Feature/v3/invest multi period

.github/CONTRIBUTING.md

@@ -1,85 +1,168 @@
 # Contributing to FlixOpt
 
-Thanks for your interest in contributing to FlixOpt! 🚀
+We warmly welcome contributions from the community! Whether you're fixing bugs, adding features, improving documentation, or sharing examples, your contributions are valuable.
 
-## Quick Start
+## Ways to Contribute
 
-1. **Fork & Clone**
+### 🐛 Report Issues
+Found a bug or have a feature request? Please [open an issue](https://github.com/flixOpt/flixopt/issues) on GitHub.
+
+When reporting issues, please include:
+- A clear description of the problem
+- Steps to reproduce the issue
+- Expected vs. actual behavior
+- Your environment (OS, Python version, FlixOpt version)
+- Minimal code example if applicable
+
+### 💡 Share Examples
+Help others learn FlixOpt by contributing examples:
+- Real-world use cases
+- Tutorial notebooks
+- Integration examples with other tools
+- Add them to the `examples/` directory
+
+### 📖 Improve Documentation
+Documentation improvements are always welcome:
+- Fix typos or clarify existing docs
+- Add missing documentation
+- Translate documentation
+- Improve code comments
+
+### 🔧 Submit Code Contributions
+Ready to contribute code? Great! See the sections below for setup and guidelines.
+
+---
+
+## Development Setup
+
+### Getting Started
+1. Fork and clone the repository:
    ```bash
-   git clone https://github.com/yourusername/flixopt.git
+   git clone https://github.com/flixOpt/flixopt.git
    cd flixopt
    ```
 
-2. **Install for Development**
+2. Install development dependencies:
    ```bash
-   pip install -e ".[full]"
+   pip install -e ".[full, dev]"
    ```
 
-3. **Make Changes & Submit PR**
+3. Set up pre-commit hooks (one-time setup):
    ```bash
-   git checkout -b feature/your-change
-   # Make your changes
-   git commit -m "Add: description of changes"
-   git push origin feature/your-change
-   # Create Pull Request on GitHub
+   pre-commit install
    ```
 
-## How to Contribute
-
-### 🐛 **Found a Bug?**
-Use our [bug report template](https://github.com/flixOpt/flixopt/issues/new?template=bug_report.yml) with:
-- Minimal code example
-- FlixOpt version, Python version, solver used
-- Expected vs actual behavior
-
-### ✨ **Have a Feature Idea?**
-Use our [feature request template](https://github.com/flixOpt/flixopt/issues/new?template=feature_request.yml) with:
-- Clear energy system use case
-- Specific examples of what you want to model
+4. Verify your setup:
+   ```bash
+   pytest
+   ```
 
-### ❓ **Need Help?**
-- Check the [documentation](https://flixopt.github.io/flixopt/latest/) first
-- Search [existing issues](https://github.com/flixOpt/flixopt/issues)
-- Start a [discussion](https://github.com/flixOpt/flixopt/discussions)
+### Working with Documentation
+FlixOpt uses [mkdocs](https://www.mkdocs.org/) to generate documentation.
 
-## Code Guidelines
+To work on documentation:
+```bash
+pip install -e ".[docs]"
+mkdocs serve
+```
+Then navigate to http://127.0.0.1:8000/
 
-- **Style**: Follow PEP 8, use descriptive names
-- **Documentation**: Add docstrings with units (kW, kWh, etc.) if applicable
-- **Energy Focus**: Use energy domain terminology consistently
-- **Testing**: Test with different solvers when applicable
+---
 
-### Example
+## Code Quality Standards
+
+### Automated Checks
+We use [Ruff](https://github.com/astral-sh/ruff) for linting and formatting. After the one-time setup above, **code quality checks run automatically on every commit**.
+
+### Manual Checks
+To run checks manually:
+- `ruff check --fix .` - Check and fix linting issues
+- `ruff format .` - Format code
+- `pre-commit run --all-files` - Run all pre-commit checks
+
+### Testing
+All tests are located in the `tests/` directory with a flat structure:
+- `test_component.py` - Component tests
+- `test_flow.py` - Flow tests
+- `test_storage.py` - Storage tests
+- etc.
+
+#### Running Tests
+- `pytest` - Run the full test suite (excluding examples by default)
+- `pytest tests/test_component.py` - Run a specific test file
+- `pytest tests/test_component.py::TestClassName` - Run a specific test class
+- `pytest tests/test_component.py::TestClassName::test_method` - Run a specific test
+- `pytest -m slow` - Run only slow tests
+- `pytest -m examples` - Run example tests (normally skipped)
+- `pytest -k "keyword"` - Run tests matching a keyword
+
+#### Common Test Patterns
+The `tests/conftest.py` file provides shared fixtures:
+- `solver_fixture` - Parameterized solver fixture (HiGHS, Gurobi)
+- `highs_solver` - HiGHS solver instance
+- Coordinate configuration fixtures for timesteps, periods, scenarios
+
+Use these fixtures by adding them as function parameters:
 ```python
-def create_storage(
-    label: str,
-    capacity_kwh: float,
-    charging_power_kw: float
-) -> Storage:
-    """
-    Create a battery storage component.
-
-    Args:
-        label: Unique identifier
-        capacity_kwh: Storage capacity [kWh]
-        charging_power_kw: Maximum charging power [kW]
-    """
+def test_my_feature(solver_fixture):
+    # solver_fixture is automatically provided by pytest
+    model = fx.FlowSystem(...)
+    model.solve(solver_fixture)
 ```
 
-## What We Welcome
+#### Testing Guidelines
+- Write tests for all new functionality
+- Ensure all tests pass before submitting a PR
+- Aim for 100% test coverage for new code
+- Use descriptive test names that explain what's being tested
+- Add the `@pytest.mark.slow` decorator for tests that take >5 seconds
 
-- 🔧 New energy components (batteries, heat pumps, etc.)
-- 📚 Documentation improvements
-- 🐛 Bug fixes
-- 🧪 Test cases
-- 💡 Energy system examples
+### Coding Guidelines
+- Follow [PEP 8](https://pep8.org/) style guidelines
+- Write clear, self-documenting code with helpful comments
+- Include type hints for function signatures
+- Create or update tests for new functionality
+- Aim for 100% test coverage for new code
 
-## Questions?
+---
 
-- 📖 [Documentation](https://flixopt.github.io/flixopt/latest/)
-- 💬 [Discussions](https://github.com/flixOpt/flixopt/discussions)
-- 📧 Contact maintainers (see README)
+## Workflow
+
+### Branches & Pull Requests
+1. Create a feature branch from `main`:
+   ```bash
+   git checkout -b feature/your-feature-name
+   ```
+
+2. Make your changes and commit them with clear messages
+
+3. Push your branch and open a Pull Request
+
+4. Ensure all CI checks pass
+
+### Branch Naming
+- Features: `feature/feature-name`
+- Bug fixes: `fix/bug-description`
+- Documentation: `docs/what-changed`
+
+### Commit Messages
+- Use clear, descriptive commit messages
+- Start with a verb (Add, Fix, Update, Remove, etc.)
+- Keep the first line under 72 characters
 
 ---
 
-**Every contribution helps advance sustainable energy solutions! 🌱⚡**
+## Releases
+
+We follow **Semantic Versioning** (MAJOR.MINOR.PATCH). Releases are created manually from the `main` branch by maintainers.
+
+---
+
+## Questions?
+
+If you have questions or need help, feel free to:
+- Open a discussion on GitHub
+- Ask in an issue
+- Reach out to the maintainers
+
+Thank you for contributing to FlixOpt!

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -6,106 +6,70 @@ body:
 - type: markdown
   attributes:
     value: |
-      Thanks for taking the time to fill out this bug report!
-
-      **Before submitting**: Please search [existing issues](https://github.com/flixOpt/flixopt/issues) to avoid duplicates.
-
-- type: checkboxes
-  id: checks
-  attributes:
-    label: Version Confirmation
-    description: Please confirm you can reproduce this on a supported version
-    options:
-    - label: I have confirmed this bug exists on the latest [release](https://github.com/flixOpt/flixopt/releases) of FlixOpt
-      required: true
+      **Quick guide**: Describe what's broken, provide code to reproduce if possible.
+      For simple bugs, just fill the first field.
 
 - type: textarea
   id: problem
   attributes:
-    label: Bug Description
-    description: Clearly describe what went wrong
-    placeholder: |
-      What happened? What did you expect to happen instead?
-
-      Include any error messages or unexpected outputs.
+    label: What's broken?
+    description: Describe the bug - what happened vs. what you expected
   validations:
     required: true
 
 - type: textarea
   id: example
   attributes:
-    label: Minimal Reproducible Example
+    label: Code to reproduce
     description: |
       Provide the smallest possible code example that reproduces the bug.
       See [how to create minimal bug reports](https://matthewrocklin.com/minimal-bug-reports).
-    placeholder: |
-      import flixopt as fx
+    value: |
       import pandas as pd
+      import numpy as np
+      import flixopt as fx
 
-      # Minimal example that reproduces the bug
-      timesteps = pd.date_range('2024-01-01', periods=24, freq='h')
-      flow_system = fx.FlowSystem(timesteps)
+      fx.CONFIG.Logging.console = True
+      fx.CONFIG.Logging.level = 'DEBUG'
+      fx.CONFIG.apply()
+      flow_system = fx.FlowSystem(pd.date_range('2020-01-01', periods=3, freq='h'))
 
-      # Add components that trigger the bug...
+      flow_system.add_elements(
+          fx.Bus('Heat'),
+          fx.Bus('Gas'),
+          fx.Effect('Costs', '€', 'Cost', is_standard=True, is_objective=True),
+          fx.linear_converters.Boiler(
+              'Boiler',
+              eta=0.5,
+              Q_th=fx.Flow(label='Heat', bus='Heat', size=50),
+              Q_fu=fx.Flow(label='Gas', bus='Gas'),
+          ),
+          fx.Sink(
+              'Sink',
+              inputs=[
+                  fx.Flow(label='Demand', bus='Heat', size=1, fixed_relative_profile=np.array([30, 0, 20]))
+              ],
+          ),
+          fx.Source(
+              'Source',
+              outputs=[fx.Flow(label='Gas', bus='Gas', size=1000, effects_per_flow_hour=0.04)],
+          ),
+      )
+
+      calculation = fx.FullCalculation('Simulation1', flow_system).do_modeling().solve(fx.solvers.HighsSolver(0.01, 60))
 
-      # Show the problematic operation
-      result = flow_system.solve()  # This should fail/behave unexpectedly
     render: python
-  validations:
-    required: true
 
 - type: textarea
   id: error-output
   attributes:
-    label: Error Output
-    description: If there's an error message, paste the full traceback here
+    label: Error message
+    description: Paste the full traceback if there is one
     render: shell
 
-- type: dropdown
-  id: solver
-  attributes:
-    label: Solver Used
-    description: Which solver were you using?
-    options:
-      - HiGHS (default)
-      - Gurobi
-      - CPLEX
-      - GLPK
-      - CBC
-      - Other (specify below)
-  validations:
-    required: true
-
-- type: input
-  id: os
-  attributes:
-    label: Operating System
-    placeholder: "e.g., Windows 11, macOS 14.2, Ubuntu 22.04"
-  validations:
-    required: true
-
-- type: input
-  id: python-version
-  attributes:
-    label: Python Version
-    placeholder: "e.g., 3.11.5"
-  validations:
-    required: true
-
 - type: textarea
-  id: environment
+  id: context
   attributes:
-    label: Environment Info
-    description: |
-      Run one of these commands and paste the output:
-      - `pip freeze`
-      - `conda env export`
-    render: shell
-    value: >
-      <details>
-
-      ```
-      Replace this with your environment info
-      ```
-
-      </details>
+    label: Additional context
+    description: Solver, Python/OS version, environment details, or anything else relevant
+    placeholder: "HiGHS solver, Python 3.11, macOS 14"

.github/ISSUE_TEMPLATE/config.yml

@@ -1,14 +1,8 @@
-blank_issues_enabled: false
+blank_issues_enabled: true
 contact_links:
   - name: 🤔 Modeling Questions
     url: https://github.com/flixOpt/flixopt/discussions/categories/q-a
     about: "How to model specific energy systems, components, and constraints"
-  - name: ⚡ Performance & Optimization
-    url: https://github.com/flixOpt/flixopt/discussions/categories/performance
-    about: "Solver performance, memory usage, and optimization speed issues"
-  - name: 💡 Ideas & Suggestions
-    url: https://github.com/flixOpt/flixopt/discussions/categories/ideas
-    about: "Share ideas and discuss potential improvements with the community"
   - name: 📖 Documentation
     url: https://flixopt.github.io/flixopt/latest/
-    about: "Browse guides, API reference, and examples"
+    about: "Guides, API reference, and examples"