package dbx

import (
	"testing"
)

func TestRoundRobinBalancer_Empty(t *testing.T) {
	b := NewRoundRobinBalancer()
	if n := b.Next(nil); n != nil {
		t.Errorf("expected nil for empty slice, got %v", n)
	}
}

func TestRoundRobinBalancer_AllHealthy(t *testing.T) {
	b := NewRoundRobinBalancer()
	nodes := makeTestNodes("a", "b", "c")

	seen := map[string]int{}
	for range 30 {
		n := b.Next(nodes)
		if n == nil {
			t.Fatal("unexpected nil")
		}
		seen[n.name]++
	}

	if len(seen) != 3 {
		t.Errorf("expected 3 distinct nodes, got %d", len(seen))
	}
	for name, count := range seen {
		if count != 10 {
			t.Errorf("node %s hit %d times, expected 10", name, count)
		}
	}
}

func TestRoundRobinBalancer_SkipsUnhealthy(t *testing.T) {
	b := NewRoundRobinBalancer()
	nodes := makeTestNodes("a", "b", "c")
	nodes[1].healthy.Store(false) // b is down

	for range 20 {
		n := b.Next(nodes)
		if n == nil {
			t.Fatal("unexpected nil")
		}
		if n.name == "b" {
			t.Error("should not return unhealthy node b")
		}
	}
}

func TestRoundRobinBalancer_AllUnhealthy(t *testing.T) {
	b := NewRoundRobinBalancer()
	nodes := makeTestNodes("a", "b")
	for _, n := range nodes {
		n.healthy.Store(false)
	}

	if n := b.Next(nodes); n != nil {
		t.Errorf("expected nil when all unhealthy, got %v", n.name)
	}
}

func makeTestNodes(names ...string) []*Node {
	nodes := make([]*Node, len(names))
	for i, name := range names {
		n := &Node{name: name}
		n.healthy.Store(true)
		nodes[i] = n
	}
	return nodes
}