pub const HeaderInstallation = union(enum) {
    file: File,
    directory: Directory,

    pub const File = struct {
        source: LazyPath,
        dest_rel_path: []const u8,

        pub fn dupe(file: File, b: *std.Build) File {
            return .{
                .source = file.source.dupe(b),
                .dest_rel_path = b.dupePath(file.dest_rel_path),
            };
        }
    };

    pub const Directory = struct {
        source: LazyPath,
        dest_rel_path: []const u8,
        options: Directory.Options,

        pub const Options = struct {
            /// File paths that end in any of these suffixes will be excluded from installation.
            exclude_extensions: []const []const u8 = &.{},
            /// Only file paths that end in any of these suffixes will be included in installation.
            /// `null` means that all suffixes will be included.
            /// `exclude_extensions` takes precedence over `include_extensions`.
            include_extensions: ?[]const []const u8 = &.{".h"},

            pub fn dupe(opts: Directory.Options, b: *std.Build) Directory.Options {
                return .{
                    .exclude_extensions = b.dupeStrings(opts.exclude_extensions),
                    .include_extensions = if (opts.include_extensions) |incs| b.dupeStrings(incs) else null,
                };
            }
        };

        pub fn dupe(dir: Directory, b: *std.Build) Directory {
            return .{
                .source = dir.source.dupe(b),
                .dest_rel_path = b.dupePath(dir.dest_rel_path),
                .options = dir.options.dupe(b),
            };
        }
    };

    pub fn getSource(installation: HeaderInstallation) LazyPath {
        return switch (installation) {
            inline .file, .directory => |x| x.source,
        };
    }

    pub fn dupe(installation: HeaderInstallation, b: *std.Build) HeaderInstallation {
        return switch (installation) {
            .file => |f| .{ .file = f.dupe(b) },
            .directory => |d| .{ .directory = d.dupe(b) },
        };
    }
}