The Strategy Pattern - TrustRosie.io

Class Diagram for the Strategy Pattern

classDiagram
    class module_Core {
        -_lodash: object
        -_OpenAI: object
        -_ChatPromptTemplate: object
        +setImportPackagesModule(dependencies: object): void
        +statusImports(): object
    }

    class module_Standard {
        +lodash: object
        +OpenAI: object
        +ChatPromptTemplate: object
    }

    class module_Edge {
        +lodash: object
        +OpenAI: object
        +ChatPromptTemplate: object
    }

    class module_Standard_test {
        +statusImports(): void
    }

    class module_EdgeTest {
        +statusImports(): void
    }

    module_Standard --|> module_Core : Configures
    module_Edge --|> module_Core : Configures
    module_Core <-- module_Standard_test : Uses
    module_Core <-- module_EdgeTest : Uses

    module_Standard : setImportPackagesModule()
    module_Edge : setImportPackagesModule()
    module_Standard_test : import { statusImports }
    module_EdgeTest : import { statusImports }

Explanation:

Classes: Each class represents a module or a component in your system. module_Core is the central module that provides core functionalities and is configured by module_Standard and module_Edge, depending on the environment.
Methods and Properties: setImportPackagesModule is a method in module_Core that takes an object containing dependencies (lodash, OpenAI, ChatPromptTemplate) and sets them within module_Core. statusImports is a function that utilizes these configured dependencies.
Relationships: The arrow (--|>) from module_Standard and module_Edge to module_Core indicates that these modules configure module_Core by calling setImportPackagesModule. The reverse open arrow (<--) from module_Standard_test and module_EdgeTest to module_Core shows usage of functionalities provided by module_Core.

How to Use This Diagram:

This diagram helps visualize the dependency injection pattern you've implemented, showing how dependencies are configured based on the environment and how module_Core serves as the central hub for core logic accessible by both test and Edge Function modules.

Mermaid diagrams offer a convenient way to document and visualize complex software architectures directly within Markdown, enhancing documentation with minimal effort.

"+" (Plus): Indicates that the member (method or property) is public. Public members are accessible from outside the class.
"-" (Minus): Indicates that the member is private. Private members are intended to be accessible only within the class itself and not from outside.

Prompt

Based on our previous chat, I tested the following files to satisfy the need for a single code base that can be called successfully from Netlify Edge Functions and Ava tests.

I'm not sure if this is referred to a pattern. Nonetheless, can you please document the how it works, pros, cons, and any other commentary you care to add.


// module_Core.js
let _lodash, _OpenAI, _ChatPromptTemplate;

function setImportPackagesModule({ lodash, OpenAI, ChatPromptTemplate }) {
  _lodash = lodash;
  _OpenAI = OpenAI;
  _ChatPromptTemplate = ChatPromptTemplate;
}

function statusImports() {
  let results = {
    lodash: _lodash ? true : false,
    OpenAI: _OpenAI ? true : false,
    ChatPromptTemplate: _ChatPromptTemplate ? true : false,
  };
  return results;
}

export { setImportPackagesModule, statusImports };


// module_Standard.js
import lodash from "lodash";
import { OpenAI } from "@langchain/openai";
import { ChatPromptTemplate } from "@langchain/core/prompts";
import { setImportPackagesModule, statusImports } from "./module_Core.js";

// Initialize module_Core with Ava-compatible imports
setImportPackagesModule({ lodash, OpenAI, ChatPromptTemplate });

export { lodash, OpenAI, ChatPromptTemplate, statusImports };


// module_Edge.js -
import lodash from "https://esm.sh/lodash";
import { OpenAI } from "https://esm.sh/@langchain/openai";
import { ChatPromptTemplate } from "https://esm.sh/@langchain/core/prompts";
import { setImportPackagesModule, statusImports } from "./module_Core.js";

// Initialize module_Core with Edge-compatible imports
setImportPackagesModule({ lodash, OpenAI, ChatPromptTemplate });

export { lodash, OpenAI, ChatPromptTemplate, statusImports };


// module_Standard.test.js
import test from "ava";
import { statusImports } from "../netlify/utils/module_Standard.js";

test("statusImports", (t) => {
  const expected = {
    lodash: true,
    OpenAI: true,
    ChatPromptTemplate: true,
  };
  const results = statusImports();
  t.deepEqual(results, expected);
});


// Netlify Edge Function module_EdgeTest.js:
import { statusImports } from "../utils/module_Edge.js";

export default async (request, context) => {
  try {
    let results = statusImports();
    console.log({ results });

    return new Response(JSON.stringify(results, null, 2), {
      headers: { "Content-Type": "application/json" },
      status: 200,
    });
  } catch (error) {
    console.log({ error });
    throw error;
  }
};

ChatGPT 4.0 Response

The pattern you've implemented for managing dependencies across different environments—such as Netlify Edge Functions and Ava tests—effectively separates environment-specific configuration from your core module logic. This setup allows for a flexible and maintainable codebase. Let's document how it works, its pros and cons, and provide some additional commentary.

How It Works

Central Configuration (module_Core.js): This module acts as the central point for configuring dependencies (lodash, OpenAI, ChatPromptTemplate). It exposes a setImportPackagesModule function to set dependencies and a statusImports function to check their presence.
Environment-specific Modules (module_Standard.js and module_Edge.js): These modules import the actual dependencies according to the environment (Ava for testing, Edge for production) and then use setImportPackagesModule from module_Core.js to set these dependencies. This allows module_Core.js to use the configured dependencies without knowing where they came from.
Unified Testing and Production Code: Both testing (module_Standard.test.js) and production code (Netlify Edge Function module_EdgeTest.js) can use statusImports from module_Core.js through their respective environment-specific modules without directly dealing with environment-specific imports.

Pros

Single Codebase: Maintains a single codebase for both production and testing environments, reducing duplication and potential for errors.
Flexibility: Easily switch between different sets of dependencies based on the environment without changing the core logic.
Decoupling: Decouples the core module functionality from the environment, enhancing modularity and testability.
Simplicity: Simplifies dependency management by centralizing the configuration, making it easier to update or change dependencies.

Cons

Initial Setup Complexity: Requires an initial setup to abstract and configure the environment-specific dependencies, which might be overhead for smaller projects.
Indirect Dependency Access: The core module indirectly accesses dependencies through set variables, which could lead to runtime errors if setImportPackagesModule is not called before other functions are used.
Environment Detection Responsibility: The responsibility to import and configure the correct environment falls on the developer, requiring careful attention to ensure the right module (module_Standard.js or module_Edge.js) is used.

Commentary

Pattern Recognition: This setup resembles a form of the Strategy pattern, where the strategy (dependencies in this case) is selected based on the runtime environment and then injected into the core logic. It's a pragmatic approach to handling different environments in JavaScript projects.
Importance of Documentation: Given the indirect nature of dependency management, thorough documentation is vital to ensure that future maintainers understand how to add or modify dependencies.
Potential for Extension: This pattern could be extended to manage not just different environments (test vs. production) but also different configurations within the same environment (e.g., different API endpoints or feature flags for staging vs. production).

Conclusion

The implemented pattern effectively addresses the challenge of maintaining a single codebase that can run in both Ava tests and Netlify Edge Functions, by abstracting environment-specific configurations. While it introduces some complexity in setup and dependency management, the benefits in terms of flexibility, decoupling, and maintainability can outweigh these costs, especially as the project grows or evolves. Proper documentation and careful management of the environment-specific modules are key to leveraging this pattern successfully.

Prompt

Can you please add the motivation behind coming up with this pattern is, as of today's date, based on the restriction that Netlify Edge Functions do not support dynamic imports, Netlify import maps, and esbuild failed in bundling local files for distribution.

ChatGPT 4.0 Response

The motivation behind developing the described pattern arises from a set of specific technical constraints and limitations present in the current implementation of Netlify Edge Functions, as well as challenges encountered with common JavaScript tooling like esbuild. As of today's date, these constraints include:

Lack of Support for Dynamic Imports in Netlify Edge Functions: Netlify Edge Functions do not support dynamic import() syntax, a JavaScript feature that allows loading modules dynamically at runtime. This limitation restricts the ability to conditionally load modules based on the execution environment (e.g., testing versus production) directly within the module code.
Netlify Import Maps Unavailability: Import maps, which provide a way to control the behavior of JavaScript imports by specifying URLs or alternative package versions, are not supported in Netlify Edge Functions. This feature could have offered a solution for managing environment-specific imports directly within the JavaScript modules.
Challenges with esbuild Bundling Local Files: When attempting to bundle local files for distribution with esbuild, issues were encountered that prevented successful bundling. This could include difficulties in resolving local modules, integrating environment-specific configurations, or handling external dependencies in a way that's compatible with Netlify Edge Functions.

Pattern Development Motivation

Given these constraints, the motivation for developing the described pattern was to create a flexible, maintainable solution that allows for:

Environment-Specific Configuration: Enabling the same codebase to work seamlessly across different environments (e.g., local development, testing with Ava, and production in Netlify Edge Functions) by abstracting away the environment-specific logic into dedicated modules (module_Standard.js and module_Edge.js).
Centralized Dependency Management: Providing a central place (module_Core.js) to manage and access dependencies throughout the application, reducing direct dependency on environment-specific features or import syntax.
Compatibility Across Tools and Platforms: Ensuring that the solution is compatible with existing JavaScript tooling (like Ava for testing) and platforms (like Netlify for deployment), despite their limitations regarding module importing and bundling.

Addressing Technical Limitations

The pattern addresses these limitations by:

Bypassing the Need for Dynamic Imports: By statically importing environment-specific modules (module_Standard.js for Ava tests and module_Edge.js for Edge Functions) and using a configuration function to set dependencies, the pattern circumvents the lack of support for dynamic imports.
Creating an Alternative to Import Maps: The use of environment-specific modules to configure the core module (module_Core.js) serves as a practical alternative to import maps, allowing for environment-aware module configuration without relying on unsupported features.
Solving esbuild Bundling Issues: By organizing imports and dependency configurations into environment-specific modules, this pattern potentially simplifies the build process, making it more straightforward for tools like esbuild to bundle the application without encountering issues related to local files or environment-specific logic.

Conclusion

The development of this pattern is a direct response to the current technical landscape and limitations of Netlify Edge Functions and the broader JavaScript ecosystem's tooling capabilities. It exemplifies a pragmatic approach to software development, where constraints drive innovation and lead to the creation of adaptable, robust solutions that ensure compatibility and maintainability across different environments and tools.

Module Interdepencies

Here's a summary of the roles and relationships between the _Core, _Standard, and _Edge modules:

_Core Modules

Purpose: Contain the shared logic that is common across all environments. This includes business logic, utility functions, or any functionality that doesn't depend on the specific runtime environment (Node.js standard environment vs. Edge environment).
Implementation: Implemented or extended by _Standard and _Edge modules to add or override functionalities specific to each environment.

_Standard Modules

Purpose: Tailored for the standard Node.js environment, these modules import and possibly extend _Core modules with additional functionalities or adjustments needed for a traditional Node.js application.
Implementation: Can use or extend _Core modules directly. They are responsible for configuring or initializing the core application logic with dependencies that are suitable for the standard Node.js environment.

_Edge Modules

Purpose: Specifically designed for Netlify Edge Functions or similar serverless/edge computing environments. These modules adapt or extend _Core modules with modifications required for optimal performance and compatibility in edge environments.
Implementation: Similar to _Standard modules, they adapt _Core modules for their specific environment. This might include using different libraries that are better suited for edge computing or adjusting configurations for the constrained execution context of Edge Functions.

Application and Endpoint Modules

All other modules or endpoints in the application will typically be either _Standard or _Edge, depending on the deployment target and runtime environment. This ensures that each part of the application is optimized for its specific execution context, leveraging the shared logic from _Core modules as needed.

Key Takeaways

Separation of Concerns: This pattern effectively separates the concerns of shared application logic and environment-specific customizations, allowing for more manageable codebase maintenance and development.
Flexibility: It provides the flexibility to adapt the application for different environments without duplicating the core logic. Changes in the shared logic only need to be made in the _Core modules.
Consistency: Despite the runtime differences between standard Node.js and Edge environments, this pattern ensures that the core business logic remains consistent across deployments.

By adhering to this architecture, your application becomes more modular, maintainable, and easier to extend for different environments while keeping the shared logic centralized.