package detect

import (
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestRingBuffer_FIFO(t *testing.T) {
	// 1. Initialize with capacity 10
	rb := newRingBuffer(10)
	assert.Equal(t, 10, rb.cap)
	assert.Equal(t, 0, rb.size)

	// 2. Fill it up
	for i := 1; i <= 10; i++ {
		rb.push(float64(i))
	}
	assert.Equal(t, 10, rb.size)
	// head should be at 0 after 10 pushes
	assert.Equal(t, 0, rb.head)

	// 3. Verify quantile (sorted view)
	// sorted: [1 2 3 4 5 6 7 8 9 10]
	// quantile 0.5 (median) of 10 items: index int(0.5 * 9) = 4 -> value 5
	assert.Equal(t, 5.0, rb.quantileVal(0.5))

	// 4. Push one more to trigger FIFO eviction
	// Should evict "1" (the oldest)
	rb.push(11.0)
	assert.Equal(t, 10, rb.size)
	assert.Equal(t, 1, rb.head)

	// 5. Verify the oldest (1.0) is gone and 11.0 is present
	// sorted: [2 3 4 5 6 7 8 9 10 11]
	// idx = int(0.4 * 9) = 3 -> value at index 3 is 5.0
	assert.Equal(t, 5.0, rb.quantileVal(0.4))
	// let's be precise: idx = int(p * 9)
	// p=0 -> idx 0 (2.0)
	// p=1 -> idx 9 (11.0)
	assert.Equal(t, 2.0, rb.quantileVal(0.0))
	assert.Equal(t, 11.0, rb.quantileVal(1.0))
}

func TestRingBuffer_Rank(t *testing.T) {
	rb := newRingBuffer(5)

	// Rank is float64(rank) / float64(n-1)
	assert.Equal(t, 0.5, rb.push(10.0)) // n=1 -> 0.5
	assert.Equal(t, 1.0, rb.push(20.0)) // n=2, sorted=[10, 20], search(20)->1. 1/(2-1)=1.0
	assert.Equal(t, 0.0, rb.push(5.0))  // n=3, sorted=[5, 10, 20], search(5)->0. 0/2=0.0

	// n=4, sorted=[5 10 10 20], search(10) -> idx 1. 1/(4-1) = 0.333...
	assert.InDelta(t, 0.3333333333333333, rb.push(10.0), 1e-9)

	rb = newRingBuffer(4)
	rb.push(1.0)
	rb.push(3.0)
	rank := rb.push(2.0) // n=3, sorted=[1, 2, 3], search(2)->idx 1. 1/(3-1)=0.5
	assert.Equal(t, 0.5, rank)
}