Add group function (#3175)

3 files changed, 29 insertions, 12 deletions

diff --git a/src/mfm/parse/index.ts b/src/mfm/parse/index.ts
index 105378343b..f2beec14ff 100644
--- a/src/mfm/parse/index.ts
+++ b/src/mfm/parse/index.ts
@@ -15,6 +15,9 @@ import { TextElementSearch } from './elements/search';
 import { TextElementTitle } from './elements/title';
 import { TextElementUrl } from './elements/url';
 import { TextElementMotion } from './elements/motion';
+import { groupOn } from '../../prelude/array';
+import * as A from '../../prelude/array';
+import * as S from '../../prelude/string';
 
 const elements = [
 	require('./elements/big'),
@@ -89,16 +92,10 @@ export default (source: string): TextElement[] => {
 		i++;
 	}
 
-	// テキストを纏める
-	return tokens.reduce((a, b) => {
-		if (a.length && a[a.length - 1].type == 'text' && b.type == 'text') {
-			const tail = a.pop();
-			return a.concat({
-				type: 'text',
-				content: tail.content + b.content
-			});
-		} else {
-			return a.concat(b);
-		}
-	}, [] as TextElement[]);
+	const combineText = (es: TextElement[]): TextElement =>
+		({ type: 'text', content: S.concat(es.map(e => e.content)) });
+
+	return A.concat(groupOn(x => x.type, tokens).map(es =>
+		es[0].type === 'text' ? [combineText(es)] : es
+	));
 };
diff --git a/src/prelude/array.ts b/src/prelude/array.ts
index 42f05dc0c9..8536e486d6 100644
--- a/src/prelude/array.ts
+++ b/src/prelude/array.ts
@@ -29,3 +29,19 @@ export function unique<T>(xs: T[]): T[] {
 export function sum(xs: number[]): number {
 	return xs.reduce((a, b) => a + b, 0);
 }
+
+export function groupBy<T>(f: (x: T, y: T) => boolean, xs: T[]): T[][] {
+	const groups = [] as T[][];
+	for (const x of xs) {
+		if (groups.length !== 0 && f(groups[groups.length - 1][0], x)) {
+			groups[groups.length - 1].push(x);
+		} else {
+			groups.push([x]);
+		}
+	}
+	return groups;
+}
+
+export function groupOn<T, S>(f: (x: T) => S, xs: T[]): T[][] {
+	return groupBy((a, b) => f(a) === f(b), xs);
+}
diff --git a/src/prelude/string.ts b/src/prelude/string.ts
index cae776bc3d..6149235e47 100644
--- a/src/prelude/string.ts
+++ b/src/prelude/string.ts
@@ -1,3 +1,7 @@
+export function concat(xs: string[]): string {
+	return xs.reduce((a, b) => a + b, "");
+}
+
 export function capitalize(s: string): string {
 	return toUpperCase(s.charAt(0)) + toLowerCase(s.slice(1));
 }