Add (prev) paragraph motion

Also improved testing facility.

Fix #1580

1 files changed, 111 insertions, 0 deletions

diff --git a/helix-core/src/test.rs b/helix-core/src/test.rs
new file mode 100644
index 00000000..983c9a57
--- /dev/null
+++ b/helix-core/src/test.rs
@@ -0,0 +1,111 @@
+//! Test helpers.
+use crate::{Range, Selection};
+use smallvec::SmallVec;
+use std::cmp::Reverse;
+
+/// Convert annotated test string to test string and selection.
+///
+/// `^` for `anchor` and `|` for head (`@` for primary), both must appear
+/// or otherwise it will panic.
+///
+/// # Examples
+///
+/// ```
+/// use helix_core::{Range, Selection, test::print};
+/// use smallvec::smallvec;
+///
+/// assert_eq!(
+///     print("^a@b|c^"),
+///     ("abc".to_owned(), Selection::new(smallvec![Range::new(0, 1), Range::new(3, 2)], 0))
+/// );
+/// ```
+///
+/// # Panics
+///
+/// Panics when missing primary or appeared more than once.
+/// Panics when missing head or anchor.
+/// Panics when head come after head or anchor come after anchor.
+pub fn print(s: &str) -> (String, Selection) {
+    let mut anchor = None;
+    let mut head = None;
+    let mut primary = None;
+    let mut ranges = SmallVec::new();
+    let mut i = 0;
+    let s = s
+        .chars()
+        .filter(|c| {
+            match c {
+                '^' if anchor != None => panic!("anchor without head {s:?}"),
+                '^' if head == None => anchor = Some(i),
+                '^' => ranges.push(Range::new(i, head.take().unwrap())),
+                '|' if head != None => panic!("head without anchor {s:?}"),
+                '|' if anchor == None => head = Some(i),
+                '|' => ranges.push(Range::new(anchor.take().unwrap(), i)),
+                '@' if primary != None => panic!("head (primary) already appeared {s:?}"),
+                '@' if head != None => panic!("head (primary) without anchor {s:?}"),
+                '@' if anchor == None => {
+                    primary = Some(ranges.len());
+                    head = Some(i);
+                }
+                '@' => {
+                    primary = Some(ranges.len());
+                    ranges.push(Range::new(anchor.take().unwrap(), i));
+                }
+                _ => {
+                    i += 1;
+                    return true;
+                }
+            };
+            false
+        })
+        .collect();
+    if head.is_some() {
+        panic!("missing anchor (|) {s:?}");
+    }
+    if anchor.is_some() {
+        panic!("missing head (^) {s:?}");
+    }
+    let primary = match primary {
+        Some(i) => i,
+        None => panic!("missing primary (@) {s:?}"),
+    };
+    let selection = Selection::new(ranges, primary);
+    (s, selection)
+}
+
+/// Convert test string and selection to annotated test string.
+///
+/// `^` for `anchor` and `|` for head (`@` for primary).
+///
+/// # Examples
+///
+/// ```
+/// use helix_core::{Range, Selection, test::plain};
+/// use smallvec::smallvec;
+///
+/// assert_eq!(
+///     plain("abc", Selection::new(smallvec![Range::new(0, 1), Range::new(3, 2)], 0)),
+///     "^a@b|c^".to_owned()
+/// );
+/// ```
+pub fn plain(s: &str, selection: Selection) -> String {
+    let primary = selection.primary_index();
+    let mut out = String::with_capacity(s.len() + 2 * selection.len());
+    out.push_str(s);
+    let mut insertion: Vec<_> = selection
+        .iter()
+        .enumerate()
+        .flat_map(|(i, range)| {
+            [
+                (range.anchor, '^'),
+                (range.head, if i == primary { '@' } else { '|' }),
+            ]
+        })
+        .collect();
+    // insert in reverse order
+    insertion.sort_unstable_by_key(|k| Reverse(k.0));
+    for (i, c) in insertion {
+        out.insert(i, c);
+    }
+    out
+}