Merge pull request #224 from helix-editor/line_ending_detection

Line ending detection

1 files changed, 252 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..fa33204c
--- /dev/null
+++ b/helix-core/src/line_ending.rs
@@ -0,0 +1,252 @@
+use crate::{Rope, RopeGraphemes, RopeSlice};
+
+#[cfg(target_os = "windows")]
+pub const DEFAULT_LINE_ENDING: LineEnding = LineEnding::Crlf;
+#[cfg(not(target_os = "windows"))]
+pub const DEFAULT_LINE_ENDING: LineEnding = LineEnding::LF;
+
+/// 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
+}
+
+impl LineEnding {
+    #[inline]
+    pub fn len_chars(&self) -> usize {
+        match self {
+            Self::Crlf => 2,
+            _ => 1,
+        }
+    }
+
+    #[inline]
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Self::Crlf => "\u{000D}\u{000A}",
+            Self::LF => "\u{000A}",
+            Self::VT => "\u{000B}",
+            Self::FF => "\u{000C}",
+            Self::CR => "\u{000D}",
+            Self::Nel => "\u{0085}",
+            Self::LS => "\u{2028}",
+            Self::PS => "\u{2029}",
+        }
+    }
+
+    #[inline]
+    pub fn from_char(ch: char) -> Option<LineEnding> {
+        match ch {
+            '\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,
+        }
+    }
+
+    // Normally we'd want to implement the FromStr trait, but in this case
+    // that would force us into a different return type than from_char or
+    // or from_rope_slice, which would be weird.
+    #[allow(clippy::should_implement_trait)]
+    #[inline]
+    pub fn from_str(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,
+        }
+    }
+
+    #[inline]
+    pub fn from_rope_slice(g: &RopeSlice) -> Option<LineEnding> {
+        if let Some(text) = g.as_str() {
+            LineEnding::from_str(text)
+        } else {
+            // Non-contiguous, so it can't be a line ending.
+            // Specifically, Ropey guarantees that CRLF is always
+            // contiguous.  And the remaining line endings are all
+            // single `char`s, and therefore trivially contiguous.
+            None
+        }
+    }
+}
+
+#[inline]
+pub fn str_is_line_ending(s: &str) -> bool {
+    LineEnding::from_str(s).is_some()
+}
+
+/// Attempts to detect what line ending the passed document uses.
+pub fn auto_detect_line_ending(doc: &Rope) -> Option<LineEnding> {
+    // Return first matched line ending. Not all possible line endings
+    // are being matched, as they might be special-use only
+    for line in doc.lines().take(100) {
+        match get_line_ending(&line) {
+            None | Some(LineEnding::VT) | Some(LineEnding::FF) | Some(LineEnding::PS) => {}
+            ending => return ending,
+        }
+    }
+    None
+}
+
+/// Returns the passed line's line ending, if any.
+pub fn get_line_ending(line: &RopeSlice) -> Option<LineEnding> {
+    // Last character as str.
+    let g1 = line
+        .slice(line.len_chars().saturating_sub(1)..)
+        .as_str()
+        .unwrap();
+
+    // Last two characters as str, or empty str if they're not contiguous.
+    // It's fine to punt on the non-contiguous case, because Ropey guarantees
+    // that CRLF is always contiguous.
+    let g2 = line
+        .slice(line.len_chars().saturating_sub(2)..)
+        .as_str()
+        .unwrap_or("");
+
+    // First check the two-character case for CRLF, then check the single-character case.
+    LineEnding::from_str(g2).or_else(|| LineEnding::from_str(g1))
+}
+
+/// Returns the passed line's line ending, if any.
+pub fn get_line_ending_of_str(line: &str) -> Option<LineEnding> {
+    if line.ends_with("\u{000D}\u{000A}") {
+        Some(LineEnding::Crlf)
+    } else if line.ends_with('\u{000A}') {
+        Some(LineEnding::LF)
+    } else if line.ends_with('\u{000B}') {
+        Some(LineEnding::VT)
+    } else if line.ends_with('\u{000C}') {
+        Some(LineEnding::FF)
+    } else if line.ends_with('\u{000D}') {
+        Some(LineEnding::CR)
+    } else if line.ends_with('\u{0085}') {
+        Some(LineEnding::Nel)
+    } else if line.ends_with('\u{2028}') {
+        Some(LineEnding::LS)
+    } else if line.ends_with('\u{2029}') {
+        Some(LineEnding::PS)
+    } else {
+        None
+    }
+}
+
+/// Returns the char index of the end of the given line, not including its line ending.
+pub fn line_end_char_index(slice: &RopeSlice, line: usize) -> usize {
+    slice.line_to_char(line + 1)
+        - get_line_ending(&slice.line(line))
+            .map(|le| le.len_chars())
+            .unwrap_or(0)
+}
+
+#[cfg(test)]
+mod line_ending_tests {
+    use super::*;
+
+    #[test]
+    fn line_ending_autodetect() {
+        assert_eq!(
+            auto_detect_line_ending(&Rope::from_str("\n")),
+            Some(LineEnding::LF)
+        );
+        assert_eq!(
+            auto_detect_line_ending(&Rope::from_str("\r\n")),
+            Some(LineEnding::Crlf)
+        );
+        assert_eq!(auto_detect_line_ending(&Rope::from_str("hello")), None);
+        assert_eq!(auto_detect_line_ending(&Rope::from_str("")), None);
+        assert_eq!(
+            auto_detect_line_ending(&Rope::from_str("hello\nhelix\r\n")),
+            Some(LineEnding::LF)
+        );
+        assert_eq!(
+            auto_detect_line_ending(&Rope::from_str("a formfeed\u{000C}")),
+            None
+        );
+        assert_eq!(
+            auto_detect_line_ending(&Rope::from_str("\n\u{000A}\n \u{000A}")),
+            Some(LineEnding::LF)
+        );
+        assert_eq!(
+            auto_detect_line_ending(&Rope::from_str(
+                "a formfeed\u{000C} with a\u{000C} linefeed\u{000A}"
+            )),
+            Some(LineEnding::LF)
+        );
+        assert_eq!(auto_detect_line_ending(&Rope::from_str("a formfeed\u{000C} with a\u{000C} carriage return linefeed\u{000D}\u{000A} and a linefeed\u{000A}")), Some(LineEnding::Crlf));
+    }
+
+    #[test]
+    fn str_to_line_ending() {
+        assert_eq!(LineEnding::from_str("\r"), Some(LineEnding::CR));
+        assert_eq!(LineEnding::from_str("\n"), Some(LineEnding::LF));
+        assert_eq!(LineEnding::from_str("\r\n"), Some(LineEnding::Crlf));
+        assert_eq!(LineEnding::from_str("hello\n"), None);
+    }
+
+    #[test]
+    fn rope_slice_to_line_ending() {
+        let r = Rope::from_str("hello\r\n");
+        assert_eq!(
+            LineEnding::from_rope_slice(&r.slice(5..6)),
+            Some(LineEnding::CR)
+        );
+        assert_eq!(
+            LineEnding::from_rope_slice(&r.slice(6..7)),
+            Some(LineEnding::LF)
+        );
+        assert_eq!(
+            LineEnding::from_rope_slice(&r.slice(5..7)),
+            Some(LineEnding::Crlf)
+        );
+        assert_eq!(LineEnding::from_rope_slice(&r.slice(..)), None);
+    }
+
+    #[test]
+    fn get_line_ending_rope_slice() {
+        let r = Rope::from_str("Hello\rworld\nhow\r\nare you?");
+        assert_eq!(get_line_ending(&r.slice(..6)), Some(LineEnding::CR));
+        assert_eq!(get_line_ending(&r.slice(..12)), Some(LineEnding::LF));
+        assert_eq!(get_line_ending(&r.slice(..17)), Some(LineEnding::Crlf));
+        assert_eq!(get_line_ending(&r.slice(..)), None);
+    }
+
+    #[test]
+    fn get_line_ending_str() {
+        let text = "Hello\rworld\nhow\r\nare you?";
+        assert_eq!(get_line_ending_of_str(&text[..6]), Some(LineEnding::CR));
+        assert_eq!(get_line_ending_of_str(&text[..12]), Some(LineEnding::LF));
+        assert_eq!(get_line_ending_of_str(&text[..17]), Some(LineEnding::Crlf));
+        assert_eq!(get_line_ending_of_str(&text[..]), None);
+    }
+
+    #[test]
+    fn line_end_char_index_rope_slice() {
+        let r = Rope::from_str("Hello\rworld\nhow\r\nare you?");
+        let s = &r.slice(..);
+        assert_eq!(line_end_char_index(s, 0), 5);
+        assert_eq!(line_end_char_index(s, 1), 11);
+        assert_eq!(line_end_char_index(s, 2), 15);
+        assert_eq!(line_end_char_index(s, 3), 25);
+    }
+}