WIP: Formatter

src/Formatter.zig

@@ -0,0 +1,57 @@
+const std = @import("std");
+
+pub const Error = error {};
+
+vtable: *const VTable,
+w: *std.Io.Writer,
+
+const Self = @This();
+
+pub const VTable = struct {
+    printField: *const fn (
+        ptr: *Self,
+        comptime field: []const u8,
+        comptime fmt: []const u8,
+        args: anytype,
+    ) Error!void,
+};
+
+pub fn printField(
+    self: *const Self,
+    comptime field: []const u8,
+    value: anytype,
+) Error!void {
+    self.vtable.field(self, field);
+    self.vtable.value(self, value);
+}
+
+pub const IndentedFormatter = struct {
+    indent: u8 = 0,
+    depth: usize = 0,
+
+    interface: Self,
+
+    pub fn init(w: *std.Io.Writer) IndentedFormatter {
+        return .{
+            .interface = .{
+                .vtable = &.{
+                    .printField = IndentedFormatter.printField,
+                },
+                .w = w,
+            },
+        };
+    }
+
+    fn printField(
+        f: *Self,
+        comptime field: []const u8,
+        comptime fmt: []const u8,
+        args: anytype,
+    ) Error!void {
+        const self: *IndentedFormatter = @alignCast(@fieldParentPtr("interface", f));
+
+        _ = try self.interface.w.splatByteAll(' ', self.indent * self.depth);
+        try self.interface.w.print(field ++ ": " ++ fmt ++ "\n", args);
+    }
+};
+