init-tracing-opentelemetry 0.30.1

use super::infer_protocol;
use opentelemetry_otlp::{ExporterBuildError, SpanExporter};
use opentelemetry_sdk::{trace::SdkTracerProvider, trace::TracerProviderBuilder, Resource};
#[cfg(feature = "tls")]
use {opentelemetry_otlp::WithTonicConfig, tonic::transport::ClientTlsConfig};

#[must_use]
pub fn identity(v: TracerProviderBuilder) -> TracerProviderBuilder {
    v
}

// see https://opentelemetry.io/docs/reference/specification/protocol/exporter/
pub fn init_tracerprovider<F>(
    resource: Resource,
    transform: F,
) -> Result<SdkTracerProvider, ExporterBuildError>
where
    F: FnOnce(TracerProviderBuilder) -> TracerProviderBuilder,
{
    debug_env();
    let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
    let protocol = infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref());

    let exporter: Option<SpanExporter> = match protocol.as_deref() {
        Some("http/protobuf") => Some(SpanExporter::builder().with_http().build()?),
        #[cfg(feature = "tls")]
        Some("grpc/tls") => Some(
            SpanExporter::builder()
                .with_tonic()
                .with_tls_config(ClientTlsConfig::new().with_enabled_roots())
                .build()?,
        ),
        Some("grpc") => Some(SpanExporter::builder().with_tonic().build()?),
        Some(x) => {
            tracing::warn!("unknown '{x}' env var set or infered for OTEL_EXPORTER_OTLP_TRACES_PROTOCOL or OTEL_EXPORTER_OTLP_PROTOCOL; no span exporter will be created");
            None
        }
        None => {
            tracing::warn!("no env var set or infered for OTEL_EXPORTER_OTLP_TRACES_PROTOCOL or OTEL_EXPORTER_OTLP_PROTOCOL; no span exporter will be created");
            None
        }
    };
    let mut trace_provider = SdkTracerProvider::builder().with_resource(resource);
    if let Some(exporter) = exporter {
        trace_provider = trace_provider.with_batch_exporter(exporter);
    }

    trace_provider = transform(trace_provider);
    Ok(trace_provider.build())
}

pub fn debug_env() {
    std::env::vars()
        .filter(|(k, _)| k.starts_with("OTEL_"))
        .for_each(|(k, v)| tracing::debug!(target: "otel::setup::env", key = %k, value = %v));
}

fn read_protocol_and_endpoint_from_env() -> (Option<String>, Option<String>) {
    let maybe_protocol = std::env::var("OTEL_EXPORTER_OTLP_TRACES_PROTOCOL")
        .or_else(|_| std::env::var("OTEL_EXPORTER_OTLP_PROTOCOL"))
        .ok();
    let maybe_endpoint = std::env::var("OTEL_EXPORTER_OTLP_TRACES_ENDPOINT")
        .or_else(|_| {
            std::env::var("OTEL_EXPORTER_OTLP_ENDPOINT").map(|endpoint| match &maybe_protocol {
                Some(protocol) if protocol.contains("http") => {
                    format!("{endpoint}/v1/traces")
                }
                _ => endpoint,
            })
        })
        .ok();
    (maybe_protocol, maybe_endpoint)
}