import time
import os
import random
import string
import uuid

from celery import current_task
from flask import _request_ctx_stack, request, g, jsonify, make_response, current_app, has_request_context
from flask_sqlalchemy import SQLAlchemy as _SQLAlchemy
from flask_marshmallow import Marshmallow
from flask_migrate import Migrate
from gds_metrics import GDSMetrics
from gds_metrics.metrics import Gauge, Histogram
from time import monotonic
from notifications_utils.clients.zendesk.zendesk_client import ZendeskClient
from notifications_utils.clients.statsd.statsd_client import StatsdClient
from notifications_utils.clients.redis.redis_client import RedisClient
from notifications_utils.clients.encryption.encryption_client import Encryption
from notifications_utils import logging, request_helper
from sqlalchemy import event
from werkzeug.exceptions import HTTPException as WerkzeugHTTPException
from werkzeug.exceptions import RequestEntityTooLarge as WerkzeugRequestEntityTooLarge
from werkzeug.local import LocalProxy

from app.celery.celery import NotifyCelery
from app.clients import NotificationProviderClients
from app.clients.cbc_proxy import CBCProxyClient
from app.clients.document_download import DocumentDownloadClient
from app.clients.email.aws_ses import AwsSesClient
from app.clients.email.aws_ses_stub import AwsSesStubClient
from app.clients.sms.firetext import FiretextClient
from app.clients.sms.mmg import MMGClient
from app.clients.performance_platform.performance_platform_client import PerformancePlatformClient


class SQLAlchemy(_SQLAlchemy):
    """We need to subclass SQLAlchemy in order to override create_engine options"""

    def apply_driver_hacks(self, app, info, options):
        super().apply_driver_hacks(app, info, options)
        if 'connect_args' not in options:
            options['connect_args'] = {}
        options['connect_args']["options"] = "-c statement_timeout={}".format(
            int(app.config['SQLALCHEMY_STATEMENT_TIMEOUT']) * 1000
        )


db = SQLAlchemy()
migrate = Migrate()
ma = Marshmallow()
notify_celery = NotifyCelery()
firetext_client = FiretextClient()
mmg_client = MMGClient()
aws_ses_client = AwsSesClient()
aws_ses_stub_client = AwsSesStubClient()
encryption = Encryption()
zendesk_client = ZendeskClient()
statsd_client = StatsdClient()
redis_store = RedisClient()
performance_platform_client = PerformancePlatformClient()
cbc_proxy_client = CBCProxyClient()
document_download_client = DocumentDownloadClient()
metrics = GDSMetrics()

notification_provider_clients = NotificationProviderClients()

api_user = LocalProxy(lambda: _request_ctx_stack.top.api_user)
authenticated_service = LocalProxy(lambda: _request_ctx_stack.top.authenticated_service)

CONCURRENT_REQUESTS = Gauge(
    'concurrent_web_request_count',
    'How many concurrent requests are currently being served',
)


def create_app(application):
    from app.config import configs

    notify_environment = os.environ['NOTIFY_ENVIRONMENT']

    application.config.from_object(configs[notify_environment])

    application.config['NOTIFY_APP_NAME'] = application.name
    init_app(application)

    # Metrics intentionally high up to give the most accurate timing and reliability that the metric is recorded
    metrics.init_app(application)
    request_helper.init_app(application)
    db.init_app(application)
    migrate.init_app(application, db=db)
    ma.init_app(application)
    zendesk_client.init_app(application)
    statsd_client.init_app(application)
    logging.init_app(application, statsd_client)
    firetext_client.init_app(application, statsd_client=statsd_client)
    mmg_client.init_app(application, statsd_client=statsd_client)

    aws_ses_client.init_app(application.config['AWS_REGION'], statsd_client=statsd_client)
    aws_ses_stub_client.init_app(
        application.config['AWS_REGION'],
        statsd_client=statsd_client,
        stub_url=application.config['SES_STUB_URL']
    )
    # If a stub url is provided for SES, then use the stub client rather than the real SES boto client
    email_clients = [aws_ses_stub_client] if application.config['SES_STUB_URL'] else [aws_ses_client]
    notification_provider_clients.init_app(sms_clients=[firetext_client, mmg_client], email_clients=email_clients)

    notify_celery.init_app(application)
    encryption.init_app(application)
    redis_store.init_app(application)
    performance_platform_client.init_app(application)
    document_download_client.init_app(application)

    cbc_proxy_client.init_app(application)

    register_blueprint(application)
    register_v2_blueprints(application)

    # avoid circular imports by importing this file later
    from app.commands import setup_commands
    setup_commands(application)

    # set up sqlalchemy events
    setup_sqlalchemy_events(application)

    return application


def register_blueprint(application):
    from app.service.rest import service_blueprint
    from app.service.callback_rest import service_callback_blueprint
    from app.user.rest import user_blueprint
    from app.template.rest import template_blueprint
    from app.status.healthcheck import status as status_blueprint
    from app.job.rest import job_blueprint
    from app.notifications.rest import notifications as notifications_blueprint
    from app.invite.rest import invite as invite_blueprint
    from app.accept_invite.rest import accept_invite
    from app.template_statistics.rest import template_statistics as template_statistics_blueprint
    from app.events.rest import events as events_blueprint
    from app.provider_details.rest import provider_details as provider_details_blueprint
    from app.email_branding.rest import email_branding_blueprint
    from app.inbound_number.rest import inbound_number_blueprint
    from app.inbound_sms.rest import inbound_sms as inbound_sms_blueprint
    from app.notifications.receive_notifications import receive_notifications_blueprint
    from app.notifications.notifications_sms_callback import sms_callback_blueprint
    from app.notifications.notifications_letter_callback import letter_callback_blueprint
    from app.authentication.auth import requires_admin_auth, requires_auth, requires_no_auth
    from app.letters.rest import letter_job
    from app.billing.rest import billing_blueprint
    from app.organisation.rest import organisation_blueprint
    from app.organisation.invite_rest import organisation_invite_blueprint
    from app.complaint.complaint_rest import complaint_blueprint
    from app.platform_stats.rest import platform_stats_blueprint
    from app.template_folder.rest import template_folder_blueprint
    from app.letter_branding.letter_branding_rest import letter_branding_blueprint
    from app.upload.rest import upload_blueprint
    from app.broadcast_message.rest import broadcast_message_blueprint

    service_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(service_blueprint, url_prefix='/service')

    user_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(user_blueprint, url_prefix='/user')

    template_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(template_blueprint)

    status_blueprint.before_request(requires_no_auth)
    application.register_blueprint(status_blueprint)

    # delivery receipts
    # TODO: make sure research mode can still trigger sms callbacks, then re-enable this
    sms_callback_blueprint.before_request(requires_no_auth)
    application.register_blueprint(sms_callback_blueprint)

    # inbound sms
    receive_notifications_blueprint.before_request(requires_no_auth)
    application.register_blueprint(receive_notifications_blueprint)

    notifications_blueprint.before_request(requires_auth)
    application.register_blueprint(notifications_blueprint)

    job_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(job_blueprint)

    invite_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(invite_blueprint)

    inbound_number_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(inbound_number_blueprint)

    inbound_sms_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(inbound_sms_blueprint)

    accept_invite.before_request(requires_admin_auth)
    application.register_blueprint(accept_invite, url_prefix='/invite')

    template_statistics_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(template_statistics_blueprint)

    events_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(events_blueprint)

    provider_details_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(provider_details_blueprint, url_prefix='/provider-details')

    email_branding_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(email_branding_blueprint, url_prefix='/email-branding')

    letter_job.before_request(requires_admin_auth)
    application.register_blueprint(letter_job)

    letter_callback_blueprint.before_request(requires_no_auth)
    application.register_blueprint(letter_callback_blueprint)

    billing_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(billing_blueprint)

    service_callback_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(service_callback_blueprint)

    organisation_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(organisation_blueprint, url_prefix='/organisations')

    organisation_invite_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(organisation_invite_blueprint)

    complaint_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(complaint_blueprint)

    platform_stats_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(platform_stats_blueprint, url_prefix='/platform-stats')

    template_folder_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(template_folder_blueprint)

    letter_branding_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(letter_branding_blueprint)

    upload_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(upload_blueprint)

    broadcast_message_blueprint.before_request(requires_admin_auth)
    application.register_blueprint(broadcast_message_blueprint)


def register_v2_blueprints(application):
    from app.v2.inbound_sms.get_inbound_sms import v2_inbound_sms_blueprint as get_inbound_sms
    from app.v2.notifications.post_notifications import v2_notification_blueprint as post_notifications
    from app.v2.notifications.get_notifications import v2_notification_blueprint as get_notifications
    from app.v2.template.get_template import v2_template_blueprint as get_template
    from app.v2.templates.get_templates import v2_templates_blueprint as get_templates
    from app.v2.template.post_template import v2_template_blueprint as post_template
    from app.authentication.auth import requires_auth

    post_notifications.before_request(requires_auth)
    application.register_blueprint(post_notifications)

    get_notifications.before_request(requires_auth)
    application.register_blueprint(get_notifications)

    get_templates.before_request(requires_auth)
    application.register_blueprint(get_templates)

    get_template.before_request(requires_auth)
    application.register_blueprint(get_template)

    post_template.before_request(requires_auth)
    application.register_blueprint(post_template)

    get_inbound_sms.before_request(requires_auth)
    application.register_blueprint(get_inbound_sms)


def init_app(app):

    @app.before_request
    def record_request_details():
        CONCURRENT_REQUESTS.inc()

        g.start = monotonic()
        g.endpoint = request.endpoint

    @app.before_request
    def check_content_length():
        if (
            request.content_length is not None
            and current_app.config['MAX_CONTENT_LENGTH'] is not None
            and request.content_length > current_app.config['MAX_CONTENT_LENGTH']
        ):
            raise WerkzeugRequestEntityTooLarge()

    @app.after_request
    def after_request(response):
        CONCURRENT_REQUESTS.dec()

        response.headers.add('Access-Control-Allow-Origin', '*')
        response.headers.add('Access-Control-Allow-Headers', 'Content-Type,Authorization')
        response.headers.add('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE')
        return response

    @app.errorhandler(Exception)
    def exception(error):
        app.logger.exception(error)
        # error.code is set for our exception types.
        msg = getattr(error, 'message', str(error))
        code = getattr(error, 'code', 500)
        return jsonify(result='error', message=msg), code

    @app.errorhandler(WerkzeugHTTPException)
    def werkzeug_exception(e):
        return make_response(
            jsonify(result='error', message=e.description),
            e.code,
            e.get_headers()
        )

    @app.errorhandler(404)
    def page_not_found(e):
        msg = e.description or "Not found"
        return jsonify(result='error', message=msg), 404


def create_uuid():
    return str(uuid.uuid4())


def create_random_identifier():
    return ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(16))


def setup_sqlalchemy_events(app):

    TOTAL_DB_CONNECTIONS = Gauge(
        'db_connection_total_connected',
        'How many db connections are currently held (potentially idle) by the server',
    )

    TOTAL_CHECKED_OUT_DB_CONNECTIONS = Gauge(
        'db_connection_total_checked_out',
        'How many db connections are currently checked out by web requests',
    )

    DB_CONNECTION_OPEN_DURATION_SECONDS = Histogram(
        'db_connection_open_duration_seconds',
        'How long db connections are held open for in seconds',
        ['method', 'host', 'path']
    )

    # need this or db.engine isn't accessible
    with app.app_context():
        @event.listens_for(db.engine, 'connect')
        def connect(dbapi_connection, connection_record):
            # connection first opened with db
            TOTAL_DB_CONNECTIONS.inc()

        @event.listens_for(db.engine, 'close')
        def close(dbapi_connection, connection_record):
            # connection closed (probably only happens with overflow connections)
            TOTAL_DB_CONNECTIONS.dec()

        @event.listens_for(db.engine, 'checkout')
        def checkout(dbapi_connection, connection_record, connection_proxy):
            try:
                # connection given to a web worker
                TOTAL_CHECKED_OUT_DB_CONNECTIONS.inc()

                # this will overwrite any previous checkout_at timestamp
                connection_record.info['checkout_at'] = time.monotonic()

                # checkin runs after the request is already torn down, therefore we add the request_data onto the
                # connection_record as otherwise it won't have that information when checkin actually runs.
                # Note: this is not a problem for checkouts as the checkout always happens within a web request or task

                # web requests
                if has_request_context():
                    connection_record.info['request_data'] = {
                        'method': request.method,
                        'host': request.host,
                        'url_rule': request.url_rule.rule if request.url_rule else 'No endpoint'
                    }
                # celery apps
                elif current_task:
                    connection_record.info['request_data'] = {
                        'method': 'celery',
                        'host': current_app.config['NOTIFY_APP_NAME'],  # worker name
                        'url_rule': current_task.name,  # task name
                    }
                # anything else. migrations possibly.
                else:
                    current_app.logger.warning('Checked out sqlalchemy connection from outside of request/task')
                    connection_record.info['request_data'] = {
                        'method': 'unknown',
                        'host': 'unknown',
                        'url_rule': 'unknown',
                    }
            except Exception:
                current_app.logger.exception("Exception caught for checkout event.")

        @event.listens_for(db.engine, 'checkin')
        def checkin(dbapi_connection, connection_record):
            try:
                # connection returned by a web worker
                TOTAL_CHECKED_OUT_DB_CONNECTIONS.dec()

                # duration that connection was held by a single web request
                duration = time.monotonic() - connection_record.info['checkout_at']

                DB_CONNECTION_OPEN_DURATION_SECONDS.labels(
                    connection_record.info['request_data']['method'],
                    connection_record.info['request_data']['host'],
                    connection_record.info['request_data']['url_rule']
                ).observe(duration)
            except Exception:
                current_app.logger.exception("Exception caught for checkin event.")