package lru

import (
	"testing"
	"time"

	"github.com/benbjohnson/clock"
)

// These tests mirror the MRU-style behavior present in this LRU package
// implementation (eviction removes the most-recently-used entry).
func TestBasicCacheEviction(t *testing.T) {
	mock := clock.NewMock()
	c := NewStringKeyCache[int](2)
	c.clock = mock

	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	if c.Len() != 0 {
		t.Fatal("cache should have size 0")
	}

	c.evict()
	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	c.Store("raven", 1)
	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	if len(c.store) != 1 {
		t.Fatalf("store should have length=1, have length=%d", len(c.store))
	}

	mock.Add(time.Second)
	c.Store("owl", 2)
	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	if len(c.store) != 2 {
		t.Fatalf("store should have length=2, have length=%d", len(c.store))
	}

	mock.Add(time.Second)
	c.Store("goat", 3)
	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	if len(c.store) != 2 {
		t.Fatalf("store should have length=2, have length=%d", len(c.store))
	}

	// Since this implementation evicts the most-recently-used item, inserting
	// "goat" when full evicts "owl" (the most recent at that time).
	mock.Add(time.Second)
	if _, ok := c.Get("owl"); ok {
		t.Fatal("store should not have an entry for owl (MRU-evicted)")
	}
	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	mock.Add(time.Second)
	c.Store("elk", 4)
	if err := c.ConsistencyCheck(); err != nil {
		t.Fatal(err)
	}

	if !c.Has("elk") {
		t.Fatal("store should contain an entry for 'elk'")
	}

	// Before storing elk, keys were: raven (older), goat (newer). Evict MRU -> goat.
	if !c.Has("raven") {
		t.Fatal("store should contain an entry for 'raven'")
	}

	if c.Has("goat") {
		t.Fatal("store should not contain an entry for 'goat'")
	}
}