Implementing an Iterator for the Attributes struct (cloudevents#26)

Signed-off-by: Pranav Bhatt <[email protected]>

Author: pranav-bhatt

src/event/attributes.rs

@@ -1,7 +1,29 @@
 use super::{AttributesV03, AttributesV10, SpecVersion};
 use chrono::{DateTime, Utc};
+use std::fmt;
 use url::Url;
 
+#[derive(Debug, PartialEq)]
+pub enum AttributeValue<'a> {
+    SpecVersion(SpecVersion),
+    String(&'a str),
+    URI(&'a Url),
+    URIRef(&'a Url),
+    Time(&'a DateTime<Utc>),
+}
+
+impl fmt::Display for AttributeValue<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            AttributeValue::SpecVersion(s) => s.fmt(f),
+            AttributeValue::String(s) => f.write_str(s),
+            AttributeValue::URI(s) => f.write_str(&s.as_str()),
+            AttributeValue::URIRef(s) => f.write_str(&s.as_str()),
+            AttributeValue::Time(s) => f.write_str(&s.to_rfc3339()),
+        }
+    }
+}
+
 /// Trait to get [CloudEvents Context attributes](https://github.com/cloudevents/spec/blob/master/spec.md#context-attributes).
 pub trait AttributesReader {
     /// Get the [id](https://github.com/cloudevents/spec/blob/master/spec.md#id).

src/event/v03/attributes.rs

@@ -1,7 +1,7 @@
-use crate::event::attributes::{AttributesConverter, DataAttributesWriter};
+use crate::event::attributes::{AttributeValue, AttributesConverter, DataAttributesWriter};
 use crate::event::AttributesV10;
 use crate::event::{AttributesReader, AttributesWriter, SpecVersion};
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, NaiveDateTime, Utc};
 use hostname::get_hostname;
 use url::Url;
 use uuid::Uuid;
@@ -17,6 +17,60 @@ pub struct Attributes {
     pub(crate) time: Option<DateTime<Utc>>,
 }
 
+impl<'a> IntoIterator for &'a Attributes {
+    type Item = (&'a str, AttributeValue<'a>);
+    type IntoIter = AttributesIntoIterator<'a>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        AttributesIntoIterator {
+            attributes: self,
+            index: 0,
+        }
+    }
+}
+
+pub struct AttributesIntoIterator<'a> {
+    attributes: &'a Attributes,
+    index: usize,
+}
+
+impl<'a> Iterator for AttributesIntoIterator<'a> {
+    type Item = (&'a str, AttributeValue<'a>);
+    fn next(&mut self) -> Option<Self::Item> {
+        let result = match self.index {
+            0 => Some(("id", AttributeValue::String(&self.attributes.id))),
+            1 => Some(("type", AttributeValue::String(&self.attributes.ty))),
+            2 => Some(("source", AttributeValue::URIRef(&self.attributes.source))),
+            3 => self
+                .attributes
+                .datacontenttype
+                .as_ref()
+                .map(|v| ("datacontenttype", AttributeValue::String(v))),
+            4 => self
+                .attributes
+                .schemaurl
+                .as_ref()
+                .map(|v| ("schemaurl", AttributeValue::URIRef(v))),
+            5 => self
+                .attributes
+                .subject
+                .as_ref()
+                .map(|v| ("subject", AttributeValue::String(v))),
+            6 => self
+                .attributes
+                .time
+                .as_ref()
+                .map(|v| ("time", AttributeValue::Time(v))),
+            _ => return None,
+        };
+        self.index += 1;
+        if result.is_none() {
+            return self.next();
+        }
+        result
+    }
+}
+
 impl AttributesReader for Attributes {
     fn get_id(&self) -> &str {
         &self.id
@@ -121,3 +175,35 @@ impl AttributesConverter for Attributes {
         }
     }
 }
+
+#[test]
+fn iterator_test_V03() {
+    let a = Attributes {
+        id: String::from("1"),
+        ty: String::from("someType"),
+        source: Url::parse("https://example.net").unwrap(),
+        datacontenttype: None,
+        schemaurl: None,
+        subject: None,
+        time: Some(DateTime::<Utc>::from_utc(
+            NaiveDateTime::from_timestamp(61, 0),
+            Utc,
+        )),
+    };
+    let b = &mut a.into_iter();
+    let time = DateTime::<Utc>::from_utc(NaiveDateTime::from_timestamp(61, 0), Utc);
+
+    assert_eq!(("id", AttributeValue::String("1")), b.next().unwrap());
+    assert_eq!(
+        ("type", AttributeValue::String("someType")),
+        b.next().unwrap()
+    );
+    assert_eq!(
+        (
+            "source",
+            AttributeValue::URIRef(&Url::parse("https://example.net").unwrap())
+        ),
+        b.next().unwrap()
+    );
+    assert_eq!(("time", AttributeValue::Time(&time)), b.next().unwrap());
+}

src/event/v10/attributes.rs

@@ -1,6 +1,6 @@
-use crate::event::attributes::{AttributesConverter, DataAttributesWriter};
+use crate::event::attributes::{AttributeValue, AttributesConverter, DataAttributesWriter};
 use crate::event::{AttributesReader, AttributesV03, AttributesWriter, SpecVersion};
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, NaiveDateTime, Utc};
 use hostname::get_hostname;
 use url::Url;
 use uuid::Uuid;
@@ -16,6 +16,60 @@ pub struct Attributes {
     pub(crate) time: Option<DateTime<Utc>>,
 }
 
+impl<'a> IntoIterator for &'a Attributes {
+    type Item = (&'a str, AttributeValue<'a>);
+    type IntoIter = AttributesIntoIterator<'a>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        AttributesIntoIterator {
+            attributes: self,
+            index: 0,
+        }
+    }
+}
+
+pub struct AttributesIntoIterator<'a> {
+    attributes: &'a Attributes,
+    index: usize,
+}
+
+impl<'a> Iterator for AttributesIntoIterator<'a> {
+    type Item = (&'a str, AttributeValue<'a>);
+    fn next(&mut self) -> Option<Self::Item> {
+        let result = match self.index {
+            0 => Some(("id", AttributeValue::String(&self.attributes.id))),
+            1 => Some(("type", AttributeValue::String(&self.attributes.ty))),
+            2 => Some(("source", AttributeValue::URIRef(&self.attributes.source))),
+            3 => self
+                .attributes
+                .datacontenttype
+                .as_ref()
+                .map(|v| ("datacontenttype", AttributeValue::String(v))),
+            4 => self
+                .attributes
+                .dataschema
+                .as_ref()
+                .map(|v| ("dataschema", AttributeValue::URI(v))),
+            5 => self
+                .attributes
+                .subject
+                .as_ref()
+                .map(|v| ("subject", AttributeValue::String(v))),
+            6 => self
+                .attributes
+                .time
+                .as_ref()
+                .map(|v| ("time", AttributeValue::Time(v))),
+            _ => return None,
+        };
+        self.index += 1;
+        if result.is_none() {
+            return self.next();
+        }
+        result
+    }
+}
+
 impl AttributesReader for Attributes {
     fn get_id(&self) -> &str {
         &self.id
@@ -120,3 +174,35 @@ impl AttributesConverter for Attributes {
         }
     }
 }
+
+#[test]
+fn iterator_test_V10() {
+    let a = Attributes {
+        id: String::from("1"),
+        ty: String::from("someType"),
+        source: Url::parse("https://example.net").unwrap(),
+        datacontenttype: None,
+        dataschema: None,
+        subject: None,
+        time: Some(DateTime::<Utc>::from_utc(
+            NaiveDateTime::from_timestamp(61, 0),
+            Utc,
+        )),
+    };
+    let b = &mut a.into_iter();
+    let time = DateTime::<Utc>::from_utc(NaiveDateTime::from_timestamp(61, 0), Utc);
+
+    assert_eq!(("id", AttributeValue::String("1")), b.next().unwrap());
+    assert_eq!(
+        ("type", AttributeValue::String("someType")),
+        b.next().unwrap()
+    );
+    assert_eq!(
+        (
+            "source",
+            AttributeValue::URIRef(&Url::parse("https://example.net").unwrap())
+        ),
+        b.next().unwrap()
+    );
+    assert_eq!(("time", AttributeValue::Time(&time)), b.next().unwrap());
+}