package dataext

import "iter"

type RingBuffer[T any] struct {
	items    []T //
	capacity int // max number of items the buffer can hold
	size     int // how many items are in the buffer
	head     int // ptr to next item
}

func NewRingBuffer[T any](capacity int) *RingBuffer[T] {
	return &RingBuffer[T]{
		items:    make([]T, capacity),
		capacity: capacity,
		size:     0,
		head:     0,
	}
}

func (rb *RingBuffer[T]) Push(item T) {
	if rb.size < rb.capacity {
		rb.size++
	}
	rb.items[rb.head] = item
	rb.head = (rb.head + 1) % rb.capacity
}

func (rb *RingBuffer[T]) Peek() (T, bool) {
	if rb.size == 0 {
		return *new(T), false
	}
	return rb.items[(rb.head-1+rb.capacity)%rb.capacity], true
}

func (rb *RingBuffer[T]) Items() []T {
	if rb.size < rb.capacity {
		return rb.items[:rb.size]
	}
	return append(rb.items[rb.head:], rb.items[:rb.head]...)
}

func (rb *RingBuffer[T]) Size() int {
	return rb.size
}

func (rb *RingBuffer[T]) Capacity() int {
	return rb.capacity
}

func (rb *RingBuffer[T]) Clear() {
	rb.size = 0
	rb.head = 0
}

func (rb *RingBuffer[T]) IsFull() bool {
	return rb.size == rb.capacity
}

func (rb *RingBuffer[T]) At(i int) T {
	if i < 0 || i >= rb.size {
		panic("Index out of bounds")
	}
	return rb.items[(rb.head+i)%rb.capacity]
}

func (rb *RingBuffer[T]) Get(i int) (T, bool) {
	if i < 0 || i >= rb.size {
		return *new(T), false
	}
	return rb.items[(rb.head+i)%rb.capacity], true
}

func (rb *RingBuffer[T]) Iter() iter.Seq[T] {
	return func(yield func(T) bool) {
		for i := 0; i < rb.size; i++ {
			if !yield(rb.At(i)) {
				return
			}
		}
	}
}

func (rb *RingBuffer[T]) Iter2() iter.Seq2[int, T] {
	return func(yield func(int, T) bool) {
		for i := 0; i < rb.size; i++ {
			if !yield(i, rb.At(i)) {
				return
			}
		}
	}
}