add(zmd): parse markdown file contents and display the parsed contents

Not everything can be parsed and displayed correctly yet, however this
will the default file format to use for adding page contents (i.e.
normal pages, blog entries, etc.)

src/widget/node2buffer.zig

@@ -0,0 +1,117 @@
+///! Transform a given `zmd.Note` into a buffer which can be used by any `vaxis.widgets.View`
+const std = @import("std");
+const vaxis = @import("vaxis");
+const zmd = @import("zmd");
+
+pub fn toBuffer(node: *zmd.Node, allocator: std.mem.Allocator, input: []const u8, array: *std.ArrayList(vaxis.Cell), s: vaxis.Cell.Style) !void {
+    const content = switch (node.token.element.type) {
+        .text => input[node.token.start..node.token.end],
+        .code, .block => node.content,
+        else => "",
+    };
+    var style = s;
+
+    // determine general styling changes
+    switch (node.token.element.type) {
+        .bold => {
+            style.bold = true;
+        },
+        .bold_close => {
+            style.bold = false;
+        },
+        .italic => {
+            style.italic = true;
+        },
+        .italic_close => {
+            style.italic = false;
+        },
+        .block => {
+            // TODO: what should I do with blocks?
+        },
+        .block_close => {
+            // TODO: what should I do with blocks?
+        },
+        .code => {
+            style.dim = true;
+        },
+        .code_close => {
+            style.dim = false;
+        },
+        else => {},
+    }
+
+    switch (node.token.element.type) {
+        .root, .none, .eof => {},
+        .linebreak, .paragraph => {
+            try array.append(.{
+                .char = .{ .grapheme = "\n" },
+                .style = style,
+            });
+            style.ul_style = .off;
+        },
+        .h1 => {
+            style.ul_style = .single;
+            try array.append(.{
+                .char = .{ .grapheme = "#" },
+                .style = style,
+            });
+        },
+        .h2 => {
+            style.ul_style = .single;
+            for (0..2) |_| {
+                try array.append(.{
+                    .char = .{ .grapheme = "#" },
+                    .style = style,
+                });
+            }
+        },
+        .h3 => {
+            style.ul_style = .single;
+            for (0..3) |_| {
+                try array.append(.{
+                    .char = .{ .grapheme = "#" },
+                    .style = style,
+                });
+            }
+        },
+        .h4 => {
+            style.ul_style = .single;
+            for (0..4) |_| {
+                try array.append(.{
+                    .char = .{ .grapheme = "#" },
+                    .style = style,
+                });
+            }
+        },
+        .h5 => {
+            style.ul_style = .single;
+            for (0..5) |_| {
+                try array.append(.{
+                    .char = .{ .grapheme = "#" },
+                    .style = style,
+                });
+            }
+        },
+        .h6 => {
+            style.ul_style = .single;
+            for (0..6) |_| {
+                try array.append(.{
+                    .char = .{ .grapheme = "#" },
+                    .style = style,
+                });
+            }
+        },
+        else => {
+            for (content, 0..) |_, i| {
+                try array.append(.{
+                    .char = .{ .grapheme = content[i .. i + 1] },
+                    .style = style,
+                });
+            }
+        },
+    }
+
+    for (node.children.items) |child_node| {
+        try toBuffer(child_node, allocator, input, array, style);
+    }
+}