flask-http-middleware 0.4.4
A module to create middleware with direct access to `request` and `response`
Keywords: flask, middleware, http, request, response

# Flask HTTP Middleware
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## Installation
```
pip install flask-http-middleware
```

## Description
A module to create flask middleware with direct access to `request` and `response`.

This module implement the starlette's (FastAPI) BaseHTTPMiddleware style to Flask.

## Changelogs
- v0.0
    - First Upload
- v0.1
    - Allow middlewares stacking
- v0.2
    - Add support for `flask>=2.2.x`
- v0.3
    - Add support for `flask>=2.3.x`
- v0.4
    - Add support for `flask>=3.x`

## How to use ?

### Example: adding a response header
```
import time
from flask import Flask
from flask_http_middleware import MiddlewareManager, BaseHTTPMiddleware

app = Flask(__name__)

class MetricsMiddleware(BaseHTTPMiddleware):
    def __init__(self):
        super().__init__()

    def dispatch(self, request, call_next):
        t0 = time.time()
        response = call_next(request)
        response_time = time.time()-t0
        response.headers.add("response_time", response_time)
        return response

app.wsgi_app = MiddlewareManager(app)
app.wsgi_app.add_middleware(MetricsMiddleware)

@app.get("/health")
def health():
    return {"message":"I'm healthy"}

if __name__ == "__main__":
    app.run()
```
- Note: you can put your `MetricsMiddleware` class in different file

Above example is equals with `app.before_request` and `app.after_request` decorated function.

```
@app.before_request
def start_metrics():
    g.t0 = time.time()

@app.after_request
def stop_metrics(response):
    response_time = time.time()-g.t0
    response.headers.add("response_time", response_time)
    return response
```

---

### Example: Authentication
```
import time
from flask import Flask, jsonify
from flask_http_middleware import MiddlewareManager, BaseHTTPMiddleware

app = Flask(__name__)

class AccessMiddleware(BaseHTTPMiddleware):
    def __init__(self):
        super().__init__()

    def dispatch(self, request, call_next):
        if request.headers.get("token") == "secret":
            return call_next(request)
        else:
            return jsonify({"message":"invalid token"})

app.wsgi_app = MiddlewareManager(app)
app.wsgi_app.add_middleware(AccessMiddleware)

@app.get("/health")
def health():
    return {"message":"I'm healthy"}

if __name__ == "__main__":
    app.run()
```

---

### Example: add some routers security
```
import time
from flask import Flask, jsonify
from flask_http_middleware import MiddlewareManager, BaseHTTPMiddleware

app = Flask(__name__)

class SecureRoutersMiddleware(BaseHTTPMiddleware):
    def __init__(self, secured_routers = []):
        super().__init__()
        self.secured_routers = secured_routers

    def dispatch(self, request, call_next):
        if request.path in self.secured_routers:
            if request.headers.get("token") == "secret":
                return call_next(request)
            else:
                return jsonify({"message":"invalid token"})
        else:
            return call_next(request)

secured_routers = ["/check_secured"]

app.wsgi_app = MiddlewareManager(app)
app.wsgi_app.add_middleware(SecureRoutersMiddleware, secured_routers=secured_routers)

@app.get("/health")
def health():
    return {"message":"I'm healthy"}

@app.get("/check_secured")
def health():
    return {"message":"Security bypassed"}

if __name__ == "__main__":
    app.run()
```

---

### Example: add error handling
```
import time
from flask import Flask, jsonify
from flask_http_middleware import MiddlewareManager, BaseHTTPMiddleware

app = Flask(__name__)

class AccessMiddleware(BaseHTTPMiddleware):
    def __init__(self):
        super().__init__()

    def dispatch(self, request, call_next):
        if request.headers.get("token") == "secret":
            return call_next(request)
        else:
            raise Exception("Authentication Failed")

    def error_handler(self, error):
        return jsonify({"error": str(error)})

app.wsgi_app = MiddlewareManager(app)
app.wsgi_app.add_middleware(AccessMiddleware)

@app.get("/health")
def health():
    return {"message":"I'm healthy"}

if __name__ == "__main__":
    app.run()
```

### Example: Stacking Middleware
You can also stack your middleware

`middleware.py`
```
import time
from flask import jsonify
from flask_http_middleware import BaseHTTPMiddleware

class AccessMiddleware(BaseHTTPMiddleware):
    def __init__(self):
        super().__init__()

    def dispatch(self, request, call_next):
        if request.headers.get("token") == "secret":
            return call_next(request)
        else:
            raise Exception("Authentication Failed")

    def error_handler(self, error):
        return jsonify({"error": str(error)})


class MetricsMiddleware(BaseHTTPMiddleware):
    def __init__(self):
        super().__init__()

    def dispatch(self, request, call_next):
        t0 = time.time()
        response = call_next(request)
        response_time = time.time()-t0
        response.headers.add("response_time", response_time)
        return response


class SecureRoutersMiddleware(BaseHTTPMiddleware):
    def __init__(self, secured_routers = []):
        super().__init__()
        self.secured_routers = secured_routers

    def dispatch(self, request, call_next):
        if request.path in self.secured_routers:
            if request.headers.get("token") == "secret":
                return call_next(request)
            else:
                return jsonify({"message":"invalid token"})
        else:
            return call_next(request)

```

your `main.py`
```
import time
from flask import Flask, jsonify
from flask_http_middleware import MiddlewareManager
from middleware import AccessMiddleware, MetricsMiddleware, SecureRoutersMiddleware

app = Flask(__name__)

my_secured_routers = ["/check_secured"]

app.wsgi_app = MiddlewareManager(app)

app.wsgi_app.add_middleware(AccessMiddleware)
app.wsgi_app.add_middleware(MetricsMiddleware)
app.wsgi_app.add_middleware(SecureRoutersMiddleware, secured_routers=my_secured_routers)

@app.get("/health")
def health():
    return {"message":"I'm healthy"}

@app.get("/check_secured")
def health():
    return {"message":"Security bypassed"}

if __name__ == "__main__":
    app.run()
```