import re
import os
import sys
import json
import requests
import time
from sys import argv
from binascii import hexlify, unhexlify
from getopt import getopt, GetoptError
from requests import ConnectTimeout, ConnectionError
from uuid import uuid4

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.serialization import load_pem_public_key, load_pem_private_key
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.exceptions import InvalidSignature, UnsupportedAlgorithm

from apps.cli.blob import Blob
from apps.cli.help import help_add_appointment, help_get_appointment
from apps.cli import (
    DEFAULT_PISA_API_SERVER,
    DEFAULT_PISA_API_PORT,
    CLI_PUBLIC_KEY,
    CLI_PRIVATE_KEY,
    PISA_PUBLIC_KEY,
    APPOINTMENTS_FOLDER_NAME,
    logger,
)

from common.constants import LOCATOR_LEN_HEX


HTTP_OK = 200


# FIXME: TESTING ENDPOINT, WON'T BE THERE IN PRODUCTION
def generate_dummy_appointment():
    get_block_count_end_point = "http://{}:{}/get_block_count".format(pisa_api_server, pisa_api_port)
    r = requests.get(url=get_block_count_end_point, timeout=5)

    current_height = r.json().get("block_count")

    dummy_appointment_data = {
        "tx": os.urandom(192).hex(),
        "tx_id": os.urandom(32).hex(),
        "start_time": current_height + 5,
        "end_time": current_height + 10,
        "dispute_delta": 20,
    }

    print("Generating dummy appointment data:" "\n\n" + json.dumps(dummy_appointment_data, indent=4, sort_keys=True))

    json.dump(dummy_appointment_data, open("dummy_appointment_data.json", "w"))

    print("\nData stored in dummy_appointment_data.json")


def sign_appointment(sk, appointment):
    data = json.dumps(appointment, sort_keys=True, separators=(",", ":")).encode("utf-8")
    return hexlify(sk.sign(data, ec.ECDSA(hashes.SHA256()))).decode("utf-8")


# Loads and returns Pisa keys from disk
def load_key_file_data(file_name):
    try:
        with open(file_name, "r") as key_file:
            key_pem = key_file.read().encode("utf-8")
        return key_pem

    except FileNotFoundError:
        raise FileNotFoundError("File not found.")


# Deserialize public key from pem data.
def load_public_key(pk_pem):
    try:
        pisa_pk = load_pem_public_key(pk_pem, backend=default_backend())
        return pisa_pk

    except UnsupportedAlgorithm:
        raise ValueError("Could not deserialize the public key (unsupported algorithm).")


# Deserialize private key from pem data.
def load_private_key(sk_pem):
    try:
        cli_sk = load_pem_private_key(sk_pem, None, backend=default_backend())
        return cli_sk

    except UnsupportedAlgorithm:
        raise ValueError("Could not deserialize the private key (unsupported algorithm).")


def compute_locator(tx_id):
    return tx_id[:LOCATOR_LEN_HEX]


# returning True or False accordingly.
def is_appointment_signature_valid(appointment, signature, pk):
    try:
        sig_bytes = unhexlify(signature.encode("utf-8"))
        data = json.dumps(appointment, sort_keys=True, separators=(",", ":")).encode("utf-8")
        pk.verify(sig_bytes, data, ec.ECDSA(hashes.SHA256()))
        return True

    except InvalidSignature:
        return False


# Makes sure that the folder APPOINTMENTS_FOLDER_NAME exists, then saves the appointment and signature in it.
def save_signed_appointment(appointment, signature):
    # Create the appointments directory if it doesn't already exist
    os.makedirs(APPOINTMENTS_FOLDER_NAME, exist_ok=True)

    timestamp = int(time.time())
    locator = appointment["locator"]
    uuid = uuid4().hex  # prevent filename collisions

    filename = "{}/appointment-{}-{}-{}.json".format(APPOINTMENTS_FOLDER_NAME, timestamp, locator, uuid)
    data = {"appointment": appointment, "signature": signature}

    with open(filename, "w") as f:
        json.dump(data, f)


def add_appointment(args):
    appointment_data = None
    use_help = "Use 'help add_appointment' for help of how to use the command."

    if not args:
        logger.error("No appointment data provided. " + use_help)
        return False

    arg_opt = args.pop(0)

    try:
        if arg_opt in ["-h", "--help"]:
            sys.exit(help_add_appointment())

        if arg_opt in ["-f", "--file"]:
            fin = args.pop(0)
            if not os.path.isfile(fin):
                logger.error("Can't find file " + fin)
                return False

            try:
                with open(fin) as f:
                    appointment_data = json.load(f)

            except IOError as e:
                logger.error("I/O error({}): {}".format(e.errno, e.strerror))
                return False
        else:
            appointment_data = json.loads(arg_opt)

    except json.JSONDecodeError:
        logger.error("Non-JSON encoded data provided as appointment. " + use_help)
        return False

    if not appointment_data:
        logger.error("The provided JSON is empty.")
        return False

    valid_locator = check_txid_format(appointment_data.get("tx_id"))

    if not valid_locator:
        logger.error("The provided locator is not valid.")
        return False

    add_appointment_endpoint = "http://{}:{}".format(pisa_api_server, pisa_api_port)
    appointment = build_appointment(
        appointment_data.get("tx"),
        appointment_data.get("tx_id"),
        appointment_data.get("start_time"),
        appointment_data.get("end_time"),
        appointment_data.get("dispute_delta"),
    )

    try:
        sk_pem = load_key_file_data(CLI_PRIVATE_KEY)
        cli_sk = load_private_key(sk_pem)

    except ValueError:
        logger.error("Failed to deserialize the public key. It might be in an unsupported format.")
        return False

    except FileNotFoundError:
        logger.error("Client's private key file not found. Please check your settings.")
        return False

    except IOError as e:
        logger.error("I/O error({}): {}".format(e.errno, e.strerror))
        return False

    signature = sign_appointment(cli_sk, appointment)
    try:
        cli_pk_pem = load_key_file_data(CLI_PUBLIC_KEY)

    except FileNotFoundError:
        logger.error("Client's private key file not found. Please check your settings.")
        return False

    except IOError as e:
        logger.error("I/O error({}): {}".format(e.errno, e.strerror))
        return False

    data = {"appointment": appointment, "signature": signature, "public_key": cli_pk_pem.decode("utf-8")}

    appointment_json = json.dumps(data, sort_keys=True, separators=(",", ":"))

    logger.info("Sending appointment to PISA")

    try:
        r = requests.post(url=add_appointment_endpoint, json=appointment_json, timeout=5)

        response_json = r.json()

    except json.JSONDecodeError:
        logger.error("The response was not valid JSON.")
        return False

    except ConnectTimeout:
        logger.error("Can't connect to pisa API. Connection timeout.")
        return False

    except ConnectionError:
        logger.error("Can't connect to pisa API. Server cannot be reached.")
        return False

    if r.status_code != HTTP_OK:
        if "error" not in response_json:
            logger.error("The server returned status code {}, but no error description.".format(r.status_code))
        else:
            error = response_json["error"]
            logger.error(
                "The server returned status code {}, and the following error: {}.".format(r.status_code, error)
            )
        return False

    if "signature" not in response_json:
        logger.error("The response does not contain the signature of the appointment.")
        return False

    signature = response_json["signature"]
    # verify that the returned signature is valid
    try:
        pk_pem = load_key_file_data(PISA_PUBLIC_KEY)
        pk = load_public_key(pk_pem)
        is_sig_valid = is_appointment_signature_valid(appointment, signature, pk)

    except ValueError:
        logger.error("Failed to deserialize the public key. It might be in an unsupported format.")
        return False

    except FileNotFoundError:
        logger.error("Pisa's public key file not found. Please check your settings.")
        return False

    except IOError as e:
        logger.error("I/O error({}): {}".format(e.errno, e.strerror))
        return False

    if not is_sig_valid:
        logger.error("The returned appointment's signature is invalid.")
        return False

    logger.info("Appointment accepted and signed by Pisa.")
    # all good, store appointment and signature
    try:
        save_signed_appointment(appointment, signature)

    except OSError as e:
        logger.error("There was an error while saving the appointment: {}".format(e))
        return False

    return True


def get_appointment(args):
    if not args:
        logger.error("No arguments were given.")
        return False

    arg_opt = args.pop(0)

    if arg_opt in ["-h", "--help"]:
        sys.exit(help_get_appointment())
    else:
        locator = arg_opt
        valid_locator = check_txid_format(locator)

    if not valid_locator:
        logger.error("The provided locator is not valid: {}".format(locator))
        return False

    get_appointment_endpoint = "http://{}:{}/get_appointment".format(pisa_api_server, pisa_api_port)
    parameters = "?locator={}".format(locator)

    try:
        r = requests.get(url=get_appointment_endpoint + parameters, timeout=5)

        print(json.dumps(r.json(), indent=4, sort_keys=True))
    except ConnectTimeout:
        logger.error("Can't connect to pisa API. Connection timeout.")
        return False

    except ConnectionError:
        logger.error("Can't connect to pisa API. Server cannot be reached.")
        return False

    return True


def build_appointment(tx, tx_id, start_time, end_time, dispute_delta):
    locator = compute_locator(tx_id)

    # FIXME: The blob data should contain more things that just the transaction. Leaving like this for now.
    blob = Blob(tx)
    encrypted_blob = blob.encrypt(tx_id)

    appointment = {
        "locator": locator,
        "start_time": start_time,
        "end_time": end_time,
        "dispute_delta": dispute_delta,
        "encrypted_blob": encrypted_blob,
    }

    return appointment


def check_txid_format(txid):
    if len(txid) != 64:
        sys.exit("locator does not matches the expected size (32-byte / 64 hex chars).")

    # TODO: #12-check-txid-regexp
    return re.search(r"^[0-9A-Fa-f]+$", txid) is not None


def show_usage():
    return (
        "USAGE: "
        "\n\tpython pisa-cli.py [global options] command [command options] [arguments]"
        "\n\nCOMMANDS:"
        "\n\tadd_appointment \tRegisters a json formatted appointment to the PISA server."
        "\n\tget_appointment \tGets json formatted data about an appointment from the PISA server."
        "\n\thelp \t\t\tShows a list of commands or help for a specific command."
        "\n\nGLOBAL OPTIONS:"
        "\n\t-s, --server \tAPI server where to send the requests. Defaults to btc.pisa.watch (modifiable in "
        "__init__.py)"
        "\n\t-p, --port \tAPI port where to send the requests. Defaults to 9814 (modifiable in __init__.py)"
        "\n\t-d, --debug \tshows debug information and stores it in pisa.log"
        "\n\t-h --help \tshows this message."
    )


if __name__ == "__main__":
    pisa_api_server = DEFAULT_PISA_API_SERVER
    pisa_api_port = DEFAULT_PISA_API_PORT
    commands = ["add_appointment", "get_appointment", "help"]
    testing_commands = ["generate_dummy_appointment"]

    try:
        opts, args = getopt(argv[1:], "s:p:h", ["server", "port", "help"])

        for opt, arg in opts:
            if opt in ["-s", "server"]:
                if arg:
                    pisa_api_server = arg

            if opt in ["-p", "--port"]:
                if arg:
                    pisa_api_port = int(arg)

            if opt in ["-h", "--help"]:
                sys.exit(show_usage())

        if args:
            command = args.pop(0)

            if command in commands:
                if command == "add_appointment":
                    add_appointment(args)

                elif command == "get_appointment":
                    get_appointment(args)

                elif command == "help":
                    if args:
                        command = args.pop(0)

                        if command == "add_appointment":
                            sys.exit(help_add_appointment())

                        elif command == "get_appointment":
                            sys.exit(help_get_appointment())

                        else:
                            logger.error("Unknown command. Use help to check the list of available commands")

                    else:
                        sys.exit(show_usage())

            # FIXME: testing command, not for production
            elif command in testing_commands:
                if command == "generate_dummy_appointment":
                    generate_dummy_appointment()

            else:
                logger.error("Unknown command. Use help to check the list of available commands")

        else:
            logger.error("No command provided. Use help to check the list of available commands.")

    except GetoptError as e:
        logger.error("{}".format(e))

    except json.JSONDecodeError as e:
        logger.error("Non-JSON encoded appointment passed as parameter.")