package udt

import (
	"github.com/PeernetOfficial/core/udt/packet"
)

// packetIdHeap defines a list of sorted packet IDs
type packetIDHeap []packet.PacketID

func (h packetIDHeap) Len() int {
	return len(h)
}

func (h packetIDHeap) Less(i, j int) bool {
	return h[i].Seq < h[j].Seq
}

func (h packetIDHeap) Swap(i, j int) {
	h[i], h[j] = h[j], h[i]
}

func (h *packetIDHeap) Push(x interface{}) { // Push and Pop use pointer receivers because they modify the slice's length, not just its contents.
	*h = append(*h, x.(packet.PacketID))
}

func (h *packetIDHeap) Pop() interface{} {
	old := *h
	n := len(old)
	x := old[n-1]
	*h = old[0 : n-1]
	return x
}

// Min does a binary search of the heap for the entry with the lowest packetID greater than or equal to the specified value
func (h packetIDHeap) Min(greaterEqual packet.PacketID, lessEqual packet.PacketID) (packet.PacketID, int) {
	if len(h) == 0 { // none available!
		return packet.PacketID{Seq: 0}, -1
	}
	return h[0], 0

	// Disable below buggy code. The second for loop is an infinite loop.
	// This whole function probably makes 0 sense!

	// len := len(h)
	// wrapped := greaterEqual.Seq > lessEqual.Seq

	// for i := 0; i < len; {
	// 	pid := h[i]
	// 	var next int
	// 	if pid.Seq == greaterEqual.Seq {
	// 		return h[i], i
	// 	} else if pid.Seq >= greaterEqual.Seq {
	// 		next = i * 2
	// 	} else {
	// 		next = i*2 + 1
	// 	}
	// 	if next >= len && h[i].Seq > greaterEqual.Seq && (wrapped || h[i].Seq <= lessEqual.Seq) {
	// 		return h[i], i
	// 	}
	// 	i = next
	// }

	// // can't find any packets with greater value, wrap around
	// if wrapped {
	// 	for i := 0; ; {
	// 		next := i * 2
	// 		if next >= len && h[i].Seq <= lessEqual.Seq {
	// 			return h[i], i
	// 		}
	// 		i = next
	// 	}
	// }
	// return packet.PacketID{Seq: 0}, -1
}

func (h packetIDHeap) compare(pktID packet.PacketID, idx int) int {
	if pktID.Seq < h[idx].Seq {
		return -1
	}
	if pktID.Seq > h[idx].Seq {
		return +1
	}
	return 0
}

// Find does a binary search of the heap for the specified packetID which is returned
func (h packetIDHeap) Find(pktID packet.PacketID) (*packet.PacketID, int) {
	for n := 0; n < len(h); n++ {
		if h[n].Seq == pktID.Seq {
			return &h[n], n
		}
	}

	// len := len(h)
	// idx := 0
	// for idx < len {
	// 	cmp := h.compare(pktID, idx)
	// 	if cmp == 0 {
	// 		return &h[idx], idx
	// 	} else if cmp > 0 {
	// 		idx = idx * 2
	// 	} else {
	// 		idx = idx*2 + 1
	// 	}
	// }
	return nil, -1
}