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// MIT License
//
// Copyright (c) 2021 TrueLayer
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
/// [`reqwest_otel_span!`](crate::reqwest_otel_span) creates a new [`tracing::Span`].
/// It empowers you to add custom properties to the span on top of the default properties provided by the macro.
///
/// Here are some convenient functions to checkout [`default_on_request_success`], [`default_on_request_failure`],
/// and [`default_on_request_end`].
///
/// # Why a macro?
///
/// [`tracing`] requires all the properties attached to a span to be declared upfront, when the span is created.
/// You cannot add new ones afterwards.
/// This makes it extremely fast, but it pushes us to reach for macros when we need some level of composition.
///
/// # Macro syntax
///
/// The first argument is a [span name](https://opentelemetry.io/docs/reference/specification/trace/api/#span).
/// The second argument passed to [`reqwest_otel_span!`](crate::reqwest_otel_span) is a reference to an [`reqwest::Request`].
///
/// ```rust
/// use reqwest_middleware::Result;
/// use http::Extensions;
/// use reqwest::{Request, Response};
/// use dogdata_reqwest_middleware::{
/// default_on_request_end, reqwest_otel_span, ReqwestOtelSpanBackend
/// };
/// use tracing::Span;
///
/// pub struct CustomReqwestOtelSpanBackend;
///
/// impl ReqwestOtelSpanBackend for CustomReqwestOtelSpanBackend {
/// fn on_request_start(req: &Request, _extension: &mut Extensions) -> Span {
/// reqwest_otel_span!(name = "reqwest-http-request", req)
/// }
///
/// fn on_request_end(span: &Span, outcome: &Result<Response>, _extension: &mut Extensions) {
/// default_on_request_end(span, outcome)
/// }
/// }
/// ```
///
/// If nothing else is specified, the span generated by `reqwest_otel_span!` is identical to the one you'd
/// get by using [`DefaultSpanBackend`]. Note that to avoid leaking sensitive information, the
/// macro doesn't include `url.full`, even though it's required by opentelemetry. You can add the
/// URL attribute explicitly by using [`SpanBackendWithUrl`] instead of `DefaultSpanBackend` or
/// adding the field on your own implementation.
///
/// You can define new fields following the same syntax of [`tracing::info_span!`] for fields:
///
/// ```rust,should_panic
/// use dogdata_reqwest_middleware::reqwest_otel_span;
/// # let request: &reqwest::Request = todo!();
///
/// // Define a `time_elapsed` field as empty. It might be populated later.
/// // (This example is just to show how to inject data - otel already tracks durations)
/// reqwest_otel_span!(name = "reqwest-http-request", request, time_elapsed = tracing::field::Empty);
///
/// // Define a `name` field with a known value, `AppName`.
/// reqwest_otel_span!(name = "reqwest-http-request", request, name = "AppName");
///
/// // Define an `app_id` field using the variable with the same name as value.
/// let app_id = "XYZ";
/// reqwest_otel_span!(name = "reqwest-http-request", request, app_id);
///
/// // All together
/// reqwest_otel_span!(name = "reqwest-http-request", request, time_elapsed = tracing::field::Empty, name = "AppName", app_id);
/// ```
///
/// You can also choose to customise the level of the generated span:
///
/// ```rust,should_panic
/// use dogdata_reqwest_middleware::reqwest_otel_span;
/// use tracing::Level;
/// # let request: &reqwest::Request = todo!();
///
/// // Reduce the log level for service endpoints/probes
/// let level = if request.method().as_str() == "POST" {
/// Level::DEBUG
/// } else {
/// Level::INFO
/// };
///
/// // `level =` and name MUST come before the request, in this order
/// reqwest_otel_span!(level = level, name = "reqwest-http-request", request);
/// ```
///
///
/// [`DefaultSpanBackend`]: crate::reqwest_otel_span_builder::DefaultSpanBackend
/// [`SpanBackendWithUrl`]: crate::reqwest_otel_span_builder::DefaultSpanBackend
/// [`default_on_request_success`]: crate::reqwest_otel_span_builder::default_on_request_success
/// [`default_on_request_failure`]: crate::reqwest_otel_span_builder::default_on_request_failure
/// [`default_on_request_end`]: crate::reqwest_otel_span_builder::default_on_request_end