# ETLPlus

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ETLPlus is a veritable Swiss Army knife for enabling simple ETL operations, offering both a Python
package and command-line interface for data extraction, validation, transformation, and loading.

- [ETLPlus](#etlplus)
  - [Features](#features)
  - [Installation](#installation)
  - [Quickstart](#quickstart)
  - [Usage](#usage)
    - [Command Line Interface](#command-line-interface)
      - [Extract Data](#extract-data)
      - [Validate Data](#validate-data)
      - [Transform Data](#transform-data)
      - [Load Data](#load-data)
    - [Python API](#python-api)
    - [Complete ETL Pipeline Example](#complete-etl-pipeline-example)
    - [Format Overrides](#format-overrides)
  - [Transformation Operations](#transformation-operations)
    - [Filter Operations](#filter-operations)
    - [Aggregation Functions](#aggregation-functions)
  - [Validation Rules](#validation-rules)
  - [Development](#development)
    - [API Client Docs](#api-client-docs)
    - [Runner Internals and Connectors](#runner-internals-and-connectors)
    - [Running Tests](#running-tests)
      - [Test Layers](#test-layers)
    - [Code Coverage](#code-coverage)
    - [Linting](#linting)
    - [Updating Demo Snippets](#updating-demo-snippets)
    - [Releasing to PyPI](#releasing-to-pypi)
  - [Links](#links)
  - [License](#license)
  - [Contributing](#contributing)
  - [Acknowledgments](#acknowledgments)

## Features

- **Extract** data from multiple sources:
  - Files (CSV, JSON, XML, YAML)
  - Databases (connection string support)
  - REST APIs (GET)

- **Validate** data with flexible rules:
  - Type checking
  - Required fields
  - Value ranges (min/max)
  - String length constraints
  - Pattern matching
  - Enum validation

- **Transform** data with powerful operations:
  - Filter records
  - Map/rename fields
  - Select specific fields
  - Sort data
  - Aggregate functions (avg, count, max, min, sum)

- **Load** data to multiple targets:
  - Files (CSV, JSON, XML, YAML)
  - Databases (connection string support)
  - REST APIs (PATCH, POST, PUT)

## Installation

```bash
pip install etlplus
```

For development:

```bash
pip install -e ".[dev]"
```

## Quickstart

Get up and running in under a minute.

[Command line interface](#command-line-interface):

```bash
# Inspect help and version
etlplus --help
etlplus --version

# One-liner: extract CSV, filter, select, and write JSON
etlplus extract file examples/data/sample.csv \
  | etlplus transform - --operations '{"filter": {"field": "age", "op": "gt", "value": 25}, "select": ["name", "email"]}' \
  -o temp/sample_output.json
```

[Python API](#python-api):

```python
from etlplus import extract, transform, validate, load

data = extract("file", "input.csv")
ops = {"filter": {"field": "age", "op": "gt", "value": 25}, "select": ["name", "email"]}
filtered = transform(data, ops)
rules = {"name": {"type": "string", "required": True}, "email": {"type": "string", "required": True}}
assert validate(filtered, rules)["valid"]
load(filtered, "file", "temp/sample_output.json", file_format="json")
```

## Usage

### Command Line Interface

ETLPlus provides a powerful CLI for ETL operations:

```bash
# Show help
etlplus --help

# Show version
etlplus --version
```

#### Extract Data

Note: For file sources, the format is normally inferred from the filename extension. Use
`--source-format` to override inference when a file lacks an extension or when you want to force a
specific parser.

Extract from JSON file:
```bash
etlplus extract file examples/data/sample.json
```

Extract from CSV file:
```bash
etlplus extract file examples/data/sample.csv
```

Extract from XML file:
```bash
etlplus extract file examples/data/sample.xml
```

Extract from REST API:
```bash
etlplus extract api https://api.example.com/data
```

Save extracted data to file:
```bash
etlplus extract file examples/data/sample.csv -o temp/sample_output.json
```

#### Validate Data

Validate data from file or JSON string:
```bash
etlplus validate '{"name": "John", "age": 30}' --rules '{"name": {"type": "string", "required": true}, "age": {"type": "number", "min": 0, "max": 150}}'
```

Validate from file:
```bash
etlplus validate examples/data/sample.json --rules '{"email": {"type": "string", "pattern": "^[\\w.-]+@[\\w.-]+\\.\\w+$"}}'
```

#### Transform Data

When piping data through `etlplus transform`, use `--source-format` whenever the SOURCE argument is
`-` or a literal payload, mirroring the `etlplus extract` semantics. Use `--target-format` to
control the emitted format for stdout or other non-file outputs, just like `etlplus load`. File
paths continue to infer formats from their extensions. Use `--from` to override the inferred source
connector type and `--to` to override the inferred target connector type, matching the `etlplus
extract`/`etlplus load` behavior.

Transform file inputs while overriding connector types:
```bash
etlplus transform --from file examples/data/sample.json \
  --operations '{"select": ["name", "email"]}' \
  --to file -o temp/selected_output.json
```

Filter and select fields:
```bash
etlplus transform '[{"name": "John", "age": 30}, {"name": "Jane", "age": 25}]' \
  --operations '{"filter": {"field": "age", "op": "gt", "value": 26}, "select": ["name"]}'
```

Sort data:
```bash
etlplus transform examples/data/sample.json --operations '{"sort": {"field": "age", "reverse": true}}'
```

Aggregate data:
```bash
etlplus transform examples/data/sample.json --operations '{"aggregate": {"field": "age", "func": "sum"}}'
```

Map/rename fields:
```bash
etlplus transform examples/data/sample.json --operations '{"map": {"name": "new_name"}}'
```

#### Load Data

`etlplus load` consumes JSON from stdin; provide only the target argument plus optional flags.

Load to JSON file:
```bash
etlplus extract file examples/data/sample.json \
  | etlplus load --to file temp/sample_output.json
```

Load to CSV file:
```bash
etlplus extract file examples/data/sample.csv \
  | etlplus load --to file temp/sample_output.csv
```

Load to REST API:
```bash
cat examples/data/sample.json \
  | etlplus load --to api https://api.example.com/endpoint
```

### Python API

Use ETLPlus as a Python library:

```python
from etlplus import extract, validate, transform, load

# Extract data
data = extract("file", "data.json")

# Validate data
validation_rules = {
    "name": {"type": "string", "required": True},
    "age": {"type": "number", "min": 0, "max": 150}
}
result = validate(data, validation_rules)
if result["valid"]:
    print("Data is valid!")

# Transform data
operations = {
    "filter": {"field": "age", "op": "gt", "value": 18},
    "select": ["name", "email"]
}
transformed = transform(data, operations)

# Load data
load(transformed, "file", "temp/sample_output.json", format="json")
```

For YAML-driven pipelines executed end-to-end (extract → validate → transform → load), see:

- Authoring: [`docs/pipeline-guide.md`](docs/pipeline-guide.md)
- Runner API and internals: [`docs/run-module.md`](docs/run-module.md)

CLI quick reference for pipelines:

```bash
# List jobs or show a pipeline summary
etlplus list --config examples/configs/pipeline.yml --jobs
etlplus list --config examples/configs/pipeline.yml --summary

# Run a job
etlplus run --config examples/configs/pipeline.yml --job file_to_file_customers

# Deprecated shim (will be removed): etlplus pipeline
```

### Complete ETL Pipeline Example

```bash
# 1. Extract from CSV
etlplus extract file examples/data/sample.csv -o temp/sample_extracted.json

# 2. Transform (filter and select fields)
etlplus transform temp/sample_extracted.json \
  --operations '{"filter": {"field": "age", "op": "gt", "value": 25}, "select": ["name", "email"]}' \
  -o temp/sample_transformed.json

# 3. Validate transformed data
etlplus validate temp/sample_transformed.json \
  --rules '{"name": {"type": "string", "required": true}, "email": {"type": "string", "required": true}}'

# 4. Load to CSV
cat temp/sample_transformed.json \
  | etlplus load --to temp/sample_output.csv
```

### Format Overrides

`--source-format` and `--target-format` override whichever format would normally be inferred from a
file extension. This is useful when an input lacks an extension (for example, `records.txt` that
actually contains CSV) or when you intentionally want to treat a file as another format.

Examples (zsh):

```zsh
# Force CSV parsing for an extension-less file
etlplus extract --from file data.txt --source-format csv

# Write CSV to a file without the .csv suffix
etlplus load --to file output.bin --target-format csv < data.json

# Leave the flags off when extensions already match the desired format
etlplus extract --from file data.csv
etlplus load --to file data.json < data.json
```

## Transformation Operations

### Filter Operations

Supported operators:
- `eq`: Equal
- `ne`: Not equal
- `gt`: Greater than
- `gte`: Greater than or equal
- `lt`: Less than
- `lte`: Less than or equal
- `in`: Value in list
- `contains`: List/string contains value

Example:
```json
{
  "filter": {
    "field": "status",
    "op": "in",
    "value": ["active", "pending"]
  }
}
```

### Aggregation Functions

Supported functions:
- `sum`: Sum of values
- `avg`: Average of values
- `min`: Minimum value
- `max`: Maximum value
- `count`: Count of values

Example:
```json
{
  "aggregate": {
    "field": "revenue",
    "func": "sum"
  }
}
```

## Validation Rules

Supported validation rules:
- `type`: Data type (string, number, integer, boolean, array, object)
- `required`: Field is required (true/false)
- `min`: Minimum value for numbers
- `max`: Maximum value for numbers
- `minLength`: Minimum length for strings
- `maxLength`: Maximum length for strings
- `pattern`: Regex pattern for strings
- `enum`: List of allowed values

Example:
```json
{
  "email": {
    "type": "string",
    "required": true,
    "pattern": "^[\\w.-]+@[\\w.-]+\\.\\w+$"
  },
  "age": {
    "type": "number",
    "min": 0,
    "max": 150
  },
  "status": {
    "type": "string",
    "enum": ["active", "inactive", "pending"]
  }
}
```

## Development

### API Client Docs

Looking for the HTTP client and pagination helpers?  See the dedicated docs in
`etlplus/api/README.md` for:

- Quickstart with `EndpointClient`
- Authentication via `EndpointCredentialsBearer`
- Pagination with `PaginationConfig` (page and cursor styles)
- Tips on `records_path` and `cursor_path`

### Runner Internals and Connectors

Curious how the pipeline runner composes API requests, pagination, and load calls?

- Runner overview and helpers: [`docs/run-module.md`](docs/run-module.md)
- Unified "connector" vocabulary (API/File/DB): `etlplus/config/connector.py`
  - API/file targets reuse the same shapes as sources; API targets typically set a `method`.

### Running Tests

```bash
pytest tests/ -v
```

#### Test Layers

We split tests into two layers:

- **Unit (`tests/unit/`)**: single function or class, no real I/O, fast, uses stubs/monkeypatch
  (e.g.  `etlplus.cli.create_parser`, transform + validate helpers).
- **Integration (`tests/integration/`)**: end-to-end flows (CLI `main()`, pipeline `run()`,
  pagination + rate limit defaults, file/API connector interactions) may touch temp files and use
  fake clients.

If a test calls `etlplus.cli.main()` or `etlplus.run.run()` it’s integration by default.  Full
criteria: [`CONTRIBUTING.md#testing`](CONTRIBUTING.md#testing).

### Code Coverage

```bash
pytest tests/ --cov=etlplus --cov-report=html
```

### Linting

```bash
flake8 etlplus/
black etlplus/
```

### Updating Demo Snippets

`DEMO.md` shows the real output of `etlplus --version` captured from a freshly built wheel. Regenerate
the snippet (and the companion file [docs/snippets/installation_version.md](docs/snippets/installation_version.md)) after changing anything that affects the version string:

```bash
make demo-snippets
```

The helper script in [tools/update_demo_snippets.py](tools/update_demo_snippets.py) builds the wheel,
installs it into a throwaway virtual environment, runs `etlplus --version`, and rewrites the snippet
between the markers in [DEMO.md](DEMO.md).

### Releasing to PyPI

`setuptools-scm` derives the package version from Git tags, so publishing is now entirely tag
driven—no hand-editing `pyproject.toml`, `setup.py`, or `etlplus/__version__.py`.

1. Ensure `main` is green and the changelog/docs are up to date.
2. Create and push a SemVer tag matching the `v*.*.*` pattern:

```bash
git tag -a v1.4.0 -m "Release v1.4.0"
git push origin v1.4.0
```

3. GitHub Actions fetches tags, builds the sdist/wheel, and publishes to PyPI via the `publish` job
   in [.github/workflows/ci.yml](.github/workflows/ci.yml).

If you want an extra smoke-test before tagging, run `make dist && pip install dist/*.whl` locally;
this exercises the same build path the workflow uses.

## Links

- API client docs: [`etlplus/api/README.md`](etlplus/api/README.md)
- Examples: [`examples/README.md`](examples/README.md)
- Pipeline authoring guide: [`docs/pipeline-guide.md`](docs/pipeline-guide.md)
- Runner internals: [`docs/run-module.md`](docs/run-module.md)
- Design notes (Mapping inputs, dict outputs): [`docs/pipeline-guide.md#design-notes-mapping-inputs-dict-outputs`](docs/pipeline-guide.md#design-notes-mapping-inputs-dict-outputs)
- Typing philosophy: [`CONTRIBUTING.md#typing-philosophy`](CONTRIBUTING.md#typing-philosophy)
- Demo and walkthrough: [`DEMO.md`](DEMO.md)
- Additional references: [`REFERENCES.md`](`REFERENCES.md)

## License

This project is licensed under the [MIT License](LICENSE).

## Contributing

Code and codeless contributions are welcome!  If you’d like to add a new feature, fix a bug, or
improve the documentation, please feel free to submit a pull request as follows:

1. Fork this repository.
2. Create a new feature branch for your changes (`git checkout -b feature/feature-name`).
3. Commit your changes (`git commit -m "Add feature"`).
4. Push to your branch (`git push origin feature-name`).
5. Submit a pull request with a detailed description.

If you choose to be a code contributor, please first refer these documents:

- Pipeline authoring guide: [`docs/pipeline-guide.md`](docs/pipeline-guide.md)
- Design notes (Mapping inputs, dict outputs):
  [`docs/pipeline-guide.md#design-notes-mapping-inputs-dict-outputs`](docs/pipeline-guide.md#design-notes-mapping-inputs-dict-outputs)
- Typing philosophy (TypedDicts as editor hints, permissive runtime):
  [`CONTRIBUTING.md#typing-philosophy`](CONTRIBUTING.md#typing-philosophy)

## Acknowledgments

ETLPlus is inspired by common work patterns in data engineering and software engineering patterns in
Python development, aiming to increase productivity and reduce boilerplate code.  Feedback and
contributions are always appreciated!

[Codecov project]: https://codecov.io/github/Dagitali/ETLPlus?branch=main
[GitHub Actions CI workflow]: https://github.com/Dagitali/ETLPlus/actions/workflows/ci.yml
[GitHub contributors]: https://github.com/Dagitali/ETLPlus/graphs/contributors
[GitHub issues]: https://github.com/Dagitali/ETLPlus/issues
[GitHub PRs]: https://github.com/Dagitali/ETLPlus/pulls
[GitHub release]: https://github.com/Dagitali/ETLPlus/releases
[PyPI package]: https://pypi.org/project/etlplus/
