refactor(generator)!: add CodeGenerator and MsGenerator classes

Author: KeJunMao

src/core/context/generator.ts

@@ -0,0 +1,62 @@
+import type { Generate, SimpleNode } from '../../types'
+import type { GeneratorOptions } from './generator'
+import { Generator } from './generator'
+
+export interface CodeGeneratorOptions extends GeneratorOptions { }
+
+/**
+ * 纯代码生成器
+ * 从 AST 节点生成代码字符串，不依赖 MagicString
+ */
+export class CodeGenerator extends Generator {
+  private generatedCode: string[] = []
+
+  /**
+   * 添加代码片段到生成结果
+   */
+  append(code: string): void {
+    this.generatedCode.push(code)
+  }
+
+  /**
+   * 处理 CodeStatement 节点
+   */
+  protected handleCodeStatement(node: SimpleNode): void {
+    this.append(node.value)
+  }
+
+  /**
+   * 处理自定义生成器返回的结果
+   */
+  protected handleGeneratorResult(node: SimpleNode, result: string): void {
+    this.append(result)
+  }
+
+  /**
+   * 保留节点（用于 unhandled: 'keep' 策略）
+   */
+  protected handleKeepNode(node: SimpleNode): void {
+    if ('value' in node && typeof node.value === 'string')
+      this.append(node.value)
+  }
+
+  /**
+   * 生成最终代码
+   */
+  private generate(): string {
+    this.generatedCode = []
+    this.walk(this.node)
+    return this.generatedCode.join('')
+  }
+
+  /**
+   * 静态方法：从 AST 节点生成代码
+   */
+  static generate(
+    node: SimpleNode,
+    generates: (Generate | undefined)[] = [],
+    options: CodeGeneratorOptions = {},
+  ): string {
+    return new CodeGenerator(node, generates, options).generate()
+  }
+}

src/core/context/generator/code-generator.ts

@@ -0,0 +1,106 @@
+import type { Generate, SimpleNode } from '../../types'
+import { findComment } from '../../utils'
+
+type UnhandledPolicy = 'throw' | 'keep' | 'remove'
+
+export interface GeneratorOptions {
+  unhandled?: UnhandledPolicy
+}
+
+/**
+ * 生成器基类
+ * 提供通用的 AST 遍历和节点处理逻辑
+ */
+export abstract class Generator {
+  constructor(
+    public readonly node: SimpleNode,
+    public readonly generates: (Generate | undefined)[] = [],
+    protected readonly options: GeneratorOptions = {},
+  ) { }
+
+  /**
+   * 遍历 AST 节点
+   */
+  walk(node: SimpleNode): void {
+    switch (node.type) {
+      case 'Program':
+        for (const child of node.body)
+          this.walk(child)
+        break
+      case 'CodeStatement':
+        this.handleCodeStatement(node)
+        break
+      default:
+        this.processWithCustomGenerators(node)
+    }
+  }
+
+  /**
+   * 处理 CodeStatement 节点
+   * 子类需要实现此方法
+   */
+  protected abstract handleCodeStatement(node: SimpleNode): void
+
+  /**
+   * 处理自定义生成器的结果
+   * 子类需要实现此方法
+   */
+  protected abstract handleGeneratorResult(node: SimpleNode, result: string): void
+
+  /**
+   * 使用自定义生成器处理节点
+   * 生成器返回值约定：
+   * - string: 处理该节点
+   * - null: 已手动处理
+   * - undefined: 不处理，交给下一个生成器
+   */
+  private processWithCustomGenerators(node: SimpleNode): void {
+    const comment = node.comment && findComment(node.comment)
+
+    for (const generate of this.generates) {
+      if (!generate)
+        continue
+
+      const result = generate.call(this as any, node, comment as any)
+
+      if (result !== undefined) {
+        if (result !== null)
+          this.handleGeneratorResult(node, String(result))
+        return
+      }
+    }
+
+    this.handleUnprocessedNode(node)
+  }
+
+  /**
+   * 处理未被任何生成器处理的节点
+   */
+  protected handleUnprocessedNode(node: SimpleNode): void {
+    const policy = this.options.unhandled ?? 'throw'
+
+    if (policy === 'remove') {
+      // 默认删除行为
+      return
+    }
+
+    if (policy === 'keep') {
+      // 保留节点
+      this.handleKeepNode(node)
+      return
+    }
+
+    throw new Error(
+      `Generator: Unhandled node type "${node.type}"${node.start != null && node.end != null
+        ? ` at position ${node.start}-${node.end}`
+        : ''
+      }`,
+    )
+  }
+
+  /**
+   * 保留节点（用于 unhandled: 'keep' 策略）
+   * 子类需要实现此方法
+   */
+  protected abstract handleKeepNode(node: SimpleNode): void
+}

src/core/context/generator/generator.ts

@@ -0,0 +1,3 @@
+export * from './code-generator'
+export * from './generator'
+export * from './ms-generator'