package coord

import "testing"

// TestFloorDiv 验证负坐标安全的向下取整除法（设计.md §4.1 踩坑）。
func TestFloorDiv(t *testing.T) {
	cases := []struct {
		a, b, want int32
	}{
		{15, 16, 0},
		{16, 16, 1},
		{-1, 16, -1},
		{-16, 16, -1},
		{-17, 16, -2},
		{0, 16, 0},
	}
	for _, c := range cases {
		if got := FloorDiv(c.a, c.b); got != c.want {
			t.Fatalf("FloorDiv(%d, %d) = %d，期望 %d", c.a, c.b, got, c.want)
		}
	}
}

// TestChunkLocal 验证区块坐标与局部坐标互转（含负数）。
func TestChunkLocal(t *testing.T) {
	for _, wx := range []int32{-33, -17, -16, -1, 0, 15, 16, 31} {
		cx := ChunkCoord(wx)
		lx := LocalCoord(wx)
		if lx < 0 || lx >= 16 {
			t.Fatalf("LocalCoord(%d) = %d 越界", wx, lx)
		}
		if cx*16+lx != wx {
			t.Fatalf("坐标还原失败: %d → cx=%d lx=%d", wx, cx, lx)
		}
	}
}