// Copyright 2023 - Nym Technologies SA <contact@nymtech.net>
// SPDX-License-Identifier: GPL-3.0-only

use crate::nym_contract_cache::cache::NymContractCache;
use crate::support::caching::cache::{SharedCache, UninitialisedCache};
use crate::support::caching::refresher::{CacheItemProvider, CacheRefresher};
use crate::support::config;
use crate::support::config::DEFAULT_NODE_DESCRIBE_BATCH_SIZE;
use futures_util::{stream, StreamExt};
use nym_api_requests::models::{
    IpPacketRouterDetails, NetworkRequesterDetails, NymNodeDescription,
};
use nym_config::defaults::{mainnet, DEFAULT_NYM_NODE_HTTP_PORT};
use nym_contracts_common::IdentityKey;
use nym_mixnet_contract_common::Gateway;
use nym_node_requests::api::client::{NymNodeApiClientError, NymNodeApiClientExt};
use std::collections::HashMap;
use thiserror::Error;

// type alias for ease of use
pub type DescribedNodes = HashMap<IdentityKey, NymNodeDescription>;

#[derive(Debug, Error)]
pub enum NodeDescribeCacheError {
    #[error("contract cache hasn't been initialised")]
    UninitialisedContractCache {
        #[from]
        source: UninitialisedCache,
    },

    #[error("gateway {gateway} has provided malformed host information ({host}: {source}")]
    MalformedHost {
        host: String,

        gateway: IdentityKey,

        #[source]
        source: NymNodeApiClientError,
    },

    #[error("gateway '{gateway}' with host '{host}' doesn't seem to expose any of the standard API ports, i.e.: 80, 443 or {}", DEFAULT_NYM_NODE_HTTP_PORT)]
    NoHttpPortsAvailable { host: String, gateway: IdentityKey },

    #[error("failed to query gateway '{gateway}': {source}")]
    ApiFailure {
        gateway: IdentityKey,

        #[source]
        source: NymNodeApiClientError,
    },

    // TODO: perhaps include more details here like whether key/signature/payload was malformed
    #[error("could not verify signed host information for gateway '{gateway}'")]
    MissignedHostInformation { gateway: IdentityKey },
}

pub struct NodeDescriptionProvider {
    // for now we only care about gateways, nothing more
    // network_gateways: SharedCache<Vec<GatewayBond>>,
    contract_cache: NymContractCache,

    batch_size: usize,
}

impl NodeDescriptionProvider {
    pub(crate) fn new(contract_cache: NymContractCache) -> NodeDescriptionProvider {
        NodeDescriptionProvider {
            contract_cache,
            batch_size: DEFAULT_NODE_DESCRIBE_BATCH_SIZE,
        }
    }

    #[must_use]
    pub(crate) fn with_batch_size(mut self, batch_size: usize) -> Self {
        self.batch_size = batch_size;
        self
    }
}

async fn try_get_client(
    gateway: &Gateway,
) -> Result<nym_node_requests::api::Client, NodeDescribeCacheError> {
    let gateway_host = &gateway.host;

    // first try the standard port in case the operator didn't put the node behind the proxy,
    // then default https (443)
    // finally default http (80)
    let addresses_to_try = vec![
        format!("http://{gateway_host}:{DEFAULT_NYM_NODE_HTTP_PORT}"),
        format!("https://{gateway_host}"),
        format!("http://{gateway_host}"),
    ];

    for address in addresses_to_try {
        // if provided host was malformed, no point in continuing
        let client = match nym_node_requests::api::Client::new_url(address, None) {
            Ok(client) => client,
            Err(err) => {
                return Err(NodeDescribeCacheError::MalformedHost {
                    host: gateway_host.clone(),
                    gateway: gateway.identity_key.clone(),
                    source: err,
                });
            }
        };
        if let Ok(health) = client.get_health().await {
            if health.status.is_up() {
                return Ok(client);
            }
        }
    }

    Err(NodeDescribeCacheError::NoHttpPortsAvailable {
        host: gateway_host.clone(),
        gateway: gateway.identity_key.clone(),
    })
}

async fn get_gateway_description(
    gateway: Gateway,
) -> Result<(IdentityKey, NymNodeDescription), NodeDescribeCacheError> {
    let client = try_get_client(&gateway).await?;

    let host_info =
        client
            .get_host_information()
            .await
            .map_err(|err| NodeDescribeCacheError::ApiFailure {
                gateway: gateway.identity_key.clone(),
                source: err,
            })?;

    if !host_info.verify_host_information() {
        return Err(NodeDescribeCacheError::MissignedHostInformation {
            gateway: gateway.identity_key,
        });
    }

    let build_info =
        client
            .get_build_information()
            .await
            .map_err(|err| NodeDescribeCacheError::ApiFailure {
                gateway: gateway.identity_key.clone(),
                source: err,
            })?;

    let websockets =
        client
            .get_mixnet_websockets()
            .await
            .map_err(|err| NodeDescribeCacheError::ApiFailure {
                gateway: gateway.identity_key.clone(),
                source: err,
            })?;

    let network_requester =
        if let Ok(nr) = client.get_network_requester().await {
            let exit_policy = client.get_exit_policy().await.map_err(|err| {
                NodeDescribeCacheError::ApiFailure {
                    gateway: gateway.identity_key.clone(),
                    source: err,
                }
            })?;
            let uses_nym_exit_policy = exit_policy.upstream_source == mainnet::EXIT_POLICY_URL;

            Some(NetworkRequesterDetails {
                address: nr.address,
                uses_exit_policy: exit_policy.enabled && uses_nym_exit_policy,
            })
        } else {
            None
        };

    let ip_packet_router = if let Ok(ipr) = client.get_ip_packet_router().await {
        Some(IpPacketRouterDetails {
            address: ipr.address,
        })
    } else {
        None
    };

    let description = NymNodeDescription {
        host_information: host_info.data,
        build_information: build_info,
        network_requester,
        ip_packet_router,
        mixnet_websockets: websockets,
    };

    Ok((gateway.identity_key, description))
}

#[async_trait]
impl CacheItemProvider for NodeDescriptionProvider {
    type Item = HashMap<IdentityKey, NymNodeDescription>;
    type Error = NodeDescribeCacheError;

    async fn wait_until_ready(&self) {
        self.contract_cache.wait_for_initial_values().await
    }

    async fn try_refresh(&self) -> Result<Self::Item, Self::Error> {
        let gateways = self.contract_cache.gateways_all().await;

        // let guard = self.network_gateways.get().await?;
        // let gateways = &*guard;

        if gateways.is_empty() {
            return Ok(HashMap::new());
        }

        // TODO: somehow bypass the 'higher-ranked lifetime error' and remove that redundant clone
        let websockets = stream::iter(
            gateways
                // .deref()
                // .clone()
                .into_iter()
                .map(|bond| bond.gateway)
                .map(get_gateway_description),
        )
        .buffer_unordered(self.batch_size)
        .filter_map(|res| async move {
            match res {
                Ok((identity, description)) => Some((identity, description)),
                Err(err) => {
                    debug!("{err}");
                    None
                }
            }
        })
        .collect::<HashMap<_, _>>()
        .await;

        Ok(websockets)
    }
}

// currently dead code : (
#[allow(dead_code)]
pub(crate) fn new_refresher(
    config: &config::TopologyCacher,
    contract_cache: NymContractCache,
    // hehe. we can't do that yet
    // network_gateways: SharedCache<Vec<GatewayBond>>,
) -> CacheRefresher<DescribedNodes, NodeDescribeCacheError> {
    CacheRefresher::new(
        Box::new(
            NodeDescriptionProvider::new(contract_cache)
                .with_batch_size(config.debug.node_describe_batch_size),
        ),
        config.debug.node_describe_caching_interval,
    )
}

pub(crate) fn new_refresher_with_initial_value(
    config: &config::TopologyCacher,
    contract_cache: NymContractCache,
    // hehe. we can't do that yet
    // network_gateways: SharedCache<Vec<GatewayBond>>,
    initial: SharedCache<DescribedNodes>,
) -> CacheRefresher<DescribedNodes, NodeDescribeCacheError> {
    CacheRefresher::new_with_initial_value(
        Box::new(
            NodeDescriptionProvider::new(contract_cache)
                .with_batch_size(config.debug.node_describe_batch_size),
        ),
        config.debug.node_describe_caching_interval,
        initial,
    )
}