gonum/internal/order/order.go

// Copyright ©2024 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package order

import (
	"cmp"
	"slices"
	"sort"

	"gonum.org/v1/gonum/graph"
)

// ByID sorts a slice of graph.Node by ID.
func ByID(n []graph.Node) {
	sort.Slice(n, func(i, j int) bool { return n[i].ID() < n[j].ID() })
}

// BySliceValues sorts a slice of []cmp.Ordered lexically by the values of
// the []cmp.Ordered.
func BySliceValues[S interface{ ~[]E }, E cmp.Ordered](c []S) {
	slices.SortFunc(c, func(a, b S) int {
		l := min(len(a), len(b))
		for k, v := range a[:l] {
			if n := cmp.Compare(v, b[k]); n != 0 {
				return n
			}
		}
		return cmp.Compare(len(a), len(b))
	})
}

// BySliceIDs sorts a slice of []graph.Node lexically by the IDs of the
// []graph.Node.
func BySliceIDs(c [][]graph.Node) {
	sort.Slice(c, func(i, j int) bool {
		a, b := c[i], c[j]
		l := len(a)
		if len(b) < l {
			l = len(b)
		}
		for k, v := range a[:l] {
			if v.ID() < b[k].ID() {
				return true
			}
			if v.ID() > b[k].ID() {
				return false
			}
		}
		return len(a) < len(b)
	})
}

// LinesByIDs sort a slice of graph.LinesByIDs lexically by the From IDs,
// then by the To IDs, finally by the Line IDs.
func LinesByIDs(n []graph.Line) {
	sort.Slice(n, func(i, j int) bool {
		a, b := n[i], n[j]
		if a.From().ID() != b.From().ID() {
			return a.From().ID() < b.From().ID()
		}
		if a.To().ID() != b.To().ID() {
			return a.To().ID() < b.To().ID()
		}
		return n[i].ID() < n[j].ID()
	})
}