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# Add Dependency Injection to Project

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<gsl-purpose>
<gsl-title>

## 1. Purpose
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<gsl-description>

Implement dependency injection in the Python project using the `dependency-injector` library to improve modularity, testability, and maintainability. Refactor core services to use containers and providers, enabling scalable architecture and easier testing.
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</gsl-purpose>

<gsl-inputs>
<gsl-title>

## 2. Inputs
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<gsl-description>

| Input                                         | Notes                                                        |
|-----------------------------------------------|--------------------------------------------------------------|
| dependency-injector (PyPI package)            | Main DI framework for Python                                 |
| "How to Set Up Dependency Injection in Python with `dependency-injector`" | Article describing steps and best practices                  |
| Existing project source code                  | Project to be refactored                                     |
| pytest (or test framework used in project)    | To validate DI wiring and mock swapping                      |

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<gsl-outputs>
<gsl-title>

## 3. Outputs
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<gsl-description>

* **Declared** `dependency-injector` as a dependency in `pyproject.toml` to enable DI capabilities.
    
* **Documented** the new container-based architecture in `README.md`, with instructions pointing users to `src/obk/containers.py` for details.
    
* **Added** an application container providing `Greeter` and `Divider` services for injection.
    
* **Moved** service classes into a standalone module (`services.py`) for cleaner injection and reuse.
    
* **Refactored** `ObkCLI` to resolve services from the container and support service overrides in tests.
    

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<gsl-workflows>
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## 4. Workflows
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<gsl-description>

<!-- List main steps or processes required for the task. -->
- Install `dependency-injector`.
- Move services to their own module.
- Create `Container` for dependency wiring.
- Refactor CLI to resolve dependencies from the container.
- Update documentation and tests.

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</gsl-workflows>

<gsl-acceptance-tests>
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## 5. Acceptance Tests
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<gsl-acceptance-test id="1">
<gsl-performed-action>

1. When I run `python -m obk hello-world`
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<gsl-expected-result>

    The console displays "hello world", confirming that the Greeter service is injected via the container.
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</gsl-acceptance-test>

<gsl-acceptance-test id="2">
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2. When I run `python -m obk divide 6 2`
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<gsl-expected-result>

    The console displays "3.0", confirming that Divider is injected via the container.
</gsl-expected-result>
</gsl-acceptance-test>

<gsl-acceptance-test id="3">
<gsl-performed-action>

3. When I run `python -m obk divide 1 0`
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<gsl-expected-result>

    The error output includes "[ERROR] cannot divide by zero" and the process exits with code 2.
</gsl-expected-result>
</gsl-acceptance-test>

<gsl-acceptance-test id="4">
<gsl-performed-action>

4. When I run `python -m obk divide 4 2 --logfile=my.log`
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<gsl-expected-result>

    The console displays "2.0" and the file "my.log" contains "Divide 4.0 by 2.0 = 2.0".
</gsl-expected-result>
</gsl-acceptance-test>

<gsl-acceptance-test id="5">
<gsl-performed-action>

5. When I override the Greeter in the DI container with a mock and run `ObkCLI(container=container).run(["hello-world"])`
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<gsl-expected-result>

    The output displays the value returned by the mock Greeter, confirming DI override.
</gsl-expected-result>
</gsl-acceptance-test>

<gsl-acceptance-test id="6">
<gsl-performed-action>

6. When I override the Divider in the DI container with a mock and run `ObkCLI(container=container).run(["divide", "1", "3"])`
</gsl-performed-action>
<gsl-expected-result>

    The output displays the value returned by the mock Divider, confirming DI override.
</gsl-expected-result>
</gsl-acceptance-test>

<gsl-acceptance-test id="7">
<gsl-performed-action>

7. When I run `python -m obk fail`
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<gsl-expected-result>

    The process exits with code 1 and error output includes "fatal", verifying error handling through the DI setup.
</gsl-expected-result>
</gsl-acceptance-test>
<gsl-acceptance-test id="8">
<gsl-performed-action>

8. When I inspect `pyproject.toml`
</gsl-performed-action>
<gsl-expected-result>

    The file declares `dependency-injector` as a required dependency.
</gsl-expected-result>
</gsl-acceptance-test>
<gsl-acceptance-test id="9">
<gsl-performed-action>

9. When I inspect the codebase
</gsl-performed-action>
<gsl-expected-result>

    Service classes exist in a standalone `services.py` module, and the DI container is implemented in `containers.py`.
</gsl-expected-result>
</gsl-acceptance-test>
</gsl-acceptance-tests>
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