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// Copyright (c) 2022-2023 Cloudflare, Inc.
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// Licensed under the Apache 2.0 license found in the LICENSE file or at:
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//     https://opensource.org/licenses/Apache-2.0
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import ts from "typescript";
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import { ensureStatementModifiers } from "./helpers";
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// This ensures that all top-level nodes have the `declare` keyword, but no
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// nodes inside `declare modules` blocks do. It also ensures no top-level
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// nodes are `export`ed.
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//
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// ```ts
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// export class A { ... }
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// declare module "thing" {
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//   declare class B { ... }
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// }
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// ```
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//
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// --- transforms to --->
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//
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// ```ts
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// declare class A { ... }
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// declare module "thing" {
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//   class B { ... }
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// }
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// ```
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export function createAmbientTransformer(): ts.TransformerFactory<ts.SourceFile> {
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  return (ctx) => {
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    return (node) => {
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      const visitor = createVisitor(ctx);
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      return ts.visitEachChild(node, visitor, ctx);
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    };
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  };
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}
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function createVisitor(ctx: ts.TransformationContext): ts.Visitor {
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  const moduleBlockChildVisitor: ts.Visitor = (node) => {
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    return ensureStatementModifiers(ctx, node, { declare: false });
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  };
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  const moduleDeclarationVisitor: ts.Visitor = (node) => {
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    if (ts.isModuleBlock(node)) {
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      return ts.visitEachChild(node, moduleBlockChildVisitor, ctx);
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    }
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    return node;
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  };
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  return (node) => {
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    if (
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      ts.isModuleDeclaration(node) &&
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      (node.flags & ts.NodeFlags.Namespace) === 0
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    ) {
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      return ts.visitEachChild(node, moduleDeclarationVisitor, ctx);
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    }
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    return ensureStatementModifiers(ctx, node, {
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      export: false,
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      declare: true,
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    });
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  };
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}