print

pub fn print(w: *Writer, comptime fmt: []const u8, args: anytype) Error!void {
    const ArgsType = @TypeOf(args);
    const args_type_info = @typeInfo(ArgsType);
    if (args_type_info != .@"struct") {
        @compileError("expected tuple or struct argument, found " ++ @typeName(ArgsType));
    }

    const field_names = args_type_info.@"struct".field_names;
    const max_format_args = @typeInfo(std.fmt.ArgSetType).int.bits;
    if (field_names.len > max_format_args) {
        @compileError("32 arguments max are supported per format call");
    }

    @setEvalBranchQuota(@as(comptime_int, fmt.len) * 1000); // NOTE: We're upcasting as 16-bit usize overflows.
    comptime var arg_state: std.fmt.ArgState = .{ .args_len = field_names.len };
    comptime var i = 0;
    comptime var literal: []const u8 = "";
    inline while (true) {
        const start_index = i;

        inline while (i < fmt.len) : (i += 1) {
            switch (fmt[i]) {
                '{', '}' => break,
                else => {},
            }
        }

        comptime var end_index = i;
        comptime var unescape_brace = false;

        // Handle {{ and }}, those are un-escaped as single braces
        if (i + 1 < fmt.len and fmt[i + 1] == fmt[i]) {
            unescape_brace = true;
            // Make the first brace part of the literal...
            end_index += 1;
            // ...and skip both
            i += 2;
        }

        literal = literal ++ fmt[start_index..end_index];

        // We've already skipped the other brace, restart the loop
        if (unescape_brace) continue;

        // Write out the literal
        if (literal.len != 0) {
            try w.writeAll(literal);
            literal = "";
        }

        if (i >= fmt.len) break;

        if (fmt[i] == '}') {
            @compileError("missing opening {");
        }

        // Get past the {
        comptime assert(fmt[i] == '{');
        i += 1;

        const fmt_begin = i;
        // Find the closing brace
        inline while (i < fmt.len and fmt[i] != '}') : (i += 1) {}
        const fmt_end = i;

        if (i >= fmt.len) {
            @compileError("missing closing }");
        }

        // Get past the }
        comptime assert(fmt[i] == '}');
        i += 1;

        const placeholder_array = fmt[fmt_begin..fmt_end].*;
        const placeholder = comptime std.fmt.Placeholder.parse(&placeholder_array);
        const arg_pos = comptime switch (placeholder.arg) {
            .none => null,
            .number => |pos| pos,
            .named => |arg_name| std.meta.fieldIndex(ArgsType, arg_name) orelse
                @compileError("no argument with name '" ++ arg_name ++ "'"),
        };

        const width = switch (placeholder.width) {
            .none => null,
            .number => |v| v,
            .named => |arg_name| blk: {
                const arg_i = comptime std.meta.fieldIndex(ArgsType, arg_name) orelse
                    @compileError("no argument with name '" ++ arg_name ++ "'");
                _ = comptime arg_state.nextArg(arg_i) orelse @compileError("too few arguments");
                break :blk @field(args, arg_name);
            },
        };

        const precision = switch (placeholder.precision) {
            .none => null,
            .number => |v| v,
            .named => |arg_name| blk: {
                const arg_i = comptime std.meta.fieldIndex(ArgsType, arg_name) orelse
                    @compileError("no argument with name '" ++ arg_name ++ "'");
                _ = comptime arg_state.nextArg(arg_i) orelse @compileError("too few arguments");
                break :blk @field(args, arg_name);
            },
        };

        const arg_to_print = comptime arg_state.nextArg(arg_pos) orelse
            @compileError("too few arguments");

        try w.printValue(
            placeholder.specifier_arg,
            .{
                .fill = placeholder.fill,
                .alignment = placeholder.alignment,
                .width = width,
                .precision = precision,
            },
            @field(args, field_names[arg_to_print]),
            std.options.fmt_max_depth,
        );
    }

    if (comptime arg_state.hasUnusedArgs()) {
        const missing_count = arg_state.args_len - @popCount(arg_state.used_args);
        switch (missing_count) {
            0 => unreachable,
            1 => @compileError("unused argument in '" ++ fmt ++ "'"),
            else => @compileError(std.fmt.comptimePrint("{d}", .{missing_count}) ++ " unused arguments in '" ++ fmt ++ "'"),
        }
    }
}