argvToCommandLineWindows

fn argvToCommandLineWindows(
    allocator: Allocator,
    argv: []const []const u8,
) ArgvToCommandLineError![:0]u16 {
    var buf = std.array_list.Managed(u8).init(allocator);
    defer buf.deinit();

    if (argv.len != 0) {
        const arg0 = argv[0];

        // The first argument must be quoted if it contains spaces or ASCII control characters
        // (excluding DEL). It also follows special quoting rules where backslashes have no special
        // interpretation, which makes it impossible to pass certain first arguments containing
        // double quotes to a child process without characters from the first argument leaking into
        // subsequent ones (which could have security implications).
        //
        // Empty arguments technically don't need quotes, but we quote them anyway for maximum
        // compatibility with different implementations of the 'CommandLineToArgvW' algorithm.
        //
        // Double quotes are illegal in paths on Windows, so for the sake of simplicity we reject
        // all first arguments containing double quotes, even ones that we could theoretically
        // serialize in unquoted form.
        var needs_quotes = arg0.len == 0;
        for (arg0) |c| {
            if (c <= ' ') {
                needs_quotes = true;
            } else if (c == '"') {
                return error.InvalidArg0;
            }
        }
        if (needs_quotes) {
            try buf.append('"');
            try buf.appendSlice(arg0);
            try buf.append('"');
        } else {
            try buf.appendSlice(arg0);
        }

        for (argv[1..]) |arg| {
            try buf.append(' ');

            // Subsequent arguments must be quoted if they contain spaces, tabs or double quotes,
            // or if they are empty. For simplicity and for maximum compatibility with different
            // implementations of the 'CommandLineToArgvW' algorithm, we also quote all ASCII
            // control characters (again, excluding DEL).
            needs_quotes = for (arg) |c| {
                if (c <= ' ' or c == '"') {
                    break true;
                }
            } else arg.len == 0;
            if (!needs_quotes) {
                try buf.appendSlice(arg);
                continue;
            }

            try buf.append('"');
            var backslash_count: usize = 0;
            for (arg) |byte| {
                switch (byte) {
                    '\\' => {
                        backslash_count += 1;
                    },
                    '"' => {
                        try buf.appendNTimes('\\', backslash_count * 2 + 1);
                        try buf.append('"');
                        backslash_count = 0;
                    },
                    else => {
                        try buf.appendNTimes('\\', backslash_count);
                        try buf.append(byte);
                        backslash_count = 0;
                    },
                }
            }
            try buf.appendNTimes('\\', backslash_count * 2);
            try buf.append('"');
        }
    }

    return try std.unicode.wtf8ToWtf16LeAllocZ(allocator, buf.items);
}