Initial public release

src/text_manip.zig

@@ -0,0 +1,63 @@
+const std = @import("std");
+const TextWriter = std.ArrayList(u8).Writer;
+
+pub fn find_first_non_ws(text: []const u8) ?usize {
+    for (text, 0..) |c, i| if (c == ' ' or c == '\t') continue else return i;
+    return null;
+}
+
+pub fn find_prefix(prefix: []const u8, text: []const u8) ?usize {
+    var start: usize = 0;
+    var pos: usize = 0;
+    var in_prefix: bool = false;
+    for (text, 0..) |c, i| {
+        if (!in_prefix) {
+            if (c == ' ' or c == '\t')
+                continue
+            else {
+                in_prefix = true;
+                start = i;
+            }
+        }
+
+        if (in_prefix) {
+            if (c == prefix[pos]) {
+                pos += 1;
+                if (prefix.len > pos) continue else return start;
+            } else return null;
+        }
+    }
+    return null;
+}
+
+fn toggle_prefix_in_line(prefix: []const u8, text: []const u8, writer: TextWriter) !void {
+    if (find_prefix(prefix, text)) |pos| {
+        _ = try writer.write(text[0..pos]);
+        if (text.len > pos + prefix.len) {
+            _ = try if (text[pos + prefix.len] == ' ')
+                writer.write(text[pos + 1 + prefix.len ..])
+            else
+                writer.write(text[pos + prefix.len ..]);
+        }
+    } else if (find_first_non_ws(text)) |pos| {
+        _ = try writer.write(text[0..pos]);
+        _ = try writer.write(prefix);
+        _ = try writer.write(" ");
+        _ = try writer.write(text[pos..]);
+    } else {
+        _ = try writer.write(prefix);
+        _ = try writer.write(text);
+    }
+}
+
+pub fn toggle_prefix_in_text(prefix: []const u8, text: []const u8, a: std.mem.Allocator) ![]const u8 {
+    var result = try std.ArrayList(u8).initCapacity(a, prefix.len + text.len);
+    const writer = result.writer();
+    var pos: usize = 0;
+    while (std.mem.indexOfScalarPos(u8, text, pos, '\n')) |next| {
+        try toggle_prefix_in_line(prefix, text[pos..next], writer);
+        _ = try writer.write("\n");
+        pos = next + 1;
+    }
+    return result.toOwnedSlice();
+}