WIP: Formatter

src/Class.zig

@@ -1,11 +1,7 @@
 const std = @import("std");
 
 const EnumFlags = @import("EnumFlags.zig").EnumFlags;
-
-pub const FieldInfo = @import("Class/FieldInfo.zig");
-pub const MethodInfo = @import("Class/MethodInfo.zig");
-pub const AttributeInfo = @import("Class/AttributeInfo.zig").AttributeInfo;
-pub const ConstantPool = @import("Class/ConstantPool.zig");
+const Formatter = @import("Formatter.zig");
 
 allocator: std.mem.Allocator,
 
@@ -23,6 +19,11 @@ attributes: []AttributeInfo,
 
 const Self = @This();
 
+pub const FieldInfo = @import("Class/FieldInfo.zig");
+pub const MethodInfo = @import("Class/MethodInfo.zig");
+pub const AttributeInfo = @import("Class/AttributeInfo.zig").AttributeInfo;
+pub const ConstantPool = @import("Class/ConstantPool.zig");
+
 pub const ClassAccessFlags = EnumFlags(enum(u16) {
     public = 0x0001,
     final = 0x0010,
@@ -198,6 +199,10 @@ pub fn jsonStringify(self: *const Self, jws: *std.json.Stringify) !void {
     try jws.endObject();
 }
 
+pub fn acceptFormatter(self: *const Self, formatter: *Formatter) Formatter.Error!void {
+    try formatter.printField("magic", "0x{X}", .{ self.magic });
+}
+
 pub fn format(self: *const Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
     const depth = 2;
     var indent: u8 = 0;

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);
+    }
+};
+

src/main.zig

@@ -2,6 +2,8 @@ const std = @import("std");
 
 const Class = @import("Class.zig");
 
+const Formatter = @import("Formatter.zig");
+
 pub fn main(init: std.process.Init) !void {
     const io = init.io;
     const allocator = init.gpa;
@@ -52,7 +54,9 @@ pub fn main(init: std.process.Init) !void {
     };
     defer class.deinit();
 
-    try stdout.print("{f}", .{ class });
+    var indented_formatter: Formatter.IndentedFormatter = .init(stdout);
+    const formatter = &indented_formatter.interface;
+    try class.acceptFormatter(formatter);
 
     try stdout.flush();
 }