add(node2buffer): convert raw and code blocks with leading line numbers

src/widget/node2buffer.zig

@@ -3,6 +3,8 @@ const std = @import("std");
 const vaxis = @import("vaxis");
 const zmd = @import("zmd");
 
+const digits = "0123456789";
+
 pub fn toBuffer(
     node: *zmd.Node,
     allocator: std.mem.Allocator,
@@ -43,6 +45,7 @@ pub fn toBuffer(
         },
         .link => {
             style.fg = .{ .index = 3 };
+            style.ul_style = .single;
         },
         else => {},
     }
@@ -128,7 +131,6 @@ pub fn toBuffer(
             }
         },
         .link => {
-            style.ul_style = .single;
             const uri = input[node.token.start + 1 + node.title.?.len + 2 .. node.token.start + 1 + node.title.?.len + 2 + node.href.?.len];
             for (content, 0..) |_, i| {
                 try array.append(.{
@@ -138,6 +140,67 @@ pub fn toBuffer(
                 });
             }
         },
+        .block_close, .code_close => {
+            // generate a `block` i.e.
+            // 01 | ...
+            // 02 | ...
+            // 03 | ...
+            // ...
+            // 10 | ...
+            var rows: usize = 0;
+            var c: usize = 0;
+            // TODO: would be cool to not have to re-iterate over the contents
+            for (content, 0..) |char, i| {
+                if (char == '\n') {
+                    // NOTE: start after the ```<language>
+                    if (c == 0) {
+                        c = i + 1;
+                    }
+                    rows += 1;
+                }
+            }
+            rows = rows -| 1;
+            const pad = vaxis.widgets.LineNumbers.numDigits(rows);
+            for (1..rows + 1) |r| {
+                try array.append(.{
+                    .char = .{ .grapheme = " " },
+                    .style = .{ .dim = true },
+                });
+                try array.append(.{
+                    .char = .{ .grapheme = " " },
+                    .style = .{ .dim = true },
+                });
+                for (1..pad + 1) |i| {
+                    const digit = vaxis.widgets.LineNumbers.extractDigit(r, pad - i);
+                    try array.append(.{
+                        .char = .{ .grapheme = digits[digit .. digit + 1] },
+                        .style = .{ .dim = true },
+                    });
+                }
+                try array.append(.{
+                    .char = .{ .grapheme = " " },
+                    .style = .{ .dim = true },
+                });
+                try array.append(.{
+                    .char = .{ .grapheme = "│" },
+                    .style = .{ .dim = true },
+                });
+                try array.append(.{
+                    .char = .{ .grapheme = " " },
+                    .style = .{ .dim = true },
+                });
+                for (c..content.len) |c_i| {
+                    try array.append(.{
+                        .char = .{ .grapheme = content[c_i .. c_i + 1] },
+                        .style = style,
+                    });
+                    if (content[c_i] == '\n') {
+                        c = c_i + 1;
+                        break;
+                    }
+                }
+            }
+        },
         else => {
             for (content, 0..) |_, i| {
                 try array.append(.{