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// Originally retired from davidB/tracing-opentelemetry-instrumentation-sdk
// which is licensed under CC0 1.0 Universal
// https://github.com/davidB/tracing-opentelemetry-instrumentation-sdk/blob/d3609ac2cc699d3a24fbf89754053cc8e938e3bf/LICENSE

use opentelemetry::propagation::{Extractor, Injector};
use opentelemetry::Context;
use tracing_opentelemetry_instrumentation_sdk as otel;

// copy from crate opentelemetry-http (to not be dependants of on 3rd: http, ...)
pub struct HeaderInjector<'a>(pub &'a mut http::HeaderMap);

impl<'a> Injector for HeaderInjector<'a> {
    /// Set a key and value in the `HeaderMap`. Does nothing if the key or value are not valid inputs.
    fn set(&mut self, key: &str, value: String) {
        if let Ok(name) = http::header::HeaderName::from_bytes(key.as_bytes()) {
            if let Ok(val) = http::header::HeaderValue::from_str(&value) {
                self.0.insert(name, val);
            }
        }
    }
}

pub struct HeaderExtractor<'a>(pub &'a http::HeaderMap);

impl<'a> Extractor for HeaderExtractor<'a> {
    /// Get a value for a key from the `HeaderMap`. If the value is not valid ASCII, returns None.
    fn get(&self, key: &str) -> Option<&str> {
        self.0.get(key).and_then(|value| value.to_str().ok())
    }

    /// Collect all the keys from the `HeaderMap`.
    fn keys(&self) -> Vec<&str> {
        self.0
            .keys()
            .map(http::HeaderName::as_str)
            .collect::<Vec<_>>()
    }
}

pub fn inject_context_on_context(context: &Context, headers: &mut http::HeaderMap) {
    let mut injector = HeaderInjector(headers);
    opentelemetry::global::get_text_map_propagator(|propagator| {
        propagator.inject_context(context, &mut injector);
    });
}

pub fn inject_context(headers: &mut http::HeaderMap) {
    let mut injector = HeaderInjector(headers);
    opentelemetry::global::get_text_map_propagator(|propagator| {
        propagator.inject_context(&otel::find_current_context(), &mut injector);
    });
}

// If remote request has no span data the propagator defaults to an unsampled context
#[must_use]
pub fn extract_context(headers: &http::HeaderMap) -> Context {
    let extractor = HeaderExtractor(headers);
    opentelemetry::global::get_text_map_propagator(|propagator| {
        propagator.extract(&extractor)
    })
}