use crate::{
    EntityChannelMessage, EntityError, Identity, LocalInfo, ProfileIdentifier,
    SecureChannelTrustInfo, TrustPolicy,
};
use core::future::Future;
use core::pin::Pin;
use ockam_channel::{
    CreateResponderChannelMessage, KeyExchangeCompleted, SecureChannel, SecureChannelInfo,
};
use ockam_core::async_trait;
use ockam_core::compat::rand::random;
use ockam_core::compat::{boxed::Box, vec::Vec};
use ockam_core::{
    route, Address, Any, Decodable, Encodable, LocalMessage, Result, Route, Routed,
    TransportMessage, Worker,
};
use ockam_key_exchange_core::NewKeyExchanger;
use ockam_key_exchange_xx::{XXNewKeyExchanger, XXVault};
use ockam_node::Context;
use serde::{Deserialize, Serialize};
use tracing::{debug, info};

#[derive(Serialize, Deserialize)]
pub(crate) struct AuthenticationConfirmation(pub Address);

trait StartSecureChannelFuture: Future<Output = Result<SecureChannelInfo>> + Send + 'static {}

impl<T> StartSecureChannelFuture for T where
    T: Future<Output = Result<SecureChannelInfo>> + Send + 'static
{
}

struct InitiatorStartChannel<I: Identity, T: TrustPolicy> {
    channel_future: Pin<Box<dyn StartSecureChannelFuture>>, // TODO: Replace with generic
    callback_address: Address,
    identity: I,
    trust_policy: T,
}

struct ResponderWaitForKex<I: Identity, T: TrustPolicy> {
    first_responder_address: Address,
    identity: I,
    trust_policy: T,
}

struct InitiatorSendProfile<I: Identity, T: TrustPolicy> {
    channel: SecureChannelInfo,
    callback_address: Address,
    identity: I,
    trust_policy: T,
}

struct ResponderWaitForProfile<I: Identity, T: TrustPolicy> {
    auth_hash: [u8; 32],
    local_secure_channel_address: Address,
    identity: I,
    trust_policy: T,
}

#[derive(Clone)]
struct Initialized {
    local_secure_channel_address: Address,
    remote_profile_secure_channel_address: Address,
    their_profile_id: ProfileIdentifier,
}

enum State<I: Identity, T: TrustPolicy> {
    InitiatorStartChannel(InitiatorStartChannel<I, T>),
    ResponderWaitForKex(ResponderWaitForKex<I, T>),
    InitiatorSendProfile(InitiatorSendProfile<I, T>),
    ResponderWaitForProfile(ResponderWaitForProfile<I, T>),
    Initialized(Initialized),
}

pub(crate) struct SecureChannelWorker<I: Identity, T: TrustPolicy> {
    is_initiator: bool,
    self_local_address: Address,
    self_remote_address: Address,
    state: Option<State<I, T>>,
}

impl<I: Identity, T: TrustPolicy> SecureChannelWorker<I, T> {
    pub async fn create_initiator(
        ctx: &Context,
        route: Route,
        identity: I,
        trust_policy: T,
        vault: impl XXVault,
    ) -> Result<Address> {
        let child_address = Address::random(0);
        let mut child_ctx = ctx.new_context(child_address.clone()).await?;

        // Generate 2 random fresh address for newly created SecureChannel.
        // One for local workers to encrypt their messages
        // Second for remote workers to decrypt their messages
        let self_local_address: Address = random();
        let self_remote_address: Address = random();

        let initiator = XXNewKeyExchanger::new(vault.async_try_clone().await?)
            .initiator()
            .await?;
        // Create regular secure channel and set self address as first responder
        let temp_ctx = ctx.new_context(Address::random(0)).await?;
        let self_remote_address_clone = self_remote_address.clone();
        let channel_future = Box::pin(async move {
            SecureChannel::create_extended(
                &temp_ctx,
                route,
                Some(self_remote_address_clone),
                initiator,
                vault,
            )
            .await
        });

        let state = State::InitiatorStartChannel(InitiatorStartChannel {
            channel_future,
            callback_address: child_address,
            identity,
            trust_policy,
        });

        let worker = SecureChannelWorker {
            is_initiator: true,
            self_local_address: self_local_address.clone(),
            self_remote_address: self_remote_address.clone(),
            state: Some(state),
        };

        ctx.start_worker(
            vec![self_local_address.clone(), self_remote_address.clone()],
            worker,
        )
        .await?;

        debug!(
            "Starting ProfileSecureChannel Initiator at local: {}, remote: {}",
            &self_local_address, &self_remote_address
        );

        let _ = child_ctx
            .receive_timeout::<AuthenticationConfirmation>(
                120, /* TODO: What is the correct timeout here? */
            )
            .await?;

        Ok(self_local_address)
    }

    pub(crate) async fn create_responder(
        ctx: &Context,
        identity: I,
        trust_policy: T,
        listener_address: Address,
        msg: Routed<CreateResponderChannelMessage>,
    ) -> Result<()> {
        let mut onward_route = msg.onward_route();
        onward_route.step()?;
        onward_route.modify().prepend(listener_address);

        let return_route = msg.return_route();
        let body = msg.body();
        // This is the address of Worker on the other end, that Initiator gave us to perform further negotiations.
        let first_responder_address = body
            .completed_callback_address()
            .clone()
            .ok_or(EntityError::SecureChannelCannotBeAuthenticated)?;

        // Generate 2 random fresh address for newly created SecureChannel.
        // One for local workers to encrypt their messages
        // Second for remote workers to decrypt their messages
        let self_local_address: Address = random();
        let self_remote_address: Address = random();

        // Change completed callback address and forward message for regular key exchange to happen
        let body = CreateResponderChannelMessage::new(
            body.payload().to_vec(),
            Some(self_local_address.clone()),
        );

        let msg = TransportMessage::v1(onward_route, return_route, body.encode()?);

        let state = State::ResponderWaitForKex(ResponderWaitForKex {
            first_responder_address,
            identity,
            trust_policy,
        });

        let worker = SecureChannelWorker {
            is_initiator: false,
            self_local_address: self_local_address.clone(),
            self_remote_address: self_remote_address.clone(),
            state: Some(state),
        };

        ctx.start_worker(
            vec![self_local_address.clone(), self_remote_address.clone()],
            worker,
        )
        .await?;

        debug!(
            "Starting ProfileSecureChannel Responder at local: {}, remote: {}",
            &self_local_address, &self_remote_address
        );

        ctx.forward(LocalMessage::new(msg, Vec::new())).await?;

        Ok(())
    }

    async fn handle_kex_done(
        &mut self,
        ctx: &mut <Self as Worker>::Context,
        msg: Routed<<Self as Worker>::Message>,
        mut state: ResponderWaitForKex<I, T>,
    ) -> Result<()> {
        let kex_msg = KeyExchangeCompleted::decode(msg.payload())?;

        // Prove we posses Profile key
        let proof = state
            .identity
            .create_auth_proof(&kex_msg.auth_hash())
            .await?;
        let msg = EntityChannelMessage::Request {
            contact: state.identity.as_contact().await?,
            proof,
        };
        ctx.send_from_address(
            route![kex_msg.address().clone(), state.first_responder_address],
            msg,
            self.self_remote_address.clone(),
        )
        .await?;
        debug!("Sent Authentication request");

        self.state = Some(State::ResponderWaitForProfile(ResponderWaitForProfile {
            auth_hash: kex_msg.auth_hash(),
            local_secure_channel_address: kex_msg.address().clone(),
            identity: state.identity,
            trust_policy: state.trust_policy,
        }));

        Ok(())
    }

    async fn handle_send_profile(
        &mut self,
        ctx: &mut <Self as Worker>::Context,
        msg: Routed<<Self as Worker>::Message>,
        mut state: InitiatorSendProfile<I, T>,
    ) -> Result<()> {
        let return_route = msg.return_route();

        // Ensure message came from dedicated SecureChannel
        if return_route.next()? != &state.channel.address() {
            return Err(EntityError::UnknownChannelMsgDestination.into());
        }

        let body = EntityChannelMessage::decode(msg.payload())?;

        // Wait for responder to send us his Profile and Profile Proof.
        // In case of using Noise XX this is m4 message.
        if let EntityChannelMessage::Request { contact, proof } = body {
            debug!("Received Authentication request");

            let their_contact = contact;
            let their_profile_id = their_contact.identifier().clone();

            let contact_result = state.identity.get_contact(&their_profile_id).await?;

            if contact_result.is_some() {
                // TODO: We're creating SecureChannel with known Profile. Need to update their Profile.
            } else {
                state.identity.verify_and_add_contact(their_contact).await?;
            }

            // Verify responder posses their Profile key
            let verified = state
                .identity
                .verify_auth_proof(&state.channel.auth_hash(), &their_profile_id, &proof)
                .await?;

            if !verified {
                return Err(EntityError::SecureChannelVerificationFailed.into());
            }
            info!(
                "Initiator verified SecureChannel from: {}",
                their_profile_id
            );

            // Check our TrustPolicy
            let trust_info = SecureChannelTrustInfo::new(their_profile_id.clone());
            let trusted = state.trust_policy.check(&trust_info).await?;
            if !trusted {
                return Err(EntityError::SecureChannelTrustCheckFailed.into());
            }
            info!(
                "Initiator checked trust policy for SecureChannel from: {}",
                &their_profile_id
            );

            // Prove we posses our Profile key
            let contact = state.identity.as_contact().await?;
            let proof = state
                .identity
                .create_auth_proof(&state.channel.auth_hash())
                .await?;

            let auth_msg = EntityChannelMessage::Response { contact, proof };

            let remote_profile_secure_channel_address = return_route.recipient();

            ctx.send_from_address(return_route, auth_msg, self.self_remote_address.clone())
                .await?;
            debug!("Sent Authentication response");

            self.state = Some(State::Initialized(Initialized {
                local_secure_channel_address: state.channel.address(),
                remote_profile_secure_channel_address,
                their_profile_id,
            }));

            info!(
                "Initialized ProfileSecureChannel Initiator at local: {}, remote: {}",
                &self.self_local_address, &self.self_remote_address
            );

            ctx.send(
                state.callback_address,
                AuthenticationConfirmation(self.self_local_address.clone()),
            )
            .await?;

            Ok(())
        } else {
            Err(EntityError::InvalidSecureChannelInternalState.into())
        }
    }

    async fn handle_receive_profile(
        &mut self,
        _ctx: &mut <Self as Worker>::Context,
        msg: Routed<<Self as Worker>::Message>,
        mut state: ResponderWaitForProfile<I, T>,
    ) -> Result<()> {
        let return_route = msg.return_route();

        // Ensure message came from dedicated SecureChannel
        if return_route.next()? != &state.local_secure_channel_address {
            return Err(EntityError::UnknownChannelMsgDestination.into());
        }

        let body = EntityChannelMessage::decode(msg.payload())?;

        // Wait for responder to send us his Profile and Profile Proof.
        // In case of using Noise XX this is m4 message.
        if let EntityChannelMessage::Response { contact, proof } = body {
            debug!("Received Authentication response");

            let their_contact = contact;
            let their_profile_id = their_contact.identifier().clone();

            let contact_result = state.identity.get_contact(&their_profile_id).await?;

            if contact_result.is_some() {
                // TODO: We're creating SecureChannel with known Profile. Need to update their Profile.
            } else {
                state
                    .identity
                    .verify_and_add_contact(their_contact.clone())
                    .await?;
            }

            // Verify initiator posses their Profile key
            let verified = state
                .identity
                .verify_auth_proof(&state.auth_hash, &their_profile_id, &proof)
                .await?;

            if !verified {
                return Err(EntityError::SecureChannelVerificationFailed.into());
            }

            info!(
                "Responder verified SecureChannel from: {}",
                &their_profile_id
            );

            // Check our TrustPolicy
            let trust_info = SecureChannelTrustInfo::new(their_profile_id.clone());
            let trusted = state.trust_policy.check(&trust_info).await?;
            if !trusted {
                return Err(EntityError::SecureChannelTrustCheckFailed.into());
            }
            info!(
                "Responder checked trust policy for SecureChannel from: {}",
                &their_profile_id
            );

            let remote_profile_secure_channel_address = return_route.recipient();

            self.state = Some(State::Initialized(Initialized {
                local_secure_channel_address: state.local_secure_channel_address,
                remote_profile_secure_channel_address,
                their_profile_id,
            }));

            Ok(())
        } else {
            Err(EntityError::InvalidSecureChannelInternalState.into())
        }
    }

    fn take_state(&mut self) -> Result<State<I, T>> {
        if let Some(s) = self.state.take() {
            Ok(s)
        } else {
            Err(EntityError::InvalidSecureChannelInternalState.into())
        }
    }

    async fn handle_encrypt(
        &mut self,
        ctx: &mut <Self as Worker>::Context,
        msg: Routed<<Self as Worker>::Message>,
        state: Initialized,
    ) -> Result<()> {
        debug!(
            "ProfileSecureChannel {} received Encrypt",
            if self.is_initiator {
                "Initiator"
            } else {
                "Responder"
            }
        );

        self.state = Some(State::Initialized(state.clone()));

        let mut onward_route = msg.onward_route();
        let mut return_route = msg.return_route();
        let payload = msg.payload().to_vec();

        // Send to the other party using local regular SecureChannel
        let _ = onward_route.step()?;
        let onward_route = onward_route
            .modify()
            .prepend(state.remote_profile_secure_channel_address)
            .prepend(state.local_secure_channel_address);

        let return_route = return_route
            .modify()
            .prepend(self.self_remote_address.clone());

        let transport_msg = TransportMessage::v1(onward_route, return_route, payload);

        ctx.forward(LocalMessage::new(transport_msg, Vec::new()))
            .await?;

        Ok(())
    }

    async fn handle_decrypt(
        &mut self,
        ctx: &mut <Self as Worker>::Context,
        msg: Routed<<Self as Worker>::Message>,
        state: Initialized,
    ) -> Result<()> {
        debug!(
            "ProfileSecureChannel {} received Decrypt",
            if self.is_initiator {
                "Initiator"
            } else {
                "Responder"
            }
        );

        self.state = Some(State::Initialized(state.clone()));

        let mut onward_route = msg.onward_route();
        let mut return_route = msg.return_route();

        // Ensure message came from dedicated SecureChannel
        if return_route.next()? != &state.local_secure_channel_address {
            return Err(EntityError::UnknownChannelMsgDestination.into());
        }

        let payload = msg.payload().to_vec();

        // Forward to local workers
        let _ = onward_route.step()?;

        let return_route = return_route
            .modify()
            .pop_front()
            .pop_front()
            .prepend(self.self_local_address.clone());

        let transport_msg = TransportMessage::v1(onward_route, return_route, payload);

        let local_info = LocalInfo::new(state.their_profile_id.clone());
        let local_info = local_info.encode()?;

        ctx.forward(LocalMessage::new(transport_msg, local_info))
            .await?;

        Ok(())
    }
}

#[async_trait]
impl<I: Identity, T: TrustPolicy> Worker for SecureChannelWorker<I, T> {
    type Message = Any;
    type Context = Context;

    async fn initialize(&mut self, _ctx: &mut Self::Context) -> Result<()> {
        if self.is_initiator {
            match self.take_state()? {
                State::InitiatorStartChannel(s) => {
                    let channel = s.channel_future.await?;

                    self.state = Some(State::InitiatorSendProfile(InitiatorSendProfile {
                        channel,
                        callback_address: s.callback_address,
                        identity: s.identity,
                        trust_policy: s.trust_policy,
                    }));
                }
                _ => return Err(EntityError::InvalidSecureChannelInternalState.into()),
            }
        }

        Ok(())
    }

    async fn handle_message(
        &mut self,
        ctx: &mut Self::Context,
        msg: Routed<Self::Message>,
    ) -> Result<()> {
        let msg_addr = msg.msg_addr();

        match self.take_state()? {
            State::InitiatorStartChannel(_) => {
                return Err(EntityError::InvalidSecureChannelInternalState.into())
            }
            State::ResponderWaitForKex(s) => {
                if msg_addr == self.self_local_address {
                    self.handle_kex_done(ctx, msg, s).await?;
                } else {
                    return Err(EntityError::UnknownChannelMsgDestination.into());
                }
            }
            State::InitiatorSendProfile(s) => {
                if msg_addr == self.self_remote_address {
                    self.handle_send_profile(ctx, msg, s).await?;
                } else {
                    return Err(EntityError::UnknownChannelMsgDestination.into());
                }
            }
            State::ResponderWaitForProfile(s) => {
                if msg_addr == self.self_remote_address {
                    self.handle_receive_profile(ctx, msg, s).await?;
                } else {
                    return Err(EntityError::UnknownChannelMsgDestination.into());
                }
            }
            State::Initialized(s) => {
                if msg_addr == self.self_local_address {
                    self.handle_encrypt(ctx, msg, s).await?;
                } else if msg_addr == self.self_remote_address {
                    self.handle_decrypt(ctx, msg, s).await?;
                } else {
                    return Err(EntityError::UnknownChannelMsgDestination.into());
                }
            }
        }

        Ok(())
    }
}