from typing import Any, Dict, Optional

from django.http import HttpRequest, HttpResponse

from zerver.decorator import api_key_only_webhook_view
from zerver.lib.request import REQ, has_request_variables
from zerver.lib.response import json_success
from zerver.lib.webhooks.common import check_send_webhook_message
from zerver.models import UserProfile

GCI_MESSAGE_TEMPLATE = u'**{actor}** {action} the task [{task_name}]({task_url}).'
GCI_SUBJECT_TEMPLATE = u'{student_name}'


def build_instance_url(instance_id: str) -> str:
    return "https://codein.withgoogle.com/dashboard/task-instances/{}/".format(instance_id)

class UnknownEventType(Exception):
    pass

def get_abandon_event_body(payload: Dict[str, Any]) -> str:
    return GCI_MESSAGE_TEMPLATE.format(
        actor=payload['task_claimed_by'],
        action='{}ed'.format(payload['event_type']),
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_submit_event_body(payload: Dict[str, Any]) -> str:
    return GCI_MESSAGE_TEMPLATE.format(
        actor=payload['task_claimed_by'],
        action='{}ted'.format(payload['event_type']),
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_comment_event_body(payload: Dict[str, Any]) -> str:
    return GCI_MESSAGE_TEMPLATE.format(
        actor=payload['author'],
        action='{}ed on'.format(payload['event_type']),
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_claim_event_body(payload: Dict[str, Any]) -> str:
    return GCI_MESSAGE_TEMPLATE.format(
        actor=payload['task_claimed_by'],
        action='{}ed'.format(payload['event_type']),
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_approve_event_body(payload: Dict[str, Any]) -> str:
    return GCI_MESSAGE_TEMPLATE.format(
        actor=payload['author'],
        action='{}d'.format(payload['event_type']),
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_approve_pending_pc_event_body(payload: Dict[str, Any]) -> str:
    template = "{} (pending parental consent).".format(GCI_MESSAGE_TEMPLATE.rstrip('.'))
    return template.format(
        actor=payload['author'],
        action='approved',
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_needswork_event_body(payload: Dict[str, Any]) -> str:
    template = "{} for more work.".format(GCI_MESSAGE_TEMPLATE.rstrip('.'))
    return template.format(
        actor=payload['author'],
        action='submitted',
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_extend_event_body(payload: Dict[str, Any]) -> str:
    template = "{} by {days} day(s).".format(GCI_MESSAGE_TEMPLATE.rstrip('.'),
                                             days=payload['extension_days'])
    return template.format(
        actor=payload['author'],
        action='extended the deadline for',
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_unassign_event_body(payload: Dict[str, Any]) -> str:
    return GCI_MESSAGE_TEMPLATE.format(
        actor=payload['author'],
        action='unassigned **{student}** from'.format(student=payload['task_claimed_by']),
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

def get_outoftime_event_body(payload: Dict[str, Any]) -> str:
    return u'The deadline for the task [{task_name}]({task_url}) has passed.'.format(
        task_name=payload['task_definition_name'],
        task_url=build_instance_url(payload['task_instance']),
    )

@api_key_only_webhook_view("Google-Code-In")
@has_request_variables
def api_gci_webhook(request: HttpRequest, user_profile: UserProfile,
                    payload: Dict[str, Any]=REQ(argument_type='body')) -> HttpResponse:
    event = get_event(payload)
    if event is not None:
        body = get_body_based_on_event(event)(payload)
        subject = GCI_SUBJECT_TEMPLATE.format(
            student_name=payload['task_claimed_by']
        )
        check_send_webhook_message(request, user_profile, subject, body)

    return json_success()

EVENTS_FUNCTION_MAPPER = {
    'abandon': get_abandon_event_body,
    'approve': get_approve_event_body,
    'approve-pending-pc': get_approve_pending_pc_event_body,
    'claim': get_claim_event_body,
    'comment': get_comment_event_body,
    'extend': get_extend_event_body,
    'needswork': get_needswork_event_body,
    'outoftime': get_outoftime_event_body,
    'submit': get_submit_event_body,
    'unassign': get_unassign_event_body,
}

def get_event(payload: Dict[str, Any]) -> Optional[str]:
    event = payload['event_type']
    if event in EVENTS_FUNCTION_MAPPER:
        return event

    raise UnknownEventType(u"Event '{}' is unknown and cannot be handled".format(event))  # nocoverage

def get_body_based_on_event(event: str) -> Any:
    return EVENTS_FUNCTION_MAPPER[event]