feat(app): edit blockquote lines in the composer (#2676)

fluxer_app/src/features/lexical/composer/blockquoteLines.ts

@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {isOffsetInsideCodeBlock, scanCodeBlocks} from '@app/features/lexical/composer/codeBlockIndent';
+import {MarkdownHl, type MarkdownSpan} from '@app/features/lexical/composer/markdownSpans';
+
+export interface BlockquoteLine {
+	start: number;
+	contentStart: number;
+	end: number;
+}
+
+export interface BlockquoteEdit {
+	start: number;
+	end: number;
+	text: string;
+	caret: number;
+}
+
+const CONTINUATION = '\n> ';
+const DROPPABLE_TRAILING_LINE_RE = /^[ \t]*(?:> [ \t]*)?$/;
+const MULTILINE_ALERT_RE = /^[ \t]*>>> \[!(?:NOTE|TIP|IMPORTANT|WARNING|CAUTION)\]/i;
+
+function isEmptyLine(line: BlockquoteLine): boolean {
+	return line.contentStart === line.end;
+}
+
+function isDirectlyAbove(upper: BlockquoteLine, lower: BlockquoteLine): boolean {
+	return upper.end + 1 === lower.start;
+}
+
+export function findBlockquoteMarkerEnds(source: string, spans: ReadonlyArray<MarkdownSpan>): Array<number> {
+	const markerEndByStart = new Map<number, number>();
+	for (const span of spans) {
+		if (span.role === 'marker' && (span.format & MarkdownHl.blockquoteMarker) !== 0) {
+			markerEndByStart.set(span.start, span.end);
+		}
+	}
+	const blocks = scanCodeBlocks(source);
+	const ends: Array<number> = [];
+	let lineStart = 0;
+	for (const line of source.split('\n')) {
+		const markerEnd = markerEndByStart.get(lineStart);
+		const insideCode = blocks.some((block) => block.start <= lineStart && lineStart <= block.end);
+		const suppressed = insideCode || MULTILINE_ALERT_RE.test(line);
+		ends.push(markerEnd == null || suppressed ? 0 : Math.min(markerEnd, lineStart + line.length) - lineStart);
+		lineStart += line.length + 1;
+	}
+	return ends;
+}
+
+export function planBlockquoteLineBreak(
+	text: string,
+	lines: ReadonlyArray<BlockquoteLine>,
+	caret: number,
+): BlockquoteEdit | null {
+	if (isOffsetInsideCodeBlock(text, caret)) {
+		return null;
+	}
+	const index = lines.findIndex((line) => line.contentStart <= caret && caret <= line.end);
+	if (index < 0) {
+		return null;
+	}
+	const line = lines[index]!;
+	const above = index > 0 ? lines[index - 1]! : null;
+	if (!isEmptyLine(line) || above == null || !isDirectlyAbove(above, line)) {
+		return {start: caret, end: caret, text: CONTINUATION, caret: caret + CONTINUATION.length};
+	}
+	let top = index;
+	while (top > 0 && isDirectlyAbove(lines[top - 1]!, lines[top]!) && isEmptyLine(lines[top - 1]!)) {
+		top -= 1;
+	}
+	return {start: lines[top]!.start, end: line.contentStart, text: '', caret: lines[top]!.start};
+}
+
+export function planBlockquoteBackspace(
+	text: string,
+	lines: ReadonlyArray<BlockquoteLine>,
+	caret: number,
+): BlockquoteEdit | null {
+	if (isOffsetInsideCodeBlock(text, caret)) {
+		return null;
+	}
+	const line = lines.find((candidate) => candidate.contentStart === caret);
+	if (line != null) {
+		return {start: line.start, end: line.contentStart, text: '', caret: line.start};
+	}
+	const above = lines.find((candidate) => candidate.end + 1 === caret && isEmptyLine(candidate));
+	if (above == null || lines.some((candidate) => candidate.start === caret)) {
+		return null;
+	}
+	return {start: above.start, end: caret, text: '', caret: above.start};
+}
+
+export function resolveBlockquoteCaret(lines: ReadonlyArray<BlockquoteLine>, caret: number): number {
+	const line = lines.find((candidate) => candidate.start <= caret && caret < candidate.contentStart);
+	return line == null ? caret : line.contentStart;
+}
+
+export function planBlockquoteArrowLeft(lines: ReadonlyArray<BlockquoteLine>, caret: number): number | null {
+	const line = lines.find((candidate) => candidate.contentStart === caret);
+	if (line == null) {
+		return null;
+	}
+	return line.start > 0 ? line.start - 1 : line.contentStart;
+}
+
+export function dropTrailingEmptyBlockquoteLines(content: string): string {
+	const blocks = scanCodeBlocks(content);
+	let end = content.length;
+	while (end > 0) {
+		const lineStart = content.lastIndexOf('\n', end - 1) + 1;
+		if (
+			!DROPPABLE_TRAILING_LINE_RE.test(content.slice(lineStart, end)) ||
+			blocks.some((block) => block.start <= lineStart && lineStart <= block.end)
+		) {
+			break;
+		}
+		end = Math.max(0, lineStart - 1);
+	}
+	return content.slice(0, end);
+}