package classes

import (
	"testing"
	"time"
)

// TestAssignSlots pins stable numbering without a database (D-30, RESEARCH
// Pitfall 5): appends fill the last file of their group, a left-out row
// keeps its number as a hole, only a renumber packs the listed rows again,
// and groups are numbered apart.
func TestAssignSlots(t *testing.T) {
	t0 := time.Date(2026, 10, 1, 0, 0, 0, 0, time.UTC)
	rows := []*Slot{}
	add := func(id uint64, grp string, at time.Duration) *Slot {
		s := &Slot{ID: id, Grp: grp, FirstSeen: t0.Add(at), Listed: true}
		rows = append(rows, s)
		return s
	}
	files := func(grp string) []int {
		var out []int
		for _, r := range rows {
			if r.Grp == grp && r.Listed && r.FileNo != nil {
				out = append(out, *r.FileNo)
			}
		}
		return out
	}
	eq := func(a []int, b ...int) bool {
		if len(a) != len(b) {
			return false
		}
		for i := range a {
			if a[i] != b[i] {
				return false
			}
		}
		return true
	}
	for i := uint64(1); i <= 5; i++ {
		add(i, "pages", 0)
	}
	add(9, "posts", 0)
	if !AssignSlots(rows, 2, true) || !eq(files("pages"), 1, 1, 2, 2, 3) || !eq(files("posts"), 1) {
		t.Fatalf("first numbering: pages %v posts %v", files("pages"), files("posts"))
	}
	if AssignSlots(rows, 2, false) {
		t.Fatal("a second pass changed numbers")
	}
	rows[1].Listed = false
	if AssignSlots(rows, 2, false) || !eq(files("pages"), 1, 2, 2, 3) || *rows[1].FileNo != 1 {
		t.Fatalf("after a delete: %v, hole %v", files("pages"), rows[1].FileNo)
	}
	add(6, "pages", time.Hour)
	add(7, "pages", 2*time.Hour)
	AssignSlots(rows, 2, false)
	if *rows[len(rows)-2].FileNo != 3 || *rows[len(rows)-1].FileNo != 4 {
		t.Fatalf("appends: %v %v", *rows[len(rows)-2].FileNo, *rows[len(rows)-1].FileNo)
	}
	AssignSlots(rows, 3, true)
	if !eq(files("pages"), 1, 1, 1, 2, 2, 2) || rows[1].FileNo != nil {
		t.Fatalf("renumber: %v, left-out row %v", files("pages"), rows[1].FileNo)
	}
	// A returning row fills its own hole when it still has one.
	rows[1].Listed = true
	n := 1
	rows[1].FileNo = &n
	AssignSlots(rows, 3, false)
	if *rows[1].FileNo != 1 {
		t.Fatalf("returning row moved to %d", *rows[1].FileNo)
	}
}