hdi 0.7.0

The HDI
Documentation 
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use crate::hash_path::path::Component;
use crate::hash_path::path::Path;
use holochain_serialized_bytes::prelude::SerializedBytes;

/// This is the root of the [`Path`] tree.
///
/// Forms the entry point to all anchors so that agents can navigate down the tree from here.
pub const ROOT: &[u8; 2] = &[0x00, 0x00];

/// An anchor can only be 1 or 2 levels deep as "type" and "text".
///
/// The second level is optional and the Strings use the standard [`TryInto`] for path [`Component`] internally.
///
/// __Anchors are required to be included in an application's [`entry_defs`](crate::prelude::entry_types)__ callback and so implement all the standard methods.
/// Technically the [`Anchor`] entry definition is the [`Path`] definition.
///
/// e.g. `entry_defs![Anchor::entry_def()]`
///
/// The methods implemented on anchor follow the patterns that predate the Path module but `Path::from(&anchor)` is always possible to use the newer APIs.
#[derive(PartialEq, SerializedBytes, serde::Serialize, serde::Deserialize, Debug, Clone)]
pub struct Anchor {
    pub anchor_type: String,
    pub anchor_text: Option<String>,
}

/// Anchors are just a special case of path, so we can move from anchor to path losslessly.
/// We simply format the anchor structure into a string that works with the path string handling.
impl From<&Anchor> for Path {
    fn from(anchor: &Anchor) -> Self {
        let mut components = vec![
            Component::new(ROOT.to_vec()),
            Component::from(anchor.anchor_type.as_bytes().to_vec()),
        ];
        if let Some(text) = anchor.anchor_text.as_ref() {
            components.push(Component::from(text.as_bytes().to_vec()));
        }
        components.into()
    }
}

#[cfg(test)]
#[test]
fn hash_path_root() {
    assert_eq!(ROOT, &[0_u8, 0]);
}

#[cfg(test)]
#[test]
fn hash_path_anchor_path() {
    let examples = [
        (
            "foo",
            None,
            Path::from(vec![
                Component::from(vec![0, 0]),
                Component::from(vec![102, 111, 111]),
            ]),
        ),
        (
            "foo",
            Some("bar".to_string()),
            Path::from(vec![
                Component::from(vec![0, 0]),
                Component::from(vec![102, 111, 111]),
                Component::from(vec![98, 97, 114]),
            ]),
        ),
    ];
    for (atype, text, path) in examples {
        assert_eq!(
            path,
            (&Anchor {
                anchor_type: atype.to_string(),
                anchor_text: text,
            })
                .into(),
        );
    }
}