1 files changed, 59 insertions, 0 deletions

diff --git a/bin/src/fix/single.rs b/bin/src/fix/single.rs
new file mode 100644
index 0000000..d430693
--- /dev/null
+++ b/bin/src/fix/single.rs
@@ -0,0 +1,59 @@
+use std::{borrow::Cow, convert::TryFrom};
+
+use lib::{Report, LINTS};
+use rnix::{TextRange, TextSize};
+
+use crate::err::SingleFixErr;
+use crate::fix::Source;
+
+pub struct SingleFixResult<'δ> {
+    pub src: Source<'δ>,
+}
+
+fn pos_to_byte(line: usize, col: usize, src: &str) -> Result<TextSize, SingleFixErr> {
+    let mut byte: TextSize = TextSize::of("");
+    for (_, l) in src.lines().enumerate().take_while(|(i, _)| i <= &line) {
+        byte += TextSize::of(l);
+    }
+    byte += TextSize::try_from(col).map_err(|_| SingleFixErr::Conversion(col))?;
+
+    if usize::from(byte) >= src.len() {
+        Err(SingleFixErr::OutOfBounds(line, col))
+    } else {
+        Ok(byte)
+    }
+}
+
+fn find(offset: TextSize, src: &str) -> Result<Report, SingleFixErr> {
+    // we don't really need the source to form a completely parsed tree
+    let parsed = rnix::parse(src);
+
+    let elem_at = parsed
+        .node()
+        .child_or_token_at_range(TextRange::empty(offset))
+        .ok_or(SingleFixErr::NoOp)?;
+
+    LINTS
+        .get(&elem_at.kind())
+        .map(|rules| {
+            rules
+                .iter()
+                .filter_map(|rule| rule.validate(&elem_at))
+                .filter(|report| report.total_suggestion_range().is_some())
+                .next()
+        })
+        .flatten()
+        .ok_or(SingleFixErr::NoOp)
+}
+
+pub fn single(line: usize, col: usize, src: &str) -> Result<SingleFixResult, SingleFixErr> {
+    let mut src = Cow::from(src);
+    let offset = pos_to_byte(line, col, &*src)?;
+    let report = find(offset, &*src)?;
+
+    report.apply(src.to_mut());
+
+    Ok(SingleFixResult {
+        src
+    })
+}