query-handler 1.0.8
This package contains Query DTO and Model Enums

# QueryDTO and Related Classes

This repository contains a Python implementation of classes used for querying and filtering data models with the help of the Pydantic library. These classes aim to provide a standardized way to build flexible and reusable query objects, with support for sorting, filtering, pagination, and field population.

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## Table of Contents
- [Features](#features)
- [Classes](#classes)
  - [Model Enum](#model-enum)
  - [Sort Class](#sort-class)
  - [Filter Class](#filter-class)
  - [Populate Class](#populate-class)
  - [Pagination Class](#pagination-class)
  - [QueryDTO Class](#querydto-class)
- [Usage](#usage)
- [Installation](#installation)
- [License](#license)

---

## Features
- **Model Identification**: Enumerate specific models using the `Model` enum class.
- **Sorting**: Specify fields and order (ascending/descending).
- **Filtering**: Create flexible queries using operators, fields, and values.
- **Population**: Specify which fields to include in the query.
- **Pagination**: Limit results by defining page numbers and sizes.
- **Logical Operations**: Define whether filters use `AND` or `OR` operations.

---

## Classes

### Model Enum
The `Model` Enum class defines constants for different models or entities.
```python
class Model(Enum):
    blog = 1
    appliance = 2
    brand = 3
    product = 4
    faq = 5
    contact = 6
    advice_article = 7
```

### Sort Class
Defines sorting parameters for a query.
```python
class Sort(BaseModel):
    field: str  # Field to sort by
    order: str  # Order ('asc' for ascending, 'desc' for descending)
```

### Filter Class
Defines filters to be applied to a query.
```python
class Filter(BaseModel):
    operator: str  # Logical operator (e.g., 'eq', 'eqi', 'contains', 'notNull', 'and','or')
    field: str     # Field to filter by
    value: str     # Value to compare the field with
```

### Populate Class
Specifies fields to include in the query response.
```python
class Populate(BaseModel):
    field: str  # Field name to populate
```

### Pagination Class
Defines pagination parameters for a query.
```python
class Pagination(BaseModel):
    page: int      # Current page number
    pagesize: int  # Number of records per page
```

### QueryDTO Class
The main Data Transfer Object (DTO) class for constructing queries. It includes options for model identification, filters, sorting, pagination, and field population.
```python
class QueryDTO(BaseModel):
    model: Optional[int] = None  # Entity or module name (from the Model enum)
    id: Optional[int] = None  # -1 for list, >0 for specific record ID
    slug: Optional[str] = None  # Slug URLs
    sorts: Optional[List[Sort]] = None  # List of sorting parameters
    filters: Optional[List[Filter]] = None  # List of filters
    union_filter_operator: Optional[str] = "and"  # Logical operator ('and', 'or')
    populate: Optional[List[Populate]] = None  # Fields to include
    pagination: Optional[Pagination] = None  # Pagination details
```

---

## Usage
To use these classes, import them into your project and instantiate them as needed. For example:

```python
from your_module import QueryDTO, Sort, Filter, Populate, Pagination

# Example query
query = QueryDTO(
    model=1,  # Refers to 'blog'
    id=-1,  # Fetch a list
    sorts=[Sort(field="created_at", order="desc")],
    filters=[
        Filter(operator="=", field="status", value="published"),
        Filter(operator=">=", field="created_at", value="2023-01-01")
    ],
    union_filter_operator="and",
    populate=[Populate(field="author")],
    pagination=Pagination(page=1, pagesize=10)
)
```

---

## Installation
1. Clone the repository.
2. Ensure you have Python 3.7 or later installed.
3. Install Pydantic:
   ```bash
   pip install pydantic
   ```

---

## License
This project is licensed under the MIT License. Feel free to use and modify it as needed.