1 files changed, 74 insertions, 0 deletions
diff --git a/helix-core/src/line_ending.rs b/helix-core/src/line_ending.rs
new file mode 100644
index 00000000..8e9b2ec0
--- /dev/null
+++ b/helix-core/src/line_ending.rs
@@ -0,0 +1,74 @@
+use crate::{Rope, RopeGraphemes, RopeSlice};
+
+/// Represents one of the valid Unicode line endings.
+#[derive(PartialEq, Copy, Clone, Debug)]
+pub enum LineEnding {
+    Crlf, // CarriageReturn followed by LineFeed
+    LF,   // U+000A -- LineFeed
+    VT,   // U+000B -- VerticalTab
+    FF,   // U+000C -- FormFeed
+    CR,   // U+000D -- CarriageReturn
+    Nel,  // U+0085 -- NextLine
+    LS,   // U+2028 -- Line Separator
+    PS,   // U+2029 -- ParagraphSeparator
+}
+
+pub fn rope_slice_to_line_ending(g: &RopeSlice) -> Option<LineEnding> {
+    if let Some(text) = g.as_str() {
+        str_to_line_ending(text)
+    } else if g == "\u{000D}\u{000A}" {
+        Some(LineEnding::Crlf)
+    } else {
+        // Not a line ending
+        None
+    }
+}
+
+pub fn str_to_line_ending(g: &str) -> Option<LineEnding> {
+    match g {
+        "\u{000D}\u{000A}" => Some(LineEnding::Crlf),
+        "\u{000A}" => Some(LineEnding::LF),
+        "\u{000B}" => Some(LineEnding::VT),
+        "\u{000C}" => Some(LineEnding::FF),
+        "\u{000D}" => Some(LineEnding::CR),
+        "\u{0085}" => Some(LineEnding::Nel),
+        "\u{2028}" => Some(LineEnding::LS),
+        "\u{2029}" => Some(LineEnding::PS),
+
+        // Not a line ending
+        _ => None,
+    }
+}
+
+pub fn auto_detect_line_ending(doc: &Rope) -> Option<LineEnding> {
+    // based on https://github.com/cessen/led/blob/27572c8838a1c664ee378a19358604063881cc1d/src/editor/mod.rs#L88-L162
+
+    let mut ending = None;
+    for line in doc.lines().take(1) {
+        // check first line only - unsure how sound this is
+        ending = match line.len_chars() {
+            1 => {
+                let g = RopeGraphemes::new(line.slice((line.len_chars() - 1)..))
+                    .last()
+                    .unwrap();
+                rope_slice_to_line_ending(&g)
+            }
+            n if n > 1 => {
+                let g = RopeGraphemes::new(line.slice((line.len_chars() - 2)..))
+                    .last()
+                    .unwrap();
+                rope_slice_to_line_ending(&g)
+            }
+            _ => None,
+        }
+    }
+    ending
+}
+
+pub fn default_line_ending() -> Option<LineEnding> {
+    if cfg!(windows) {
+        Some(LineEnding::Crlf)
+    } else {
+        Some(LineEnding::LF)
+    }
+}