1 files changed, 55 insertions, 0 deletions
diff --git a/modal.zig b/modal.zig
index 3038c430..2a195432 100644
--- a/modal.zig
+++ b/modal.zig
@@ -306,6 +306,38 @@ pub fn deleteLines(alloc: std.mem.Allocator, content: []const u8, r0: usize, r1:
     return .{ .content = try out.toOwnedSlice(alloc), .deleted = try deleted.toOwnedSlice(alloc) };
 }
 
+// normalize two cursors into document order (lo <= hi), then byte offsets of the
+// INCLUSIVE range [lo .. hi] (the char under hi is included). e == s means empty.
+fn rangeBytes(content: []const u8, a: Cursor, b: Cursor) struct { s: usize, e: usize } {
+    var lo = a;
+    var hi = b;
+    if (hi.row < lo.row or (hi.row == lo.row and hi.col < lo.col)) {
+        lo = b;
+        hi = a;
+    }
+    const s = lineStartOffset(content, lo.row) + @min(lo.col, lineSlice(content, lo.row).len);
+    var e = lineStartOffset(content, hi.row) + @min(hi.col, lineSlice(content, hi.row).len);
+    if (e < content.len) e += 1; // include the char under the head
+    return .{ .s = s, .e = @max(s, e) };
+}
+
+// the text of the inclusive char range [a, b] (cursors in either order). Caller frees.
+pub fn rangeText(alloc: std.mem.Allocator, content: []const u8, a: Cursor, b: Cursor) ![]u8 {
+    const r = rangeBytes(content, a, b);
+    return alloc.dupe(u8, content[r.s..r.e]);
+}
+
+// delete the inclusive char range [a, b]. returns new content + the removed text.
+pub fn deleteRange(alloc: std.mem.Allocator, content: []const u8, a: Cursor, b: Cursor) !Deleted {
+    const r = rangeBytes(content, a, b);
+    const deleted = try alloc.dupe(u8, content[r.s..r.e]);
+    errdefer alloc.free(deleted);
+    var out: std.ArrayList(u8) = .empty;
+    try out.appendSlice(alloc, content[0..r.s]);
+    try out.appendSlice(alloc, content[r.e..]);
+    return .{ .content = try out.toOwnedSlice(alloc), .deleted = deleted };
+}
+
 // replace line `row`'s text with "" (keep the line, empty it). For `c`hange line.
 pub fn clearLine(alloc: std.mem.Allocator, content: []const u8, row: usize) ![]u8 {
     const line = lineSlice(content, row);
@@ -884,6 +916,29 @@ test "deleteLines only line" {
     try std.testing.expectEqualStrings("only", d.deleted);
 }
 
+test "rangeText + deleteRange (char-wise select)" {
+    const a = std.testing.allocator;
+    const content = "hello\nworld\nfoo";
+    // same-line inclusive range: "hello"[1..3] -> "ell"
+    const t1 = try rangeText(a, content, .{ .row = 0, .col = 1 }, .{ .row = 0, .col = 3 });
+    defer a.free(t1);
+    try std.testing.expectEqualStrings("ell", t1);
+    // reversed cursors give the same range
+    const t2 = try rangeText(a, content, .{ .row = 0, .col = 3 }, .{ .row = 0, .col = 1 });
+    defer a.free(t2);
+    try std.testing.expectEqualStrings("ell", t2);
+    // cross-line range includes the newline: row0 col3 .. row1 col1 -> "lo\nwo"
+    const t3 = try rangeText(a, content, .{ .row = 0, .col = 3 }, .{ .row = 1, .col = 1 });
+    defer a.free(t3);
+    try std.testing.expectEqualStrings("lo\nwo", t3);
+    // delete the same cross-line range
+    const d = try deleteRange(a, content, .{ .row = 0, .col = 3 }, .{ .row = 1, .col = 1 });
+    defer a.free(d.content);
+    defer a.free(d.deleted);
+    try std.testing.expectEqualStrings("helrld\nfoo", d.content);
+    try std.testing.expectEqualStrings("lo\nwo", d.deleted);
+}
+
 test "clearLine" {
     const content = "keep\nzap me\nkeep2";
     const a = std.testing.allocator;