WindowsCommandLineCache

const WindowsCommandLineCache = struct {
    cmd_line: ?[:0]u16 = null,
    script_cmd_line: ?[:0]u16 = null,
    cmd_exe_path: ?[:0]u16 = null,
    argv: []const []const u8,
    allocator: Allocator,

    fn init(allocator: Allocator, argv: []const []const u8) WindowsCommandLineCache {
        return .{
            .allocator = allocator,
            .argv = argv,
        };
    }

    fn deinit(self: *WindowsCommandLineCache) void {
        if (self.cmd_line) |cmd_line| self.allocator.free(cmd_line);
        if (self.script_cmd_line) |script_cmd_line| self.allocator.free(script_cmd_line);
        if (self.cmd_exe_path) |cmd_exe_path| self.allocator.free(cmd_exe_path);
    }

    fn commandLine(self: *WindowsCommandLineCache) ![:0]u16 {
        if (self.cmd_line == null) {
            self.cmd_line = try argvToCommandLineWindows(self.allocator, self.argv);
        }
        return self.cmd_line.?;
    }

    /// Not cached, since the path to the batch script will change during PATH searching.
    /// `script_path` should be as qualified as possible, e.g. if the PATH is being searched,
    /// then script_path should include both the search path and the script filename
    /// (this allows avoiding cmd.exe having to search the PATH again).
    fn scriptCommandLine(self: *WindowsCommandLineCache, script_path: []const u16) ![:0]u16 {
        if (self.script_cmd_line) |v| self.allocator.free(v);
        self.script_cmd_line = try argvToScriptCommandLineWindows(
            self.allocator,
            script_path,
            self.argv[1..],
        );
        return self.script_cmd_line.?;
    }

    fn cmdExePath(self: *WindowsCommandLineCache) Allocator.Error![:0]u16 {
        if (self.cmd_exe_path == null) {
            // Remove trailing slash from system directory path; we'll re-add it below
            const system_dir = std.mem.trimEnd(u16, windows.getSystemDirectoryWtf16Le(), &.{ '/', '\\' });
            const suffix = std.unicode.utf8ToUtf16LeStringLiteral("\\cmd.exe");
            const buf = try self.allocator.allocSentinel(u16, system_dir.len + suffix.len, 0);
            errdefer comptime unreachable;
            @memcpy(buf[0..system_dir.len], system_dir);
            @memcpy(buf[system_dir.len..], suffix);
            self.cmd_exe_path = buf;
        }
        return self.cmd_exe_path.?;
    }
}