import flask
import requests
from urllib.parse import urljoin

##
# Return a error response to the client.
#
# @param abort_status_code status code to return along the response.
# @param params _kw_ arguments to passed verbatim to the templating engine.
def err_abort(abort_status_code, **params):
    t = flask.render_template("templates/error.html", **params)
    flask.abort(flask.make_response(t, abort_status_code))

##
# POST a request to the backend, and return a error
# response if any error occurs.
#
# @param endpoint the backend endpoint where to POST
#        this request.
# @param json the POST's body.
# @return the backend response (JSON format).
def backend_post(backend_url, endpoint, json):
    headers = {"Authorization": "ApiKey sandbox"}
    final_url = urljoin(backend_url, endpoint)
    print("POSTing to: " + final_url)
    try:
        resp = requests.post(
            final_url, json=json, headers=headers
        )
    except requests.ConnectionError:
        err_abort(500, message="Could not establish connection to backend")
    try:
        response_json = resp.json()
    except ValueError:
        err_abort(
            500,
            message="Could not parse response from backend",
            status_code=resp.status_code
        )
    if resp.status_code != 200:
        err_abort(
            500,
            message="Backend returned error status",
            json=response_json,
            status_code=resp.status_code
        )
    return response_json


##
# Issue a GET request to the backend.
#
# @param endpoint the backend endpoint where to issue the request.
# @param params (dict type of) URL parameters to append to the request.
# @return the JSON response from the backend, or a error response
#         if something unexpected happens.
def backend_get(backend_url, endpoint, params):
    headers = {"Authorization": "ApiKey sandbox"}
    try:
        resp = requests.get(
            urljoin(backend_url, endpoint), params=params, headers=headers
        )
    except requests.ConnectionError:
        err_abort(500, message="Could not establish connection to backend")
    try:
        response_json = resp.json()
    except ValueError:
        err_abort(500, message="Could not parse response from backend")
    if resp.status_code != 200:
        err_abort(
            500,
            message="Backend returned error status",
            json=response_json,
            status_code=resp.status_code
        )
    return response_json