Populate standard properties.

src/wasm/standard_properties.rs

@@ -1,19 +1,71 @@
 use organic::types::PostBlank;
+use organic::types::StandardProperties;
 use serde::Deserialize;
 use serde::Serialize;
 
-use super::macros::to_wasm;
+use super::to_wasm::ToWasmContext;
+use super::to_wasm::ToWasmStandardProperties;
 
 #[derive(Serialize, Deserialize)]
 pub(crate) struct WasmStandardProperties {
-    begin: Option<usize>,
-    end: Option<usize>,
+    begin: usize,
+    end: usize,
     contents_begin: Option<usize>,
     contents_end: Option<usize>,
-    post_blank: Option<PostBlank>,
+    post_blank: PostBlank,
 }
 
-to_wasm!(WasmStandardProperties, Document<'s>, original, document, {
-    // foo
-    todo!()
-});
+impl<'s, SP: StandardProperties<'s>> ToWasmStandardProperties for SP {
+    type Output = WasmStandardProperties;
+
+    fn to_wasm_standard_properties(
+        &self,
+        wasm_context: ToWasmContext<'_>,
+    ) -> Result<Self::Output, crate::error::CustomError> {
+        let (begin, end) = get_char_indices(wasm_context.full_document, self.get_source());
+        let (contents_begin, contents_end) = match self.get_contents() {
+            Some(contents) => {
+                let (begin, end) = get_char_indices(wasm_context.full_document, contents);
+                (Some(begin), Some(end))
+            }
+            None => (None, None),
+        };
+
+        let post_blank = self.get_post_blank();
+        Ok(WasmStandardProperties {
+            begin,
+            end,
+            contents_begin,
+            contents_end,
+            post_blank,
+        })
+    }
+}
+
+fn get_char_indices(original_document: &str, subset: &str) -> (usize, usize) {
+    let (begin_byte, end_byte) = get_rust_byte_offsets(original_document, subset);
+    // Add 1 to make this 1-based to match emacs.
+    let begin_char = original_document[..begin_byte].chars().count() + 1;
+    // Also 1-based:
+    let end_char = begin_char + original_document[begin_byte..end_byte].chars().count();
+    (begin_char, end_char)
+}
+
+/// Get the byte offset into source that the string slice exists at.
+///
+/// These offsets are zero-based.
+fn get_rust_byte_offsets(original_document: &str, subset: &str) -> (usize, usize) {
+    debug_assert!(is_slice_of(original_document, subset));
+    let offset = subset.as_ptr() as usize - original_document.as_ptr() as usize;
+    let end = offset + subset.len();
+    (offset, end)
+}
+
+/// Check if the child string slice is a slice of the parent string slice.
+fn is_slice_of(parent: &str, child: &str) -> bool {
+    let parent_start = parent.as_ptr() as usize;
+    let parent_end = parent_start + parent.len();
+    let child_start = child.as_ptr() as usize;
+    let child_end = child_start + child.len();
+    child_start >= parent_start && child_end <= parent_end
+}