//! Production console backend.

use std::net::IpAddr;
use std::str::FromStr;
use std::sync::Arc;
use std::time::Duration;

use ::http::HeaderName;
use ::http::header::AUTHORIZATION;
use bytes::Bytes;
use futures::TryFutureExt;
use hyper::StatusCode;
use postgres_client::config::SslMode;
use tokio::time::Instant;
use tracing::{Instrument, debug, info, info_span, warn};

use super::super::messages::{ControlPlaneErrorMessage, GetEndpointAccessControl, WakeCompute};
use crate::auth::backend::ComputeUserInfo;
use crate::auth::backend::jwt::AuthRule;
use crate::context::RequestContext;
use crate::control_plane::caches::ApiCaches;
use crate::control_plane::errors::{
    ControlPlaneError, GetAuthInfoError, GetEndpointJwksError, WakeComputeError,
};
use crate::control_plane::locks::ApiLocks;
use crate::control_plane::messages::{ColdStartInfo, EndpointJwksResponse, Reason};
use crate::control_plane::{
    AccessBlockerFlags, AuthInfo, AuthSecret, CachedNodeInfo, EndpointAccessControl, NodeInfo,
    RoleAccessControl,
};
use crate::metrics::Metrics;
use crate::rate_limiter::WakeComputeRateLimiter;
use crate::types::{EndpointCacheKey, EndpointId, RoleName};
use crate::{compute, http, scram};

pub(crate) const X_REQUEST_ID: HeaderName = HeaderName::from_static("x-request-id");

#[derive(Clone)]
pub struct NeonControlPlaneClient {
    endpoint: http::Endpoint,
    pub caches: &'static ApiCaches,
    pub(crate) locks: &'static ApiLocks<EndpointCacheKey>,
    pub(crate) wake_compute_endpoint_rate_limiter: Arc<WakeComputeRateLimiter>,
    // put in a shared ref so we don't copy secrets all over in memory
    jwt: Arc<str>,
}

impl NeonControlPlaneClient {
    /// Construct an API object containing the auth parameters.
    pub fn new(
        endpoint: http::Endpoint,
        jwt: Arc<str>,
        caches: &'static ApiCaches,
        locks: &'static ApiLocks<EndpointCacheKey>,
        wake_compute_endpoint_rate_limiter: Arc<WakeComputeRateLimiter>,
    ) -> Self {
        Self {
            endpoint,
            caches,
            locks,
            wake_compute_endpoint_rate_limiter,
            jwt,
        }
    }

    pub(crate) fn url(&self) -> &str {
        self.endpoint.url().as_str()
    }

    async fn do_get_auth_req(
        &self,
        ctx: &RequestContext,
        endpoint: &EndpointId,
        role: &RoleName,
    ) -> Result<AuthInfo, GetAuthInfoError> {
        async {
            let response = {
                let request = self
                    .endpoint
                    .get_path("get_endpoint_access_control")
                    .header(X_REQUEST_ID, ctx.session_id().to_string())
                    .header(AUTHORIZATION, format!("Bearer {}", &self.jwt))
                    .query(&[("session_id", ctx.session_id())])
                    .query(&[
                        ("application_name", ctx.console_application_name().as_str()),
                        ("endpointish", endpoint.as_str()),
                        ("role", role.as_str()),
                    ])
                    .build()?;

                debug!(url = request.url().as_str(), "sending http request");
                let start = Instant::now();
                let _pause = ctx.latency_timer_pause_at(start, crate::metrics::Waiting::Cplane);
                let response = self.endpoint.execute(request).await?;

                info!(duration = ?start.elapsed(), "received http response");

                response
            };

            let body = match parse_body::<GetEndpointAccessControl>(
                response.status(),
                response.bytes().await?,
            ) {
                Ok(body) => body,
                // Error 404 is special: it's ok not to have a secret.
                // TODO(anna): retry
                Err(e) => {
                    return if e.get_reason().is_not_found() {
                        // TODO: refactor this because it's weird
                        // this is a failure to authenticate but we return Ok.
                        Ok(AuthInfo::default())
                    } else {
                        Err(e.into())
                    };
                }
            };

            let secret = if body.role_secret.is_empty() {
                None
            } else {
                let secret = scram::ServerSecret::parse(&body.role_secret)
                    .map(AuthSecret::Scram)
                    .ok_or(GetAuthInfoError::BadSecret)?;
                Some(secret)
            };
            let allowed_ips = body.allowed_ips.unwrap_or_default();
            Metrics::get()
                .proxy
                .allowed_ips_number
                .observe(allowed_ips.len() as f64);
            let allowed_vpc_endpoint_ids = body.allowed_vpc_endpoint_ids.unwrap_or_default();
            Metrics::get()
                .proxy
                .allowed_vpc_endpoint_ids
                .observe(allowed_vpc_endpoint_ids.len() as f64);
            let block_public_connections = body.block_public_connections.unwrap_or_default();
            let block_vpc_connections = body.block_vpc_connections.unwrap_or_default();
            Ok(AuthInfo {
                secret,
                allowed_ips,
                allowed_vpc_endpoint_ids,
                project_id: body.project_id,
                account_id: body.account_id,
                access_blocker_flags: AccessBlockerFlags {
                    public_access_blocked: block_public_connections,
                    vpc_access_blocked: block_vpc_connections,
                },
            })
        }
        .inspect_err(|e| tracing::debug!(error = ?e))
        .instrument(info_span!("do_get_auth_info"))
        .await
    }

    async fn do_get_endpoint_jwks(
        &self,
        ctx: &RequestContext,
        endpoint: &EndpointId,
    ) -> Result<Vec<AuthRule>, GetEndpointJwksError> {
        if !self
            .caches
            .endpoints_cache
            .is_valid(ctx, &endpoint.normalize())
        {
            return Err(GetEndpointJwksError::EndpointNotFound);
        }
        let request_id = ctx.session_id().to_string();
        async {
            let request = self
                .endpoint
                .get_with_url(|url| {
                    url.path_segments_mut()
                        .push("endpoints")
                        .push(endpoint.as_str())
                        .push("jwks");
                })
                .header(X_REQUEST_ID, &request_id)
                .header(AUTHORIZATION, format!("Bearer {}", &self.jwt))
                .query(&[("session_id", ctx.session_id())])
                .build()
                .map_err(GetEndpointJwksError::RequestBuild)?;

            debug!(url = request.url().as_str(), "sending http request");
            let start = Instant::now();
            let pause = ctx.latency_timer_pause(crate::metrics::Waiting::Cplane);
            let response = self
                .endpoint
                .execute(request)
                .await
                .map_err(GetEndpointJwksError::RequestExecute)?;
            drop(pause);
            info!(duration = ?start.elapsed(), "received http response");

            let body = parse_body::<EndpointJwksResponse>(
                response.status(),
                response.bytes().await.map_err(ControlPlaneError::from)?,
            )?;

            let rules = body
                .jwks
                .into_iter()
                .map(|jwks| AuthRule {
                    id: jwks.id,
                    jwks_url: jwks.jwks_url,
                    audience: jwks.jwt_audience,
                    role_names: jwks.role_names,
                })
                .collect();

            Ok(rules)
        }
        .inspect_err(|e| tracing::debug!(error = ?e))
        .instrument(info_span!("do_get_endpoint_jwks"))
        .await
    }

    async fn do_wake_compute(
        &self,
        ctx: &RequestContext,
        user_info: &ComputeUserInfo,
    ) -> Result<NodeInfo, WakeComputeError> {
        let request_id = ctx.session_id().to_string();
        let application_name = ctx.console_application_name();
        async {
            let mut request_builder = self
                .endpoint
                .get_path("wake_compute")
                .header("X-Request-ID", &request_id)
                .header("Authorization", format!("Bearer {}", &self.jwt))
                .query(&[("session_id", ctx.session_id())])
                .query(&[
                    ("application_name", application_name.as_str()),
                    ("endpointish", user_info.endpoint.as_str()),
                ]);

            let options = user_info.options.to_deep_object();
            if !options.is_empty() {
                request_builder = request_builder.query(&options);
            }

            let request = request_builder.build()?;

            debug!(url = request.url().as_str(), "sending http request");
            let start = Instant::now();
            let pause = ctx.latency_timer_pause(crate::metrics::Waiting::Cplane);
            let response = self.endpoint.execute(request).await?;
            drop(pause);
            info!(duration = ?start.elapsed(), "received http response");
            let body = parse_body::<WakeCompute>(response.status(), response.bytes().await?)?;

            // Unfortunately, ownership won't let us use `Option::ok_or` here.
            let (host, port) = match parse_host_port(&body.address) {
                None => return Err(WakeComputeError::BadComputeAddress(body.address)),
                Some(x) => x,
            };

            let host_addr = IpAddr::from_str(host).ok();

            let ssl_mode = match &body.server_name {
                Some(_) => SslMode::Require,
                None => SslMode::Disable,
            };
            let host_name = match body.server_name {
                Some(host) => host,
                None => host.to_owned(),
            };

            // Don't set anything but host and port! This config will be cached.
            // We'll set username and such later using the startup message.
            // TODO: add more type safety (in progress).
            let mut config = compute::ConnCfg::new(host_name, port);

            if let Some(addr) = host_addr {
                config.set_host_addr(addr);
            }

            config.ssl_mode(ssl_mode);

            let node = NodeInfo {
                config,
                aux: body.aux,
            };

            Ok(node)
        }
        .inspect_err(|e| tracing::debug!(error = ?e))
        .instrument(info_span!("do_wake_compute"))
        .await
    }
}

impl super::ControlPlaneApi for NeonControlPlaneClient {
    #[tracing::instrument(skip_all)]
    async fn get_role_access_control(
        &self,
        ctx: &RequestContext,
        endpoint: &EndpointId,
        role: &RoleName,
    ) -> Result<RoleAccessControl, crate::control_plane::errors::GetAuthInfoError> {
        let normalized_ep = &endpoint.normalize();
        if let Some(secret) = self
            .caches
            .project_info
            .get_role_secret(normalized_ep, role)
        {
            return Ok(secret);
        }

        if !self.caches.endpoints_cache.is_valid(ctx, normalized_ep) {
            info!("endpoint is not valid, skipping the request");
            return Err(GetAuthInfoError::UnknownEndpoint);
        }

        let auth_info = self.do_get_auth_req(ctx, endpoint, role).await?;

        let control = EndpointAccessControl {
            allowed_ips: Arc::new(auth_info.allowed_ips),
            allowed_vpce: Arc::new(auth_info.allowed_vpc_endpoint_ids),
            flags: auth_info.access_blocker_flags,
        };
        let role_control = RoleAccessControl {
            secret: auth_info.secret,
        };

        if let Some(project_id) = auth_info.project_id {
            let normalized_ep_int = normalized_ep.into();

            self.caches.project_info.insert_endpoint_access(
                auth_info.account_id,
                project_id,
                normalized_ep_int,
                role.into(),
                control,
                role_control.clone(),
            );
            ctx.set_project_id(project_id);
        }

        Ok(role_control)
    }

    #[tracing::instrument(skip_all)]
    async fn get_endpoint_access_control(
        &self,
        ctx: &RequestContext,
        endpoint: &EndpointId,
        role: &RoleName,
    ) -> Result<EndpointAccessControl, GetAuthInfoError> {
        let normalized_ep = &endpoint.normalize();
        if let Some(control) = self.caches.project_info.get_endpoint_access(normalized_ep) {
            return Ok(control);
        }

        if !self.caches.endpoints_cache.is_valid(ctx, normalized_ep) {
            info!("endpoint is not valid, skipping the request");
            return Err(GetAuthInfoError::UnknownEndpoint);
        }

        let auth_info = self.do_get_auth_req(ctx, endpoint, role).await?;

        let control = EndpointAccessControl {
            allowed_ips: Arc::new(auth_info.allowed_ips),
            allowed_vpce: Arc::new(auth_info.allowed_vpc_endpoint_ids),
            flags: auth_info.access_blocker_flags,
        };
        let role_control = RoleAccessControl {
            secret: auth_info.secret,
        };

        if let Some(project_id) = auth_info.project_id {
            let normalized_ep_int = normalized_ep.into();

            self.caches.project_info.insert_endpoint_access(
                auth_info.account_id,
                project_id,
                normalized_ep_int,
                role.into(),
                control.clone(),
                role_control,
            );
            ctx.set_project_id(project_id);
        }

        Ok(control)
    }

    #[tracing::instrument(skip_all)]
    async fn get_endpoint_jwks(
        &self,
        ctx: &RequestContext,
        endpoint: &EndpointId,
    ) -> Result<Vec<AuthRule>, GetEndpointJwksError> {
        self.do_get_endpoint_jwks(ctx, endpoint).await
    }

    #[tracing::instrument(skip_all)]
    async fn wake_compute(
        &self,
        ctx: &RequestContext,
        user_info: &ComputeUserInfo,
    ) -> Result<CachedNodeInfo, WakeComputeError> {
        let key = user_info.endpoint_cache_key();

        macro_rules! check_cache {
            () => {
                if let Some(cached) = self.caches.node_info.get(&key) {
                    let (cached, info) = cached.take_value();
                    let info = info.map_err(|c| {
                        info!(key = &*key, "found cached wake_compute error");
                        WakeComputeError::ControlPlane(ControlPlaneError::Message(Box::new(*c)))
                    })?;

                    debug!(key = &*key, "found cached compute node info");
                    ctx.set_project(info.aux.clone());
                    return Ok(cached.map(|()| info));
                }
            };
        }

        // Every time we do a wakeup http request, the compute node will stay up
        // for some time (highly depends on the console's scale-to-zero policy);
        // The connection info remains the same during that period of time,
        // which means that we might cache it to reduce the load and latency.
        check_cache!();

        let permit = self.locks.get_permit(&key).await?;

        // after getting back a permit - it's possible the cache was filled
        // double check
        if permit.should_check_cache() {
            // TODO: if there is something in the cache, mark the permit as success.
            check_cache!();
        }

        // check rate limit
        if !self
            .wake_compute_endpoint_rate_limiter
            .check(user_info.endpoint.normalize_intern(), 1)
        {
            return Err(WakeComputeError::TooManyConnections);
        }

        let node = permit.release_result(self.do_wake_compute(ctx, user_info).await);
        match node {
            Ok(node) => {
                ctx.set_project(node.aux.clone());
                debug!(key = &*key, "created a cache entry for woken compute node");

                let mut stored_node = node.clone();
                // store the cached node as 'warm_cached'
                stored_node.aux.cold_start_info = ColdStartInfo::WarmCached;

                let (_, cached) = self.caches.node_info.insert_unit(key, Ok(stored_node));

                Ok(cached.map(|()| node))
            }
            Err(err) => match err {
                WakeComputeError::ControlPlane(ControlPlaneError::Message(err)) => {
                    let Some(status) = &err.status else {
                        return Err(WakeComputeError::ControlPlane(ControlPlaneError::Message(
                            err,
                        )));
                    };

                    let reason = status
                        .details
                        .error_info
                        .map_or(Reason::Unknown, |x| x.reason);

                    // if we can retry this error, do not cache it.
                    if reason.can_retry() {
                        return Err(WakeComputeError::ControlPlane(ControlPlaneError::Message(
                            err,
                        )));
                    }

                    // at this point, we should only have quota errors.
                    debug!(
                        key = &*key,
                        "created a cache entry for the wake compute error"
                    );

                    self.caches.node_info.insert_ttl(
                        key,
                        Err(err.clone()),
                        Duration::from_secs(30),
                    );

                    Err(WakeComputeError::ControlPlane(ControlPlaneError::Message(
                        err,
                    )))
                }
                err => return Err(err),
            },
        }
    }
}

/// Parse http response body, taking status code into account.
fn parse_body<T: for<'a> serde::Deserialize<'a>>(
    status: StatusCode,
    body: Bytes,
) -> Result<T, ControlPlaneError> {
    if status.is_success() {
        // We shouldn't log raw body because it may contain secrets.
        info!("request succeeded, processing the body");
        return Ok(serde_json::from_slice(&body).map_err(std::io::Error::other)?);
    }

    // Log plaintext to be able to detect, whether there are some cases not covered by the error struct.
    info!("response_error plaintext: {:?}", body);

    // Don't throw an error here because it's not as important
    // as the fact that the request itself has failed.
    let mut body = serde_json::from_slice(&body).unwrap_or_else(|e| {
        warn!("failed to parse error body: {e}");
        Box::new(ControlPlaneErrorMessage {
            error: "reason unclear (malformed error message)".into(),
            http_status_code: status,
            status: None,
        })
    });
    body.http_status_code = status;

    warn!("console responded with an error ({status}): {body:?}");
    Err(ControlPlaneError::Message(body))
}

fn parse_host_port(input: &str) -> Option<(&str, u16)> {
    let (host, port) = input.rsplit_once(':')?;
    let ipv6_brackets: &[_] = &['[', ']'];
    Some((host.trim_matches(ipv6_brackets), port.parse().ok()?))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parse_host_port_v4() {
        let (host, port) = parse_host_port("127.0.0.1:5432").expect("failed to parse");
        assert_eq!(host, "127.0.0.1");
        assert_eq!(port, 5432);
    }

    #[test]
    fn test_parse_host_port_v6() {
        let (host, port) = parse_host_port("[2001:db8::1]:5432").expect("failed to parse");
        assert_eq!(host, "2001:db8::1");
        assert_eq!(port, 5432);
    }

    #[test]
    fn test_parse_host_port_url() {
        let (host, port) = parse_host_port("compute-foo-bar-1234.default.svc.cluster.local:5432")
            .expect("failed to parse");
        assert_eq!(host, "compute-foo-bar-1234.default.svc.cluster.local");
        assert_eq!(port, 5432);
    }
}