feat(plugin): add keyword Tab indentation and selection formatting

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/plugin/src/indentation.js b/plugin/src/indentation.js
new file mode 100644
index 0000000..c8af770
--- /dev/null
+++ b/plugin/src/indentation.js
@@ -0,0 +1,58 @@
+'use strict';
+
+const { codeOnly } = require('./lexical');
+const closers = {
+	ENDIF: 'IF', ENDWHILE: 'WHILE', UNTIL: 'REPEAT', NEXT: 'FOR',
+	ENDFUNCTION: 'FUNCTION', ENDPROCEDURE: 'PROCEDURE', ENDTYPE: 'TYPE'
+};
+
+function lineDepths(lines) {
+	const stack = [];
+	const depth = () => stack.filter(block => block.active).length;
+	return lines.map(line => {
+		const code = codeOnly(line).trim();
+		const keyword = /^([A-Za-z][A-Za-z0-9_]*)\b/.exec(code)?.[1];
+		if (closers[keyword] || keyword === 'ELSE') {
+			const kind = keyword === 'ELSE' ? 'IF' : closers[keyword];
+			const index = stack.findLastIndex(block => block.kind === kind);
+			if (index >= 0) {
+				stack.length = index;
+				const current = depth();
+				if (keyword === 'ELSE') stack.push({ kind: 'IF', active: true });
+				return current;
+			}
+			// Incomplete code should still format without negative indentation.
+			return depth();
+		}
+
+		const current = depth();
+		if (keyword === 'THEN' || keyword === 'DO') {
+			const top = stack[stack.length - 1];
+			if (top?.kind === (keyword === 'THEN' ? 'IF' : 'WHILE')) top.active = true;
+		} else if (keyword === 'IF' || keyword === 'WHILE') {
+			stack.push({ kind: keyword, active: new RegExp(
+				keyword === 'IF' ? '\\bTHEN\\b' : '\\bDO\\b').test(code) });
+		} else if (['FOR', 'REPEAT', 'FUNCTION', 'PROCEDURE'].includes(keyword)) {
+			stack.push({ kind: keyword, active: true });
+		} else if (/^TYPE\s+[A-Za-z][A-Za-z0-9_]*$/.test(code)) {
+			stack.push({ kind: 'TYPE', active: true });
+		}
+		return current;
+	});
+}
+
+function indentationEdits(lines, startLine, endLine, keepBlankIndent = false) {
+	const depths = lineDepths(lines.slice(0, endLine + 1));
+	const edits = [];
+	for (let line = startLine; line <= endLine; line++) {
+		const oldIndent = /^[\t ]*/.exec(lines[line])[0];
+		const blank = lines[line].trim() === '';
+		const newIndent = blank && !keepBlankIndent ? '' : '\t'.repeat(depths[line]);
+		if (oldIndent !== newIndent) {
+			edits.push({ line, length: oldIndent.length, text: newIndent });
+		}
+	}
+	return edits;
+}
+
+module.exports = { lineDepths, indentationEdits };