package routing_test

import (
	"testing"

	"github.com/mathiasbq/supervisor/internal/routing"
	"github.com/stretchr/testify/assert"
)

func TestCanonicalHashDeterministic(t *testing.T) {
	a := routing.CanonicalHash("system one", "user one")
	b := routing.CanonicalHash("system one", "user one")
	assert.Equal(t, a, b, "same inputs must produce same hash")
}

func TestCanonicalHashDistinguishesInputs(t *testing.T) {
	cases := [][2]string{
		{"sys", "user"},
		{"sys", "user2"},
		{"sys2", "user"},
		{"", "system\x00user"}, // separator collision attempt
		{"system\x00user", ""},
	}
	seen := make(map[uint64]bool)
	for _, c := range cases {
		h := routing.CanonicalHash(c[0], c[1])
		assert.False(t, seen[h], "collision on %v", c)
		seen[h] = true
	}
}

func TestCanonicalHashLowBitDistribution(t *testing.T) {
	// Sanity check: across 1000 distinct inputs, low-bit split is roughly even.
	zeros, ones := 0, 0
	for i := 0; i < 1000; i++ {
		h := routing.CanonicalHash("sys", string(rune('a'+(i%26)))+string(rune(i)))
		if h&1 == 0 {
			zeros++
		} else {
			ones++
		}
	}
	// Allow ±15% deviation from 500/500. Tighter would be flaky on real data.
	assert.InDelta(t, 500, zeros, 150)
	assert.InDelta(t, 500, ones, 150)
}