package ds

import (
	"math/rand"
	"sort"
	"testing"
)

func TestHeapMinOrder(t *testing.T) {
	h := NewHeap[int](func(a, b int) bool { return a < b })
	for _, v := range []int{5, 3, 8, 1, 4, 7, 9, 2, 6} {
		h.Push(v)
	}
	var got []int
	for !h.Empty() {
		v, _ := h.Pop()
		got = append(got, v)
	}
	want := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("Pop 顺序[%d] = %d, want %d", i, got[i], want[i])
		}
	}
}

func TestHeapMaxOrder(t *testing.T) {
	h := NewHeap[int](func(a, b int) bool { return a > b }) // 大顶堆
	for _, v := range []int{5, 3, 8, 1, 4} {
		h.Push(v)
	}
	top, _ := h.Peek()
	if top != 8 {
		t.Fatalf("大顶堆 Peek = %d, want 8", top)
	}
	var got []int
	for !h.Empty() {
		v, _ := h.Pop()
		got = append(got, v)
	}
	want := []int{8, 5, 4, 3, 1}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("大顶堆 Pop[%d] = %d, want %d", i, got[i], want[i])
		}
	}
}

func TestHeapInit(t *testing.T) {
	h := NewHeap[int](func(a, b int) bool { return a < b })
	data := []int{9, 5, 2, 7, 1, 8, 3}
	// Init 后 h 持有 data 的底层数组,Pop 会原地修改它。
	// 所以 ref 必须在 Init 之前拷贝,避免被破坏。
	ref := make([]int, len(data))
	copy(ref, data)
	sort.Ints(ref)

	h.Init(data)
	if top, _ := h.Peek(); top != 1 {
		t.Fatalf("Init 后 Peek = %d, want 1", top)
	}
	var got []int
	for !h.Empty() {
		v, _ := h.Pop()
		got = append(got, v)
	}
	for i := range ref {
		if got[i] != ref[i] {
			t.Fatalf("Init+Pop[%d] = %d, want %d", i, got[i], ref[i])
		}
	}
}

func TestHeapEmpty(t *testing.T) {
	h := NewHeap[int](func(a, b int) bool { return a < b })
	if _, ok := h.Pop(); ok {
		t.Fatal("空堆 Pop 应返回 false")
	}
	if _, ok := h.Peek(); ok {
		t.Fatal("空堆 Peek 应返回 false")
	}
}

func TestHeapRandomVsSort(t *testing.T) {
	// 随机数据:堆弹出顺序应与排序结果一致。
	h := NewHeap[int](func(a, b int) bool { return a < b })
	rng := rand.New(rand.NewSource(42))
	const N = 2000
	ref := make([]int, N)
	for i := 0; i < N; i++ {
		v := rng.Intn(10000)
		h.Push(v)
		ref[i] = v
	}
	sort.Ints(ref)
	for i := 0; i < N; i++ {
		v, ok := h.Pop()
		if !ok || v != ref[i] {
			t.Fatalf("随机测试[%d] = %d,%v, want %d", i, v, ok, ref[i])
		}
	}
}

func TestHeapString(t *testing.T) {
	h := NewHeap[string](func(a, b string) bool { return a < b })
	for _, s := range []string{"banana", "apple", "cherry"} {
		h.Push(s)
	}
	first, _ := h.Pop()
	if first != "apple" {
		t.Fatalf("字符串堆 Pop = %q, want \"apple\"", first)
	}
}