use std::collections::HashMap;

use codex_protocol::protocol::W3cTraceContext;
use opentelemetry::Context;
use opentelemetry::propagation::TextMapPropagator;
use opentelemetry::trace::TraceContextExt;
use opentelemetry_sdk::propagation::TraceContextPropagator;
use tracing::Span;
use tracing_opentelemetry::OpenTelemetrySpanExt;

pub fn current_span_w3c_trace_context() -> Option<W3cTraceContext> {
    let context = Span::current().context();
    if !context.span().span_context().is_valid() {
        return None;
    }

    let mut headers = HashMap::new();
    TraceContextPropagator::new().inject_context(&context, &mut headers);

    Some(W3cTraceContext {
        traceparent: headers.remove("traceparent"),
        tracestate: headers.remove("tracestate"),
    })
}

pub fn context_from_w3c_trace_context(trace: &W3cTraceContext) -> Option<Context> {
    context_from_trace_headers(trace.traceparent.as_deref(), trace.tracestate.as_deref())
}

pub fn set_parent_from_w3c_trace_context(span: &Span, trace: &W3cTraceContext) -> bool {
    if let Some(context) = context_from_w3c_trace_context(trace) {
        set_parent_from_context(span, context);
        true
    } else {
        false
    }
}

pub fn set_parent_from_context(span: &Span, context: Context) {
    let _ = span.set_parent(context);
}

pub(crate) fn context_from_trace_headers(
    traceparent: Option<&str>,
    tracestate: Option<&str>,
) -> Option<Context> {
    let traceparent = traceparent?;
    let mut headers = HashMap::new();
    headers.insert("traceparent".to_string(), traceparent.to_string());
    if let Some(tracestate) = tracestate {
        headers.insert("tracestate".to_string(), tracestate.to_string());
    }

    let context = TraceContextPropagator::new().extract(&headers);
    if !context.span().span_context().is_valid() {
        return None;
    }
    Some(context)
}

#[cfg(test)]
mod tests {
    use super::context_from_trace_headers;
    use super::context_from_w3c_trace_context;
    use codex_protocol::protocol::W3cTraceContext;
    use opentelemetry::trace::SpanId;
    use opentelemetry::trace::TraceContextExt;
    use opentelemetry::trace::TraceId;
    use pretty_assertions::assert_eq;

    #[test]
    fn parses_valid_w3c_trace_context() {
        let trace_id = "00000000000000000000000000000001";
        let span_id = "0000000000000002";
        let context = context_from_w3c_trace_context(&W3cTraceContext {
            traceparent: Some(format!("00-{trace_id}-{span_id}-01")),
            tracestate: None,
        })
        .expect("trace context");

        let span = context.span();
        let span_context = span.span_context();
        assert_eq!(
            span_context.trace_id(),
            TraceId::from_hex(trace_id).unwrap()
        );
        assert_eq!(span_context.span_id(), SpanId::from_hex(span_id).unwrap());
        assert!(span_context.is_remote());
    }

    #[test]
    fn invalid_traceparent_returns_none() {
        assert!(context_from_trace_headers(Some("not-a-traceparent"), None).is_none());
    }

    #[test]
    fn missing_traceparent_returns_none() {
        assert!(
            context_from_w3c_trace_context(&W3cTraceContext {
                traceparent: None,
                tracestate: Some("vendor=value".to_string()),
            })
            .is_none()
        );
    }
}