use opentelemetry_otlp::{SpanExporter, WithExportConfig, WithHttpConfig};
use opentelemetry_sdk::Resource;
use opentelemetry_sdk::trace::{Sampler, SdkTracerProvider};

use crate::config::{SamplerKind, TelemetryConfig};

pub fn build(
    config: &TelemetryConfig,
    resource: Resource,
    warnings: &mut Vec<String>,
) -> SdkTracerProvider {
    let mut builder = SdkTracerProvider::builder()
        .with_resource(resource)
        .with_sampler(sampler(config));

    if let Some(endpoint) = config.traces_url() {
        match exporter(config, &endpoint) {
            Ok(exporter) => builder = builder.with_batch_exporter(exporter),
            Err(error) => warnings.push(format!(
                "otlp span exporter disabled: {error} (endpoint {endpoint})"
            )),
        }
    }

    builder.build()
}

fn exporter(
    config: &TelemetryConfig,
    endpoint: &str,
) -> Result<SpanExporter, opentelemetry_otlp::ExporterBuildError> {
    let mut builder = SpanExporter::builder()
        .with_http()
        .with_endpoint(endpoint)
        .with_timeout(config.timeout);
    if !config.traces.headers.is_empty() {
        builder = builder.with_headers(config.traces.headers.clone());
    }
    builder.build()
}

fn sampler(config: &TelemetryConfig) -> Sampler {
    match config.sampler {
        SamplerKind::AlwaysOn => Sampler::AlwaysOn,
        SamplerKind::AlwaysOff => Sampler::AlwaysOff,
        SamplerKind::ParentBasedAlwaysOn => Sampler::ParentBased(Box::new(Sampler::AlwaysOn)),
        SamplerKind::ParentBasedAlwaysOff => Sampler::ParentBased(Box::new(Sampler::AlwaysOff)),
        SamplerKind::TraceIdRatio => Sampler::TraceIdRatioBased(config.sample_ratio),
        SamplerKind::ParentBasedTraceIdRatio => {
            Sampler::ParentBased(Box::new(Sampler::TraceIdRatioBased(config.sample_ratio)))
        }
    }
}