Add support for DirectivesEstimator, include and skip directives and added shortcuts for complexity calculation

README.md

@@ -1,2 +1,166 @@
 # graphql-complexity
 Python library to compute the complexity of a GraphQL operation
+
+![Unit Tests](https://github.com/Checho3388/graphql-complexity/actions/workflows/python-package.yml/badge.svg)
+
+
+## Usage
+The library uses the query complexity algorithm to compute the complexity of a GraphQL operation. The algorithm is 
+based on the number of fields requested in the operation and the depth of the query.
+
+```python
+from graphql_complexity import (get_complexity, SimpleEstimator)
+
+query = """
+    query SomeQuery {
+        user {
+            id
+            name
+        }
+    }
+"""
+
+complexity = get_complexity(query, estimator=SimpleEstimator(complexity=1, multiplier=1))
+if complexity > 10:
+    raise Exception("Query is too complex")
+```
+
+## Estimators
+In order to get the complexity of a query, an estimator needs to be defined. The main responsibility of
+the estimator is to give each node an integer value representing its complexity and (optionally) a
+multiplier that reflects the complexity in relation to the depth of the query.
+
+There are two built-in estimators, plus the capability to create any new estimator by
+implementing the `ComplexityEstimator` interface.
+
+### Estimate fields complexity based on constants for complexity and multiplier
+
+This estimator assigns a **constant** complexity value to each field and multiplies
+it by another **constant** which is propagated along the depth of the query.
+
+```python
+from graphql_complexity import SimpleEstimator
+
+
+estimator = SimpleEstimator(complexity=2, multiplier=1)
+```
+
+Given the following query:
+```qgl
+query {
+    user {
+        name
+        email
+    }
+}
+```
+As the complexity and multiplier are constant, the complexity of the fields will be:
+
+| Field | Complexity    |
+|-------|---------------|
+| user  | `1`           |
+| name  | `2 * (2 * 1)` |
+| email | `2 * (2 * 1)` |
+
+And the total complexity will be `6`.
+
+### Define fields complexity using schema directives
+
+Assigns a complexity value to each field and multiplies it by the depth of the query. 
+It also supports the `@complexity` directive to assign a custom complexity value to a field.
+
+This approach requires to provide the schema to the estimator.
+
+```python
+from graphql_complexity import DirectivesEstimator
+
+
+schema = """
+directive @complexity(
+  value: Int!
+) on FIELD_DEFINITION
+
+type Query {
+  oneField: String @complexity(value: 5)
+  otherField: String @complexity(value: 1)
+  withoutDirective: String
+}
+"""
+
+estimator = DirectivesEstimator(schema)
+```
+
+Given the schema from above and the following query:
+```qgl
+query {
+    oneField
+    otherField
+    withoutDirective
+}
+```
+
+The complexity of the fields will be:
+
+| Field            | Complexity | Comment                                                                                           |
+|------------------|------------|---------------------------------------------------------------------------------------------------|
+| oneField         | `5`        |                                                                                                   |
+| otherField       | `1`        |                                                                                                   |
+| withoutDirective | `1`        | The default complexity for fields without directive is `1`, this can be modified by parameters.   |
+
+And the total complexity will be `7`.
+
+### Create a custom estimator
+This option allows to define a custom estimator to compute the complexity of a field using the `ComplexityEstimator` interface. For example:
+
+```python
+from graphql_complexity import ComplexityEstimator
+
+
+class CustomEstimator(ComplexityEstimator):
+    def get_field_complexity(self, node, key, parent, path, ancestors) -> int:
+        if node.name.value == "specificField":
+            return 100
+        return 1
+
+    def get_field_multiplier(self, node, key, parent, path, ancestors) -> int:
+        return 1
+```
+
+
+## Supported libraries (based on GraphQL-core)
+The library is compatible with the following GraphQL libraries:
+
+### Strawberry
+
+
+The library is compatible with [strawberry-graphql](https://pypi.org/project/strawberry-graphql/). 
+To use the library with strawberry-graphql, you need to install the library with the `strawberry-graphql` extra.
+```shell
+poetry install --extras strawberry-graphql
+```
+
+To use the library with [strawberry-graphql](https://pypi.org/project/strawberry-graphql/), you need to use the `build_complexity_extension` method to build
+the complexity extension and add it to the schema. This method receives an estimator and returns a complexity 
+extension that can be added to the schema.
+
+```python
+import strawberry
+from graphql_complexity.extensions.strawberry_graphql import build_complexity_extension
+
+@strawberry.type
+class Query:
+    @strawberry.field()
+    def hello_world(self) -> str:
+        return "Hello world!"
+
+extension = build_complexity_extension()
+schema = strawberry.Schema(query=Query, extensions=[extension])
+
+schema.execute_sync("query { helloWorld }")
+```
+The `build_complexity_extension` method accepts an estimator as optional argument giving the possibility to use one
+of the built-in estimators or a custom estimator.
+
+## Credits
+
+Estimators idea was heavily inspired by [graphql-query-complexity](https://github.com/slicknode/graphql-query-complexity).

pyproject.toml

@@ -1,8 +1,11 @@
 [tool.poetry]
-name = "graphql-complexity"
+name = "graphql_complexity"
 version = "0.1.0"
 description = "A python library that provides complexity calculation helpers for GraphQL"
 authors = ["Checho3388 <[email protected]>"]
+packages = [
+    { include = "graphql_complexity", from = "src" },
+]
 license = "MIT"
 readme = "README.md"
 

src/graphql_complexity/__init__.py

@@ -0,0 +1,14 @@
+from graphql_complexity.evaluator.complexity import get_complexity
+
+from .estimators import (
+    ComplexityEstimator,
+    DirectivesEstimator,
+    SimpleEstimator
+)
+
+__all__ = [
+    "get_complexity",
+    "SimpleEstimator",
+    "ComplexityEstimator",
+    "DirectivesEstimator",
+]

src/graphql_complexity/estimators/__init__.py

@@ -0,0 +1,5 @@
+from .base import ComplexityEstimator
+from .directive import DirectivesEstimator
+from .simple import SimpleEstimator
+
+__all__ = ["ComplexityEstimator", "SimpleEstimator", "DirectivesEstimator"]

src/graphql_complexity/estimators/base.py

@@ -0,0 +1,11 @@
+import abc
+
+
+class ComplexityEstimator(abc.ABC):
+    @abc.abstractmethod
+    def get_field_complexity(self, node, key, parent, path, ancestors) -> int:
+        """Return the complexity of the field."""
+
+    @abc.abstractmethod
+    def get_field_multiplier(self, node, key, parent, path, ancestors) -> int:
+        """Return the multiplier that will be applied to the children of the given node."""