"""
List of functions to get data from Flux Kustomizations and Helmreleases
"""
import crypt
import secrets
import string

import jinja2
import yaml
from kubernetes import client, config
from kubernetes.client import api_client
from kubernetes.client.exceptions import ApiException
from kubernetes.utils import create_from_yaml
from kubernetes.utils.create_from_yaml import FailToCreateError
from flask import current_app

# Load the kube config once
#
# By default this loads whatever we define in the `KUBECONFIG` env variable,
# otherwise loads the config from default locations, similar to what kubectl
# does.
config.load_kube_config()

def create_variables_secret(app_slug, variables_filepath):
    """Checks if a variables secret for app_name already exists, generates it if necessary.

    If a secret already exists, loops through keys from the template, and adds
    values for keys that miss in the Kubernetes secret, but are available in
    the template.

    :param app_slug: The slug of the app, used in the oauth secrets
    :type app_slug: string
    :param variables_filepath: The path to an existing jinja2 template
    :type variables_filepath: string
    :return: returns True, unless an exception gets raised by the Kubernetes API
    :rtype: boolean
    """
    new_secret_dict = read_template_to_dict(
            variables_filepath,
            {"app": app_slug})
    secret_name, secret_namespace = get_secret_metadata(new_secret_dict)
    current_secret_data = get_kubernetes_secret_data(
        secret_name, secret_namespace
    )
    if current_secret_data is None:
        # Create new secret
        update_secret = False
    elif current_secret_data.keys() != new_secret_dict["data"].keys():
        # Update current secret with new keys
        update_secret = True
        current_app.logger.info(
            f"Secret {secret_name} in namespace {secret_namespace}"
            " already exists. Merging..."
        )
        # Merge dicts. Values from current_secret_data take precedence
        new_secret_dict["data"] |= current_secret_data
    else:
        # Do Nothing
        current_app.logger.info(
            f"Secret {secret_name} in namespace {secret_namespace}"
            " is already in a good state, doing nothing."
        )
        return True
    current_app.logger.info(
        f"Storing secret {secret_name} in namespace"
        f" {secret_namespace} in cluster."
    )
    store_kubernetes_secret(
        new_secret_dict, secret_namespace, update=update_secret
    )
    return True


def get_secret_metadata(secret_dict):
    """
    Returns secret name and namespace from metadata field in a yaml string.

    :param secret_dict: Dictionary of the secret as returned by read_namespaced_secret
    :type secret_dict: dict
    :return: Tuple containing secret name and secret namespace
    :rtype: tuple
    """
    secret_name = secret_dict["metadata"]["name"]
    # default namespace is flux-system, but other namespace can be
    # provided in secret metadata
    if "namespace" in secret_dict["metadata"]:
        secret_namespace = secret_dict["metadata"]["namespace"]
    else:
        secret_namespace = "flux-system"
    return secret_name, secret_namespace


def get_kubernetes_secret_data(secret_name, namespace):
    """
    Get secret from Kubernetes

    :param secret_name: Name of the  secret
    :type secret_name: string
    :param namespace: Namespace of the secret
    :type namespace: string

    :return: The contents of a kubernetes secret or None if the secret does not exist.
    :rtype: dict or None
    """
    api_client_instance = api_client.ApiClient()
    api_instance = client.CoreV1Api(api_client_instance)
    try:
        secret = api_instance.read_namespaced_secret(secret_name, namespace).data
    except ApiException as ex:
        # 404 is expected when the optional secret does not exist.
        if ex.status != 404:
            raise ex
        return None
    return secret


def store_kubernetes_secret(secret_dict, namespace, update=False):
    """
    Stores either a new secret in the cluster, or updates an existing one.

    :param secret_dict: Dictionary of the secret as returned by read_namespaced_secret
    :type secret_dict: dict
    :param namespace: Namespace of the secret
    :type namespace: string
    :param update: If True, use `patch_kubernetes_secret`,
                   otherwise use `create_from_yaml` (default: False)
    :type update: boolean

    :return: None
    :rtype: None
    """
    api_client_instance = api_client.ApiClient()
    if update:
        verb = "updated"
        api_response = patch_kubernetes_secret(secret_dict, namespace)
    else:
        verb = "created"
        try:
            api_response = create_from_yaml(
                api_client_instance,
                yaml_objects=[secret_dict],
                namespace=namespace
            )
        except FailToCreateError as ex:
            current_app.logger.info(f"Secret not created because of exception {ex}")
            raise ex
    current_app.logger.info(f"Secret {verb} with api response: {api_response}")


def store_kustomization(kustomization_template_filepath, app_slug):
    """
    Add a kustomization that installs app {app_slug} to the cluster.

    :param kustomization_template_filepath: Path to the template that describes
        the kustomization. The template should have an `{{ app }}` entry.
    :type kustomization_template_filepath: string
    :param app_slug: Slug for the app, used to replace `{{ app }}` in the
        template
    :return: True on success
    :rtype: boolean
    """
    kustomization_dict = read_template_to_dict(kustomization_template_filepath,
            {"app": app_slug})
    custom_objects_api = client.CustomObjectsApi()
    try:
        api_response = custom_objects_api.create_namespaced_custom_object(
            group="kustomize.toolkit.fluxcd.io",
            version="v1beta2",
            namespace="flux-system",
            plural="kustomizations",
            body=kustomization_dict)
    except FailToCreateError as ex:
        current_app.logger.info(
            f"Could not create {app_slug} Kustomization because of exception {ex}")
        raise ex
    current_app.logger.debug(f"Kustomization created with api response: {api_response}")
    return True

def delete_kustomization(kustomization_name):
    """
    Deletes a kustomization.

    Note that this can also result in the deletion of an app's HelmReleases,
    PVCs (user data!), OAuth2Client, etc. Nothing will remain

    :param kustomization_name: name of the kustomization to delete
    :type kustomization_name: string

    :return: Response of delete API call
    :rtype: dict
    """
    custom_objects_api = client.CustomObjectsApi()
    body = client.V1DeleteOptions()
    try:
        api_response = custom_objects_api.delete_namespaced_custom_object(
            group="kustomize.toolkit.fluxcd.io",
            version="v1beta2",
            namespace="flux-system",
            plural="kustomizations",
            name=kustomization_name,
            body=body)
    except ApiException as ex:
        current_app.logger.info(
            f"Could not delete {kustomization_name} Kustomization because of exception {ex}")
        raise ex
    current_app.logger.debug(f"Kustomization deleted with api response: {api_response}")
    return api_response


def read_template_to_dict(template_filepath, template_globals):
    """
    Reads a Jinja2 template that contains yaml and turns it into a dict.

    :param template_filepath: The path to an existing Jinja2 template
    :type template_filepath: string
    :param template_globals: The variables substituted in the template
    :type template_globals: dict
    :return: dict, or None if anything fails
    """
    env = jinja2.Environment(
        extensions=["jinja2_base64_filters.Base64Filters"])
    env.filters["generate_password"] = generate_password
    # Check if k8s secret already exists, if not, generate it
    with open(template_filepath, encoding="UTF-8") as template_file:
        lines = template_file.read()
        templated_dict = yaml.safe_load(
            env.from_string(lines, globals=template_globals).render()
        )
        return templated_dict
    return None


def patch_kubernetes_secret(secret_dict, namespace):
    """
    Patches secret in the cluster with new data.

    Warning: currently ignores everything that's not in secret_dict["data"]

    :param secret_dict: Dictionary of the secret as returned by read_namespaced_secret
    :type secret_dict: dict
    :param namespace: Namespace of the secret
    :type namespace: string
    :return: Response of the patch API call
    """
    api_client_instance = api_client.ApiClient()
    api_instance = client.CoreV1Api(api_client_instance)
    name = secret_dict["metadata"]["name"]
    body = {}
    body["data"] = secret_dict["data"]
    return api_instance.patch_namespaced_secret(name, namespace, body)


def generate_password(length):
    """
    Generates a password with letters and digits.

    :param length: The amount of characters in the password
    :type length: int
    :return: Generated password
    :rtype: string
    """
    length = int(length)
    password = "".join((secrets.choice(string.ascii_letters + string.digits)
                        for i in range(length)))
    return password


def gen_htpasswd(user, password):
    """
    Generate htpasswd entry for user with password.

    :param user: Username used in the htpasswd entry
    :type user: string
    :param password: Password for the user, will get encrypted.
    :type password: string
    :return: htpassword line entry
    :rtype: string
    """
    return f"{user}:{crypt.crypt(password, crypt.mksalt(crypt.METHOD_SHA512))}"


def get_all_kustomizations(namespace='flux-system'):
    """
    Returns all flux kustomizations in a namespace.
    :param namespace: namespace that contains kustomizations. Default: `flux-system`
    :type namespace: str
    :return: 'items' in dict returned by CustomObjectsApi.list_namespaced_custom_object()
    :rtype: dict[]
    """
    api = client.CustomObjectsApi()
    api_response = api.list_namespaced_custom_object(
        group="kustomize.toolkit.fluxcd.io",
        version="v1beta1",
        plural="kustomizations",
        namespace=namespace,
    )
    return api_response


def get_all_helmreleases(namespace='stackspin', label_selector=""):
    """
    Lists all helmreleases in a certain namespace (stackspin by default)

    :param namespace: namespace that contains helmreleases. Default: `stackspin-apps`
    :type namespace: str
    :param label_selector: a label selector to limit the list (optional)
    :type label_selector: str

    :return: List of helmreleases
    :rtype: dict[]
    """
    api_instance = client.CustomObjectsApi()

    try:
        api_response = api_instance.list_namespaced_custom_object(
                group="helm.toolkit.fluxcd.io",
                version="v2beta1",
                namespace=namespace,
                plural="helmreleases",
                label_selector=label_selector)
    except ApiException as error:
        if error.status == 404:
            return None
        # Raise all non-404 errors
        raise error
    return api_response['items']


def get_kustomization(name, namespace='flux-system'):
    """
    Returns all info of a Flux kustomization with name 'name'

    :param name: Name of the kustomizatoin
    :type name: string
    :param namespace: Namespace of the kustomization
    :type namespace: string
    :return: kustomization as returned by the API
    :rtype: dict
    """
    api = client.CustomObjectsApi()
    try:
        resource = api.get_namespaced_custom_object(
            group="kustomize.toolkit.fluxcd.io",
            version="v1beta1",
            name=name,
            namespace=namespace,
            plural="kustomizations",
        )
    except client.exceptions.ApiException as error:
        if error.status == 404:
            return None
        # Raise all non-404 errors
        raise error
    return resource