Feat: wire up a very basic dom updater

packages/core/src/patch.rs

@@ -0,0 +1,79 @@
+use fxhash::FxHashMap;
+
+use crate::innerlude::{VNode, VText};
+
+/// A Patch encodes an operation that modifies a real DOM element.
+///
+/// To update the real DOM that a user sees you'll want to first diff your
+/// old virtual dom and new virtual dom.
+///
+/// This diff operation will generate `Vec<Patch>` with zero or more patches that, when
+/// applied to your real DOM, will make your real DOM look like your new virtual dom.
+///
+/// Each Patch has a u32 node index that helps us identify the real DOM node that it applies to.
+///
+/// Our old virtual dom's nodes are indexed depth first, as shown in this illustration
+/// (0 being the root node, 1 being it's first child, 2 being it's first child's first child).
+///
+/// ```text
+///             .─.
+///            ( 0 )
+///             `┬'
+///         ┌────┴──────┐
+///         │           │
+///         ▼           ▼
+///        .─.         .─.
+///       ( 1 )       ( 4 )
+///        `┬'         `─'
+///    ┌────┴───┐       ├─────┬─────┐
+///    │        │       │     │     │
+///    ▼        ▼       ▼     ▼     ▼
+///   .─.      .─.     .─.   .─.   .─.
+///  ( 2 )    ( 3 )   ( 5 ) ( 6 ) ( 7 )
+///   `─'      `─'     `─'   `─'   `─'                  
+/// ```
+///
+/// The patching process is tested in a real browser in crates/virtual-dom-rs/tests/diff_patch.rs
+
+pub enum Patch<'a> {
+    /// Append a vector of child nodes to a parent node id.
+    AppendChildren(NodeIdx, Vec<&'a VNode<'a>>),
+
+    /// For a `node_i32`, remove all children besides the first `len`
+    TruncateChildren(NodeIdx, usize),
+
+    /// Replace a node with another node. This typically happens when a node's tag changes.
+    /// ex: <div> becomes <span>
+    Replace(NodeIdx, &'a VNode<'a>),
+
+    /// Add attributes that the new node has that the old node does not
+    AddAttributes(NodeIdx, FxHashMap<&'a str, &'a str>),
+
+    /// Remove attributes that the old node had that the new node doesn't
+    RemoveAttributes(NodeIdx, Vec<&'a str>),
+
+    /// Change the text of a Text node.
+    ChangeText(NodeIdx, &'a VText<'a>),
+}
+
+type NodeIdx = usize;
+
+impl<'a> Patch<'a> {
+    /// Every Patch is meant to be applied to a specific node within the DOM. Get the
+    /// index of the DOM node that this patch should apply to. DOM nodes are indexed
+    /// depth first with the root node in the tree having index 0.
+    pub fn node_idx(&self) -> usize {
+        match self {
+            Patch::AppendChildren(node_idx, _) => *node_idx,
+            Patch::TruncateChildren(node_idx, _) => *node_idx,
+            Patch::Replace(node_idx, _) => *node_idx,
+            Patch::AddAttributes(node_idx, _) => *node_idx,
+            Patch::RemoveAttributes(node_idx, _) => *node_idx,
+            Patch::ChangeText(node_idx, _) => *node_idx,
+        }
+    }
+}
+
+pub struct PatchList<'a> {
+    patches: Vec<Patch<'a>>,
+}