1 files changed, 137 insertions, 0 deletions

diff --git a/xtask/src/codegen/gen_assists_docs.rs b/xtask/src/codegen/gen_assists_docs.rs
new file mode 100644
index 000000000..05afda8f1
--- /dev/null
+++ b/xtask/src/codegen/gen_assists_docs.rs
@@ -0,0 +1,137 @@
+use std::{fs, path::Path};
+
+use crate::{
+    codegen::{self, extract_comment_blocks_with_empty_lines, Mode},
+    project_root, Result,
+};
+
+pub fn generate_assists_docs(mode: Mode) -> Result<()> {
+    let assists = collect_assists()?;
+    generate_tests(&assists, mode)?;
+    generate_docs(&assists, mode)?;
+    Ok(())
+}
+
+#[derive(Debug)]
+struct Assist {
+    id: String,
+    doc: String,
+    before: String,
+    after: String,
+}
+
+fn collect_assists() -> Result<Vec<Assist>> {
+    let mut res = Vec::new();
+    for entry in fs::read_dir(project_root().join(codegen::ASSISTS_DIR))? {
+        let entry = entry?;
+        let path = entry.path();
+        if path.is_file() {
+            collect_file(&mut res, path.as_path())?;
+        }
+    }
+    res.sort_by(|lhs, rhs| lhs.id.cmp(&rhs.id));
+    return Ok(res);
+
+    fn collect_file(acc: &mut Vec<Assist>, path: &Path) -> Result<()> {
+        let text = fs::read_to_string(path)?;
+        let comment_blocks = extract_comment_blocks_with_empty_lines(&text);
+
+        for block in comment_blocks {
+            // FIXME: doesn't support blank lines yet, need to tweak
+            // `extract_comment_blocks` for that.
+            let mut lines = block.iter();
+            let first_line = lines.next().unwrap();
+            if !first_line.starts_with("Assist: ") {
+                continue;
+            }
+            let id = first_line["Assist: ".len()..].to_string();
+            assert!(
+                id.chars().all(|it| it.is_ascii_lowercase() || it == '_'),
+                "invalid assist id: {:?}",
+                id
+            );
+
+            let doc = take_until(lines.by_ref(), "```").trim().to_string();
+            assert!(
+                doc.chars().next().unwrap().is_ascii_uppercase() && doc.ends_with('.'),
+                "\n\n{}: assist docs should be proper sentences, with capitalization and a full stop at the end.\n\n{}\n\n",
+                id, doc,
+            );
+
+            let before = take_until(lines.by_ref(), "```");
+
+            assert_eq!(lines.next().unwrap().as_str(), "->");
+            assert_eq!(lines.next().unwrap().as_str(), "```");
+            let after = take_until(lines.by_ref(), "```");
+            acc.push(Assist { id, doc, before, after })
+        }
+
+        fn take_until<'a>(lines: impl Iterator<Item = &'a String>, marker: &str) -> String {
+            let mut buf = Vec::new();
+            for line in lines {
+                if line == marker {
+                    break;
+                }
+                buf.push(line.clone());
+            }
+            buf.join("\n")
+        }
+        Ok(())
+    }
+}
+
+fn generate_tests(assists: &[Assist], mode: Mode) -> Result<()> {
+    let mut buf = String::from("use super::check;\n");
+
+    for assist in assists.iter() {
+        let test = format!(
+            r######"
+#[test]
+fn doctest_{}() {{
+    check(
+        "{}",
+r#####"
+{}
+"#####, r#####"
+{}
+"#####)
+}}
+"######,
+            assist.id, assist.id, assist.before, assist.after
+        );
+
+        buf.push_str(&test)
+    }
+    let buf = codegen::reformat(buf)?;
+    codegen::update(&project_root().join(codegen::ASSISTS_TESTS), &buf, mode)
+}
+
+fn generate_docs(assists: &[Assist], mode: Mode) -> Result<()> {
+    let mut buf = String::from(
+        "# Assists\n\nCursor position or selection is signified by `┃` character.\n\n",
+    );
+
+    for assist in assists {
+        let before = assist.before.replace("<|>", "┃"); // Unicode pseudo-graphics bar
+        let after = assist.after.replace("<|>", "┃");
+        let docs = format!(
+            "
+## `{}`
+
+{}
+
+```rust
+// BEFORE
+{}
+
+// AFTER
+{}
+```
+",
+            assist.id, assist.doc, before, after
+        );
+        buf.push_str(&docs);
+    }
+
+    codegen::update(&project_root().join(codegen::ASSISTS_DOCS), &buf, mode)
+}