package cooler

import (
	"bytes"
	"fmt"
	"strconv"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

// pullRace sets key to want, lets pullers goroutines Pull it at once behind
// a start barrier and returns how many saw found=true. Any error, a winner
// with the wrong bytes or a loser with a value fails the test.
func pullRace(t *testing.T, c Cache, key string, want []byte, pullers int) int32 {
	t.Helper()
	ctx := t.Context()
	if err := c.Set(ctx, key, want, time.Minute); err != nil {
		t.Fatal(err)
	}
	var (
		wg      sync.WaitGroup
		winners atomic.Int32
	)
	start := make(chan struct{})
	errs := make(chan error, pullers)
	for range pullers {
		wg.Add(1)
		go func() {
			defer wg.Done()
			<-start
			v, ok, err := c.Pull(ctx, key)
			switch {
			case err != nil:
				errs <- err
			case ok && !bytes.Equal(v, want):
				errs <- fmt.Errorf("winner got %q, want %q", v, want)
			case ok:
				winners.Add(1)
			case v != nil:
				errs <- fmt.Errorf("a loser got the value %q", v)
			}
		}()
	}
	close(start)
	wg.Wait()
	close(errs)
	for err := range errs {
		t.Fatal(err)
	}
	return winners.Load()
}

// TestPullConcurrent: 64 concurrent Pulls of one key yield exactly one
// found=true with the stored bytes, and the key is gone afterwards (D-08),
// on the memory driver and on Redis (miniredis), 20 rounds each.
func TestPullConcurrent(t *testing.T) {
	const pullers, rounds = 64, 20
	run := func(t *testing.T, c Cache) {
		t.Helper()
		for round := range rounds {
			key := "code-" + strconv.Itoa(round)
			want := []byte("one-time-value-" + strconv.Itoa(round))
			if n := pullRace(t, c, key, want, pullers); n != 1 {
				t.Fatalf("round %d: %d of %d Pulls found the value, want exactly 1", round, n, pullers)
			}
			if v, ok, err := c.Get(t.Context(), key); err != nil || ok || v != nil {
				t.Fatalf("round %d: Get after the race = %q %v %v, want nil false nil", round, v, ok, err)
			}
		}
	}
	t.Run("memory", func(t *testing.T) {
		run(t, newMemory(t, "acme:", DefaultMaxEntries))
	})
	t.Run("miniredis", func(t *testing.T) {
		_, client := miniClient(t)
		run(t, NewRedisCache(client, "acme:"))
	})
}

// TestPullExpired: an expired value is never returned and is gone after the
// Pull, on both drivers.
func TestPullExpired(t *testing.T) {
	t.Run("memory", func(t *testing.T) {
		ctx := t.Context()
		m := newMemory(t, "acme:", DefaultMaxEntries)
		if err := m.Set(ctx, "short", []byte("x"), 30*time.Millisecond); err != nil {
			t.Fatal(err)
		}
		time.Sleep(60 * time.Millisecond)
		if v, ok, err := m.Pull(ctx, "short"); err != nil || ok || v != nil {
			t.Fatalf("Pull of an expired key = %q %v %v, want nil false nil", v, ok, err)
		}
		if _, ok := m.c.GetIfPresent(m.key("short")); ok {
			t.Fatal("the expired entry is still stored after Pull")
		}
		// An entry stored already past its expiry (the eviction has not run
		// yet) is refused and removed by Pull itself.
		m.c.Set(m.key("stale"), memEntry{val: []byte("old"), expiresAt: time.Now().Add(-time.Second)})
		if v, ok, err := m.Pull(ctx, "stale"); err != nil || ok || v != nil {
			t.Fatalf("Pull of a stale entry = %q %v %v, want nil false nil", v, ok, err)
		}
		if _, ok := m.c.GetIfPresent(m.key("stale")); ok {
			t.Fatal("Pull left the stale entry stored")
		}
		if v, ok, err := m.Get(ctx, "stale"); err != nil || ok || v != nil {
			t.Fatalf("Get after Pull = %q %v %v", v, ok, err)
		}
	})
	t.Run("miniredis", func(t *testing.T) {
		ctx := t.Context()
		mr, client := miniClient(t)
		c := NewRedisCache(client, "acme:")
		if err := c.Set(ctx, "short", []byte("x"), time.Second); err != nil {
			t.Fatal(err)
		}
		mr.FastForward(2 * time.Second)
		if v, ok, err := c.Pull(ctx, "short"); err != nil || ok || v != nil {
			t.Fatalf("Pull of an expired key = %q %v %v, want nil false nil", v, ok, err)
		}
		if mr.Exists("acme:cache:short") {
			t.Fatal("the expired key still exists after Pull")
		}
		// A live key with a TTL is returned once and removed.
		if err := c.Set(ctx, "live", []byte("y"), time.Minute); err != nil {
			t.Fatal(err)
		}
		if v, ok, err := c.Pull(ctx, "live"); err != nil || !ok || string(v) != "y" {
			t.Fatalf("Pull of a live key = %q %v %v", v, ok, err)
		}
		if mr.Exists("acme:cache:live") {
			t.Fatal("Pull did not remove the live key")
		}
	})
}

// TestPullPrefixIsolation: two applications with different prefixes share
// one Redis; Pull on one removes only its own <prefix>cache:<key>, never the
// other's key nor a key outside its cache namespace.
func TestPullPrefixIsolation(t *testing.T) {
	ctx := t.Context()
	mr, client := miniClient(t)
	first := NewRedisCache(client, "first:")
	second := NewRedisCache(client, "second:")
	for _, c := range []Cache{first, second} {
		if err := c.Set(ctx, "code", []byte("v"), time.Minute); err != nil {
			t.Fatal(err)
		}
	}
	if err := mr.Set("first:rl:code", "keep"); err != nil {
		t.Fatal(err)
	}
	if v, ok, err := first.Pull(ctx, "code"); err != nil || !ok || string(v) != "v" {
		t.Fatalf("first Pull = %q %v %v", v, ok, err)
	}
	if mr.Exists("first:cache:code") {
		t.Fatal("Pull did not remove first:cache:code")
	}
	for _, k := range []string{"second:cache:code", "first:rl:code"} {
		if !mr.Exists(k) {
			t.Fatalf("Pull on the first prefix removed %s", k)
		}
	}
	if v, ok, err := second.Pull(ctx, "code"); err != nil || !ok || string(v) != "v" {
		t.Fatalf("second Pull = %q %v %v", v, ok, err)
	}
	if v, ok, err := first.Pull(ctx, "code"); err != nil || ok || v != nil {
		t.Fatalf("first Pull again = %q %v %v, want nil false nil", v, ok, err)
	}
}