from flask import Flask, request, jsonify

data_store = {}

app = Flask(__name__)

@app.route("/counters", methods=['GET', 'POST'])
def handle_counters_endpoint():
    if request.method == 'GET':
        response_dict = {
            'all_counters': data_store
        }
        return jsonify(response_dict), 200
    elif request.method == 'POST':
        if request.content_type == 'application/json':
            body = request.get_json()

            if not "new_counter_name" in body.keys() or not "new_counter_starting_value" in body.keys():
                error_response = {
                    'status': 'ERROR',
                    'reason': 'Body for posting to /counters endpoint must contain both new_counter_name and new_counter_starting_value',
                    'input_body': body
                }
                return jsonify(error_response), 400

            data_store[request.get_json()['new_counter_name']] = request.get_json()['new_counter_starting_value']
            return jsonify({'status': 'OK'}), 200
        else:
            error_response = {
                'status': 'ERROR',
                'reason': 'Content Type for endpoint /counters must be application/json'
            }
            return jsonify(error_response), 400

@app.route("/counters/<counter_name>", methods=['GET'])
def handle_counters_subcounter_endpoint(counter_name):
    if not counter_name in data_store.keys():
        error_response = {
            'status': 'ERROR',
            'reason': 'Counter name {counter} does not exist'.format(counter=counter_name)
        }
        return jsonify(error_response), 404
    
    data_response = {
        'counter_name': counter_name,
        'counter_value': data_store[counter_name]
    }

    return jsonify(data_response), 200

@app.route("/counters/<counter_name>/increment", methods=['POST'])
def handle_counters_subcounter_increment(counter_name):
    if not counter_name in data_store.keys():
        error_response = {
            'status': 'ERROR',
            'reason': 'Counter name {counter} does not exist'.format(counter=counter_name)
        }
        return jsonify(error_response), 404
    
    data_response = {
        'counter_name': counter_name,
        'old_value': data_store[counter_name],
        'new_value': data_store[counter_name] + 1
    }

    data_store[counter_name] = data_store[counter_name] + 1

    return jsonify(data_response), 200

@app.route("/counters/<counter_name>/decrement", methods=['POST'])
def handle_counters_subcounter_decrement(counter_name):
    if not counter_name in data_store.keys():
        error_response = {
            'status': 'ERROR',
            'reason': 'Counter name {counter} does not exist'.format(counter=counter_name)
        }
        return jsonify(error_response), 404
    
    data_response = {
        'counter_name': counter_name,
        'old_value': data_store[counter_name],
        'new_value': data_store[counter_name] - 1
    }

    data_store[counter_name] = data_store[counter_name] - 1

    return jsonify(data_response), 200
    

if __name__ == '__main__':
    app.run(debug=True)