package browser

import (
	"sort"
	"strings"
)

// SortMode defines how entries should be sorted.
type SortMode int

const (
	SortModeNameAsc  SortMode = iota // Name ascending (A-Z)
	SortModeNameDesc                 // Name descending (Z-A)
	SortModeDateAsc                  // Date ascending (oldest first)
	SortModeDateDesc                 // Date descending (newest first)
	// Total sort modes: 4
)

// sortEntries sorts entries in-place according to the given SortMode.
// Directories and files are interleaved naturally. Case-insensitive
// comparison is used for name-based sorting. Equal keys are broken
// by name (ascending).
func sortEntries(entries []Entry, mode SortMode) {
	if len(entries) <= 1 {
		return
	}

	cmp := comparator(mode)

	sort.SliceStable(entries, func(i, j int) bool {
		return cmp(entries[i], entries[j]) < 0
	})
}

// comparator returns a comparison function for the given SortMode.
// Returns negative if a < b, zero if equal, positive if a > b.
func comparator(mode SortMode) func(a, b Entry) int {
	switch mode {
	case SortModeNameAsc:
		return func(a, b Entry) int {
			if c := strings.Compare(strings.ToLower(a.Name), strings.ToLower(b.Name)); c != 0 {
				return c
			}
			return strings.Compare(a.Name, b.Name)
		}
	case SortModeNameDesc:
		return func(a, b Entry) int {
			if c := strings.Compare(strings.ToLower(b.Name), strings.ToLower(a.Name)); c != 0 {
				return c
			}
			return strings.Compare(b.Name, a.Name)
		}
	case SortModeDateAsc:
		return func(a, b Entry) int {
			if c := a.ModTime.Compare(b.ModTime); c != 0 {
				return c
			}
			return strings.Compare(strings.ToLower(a.Name), strings.ToLower(b.Name))
		}
	case SortModeDateDesc:
		return func(a, b Entry) int {
			if c := b.ModTime.Compare(a.ModTime); c != 0 {
				return c
			}
			return strings.Compare(strings.ToLower(a.Name), strings.ToLower(b.Name))
		}
	default:
		// Invalid mode: no-op (preserve order)
		return func(a, b Entry) int { return 0 }
	}
}