// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::collections::BTreeMap;
use std::sync::Arc;

use dashmap::DashMap;

use matrix_sdk_common::{
    api::r0::to_device::{send_event_to_device::Request as ToDeviceRequest, DeviceIdOrAllDevices},
    events::{
        key::verification::start::StartEventContent, AnyToDeviceEvent, AnyToDeviceEventContent,
        EventType,
    },
    identifiers::{DeviceId, UserId},
    uuid::Uuid,
};

use super::Sas;
use crate::{Account, CryptoStore, CryptoStoreError};

#[derive(Clone, Debug)]
struct VerificationMachine {
    account: Account,
    store: Arc<Box<dyn CryptoStore>>,
    verifications: Arc<DashMap<String, Sas>>,
    outgoing_to_device_messages: Arc<DashMap<String, ToDeviceRequest>>,
}

impl VerificationMachine {
    pub(crate) fn new(account: Account, store: Box<dyn CryptoStore>) -> Self {
        Self {
            account,
            store: Arc::new(store),
            verifications: Arc::new(DashMap::new()),
            outgoing_to_device_messages: Arc::new(DashMap::new()),
        }
    }

    fn get_sas(&self, transaction_id: &str) -> Option<Sas> {
        self.verifications.get(transaction_id).map(|s| s.clone())
    }

    fn content_to_request(
        &self,
        recipient: &UserId,
        recipient_device: &DeviceId,
        content: AnyToDeviceEventContent,
    ) -> ToDeviceRequest {
        let mut messages = BTreeMap::new();
        let mut user_messages = BTreeMap::new();

        user_messages.insert(
            DeviceIdOrAllDevices::DeviceId(recipient_device.into()),
            serde_json::value::to_raw_value(&content).expect("Can't serialize to-device content"),
        );
        messages.insert(recipient.clone(), user_messages);

        ToDeviceRequest {
            txn_id: Uuid::new_v4().to_string(),
            event_type: EventType::KeyVerificationAccept,
            messages,
        }
    }

    fn queue_up_content(
        &self,
        recipient: &UserId,
        recipient_device: &DeviceId,
        content: AnyToDeviceEventContent,
    ) {
        let request = self.content_to_request(recipient, recipient_device, content);

        self.outgoing_to_device_messages
            .insert(request.txn_id.clone(), request);
    }

    fn recieve_event_helper(&self, sas: &Sas, event: &mut AnyToDeviceEvent) {
        if let Some(c) = sas.receive_event(event) {
            self.queue_up_content(sas.other_user_id(), sas.other_device_id(), c);
        }
    }

    pub fn mark_requests_as_sent(&self, uuid: &str) {
        self.outgoing_to_device_messages.remove(uuid);
    }

    async fn receive_event(&self, event: &mut AnyToDeviceEvent) -> Result<(), CryptoStoreError> {
        match event {
            AnyToDeviceEvent::KeyVerificationStart(e) => match &e.content {
                StartEventContent::MSasV1(content) => {
                    if let Some(d) = self
                        .store
                        .get_device(&e.sender, &content.from_device)
                        .await?
                    {
                        match Sas::from_start_event(self.account.clone(), d, e) {
                            Ok(s) => {
                                self.verifications.insert(content.transaction_id.clone(), s);
                            }
                            Err(c) => self.queue_up_content(&e.sender, &content.from_device, c),
                        }
                    };
                }
                _ => (),
            },
            AnyToDeviceEvent::KeyVerificationCancel(e) => {
                self.verifications.remove(&e.content.transaction_id);
            }
            AnyToDeviceEvent::KeyVerificationAccept(e) => {
                if let Some(s) = self.get_sas(&e.content.transaction_id) {
                    self.recieve_event_helper(&s, event)
                };
            }
            AnyToDeviceEvent::KeyVerificationKey(e) => {
                if let Some(s) = self.get_sas(&e.content.transaction_id) {
                    self.recieve_event_helper(&s, event)
                };
            }
            AnyToDeviceEvent::KeyVerificationMac(e) => {
                if let Some(s) = self.get_sas(&e.content.transaction_id) {
                    self.recieve_event_helper(&s, event)
                };
            }
            _ => (),
        }
        Ok(())
    }
}

#[cfg(test)]
mod test {

    use std::convert::TryFrom;

    use matrix_sdk_common::{
        events::AnyToDeviceEventContent,
        identifiers::{DeviceId, UserId},
    };

    use super::{Sas, VerificationMachine};
    use crate::verification::test::wrap_any_to_device_content;
    use crate::{store::memorystore::MemoryStore, Account, CryptoStore, Device};

    fn alice_id() -> UserId {
        UserId::try_from("@alice:example.org").unwrap()
    }

    fn alice_device_id() -> Box<DeviceId> {
        "JLAFKJWSCS".into()
    }

    fn bob_id() -> UserId {
        UserId::try_from("@bob:example.org").unwrap()
    }

    fn bob_device_id() -> Box<DeviceId> {
        "BOBDEVCIE".into()
    }

    async fn setup_verification_machine() -> (VerificationMachine, Sas) {
        let alice = Account::new(&alice_id(), &alice_device_id());
        let bob = Account::new(&bob_id(), &bob_device_id());
        let store = MemoryStore::new();

        let bob_device = Device::from_account(&bob).await;
        let alice_device = Device::from_account(&alice).await;

        store.save_devices(&[bob_device]).await.unwrap();

        let machine = VerificationMachine::new(alice, Box::new(store));
        let (bob_sas, start_content) = Sas::start(bob, alice_device);
        machine
            .receive_event(&mut wrap_any_to_device_content(
                bob_sas.user_id(),
                AnyToDeviceEventContent::KeyVerificationStart(start_content),
            ))
            .await
            .unwrap();

        (machine, bob_sas)
    }

    #[test]
    fn create() {
        let alice = Account::new(&alice_id(), &alice_device_id());
        let store = MemoryStore::new();
        let _ = VerificationMachine::new(alice, Box::new(store));
    }

    #[tokio::test]
    async fn full_flow() {
        let (alice_machine, bob) = setup_verification_machine().await;

        let alice = alice_machine.verifications.get(bob.flow_id()).unwrap();

        let mut event = alice
            .accept()
            .map(|c| {
                wrap_any_to_device_content(
                    alice.user_id(),
                    AnyToDeviceEventContent::KeyVerificationAccept(c),
                )
            })
            .unwrap();

        let mut event = bob
            .receive_event(&mut event)
            .map(|c| wrap_any_to_device_content(bob.user_id(), c))
            .unwrap();

        assert!(alice_machine.outgoing_to_device_messages.is_empty());
        alice_machine.receive_event(&mut event).await.unwrap();
        assert!(!alice_machine.outgoing_to_device_messages.is_empty());

        let request = alice_machine
            .outgoing_to_device_messages
            .iter()
            .next()
            .unwrap();

        let txn_id = request.txn_id.clone();

        let mut event = wrap_any_to_device_content(
            alice.user_id(),
            AnyToDeviceEventContent::KeyVerificationKey(
                serde_json::from_str(
                    request
                        .messages
                        .values()
                        .next()
                        .unwrap()
                        .values()
                        .next()
                        .unwrap()
                        .get(),
                )
                .unwrap(),
            ),
        );
        drop(request);
        alice_machine.mark_requests_as_sent(&txn_id);

        assert!(bob.receive_event(&mut event).is_none());

        assert!(alice.emoji().is_some());
        assert!(bob.emoji().is_some());

        assert_eq!(alice.emoji(), bob.emoji());

        let mut event = wrap_any_to_device_content(
            alice.user_id(),
            AnyToDeviceEventContent::KeyVerificationMac(alice.confirm().unwrap()),
        );
        bob.receive_event(&mut event);

        let mut event = wrap_any_to_device_content(
            bob.user_id(),
            AnyToDeviceEventContent::KeyVerificationMac(bob.confirm().unwrap()),
        );
        alice.receive_event(&mut event);

        assert!(alice.is_done());
        assert!(bob.is_done());
    }
}