From 858c0ae9a52d9b98267db92bbb383ef2b676444f Mon Sep 17 00:00:00 2001
From: Christian Schneider <christian.schneider@typefox.io>
Date: Fri, 26 May 2023 00:16:16 +0200
Subject: [PATCH] Contribution of a generator implementation using
 `expandToNode` and `joinToNode`

---
 src/arithmeticsEditor/index.ts        |  2 +-
 src/generator/generator-with-nodes.ts | 93 +++++++++++++++++++++++++++
 2 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 src/generator/generator-with-nodes.ts

diff --git a/src/arithmeticsEditor/index.ts b/src/arithmeticsEditor/index.ts
index 0f06b82..f56418a 100644
--- a/src/arithmeticsEditor/index.ts
+++ b/src/arithmeticsEditor/index.ts
@@ -8,7 +8,7 @@ import { expandToString } from 'langium';
 import { buildWorkerDefinition } from 'monaco-editor-workers';
 import { CodeEditorConfig, MonacoEditorLanguageClientWrapper, WorkerConfigOptions } from 'monaco-editor-wrapper';
 import { Diagnostic, DiagnosticSeverity, NotificationType } from 'vscode-languageserver/browser.js';
-import { generate } from '../generator/generator.js';
+import { generate } from '../generator/generator-with-nodes.js';
 
 type DocumentChange = { uri: string, content: string, diagnostics: Diagnostic[] };
 
diff --git a/src/generator/generator-with-nodes.ts b/src/generator/generator-with-nodes.ts
new file mode 100644
index 0000000..f026617
--- /dev/null
+++ b/src/generator/generator-with-nodes.ts
@@ -0,0 +1,93 @@
+/******************************************************************************
+ * Copyright 2023 TypeFox GmbH
+ * This program and the accompanying materials are made available under the
+ * terms of the MIT License, which is available in the project root.
+ ******************************************************************************/
+
+import { DefaultAstNodeLocator, DefaultJsonSerializer, DefaultNameProvider, expandToNode, Generated, joinToNode, toString } from 'langium';
+import { Definition, Evaluation, Expression, isBinaryExpression, isDefinition, isFunctionCall, isNumberLiteral, Module, Statement } from 'langium-arithmetics-dsl/api';
+
+export function generate({uri, content}: { uri: string, content: string | Module }): string {
+    if (typeof content === 'string') {
+        content = deserializeModule(content);
+    }
+
+    return toString(
+        generateModule(content)
+    );
+}
+
+function generateModule(root: Module): Generated {
+    return expandToNode`
+        "use strict";
+        (() => {
+          ${generateModuleContent(root)}
+        })
+    `;
+}
+
+const lastComputableExpressionValueVarName = 'lastComputableExpressionValue';
+
+function generateModuleContent(module: Module): Generated {
+    return expandToNode`
+        let ${lastComputableExpressionValueVarName};
+        ${ joinToNode(module.statements, generateStatement, { appendNewLineIfNotEmpty: true }) }
+
+        return ${lastComputableExpressionValueVarName};
+    `;
+}
+
+function generateStatement(stmt: Statement): Generated {
+    if (isDefinition(stmt))
+        return generateDefinition(stmt);
+    else
+        return generateEvaluation(stmt);
+}
+
+function generateDefinition(def: Definition): Generated {
+    return def.args && def.args.length ?
+        expandToNode`
+            const ${def.name} = (${joinToNode(def.args, arg => arg.name, { separator: ', '})}) => ${generateExpression(def.expr)};
+        ` : expandToNode`
+            const ${def.name} = ${lastComputableExpressionValueVarName} = ${generateExpression(def.expr)};
+        `;
+}
+
+function generateEvaluation(evaln: Evaluation): Generated {
+    return expandToNode`
+        ${lastComputableExpressionValueVarName} = ${generateExpression(evaln.expression)};
+    `;
+}
+
+function generateExpression(expr: Expression): Generated {
+    if (isNumberLiteral(expr)) {
+        return expr.value.toString();
+
+    } else if (isBinaryExpression(expr)) {
+        const leftAsIs  = isNumberLiteral(expr.left)  || isFunctionCall(expr.left);
+        const rightAsIs = isNumberLiteral(expr.right) || isFunctionCall(expr.right);
+        const left  = leftAsIs  ? generateExpression(expr.left)  : expandToNode`(${generateExpression(expr.left )})`;
+        const right = rightAsIs ? generateExpression(expr.right) : expandToNode`(${generateExpression(expr.right)})`;
+        return expandToNode`
+            ${left} ${expr.operator} ${right}
+        `;
+
+    } else {
+        return expandToNode`${expr.func.ref?.name}`.appendTemplateIf(!!expr.args.length)`
+            (
+                ${joinToNode(expr.args, generateExpression, { separator: ', ' })}
+            )
+        `;
+    };
+}
+
+function deserializeModule(input: string): Module {
+    return new DefaultJsonSerializer({
+        workspace: {
+            AstNodeLocator: new DefaultAstNodeLocator()
+        },
+        references: {
+            NameProvider: new DefaultNameProvider()
+        }
+    } as any).deserialize(input) as Module;
+}
\ No newline at end of file