// Copyright 2025 The NativeLink Authors. All rights reserved.

//

// 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 core::default::Default;

use std::env;

use std::sync::OnceLock;

use base64::Engine;

use base64::prelude::BASE64_STANDARD_NO_PAD;

use hyper::http::Response;

use nativelink_error::{Code, ResultExt, make_err};

use nativelink_proto::build::bazel::remote::execution::v2::RequestMetadata;

use opentelemetry::propagation::TextMapCompositePropagator;

use opentelemetry::trace::{TraceContextExt, Tracer, TracerProvider};

use opentelemetry::{KeyValue, global};

use opentelemetry_appender_tracing::layer::OpenTelemetryTracingBridge;

use opentelemetry_http::HeaderExtractor;

use opentelemetry_otlp::{LogExporter, MetricExporter, Protocol, SpanExporter, WithExportConfig};

use opentelemetry_sdk::Resource;

use opentelemetry_sdk::logs::SdkLoggerProvider;

use opentelemetry_sdk::metrics::SdkMeterProvider;

use opentelemetry_sdk::propagation::{BaggagePropagator, TraceContextPropagator};

use opentelemetry_sdk::trace::SdkTracerProvider;

use opentelemetry_semantic_conventions::attribute::ENDUSER_ID;

use prost::Message;

use tracing::debug;

use tracing::metadata::LevelFilter;

use tracing_opentelemetry::{MetricsLayer, layer};

use tracing_subscriber::filter::Directive;

use tracing_subscriber::prelude::__tracing_subscriber_SubscriberExt;

use tracing_subscriber::util::SubscriberInitExt;

use tracing_subscriber::{EnvFilter, Layer, Registry, fmt, registry};

use uuid::Uuid;

/// The OTLP "service.name" field for all nativelink services.

const NATIVELINK_SERVICE_NAME: &str = "nativelink";

// An `EnvFilter` to filter out non-nativelink information.

//

// See: https://github.com/open-telemetry/opentelemetry-rust/issues/2877

//

// Note that `EnvFilter` doesn't implement `clone`, so create a new one for

// each telemetry kind.

fn otlp_filter() -> EnvFilter {

    fn expect_parse(directive: &str) -> Directive {

        directive

            .parse()

            .unwrap_or_else(|_| panic!("Static directive '{directive}' failed to parse"))

    }

    EnvFilter::builder()

        .with_default_directive(LevelFilter::INFO.into())

        .from_env_lossy()

        .add_directive(expect_parse("hyper=off"))

        .add_directive(expect_parse("tonic=off"))

        .add_directive(expect_parse("h2=off"))

        .add_directive(expect_parse("reqwest=off"))

        .add_directive(expect_parse("tower=off"))

}

// Create a tracing layer intended for stdout printing.

//

// The output of this layer is configurable via the `NL_LOG_FMT` environment

// variable.

fn tracing_stdout_layer() -> impl Layer<Registry> {

    let nl_log_fmt = env::var("NL_LOG").unwrap_or_else(|_| "pretty".to_string());

    let stdout_filter = otlp_filter();

    match nl_log_fmt.as_str() {

        "compact" => fmt::layer()

            .compact()

            .with_timer(fmt::time::time())

            .with_filter(stdout_filter)

            .boxed(),

        "json" => fmt::layer()

            .json()

            .with_timer(fmt::time::time())

            .with_filter(stdout_filter)

            .boxed(),

        _ => fmt::layer()

            .pretty()

            .with_timer(fmt::time::time())

            .with_filter(stdout_filter)

            .boxed(),

    }

}

/// Initialize tracing with OpenTelemetry support.

///

/// # Errors

///

/// Returns `Err` if logging was already initialized or if the exporters can't

/// be initialized.

pub fn init_tracing() -> Result<(), nativelink_error::Error> {

    static INITIALIZED: OnceLock<()> = OnceLock::new();

    if INITIALIZED.get().is_some() {

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        return Err(make_err!(Code::Internal, "Logging already initialized"));

    }

    // We currently use a UUIDv4 for "service.instance.id" as per:

    // https://opentelemetry.io/docs/specs/semconv/attributes-registry/service/

    // This might change as we get a better understanding of its usecases in the

    // context of broader observability infrastructure.

    let resource = Resource::builder()

        .with_service_name(NATIVELINK_SERVICE_NAME)

        .with_attribute(KeyValue::new(

            "service.instance.id",

            Uuid::new_v4().to_string(),

        ))

        .build();

    let propagator = TextMapCompositePropagator::new(vec![

        Box::new(BaggagePropagator::new()),

        Box::new(TraceContextPropagator::new()),

    ]);

    global::set_text_map_propagator(propagator);

    // Logs

    let otlp_log_layer = OpenTelemetryTracingBridge::new(

        &SdkLoggerProvider::builder()

            .with_resource(resource.clone())

            .with_batch_exporter(

                LogExporter::builder()

                    .with_tonic()

                    .with_protocol(Protocol::Grpc)

                    .build()

                    .map_err(|e| make_err!(Code::Internal, "{e}"))

                    .err_tip(|| "While creating OpenTelemetry OTLP Log exporter")?,

            )

            .build(),

    )

    .with_filter(otlp_filter());

    // Traces

    let otlp_trace_layer = layer()

        .with_tracer(

            SdkTracerProvider::builder()

                .with_resource(resource.clone())

                .with_batch_exporter(

                    SpanExporter::builder()

                        .with_tonic()

                        .with_protocol(Protocol::Grpc)

                        .build()

                        .map_err(|e| make_err!(Code::Internal, "{e}"))

                        .err_tip(|| "While creating OpenTelemetry OTLP Span exporter")?,

                )

                .build()

                .tracer(NATIVELINK_SERVICE_NAME),

        )

        .with_filter(otlp_filter());

    // Metrics

    let meter_provider = SdkMeterProvider::builder()

        .with_resource(resource)

        .with_periodic_exporter(

            MetricExporter::builder()

                .with_tonic()

                .with_protocol(Protocol::Grpc)

                .build()

                .map_err(|e| make_err!(Code::Internal, "{e}"))

                .err_tip(|| "While creating OpenTelemetry OTLP Metric exporter")?,

        )

        .build();

    global::set_meter_provider(meter_provider.clone());

    let otlp_metrics_layer = MetricsLayer::new(meter_provider).with_filter(otlp_filter());

    registry()

        .with(tracing_stdout_layer())

        .with(otlp_log_layer)

        .with(otlp_trace_layer)

        .with(otlp_metrics_layer)

        .init();

    INITIALIZED.set(()).unwrap_or(());

    Ok(())

}

/// Custom metadata key field for Bazel metadata.

const BAZEL_METADATA_KEY: &str = "bazel.metadata";

/// This is the header that bazel sends when using the `--remote_header` flag.

/// TODO(aaronmondal): There are various other headers that bazel supports.

///                    Optimize their usage.

const BAZEL_REQUESTMETADATA_HEADER: &str = "build.bazel.remote.execution.v2.requestmetadata-bin";

use opentelemetry::baggage::BaggageExt;

use opentelemetry::context::FutureExt;

#[derive(Debug, Clone)]

pub struct OtlpMiddleware<S> {

    inner: S,

    identity_required: bool,

}

impl<S> OtlpMiddleware<S> {

    const fn new(inner: S, identity_required: bool) -> Self {

        Self {

            inner,

            identity_required,

        }

    }

}

impl<S, ReqBody, ResBody> tower::Service<hyper::http::Request<ReqBody>> for OtlpMiddleware<S>

where

    S: tower::Service<hyper::http::Request<ReqBody>, Response = Response<ResBody>>

        + Clone

        + Send

        + 'static,

    S::Future: Send + 'static,

    ReqBody: core::fmt::Debug + Send + 'static,

    ResBody: From<String> + Send + 'static + Default,

{

    type Response = S::Response;

    type Error = S::Error;

    type Future = futures::future::BoxFuture<'static, Result<Self::Response, Self::Error>>;

    fn poll_ready(

        &mut self,

        cx: &mut core::task::Context<'_>,

    ) -> core::task::Poll<Result<(), Self::Error>> {

        self.inner.poll_ready(cx)

    }

    fn call(&mut self, req: hyper::http::Request<ReqBody>) -> Self::Future {

        // We must take the current `inner` and not the clone.

        // See: https://docs.rs/tower/latest/tower/trait.Service.html#be-careful-when-cloning-inner-services

        let clone = self.inner.clone();

        let mut inner = core::mem::replace(&mut self.inner, clone);

        let parent_cx = global::get_text_map_propagator(|propagator| {

            propagator.extract(&HeaderExtractor(req.headers()))

        });

        let identity = parent_cx

            .baggage()

            .get(ENDUSER_ID)

            .map(|value| value.as_str().to_string())

            .unwrap_or_default();

        if identity.is_empty() && self.identity_required {

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            return Box::pin(async move {

                Ok(tonic::Status::failed_precondition(

                    r"

NativeLink instance configured to require this OpenTelemetry Baggage header:

    `Baggage: enduser.id=YOUR_IDENTITY`

",

                )

                .into_http())

            });

        }

        debug!("Baggage enduser.id: {identity}");

        let tracer = global::tracer("origin_middleware");

        let span = tracer

            .span_builder("origin_request")

            .with_kind(opentelemetry::trace::SpanKind::Server)

            .start_with_context(&tracer, &parent_cx);

        let mut cx = parent_cx.with_span(span);

        if let Some(bazel_header) = req.headers().get(BAZEL_REQUESTMETADATA_HEADER) {

  Branch (282:16): [Folded - Ignored]

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            if let Ok(decoded) = BASE64_STANDARD_NO_PAD.decode(bazel_header.as_bytes()) {

  Branch (283:20): [Folded - Ignored]

  Branch (283:20): [Folded - Ignored]

                if let Ok(metadata) = RequestMetadata::decode(decoded.as_slice()) {

  Branch (284:24): [Folded - Ignored]

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                    let metadata_str = format!("{metadata:?}");

                    debug!("Baggage Bazel request metadata: {metadata_str}");

                    cx = cx.with_baggage(vec![

                        KeyValue::new(BAZEL_METADATA_KEY, metadata_str),

                        KeyValue::new(ENDUSER_ID, identity),

                    ]);

                }

            }

        }

        Box::pin(async move { inner.call(req).with_context(cx).await })

    }

}

#[derive(Debug, Clone, Copy)]

pub struct OtlpLayer {

    identity_required: bool,

}

impl OtlpLayer {

    pub const fn new(identity_required: bool) -> Self {

        Self { identity_required }

    }

}

impl<S> tower::Layer<S> for OtlpLayer {

    type Service = OtlpMiddleware<S>;

    fn layer(&self, service: S) -> Self::Service {

        OtlpMiddleware::new(service, self.identity_required)

    }

}