From bf4359a72f51044a3c6673580c9ea3647638144f Mon Sep 17 00:00:00 2001
From: Michael Nitschinger <michael@nitschinger.at>
Date: Tue, 13 Mar 2018 14:09:23 +0100
Subject: [PATCH] WIP: Span

---
 opentracing-api/src/lib.rs  |  4 ++-
 opentracing-api/src/span.rs | 61 +++++++++++++++++++++++++++++++++++++
 opentracing-api/src/tag.rs  |  6 ++++
 opentracing-noop/src/lib.rs | 52 ++++++++++++++++++++++++++++++-
 4 files changed, 121 insertions(+), 2 deletions(-)
 create mode 100644 opentracing-api/src/span.rs

diff --git a/opentracing-api/src/lib.rs b/opentracing-api/src/lib.rs
index ac6ec50..a8500a3 100644
--- a/opentracing-api/src/lib.rs
+++ b/opentracing-api/src/lib.rs
@@ -3,7 +3,9 @@
 mod context;
 mod tag;
 mod field;
+mod span;
 
 pub use context::SpanContext;
-pub use tag::{ParseTagsError, Tags};
+pub use tag::{ParseTagsError, TagValue, Tags};
 pub use field::{Fields, ParseFieldsError};
+pub use span::{FinishedSpan, Span};
diff --git a/opentracing-api/src/span.rs b/opentracing-api/src/span.rs
new file mode 100644
index 0000000..0e75c8c
--- /dev/null
+++ b/opentracing-api/src/span.rs
@@ -0,0 +1,61 @@
+use SpanContext;
+use TagValue;
+
+/// The `Span` represents the OpenTracing specification's Span contract.
+pub trait Span<'a> {
+    /// The associated `SpanContext`.
+    type Context: SpanContext<'a>;
+
+    /// Retrieve the associated `SpanContext`.
+    ///
+    /// This may be called any time, including after `finish`.
+    fn context(&self) -> &Self::Context;
+
+    /// Sets a key:value tag on the `Span`.
+    fn set_tag(&mut self, key: &str, value: TagValue);
+
+    /// Returns a tag value if set, none otherwise
+    fn tag(&self, key: &str) -> Option<&'a TagValue>;
+
+    /// Record an event at the current walltime timestamp.
+    fn log(&mut self, event: String);
+
+    /// Record an event at the given walltime timestamp.
+    fn log_at(&mut self, timestamp: u64, event: String);
+
+    /// Sets a baggage item in the Span (and its SpanContext) as a key/value pair.
+    fn set_baggage_item(&mut self, key: &str, value: String);
+
+    /// the value of the baggage item identified by the given key, or None if no such item
+    /// could be found.
+    fn baggage_item(&self, key: &str) -> Option<&'a String>;
+
+    /// Sets the string name for the logical operation this span represents.
+    fn set_operation_name(&mut self, name: &str);
+
+    /// Returns the operation name if set, None otherwise.
+    fn operation_name(&self) -> Option<&'a str>;
+
+    /// Sets the end timestamp to now and finishes (records) the span.
+    fn finish(self) -> FinishedSpan<Self::Context>;
+
+    /// Sets an explicit end timestamp and finishes (records) the span.
+    fn finish_at(self, timestamp: u64) -> FinishedSpan<Self::Context>;
+}
+
+pub struct FinishedSpan<C> {
+    context: C,
+}
+
+impl<'a, C> FinishedSpan<C>
+where
+    C: SpanContext<'a>,
+{
+    pub fn new(context: C) -> Self {
+        FinishedSpan { context }
+    }
+
+    pub fn context(&self) -> &C {
+        &self.context
+    }
+}
diff --git a/opentracing-api/src/tag.rs b/opentracing-api/src/tag.rs
index 9f3123d..faaee88 100644
--- a/opentracing-api/src/tag.rs
+++ b/opentracing-api/src/tag.rs
@@ -171,6 +171,12 @@ impl fmt::Display for ParseTagsError {
     }
 }
 
+pub enum TagValue {
+    String(String),
+    Boolean(bool),
+    Number(f64),
+}
+
 #[cfg(test)]
 mod tests {
 
diff --git a/opentracing-noop/src/lib.rs b/opentracing-noop/src/lib.rs
index abf365c..bbe5877 100644
--- a/opentracing-noop/src/lib.rs
+++ b/opentracing-noop/src/lib.rs
@@ -4,7 +4,7 @@
 
 extern crate opentracing_api;
 
-use opentracing_api::SpanContext;
+use opentracing_api::{FinishedSpan, Span, SpanContext, TagValue};
 use std::iter::{empty, Empty};
 
 /// The `NoopSpanContext` just returns an empty iterator on
@@ -25,6 +25,56 @@ impl<'a> SpanContext<'a> for NoopSpanContext {
     }
 }
 
+pub struct NoopSpan {
+    ctx: NoopSpanContext,
+}
+
+impl NoopSpan {
+    pub fn new() -> Self {
+        NoopSpan {
+            ctx: NoopSpanContext::default(),
+        }
+    }
+}
+
+impl<'a> Span<'a> for NoopSpan {
+    type Context = NoopSpanContext;
+
+    fn context(&self) -> &Self::Context {
+        &self.ctx
+    }
+
+    fn set_tag(&mut self, _key: &str, _value: TagValue) {}
+
+    fn tag(&self, _key: &str) -> Option<&'a TagValue> {
+        None
+    }
+
+    fn log(&mut self, _event: String) {}
+
+    fn log_at(&mut self, _timestamp: u64, _event: String) {}
+
+    fn set_baggage_item(&mut self, _key: &str, _value: String) {}
+
+    fn baggage_item(&self, _key: &str) -> Option<&'a String> {
+        None
+    }
+
+    fn set_operation_name(&mut self, _name: &str) {}
+
+    fn operation_name(&self) -> Option<&'a str> {
+        None
+    }
+
+    fn finish(self) -> FinishedSpan<Self::Context> {
+        FinishedSpan::new(self.ctx)
+    }
+
+    fn finish_at(self, _timestamp: u64) -> FinishedSpan<Self::Context> {
+        FinishedSpan::new(self.ctx)
+    }
+}
+
 #[cfg(test)]
 mod tests {