orderby.go

package go2linq

import (
	"cmp"
	"iter"
	"slices"
	"sort"

	"github.com/solsw/errorhelper"
)

func orderByLsPrim[Source any](source iter.Seq[Source], less func(Source, Source) bool) iter.Seq[Source] {
	ss := slices.Collect(source)
	sort.SliceStable(ss, func(i, j int) bool {
		return less(ss[i], ss[j])
	})
	return slices.Values(ss)
}

// [OrderBy] sorts the elements of a sequence in ascending order.
//
// [OrderBy]: https://learn.microsoft.com/dotnet/api/system.linq.enumerable.orderby
func OrderBy[Source cmp.Ordered](source iter.Seq[Source]) (iter.Seq[Source], error) {
	if source == nil {
		return nil, errorhelper.CallerError(ErrNilSource)
	}
	return orderByLsPrim(source, cmp.Less), nil
}

// [OrderByLs] sorts the elements of a sequence in ascending order using a specified 'less' function.
//
// [OrderByLs]: https://learn.microsoft.com/dotnet/api/system.linq.enumerable.orderby
func OrderByLs[Source any](source iter.Seq[Source], less func(Source, Source) bool) (iter.Seq[Source], error) {
	if source == nil {
		return nil, errorhelper.CallerError(ErrNilSource)
	}
	if less == nil {
		return nil, errorhelper.CallerError(ErrNilLess)
	}
	return orderByLsPrim(source, less), nil
}

// [OrderByDesc] sorts the elements of a sequence in descending order.
//
// [OrderByDesc]: https://learn.microsoft.com/dotnet/api/system.linq.enumerable.orderbydescending
func OrderByDesc[Source cmp.Ordered](source iter.Seq[Source]) (iter.Seq[Source], error) {
	if source == nil {
		return nil, errorhelper.CallerError(ErrNilSource)
	}
	return orderByLsPrim(source, ReverseLess(cmp.Less[Source])), nil
}

// [OrderByDescLs] sorts the elements of a sequence in descending order using a specified 'less' function.
//
// [OrderByDescLs]: https://learn.microsoft.com/dotnet/api/system.linq.enumerable.orderbydescending
func OrderByDescLs[Source any](source iter.Seq[Source], less func(Source, Source) bool) (iter.Seq[Source], error) {
	if source == nil {
		return nil, errorhelper.CallerError(ErrNilSource)
	}
	if less == nil {
		return nil, errorhelper.CallerError(ErrNilLess)
	}
	return orderByLsPrim(source, ReverseLess(less)), nil
}