chore: apply review suggestions

* pref: optimize `common` rules and matchers
* chore: rename diagrams services to short form
* chore: sort imports

packages/parser/src/language/common/valueConverter.ts

@@ -0,0 +1,82 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
+import type { CstNode, GrammarAST, ValueType } from 'langium';
+import { DefaultValueConverter } from 'langium';
+
+import { accessibilityDescrRegex, accessibilityTitleRegex, titleRegex } from './matcher.js';
+
+const rulesRegexes: Record<string, RegExp> = {
+  ACC_DESCR: accessibilityDescrRegex,
+  ACC_TITLE: accessibilityTitleRegex,
+  TITLE: titleRegex,
+};
+
+export abstract class MermaidValueConverter extends DefaultValueConverter {
+  /**
+   * A method contains convert logic to be used by class.
+   *
+   * @param rule - Parsed rule.
+   * @param input - Matched string.
+   * @param cstNode - Node in the Concrete Syntax Tree (CST).
+   * @returns converted the value if it's available or `undefined` if it's not.
+   */
+  protected abstract runCustomConverter(
+    rule: GrammarAST.AbstractRule,
+    input: string,
+    cstNode: CstNode
+  ): ValueType | undefined;
+
+  protected override runConverter(
+    rule: GrammarAST.AbstractRule,
+    input: string,
+    cstNode: CstNode
+  ): ValueType {
+    let value: ValueType | undefined = this.runCommonConverter(rule, input, cstNode);
+
+    if (value === undefined) {
+      value = this.runCustomConverter(rule, input, cstNode);
+    }
+    if (value === undefined) {
+      return super.runConverter(rule, input, cstNode);
+    }
+
+    return value;
+  }
+
+  private runCommonConverter(
+    rule: GrammarAST.AbstractRule,
+    input: string,
+    _cstNode: CstNode
+  ): ValueType | undefined {
+    const regex: RegExp | undefined = rulesRegexes[rule.name];
+    if (regex === undefined) {
+      return undefined;
+    }
+    const match = regex.exec(input);
+    if (match === null) {
+      return undefined;
+    }
+    // single line title, accTitle, accDescr
+    if (match[1] !== undefined) {
+      return match[1].trim().replace(/[\t ]{2,}/gm, ' ');
+    }
+    // multi line accDescr
+    if (match[2] !== undefined) {
+      return match[2]
+        .replace(/^\s*/gm, '')
+        .replace(/\s+$/gm, '')
+        .replace(/[\t ]{2,}/gm, ' ')
+        .replace(/[\n\r]{2,}/gm, '\n');
+    }
+    return undefined;
+  }
+}
+
+export class CommonValueConverter extends MermaidValueConverter {
+  protected runCustomConverter(
+    _rule: GrammarAST.AbstractRule,
+    _input: string,
+    _cstNode: CstNode
+  ): ValueType | undefined {
+    return undefined;
+  }
+}