-        let completionCount = this.countCompletions(),
-            selectionOffset = (completionCount + this.state.selectionOffset - 1) % completionCount;
+    onUpArrow(): ?Completion {
+        const completionCount = this.countCompletions();
+        // completionCount + 1, since 0 means composer is selected
+        const selectionOffset = (completionCount + 1 + this.state.selectionOffset - 1)
+            % (completionCount + 1);
         if (!completionCount) {
-            return false;
+            return null;
         }
         this.setSelection(selectionOffset);
-        return true;
+        return selectionOffset === COMPOSER_SELECTED ? null : this.state.completionList[selectionOffset - 1];
     }
 
     // called from MessageComposerInput
-    onDownArrow(): boolean {
-        let completionCount = this.countCompletions(),
-            selectionOffset = (this.state.selectionOffset + 1) % completionCount;
+    onDownArrow(): ?Completion {
+        const completionCount = this.countCompletions();
+        // completionCount + 1, since 0 means composer is selected
+        const selectionOffset = (this.state.selectionOffset + 1) % (completionCount + 1);
         if (!completionCount) {
-            return false;
+            return null;
         }
         this.setSelection(selectionOffset);
-        return true;
+        return selectionOffset === COMPOSER_SELECTED ? null : this.state.completionList[selectionOffset - 1];
+    }
+
+    onEscape(e): boolean {
+        const completionCount = this.countCompletions();
+        if (completionCount === 0) {
+            // autocomplete is already empty, so don't preventDefault
+            return;
+        }
+
+        e.preventDefault();
+
+        // selectionOffset = 0, so we don't end up completing when autocomplete is hidden
+        this.setState({hide: true, selectionOffset: 0});
+    }
+
+    forceComplete() {
+        this.setState({
+            forceComplete: true,
+        }, () => {
+            this.complete(this.props.query, this.props.selection);
+        });
     }
 
     /** called from MessageComposerInput
      * @returns {boolean} whether confirmation was handled
      */
     onConfirm(): boolean {
-        if (this.countCompletions() === 0) {
+        if (this.countCompletions() === 0 || this.state.selectionOffset === COMPOSER_SELECTED) {
             return false;
         }
 
-        let selectedCompletion = this.state.completionList[this.state.selectionOffset];
+        let selectedCompletion = this.state.completionList[this.state.selectionOffset - 1];
         this.props.onConfirm(selectedCompletion.range, selectedCompletion.completion);
 
         return true;
@@ -117,7 +181,7 @@ export default class Autocomplete extends React.Component {
     render() {
         const EmojiText = sdk.getComponent('views.elements.EmojiText');
 
-        let position = 0;
+        let position = 1;
         let renderedCompletions = this.state.completions.map((completionResult, i) => {
             let completions = completionResult.completions.map((completion, i) => {
 
@@ -135,7 +199,7 @@ export default class Autocomplete extends React.Component {
 
                 return React.cloneElement(completion.component, {
                     key: i,
-                    ref: `completion${i}`,
+                    ref: `completion${position - 1}`,
                     className,
                     onMouseOver,
                     onClick,
@@ -151,7 +215,7 @@ export default class Autocomplete extends React.Component {
             ) : null;
         }).filter(completion => !!completion);
 
-        return renderedCompletions.length > 0 ? (
+        return !this.state.hide && renderedCompletions.length > 0 ? (
             <div className="mx_Autocomplete" ref={(e) => this.container = e}>
                 {renderedCompletions}
             </div>

src/components/views/rooms/MessageComposer.js

@@ -166,7 +166,7 @@ export default class MessageComposer extends React.Component {
 
     _onAutocompleteConfirm(range, completion) {
         if (this.messageComposerInput) {
-            this.messageComposerInput.onConfirmAutocompletion(range, completion);
+            this.messageComposerInput.setDisplayedCompletion(range, completion);
         }
     }
 
@@ -313,7 +313,6 @@ export default class MessageComposer extends React.Component {
 
         return (
             <div className="mx_MessageComposer mx_fadable" style={{ opacity: this.props.opacity }}>
-                {autoComplete}
                 <div className="mx_MessageComposer_wrapper">
                     <div className="mx_MessageComposer_row">
                         {controls}

src/components/views/rooms/MessageComposerInput.js

@@ -34,6 +34,7 @@ import {Editor, EditorState, RichUtils, CompositeDecorator,
 import {stateToMarkdown as __stateToMarkdown} from 'draft-js-export-markdown';
 import classNames from 'classnames';
 import escape from 'lodash/escape';
+import Q from 'q';
 
 import MatrixClientPeg from '../../../MatrixClientPeg';
 import type {MatrixClient} from 'matrix-js-sdk/lib/matrix';
@@ -46,6 +47,8 @@ import KeyCode from '../../../KeyCode';
 import UserSettingsStore from '../../../UserSettingsStore';
 
 import * as RichText from '../../../RichText';
+import Autocomplete from './Autocomplete';
+import {Completion} from "../../../autocomplete/Autocompleter";
 
 const TYPING_USER_TIMEOUT = 10000, TYPING_SERVER_TIMEOUT = 30000;
 
@@ -88,34 +91,52 @@ export default class MessageComposerInput extends React.Component {
         return getDefaultKeyBinding(e);
     }
 
+    static getBlockStyle(block: ContentBlock): ?string {
+        if (block.getType() === 'strikethrough') {
+            return 'mx_Markdown_STRIKETHROUGH';
+        }
+
+        return null;
+    }
+
     client: MatrixClient;
+    autocomplete: Autocomplete;
 
     constructor(props, context) {
         super(props, context);
         this.onAction = this.onAction.bind(this);
         this.handleReturn = this.handleReturn.bind(this);
         this.handleKeyCommand = this.handleKeyCommand.bind(this);
+        this.onEditorContentChanged = this.onEditorContentChanged.bind(this);
         this.setEditorState = this.setEditorState.bind(this);
         this.onUpArrow = this.onUpArrow.bind(this);
         this.onDownArrow = this.onDownArrow.bind(this);
         this.onTab = this.onTab.bind(this);
-        this.onConfirmAutocompletion = this.onConfirmAutocompletion.bind(this);
+        this.onEscape = this.onEscape.bind(this);
+        this.setDisplayedCompletion = this.setDisplayedCompletion.bind(this);
         this.onMarkdownToggleClicked = this.onMarkdownToggleClicked.bind(this);
 
         const isRichtextEnabled = UserSettingsStore.getSyncedSetting('MessageComposerInput.isRichTextEnabled', true);
 
         this.state = {
+            // whether we're in rich text or markdown mode
             isRichtextEnabled,
+
+            // the currently displayed editor state (note: this is always what is modified on input)
             editorState: null,
+
+            // the original editor state, before we started tabbing through completions
+            originalEditorState: null,
         };
 
         // bit of a hack, but we need to do this here since createEditorState needs isRichtextEnabled
+        /* eslint react/no-direct-mutation-state:0 */
         this.state.editorState = this.createEditorState();
 
         this.client = MatrixClientPeg.get();
     }
 
-    /**
+    /*
      * "Does the right thing" to create an EditorState, based on:
      * - whether we've got rich text mode enabled
      * - contentState was passed in
@@ -234,10 +255,6 @@ export default class MessageComposerInput extends React.Component {
             this.refs.editor,
             this.props.room.roomId
         );
-        // this is disabled for now, since https://github.com/matrix-org/matrix-react-sdk/pull/296 will land soon
-        // if (this.props.tabComplete) {
-        //     this.props.tabComplete.setEditor(this.refs.editor);
-        // }
     }
 
     componentWillUnmount() {
@@ -273,7 +290,7 @@ export default class MessageComposerInput extends React.Component {
                 );
                 let editorState = EditorState.push(this.state.editorState, contentState, 'insert-characters');
                 editorState = EditorState.forceSelection(editorState, contentState.getSelectionAfter());
-                this.setEditorState(editorState);
+                this.onEditorContentChanged(editorState);
                 editor.focus();
             }
             break;
@@ -295,10 +312,11 @@ export default class MessageComposerInput extends React.Component {
                         startSelection,
                         blockMap);
                     startSelection = SelectionState.createEmpty(contentState.getFirstBlock().getKey());
-                    if (this.state.isRichtextEnabled)
+                    if (this.state.isRichtextEnabled) {
                         contentState = Modifier.setBlockType(contentState, startSelection, 'blockquote');
+                    }
                     let editorState = EditorState.push(this.state.editorState, contentState, 'insert-characters');
-                    this.setEditorState(editorState);
+                    this.onEditorContentChanged(editorState);
                     editor.focus();
                 }
             }
@@ -372,10 +390,16 @@ export default class MessageComposerInput extends React.Component {
         }
     }
 
-
-    setEditorState(editorState: EditorState, cb = () => null) {
+    // Called by Draft to change editor contents, and by setEditorState
+    onEditorContentChanged(editorState: EditorState, didRespondToUserInput: boolean = true) {
         editorState = RichText.attachImmutableEntitiesToEmoji(editorState);
-        this.setState({editorState}, cb);
+
+        const setPromise = Q.defer();
+        /* If a modification was made, set originalEditorState to null, since newState is now our original */
+        this.setState({
+            editorState,
+            originalEditorState: didRespondToUserInput ? null : this.state.originalEditorState,
+        }, () => setPromise.resolve());
 
         if (editorState.getCurrentContent().hasText()) {
             this.onTypingActivity();
@@ -390,6 +414,11 @@ export default class MessageComposerInput extends React.Component {
 
             this.props.onContentChanged(textContent, selection);
         }
+        return setPromise;
+    }
+
+    setEditorState(editorState: EditorState) {
+        this.onEditorContentChanged(editorState, false);
     }
 
     enableRichtext(enabled: boolean) {
@@ -470,7 +499,7 @@ export default class MessageComposerInput extends React.Component {
 
     handleReturn(ev) {
         if (ev.shiftKey) {
-            this.setEditorState(RichUtils.insertSoftNewline(this.state.editorState));
+            this.onEditorContentChanged(RichUtils.insertSoftNewline(this.state.editorState));
             return true;
         }
 
@@ -547,41 +576,68 @@ export default class MessageComposerInput extends React.Component {
         return true;
     }
 
-    onUpArrow(e) {
-        if (this.props.onUpArrow && this.props.onUpArrow()) {
+    async onUpArrow(e) {
+        const completion = this.autocomplete.onUpArrow();
+        if (completion != null) {
             e.preventDefault();
         }
+        return await this.setDisplayedCompletion(completion);
+    }
+
+    async onDownArrow(e) {
+        const completion = this.autocomplete.onDownArrow();
+        e.preventDefault();
+        return await this.setDisplayedCompletion(completion);
+    }
+
+    // tab and shift-tab are mapped to down and up arrow respectively
+    async onTab(e) {
+        e.preventDefault(); // we *never* want tab's default to happen, but we do want up/down sometimes
+        const didTab = await (e.shiftKey ? this.onUpArrow : this.onDownArrow)(e);
+        if (!didTab && this.autocomplete) {
+            this.autocomplete.forceComplete();
+        }
     }
 
-    onDownArrow(e) {
-        if (this.props.onDownArrow && this.props.onDownArrow()) {
-            e.preventDefault();
+    onEscape(e) {
+        e.preventDefault();
+        if (this.autocomplete) {
+            this.autocomplete.onEscape(e);
         }
+        this.setDisplayedCompletion(null); // restore originalEditorState
     }
 
-    onTab(e) {
-        if (this.props.tryComplete) {
-            if (this.props.tryComplete()) {
-                e.preventDefault();
+    /* If passed null, restores the original editor content from state.originalEditorState.
+     * If passed a non-null displayedCompletion, modifies state.originalEditorState to compute new state.editorState.
+     */
+    async setDisplayedCompletion(displayedCompletion: ?Completion): boolean {
+        const activeEditorState = this.state.originalEditorState || this.state.editorState;
+
+        if (displayedCompletion == null) {
+            if (this.state.originalEditorState) {
+                this.setEditorState(this.state.originalEditorState);
             }
+            return false;
         }
-    }
 
-    onConfirmAutocompletion(range, content: string) {
+        const {range = {}, completion = ''} = displayedCompletion;
+
         let contentState = Modifier.replaceText(
-            this.state.editorState.getCurrentContent(),
-            RichText.textOffsetsToSelectionState(range, this.state.editorState.getCurrentContent().getBlocksAsArray()),
-            content
+            activeEditorState.getCurrentContent(),
+            RichText.textOffsetsToSelectionState(range, activeEditorState.getCurrentContent().getBlocksAsArray()),
+            completion
         );
 
-        let editorState = EditorState.push(this.state.editorState, contentState, 'insert-characters');
-
+        let editorState = EditorState.push(activeEditorState, contentState, 'insert-characters');
         editorState = EditorState.forceSelection(editorState, contentState.getSelectionAfter());
+        const originalEditorState = activeEditorState;
 
-        this.setEditorState(editorState);
+        await this.setEditorState(editorState);
+        this.setState({originalEditorState});
 
         // for some reason, doing this right away does not update the editor :(
         setTimeout(() => this.refs.editor.focus(), 50);
+        return true;
     }
 
     onFormatButtonClicked(name: "bold" | "italic" | "strike" | "code" | "underline" | "quote" | "bullet" | "numbullet", e) {
@@ -632,22 +688,14 @@ export default class MessageComposerInput extends React.Component {
         this.handleKeyCommand('toggle-mode');
     }
 
-    getBlockStyle(block: ContentBlock): ?string {
-        if (block.getType() === 'strikethrough') {
-            return 'mx_Markdown_STRIKETHROUGH';
-        }
-
-        return null;
-    }
-
     render() {
-        const {editorState} = this.state;
+        const activeEditorState = this.state.originalEditorState || this.state.editorState;
 
         // From https://github.com/facebook/draft-js/blob/master/examples/rich/rich.html#L92
         // If the user changes block type before entering any text, we can
         // either style the placeholder or hide it.
         let hidePlaceholder = false;
-        const contentState = editorState.getCurrentContent();
+        const contentState = activeEditorState.getCurrentContent();
         if (!contentState.hasText()) {
             if (contentState.getBlockMap().first().getType() !== 'unstyled') {
                 hidePlaceholder = true;
@@ -655,28 +703,43 @@ export default class MessageComposerInput extends React.Component {
         }
 
         const className = classNames('mx_MessageComposer_input', {
-            mx_MessageComposer_input_empty: hidePlaceholder,
+                mx_MessageComposer_input_empty: hidePlaceholder,
         });
 
+        const content = activeEditorState.getCurrentContent();
+        const contentText = content.getPlainText();
+        const selection = RichText.selectionStateToTextOffsets(activeEditorState.getSelection(),
+            activeEditorState.getCurrentContent().getBlocksAsArray());
+
         return (
-            <div className={className}>
-                <img className="mx_MessageComposer_input_markdownIndicator"
-                     onMouseDown={this.onMarkdownToggleClicked}
-                     title={`Markdown is ${this.state.isRichtextEnabled ? 'disabled' : 'enabled'}`}
-                     src={`img/button-md-${!this.state.isRichtextEnabled}.png`} />
-                <Editor ref="editor"
-                        placeholder="Type a message…"
-                        editorState={this.state.editorState}
-                        onChange={this.setEditorState}
-                        blockStyleFn={this.getBlockStyle}
-                        keyBindingFn={MessageComposerInput.getKeyBinding}
-                        handleKeyCommand={this.handleKeyCommand}
-                        handleReturn={this.handleReturn}
-                        stripPastedStyles={!this.state.isRichtextEnabled}
-                        onTab={this.onTab}
-                        onUpArrow={this.onUpArrow}
-                        onDownArrow={this.onDownArrow}
-                        spellCheck={true} />
+            <div className="mx_MessageComposer_input_wrapper">
+                <div className="mx_MessageComposer_autocomplete_wrapper">
+                    <Autocomplete
+                        ref={(e) => this.autocomplete = e}
+                        onConfirm={this.setDisplayedCompletion}
+                        query={contentText}
+                        selection={selection} />
+                </div>
+                <div className={className}>
+                    <img className="mx_MessageComposer_input_markdownIndicator"
+                         onMouseDown={this.onMarkdownToggleClicked}
+                         title={`Markdown is ${this.state.isRichtextEnabled ? 'disabled' : 'enabled'}`}
+                         src={`img/button-md-${!this.state.isRichtextEnabled}.png`} />
+                    <Editor ref="editor"
+                            placeholder="Type a message…"
+                            editorState={this.state.editorState}
+                            onChange={this.onEditorContentChanged}
+                            blockStyleFn={MessageComposerInput.getBlockStyle}
+                            keyBindingFn={MessageComposerInput.getKeyBinding}
+                            handleKeyCommand={this.handleKeyCommand}
+                            handleReturn={this.handleReturn}
+                            stripPastedStyles={!this.state.isRichtextEnabled}
+                            onTab={this.onTab}
+                            onUpArrow={this.onUpArrow}
+                            onDownArrow={this.onDownArrow}
+                            onEscape={this.onEscape}
+                            spellCheck={true} />
+                </div>
             </div>
         );
     }