package ratelimit

import (
	"context"
	"errors"
	"testing"
	"time"
)

func TestMemoryWindow(t *testing.T) {
	now := time.Date(2026, 9, 4, 12, 0, 0, 0, time.UTC)
	m := NewMemory()
	m.Now = func() time.Time { return now }

	ctx := context.Background()

	for i := 1; i <= 3; i++ {
		res, err := m.Allow(ctx, "k", 3, time.Minute)
		if err != nil || !res.Allowed {
			t.Fatalf("request %d: allowed=%v err=%v", i, res.Allowed, err)
		}
		if res.Remaining != 3-i {
			t.Errorf("request %d: remaining %d, want %d", i, res.Remaining, 3-i)
		}
	}

	res, _ := m.Allow(ctx, "k", 3, time.Minute)
	if res.Allowed {
		t.Error("4th request allowed past a limit of 3")
	}
	if res.RetryAfter <= 0 {
		t.Error("RetryAfter not set on a rejection")
	}

	// Window rolls over.
	now = now.Add(time.Minute + time.Second)
	if res, _ := m.Allow(ctx, "k", 3, time.Minute); !res.Allowed {
		t.Error("request rejected after the window expired")
	}
}

func TestMemoryKeysAreIndependent(t *testing.T) {
	m := NewMemory()
	ctx := context.Background()

	for i := 0; i < 5; i++ {
		m.Allow(ctx, "a", 5, time.Minute)
	}

	if res, _ := m.Allow(ctx, "a", 5, time.Minute); res.Allowed {
		t.Error("key a not limited")
	}
	if res, _ := m.Allow(ctx, "b", 5, time.Minute); !res.Allowed {
		t.Error("key b affected by key a")
	}
}

func TestMemoryZeroLimitIsUnlimited(t *testing.T) {
	m := NewMemory()
	for i := 0; i < 1000; i++ {
		if res, _ := m.Allow(context.Background(), "k", 0, time.Minute); !res.Allowed {
			t.Fatalf("zero limit rejected at %d", i)
		}
	}
}

func TestMemorySweep(t *testing.T) {
	now := time.Now()
	m := NewMemory()
	m.Now = func() time.Time { return now }

	m.Allow(context.Background(), "a", 5, time.Minute)
	m.Allow(context.Background(), "b", 5, time.Hour)

	if n := m.Sweep(); n != 0 {
		t.Errorf("swept %d live windows", n)
	}

	now = now.Add(2 * time.Minute)

	if n := m.Sweep(); n != 1 {
		t.Errorf("swept %d, want 1 (a expired, b did not)", n)
	}
}

func TestMemoryIsConcurrencySafe(t *testing.T) {
	m := NewMemory()
	ctx := context.Background()

	const goroutines, each = 20, 50

	done := make(chan int, goroutines)

	for g := 0; g < goroutines; g++ {
		go func() {
			allowed := 0
			for i := 0; i < each; i++ {
				if res, _ := m.Allow(ctx, "shared", 100, time.Minute); res.Allowed {
					allowed++
				}
			}
			done <- allowed
		}()
	}

	total := 0
	for g := 0; g < goroutines; g++ {
		total += <-done
	}

	// Exactly 100 of the 1000 attempts may pass. A check-then-increment race
	// would let more through.
	if total != 100 {
		t.Errorf("%d requests allowed under concurrency, want exactly 100", total)
	}
}

// fakeRunner stands in for Redis so the script result handling can be tested.
type fakeRunner struct {
	ret  any
	err  error
	keys []string
	args []any
}

func (f *fakeRunner) Eval(_ context.Context, _ string, keys []string, args ...any) (any, error) {
	f.keys, f.args = keys, args
	return f.ret, f.err
}

func TestRedisResultParsing(t *testing.T) {
	ctx := context.Background()

	t.Run("under limit", func(t *testing.T) {
		f := &fakeRunner{ret: []any{int64(3), int64(45000)}}
		r := NewRedis(f)

		res, err := r.Allow(ctx, "key:1", 10, time.Minute)
		if err != nil {
			t.Fatal(err)
		}
		if !res.Allowed || res.Remaining != 7 {
			t.Errorf("allowed=%v remaining=%d, want true/7", res.Allowed, res.Remaining)
		}
		if res.RetryAfter != 45*time.Second {
			t.Errorf("RetryAfter %v, want 45s", res.RetryAfter)
		}
		if len(f.keys) != 1 || f.keys[0] != "rl:key:1" {
			t.Errorf("keys %v, want [rl:key:1]", f.keys)
		}
	})

	t.Run("over limit", func(t *testing.T) {
		r := NewRedis(&fakeRunner{ret: []any{int64(11), int64(1000)}})
		res, _ := r.Allow(ctx, "k", 10, time.Minute)
		if res.Allowed || res.Remaining != 0 {
			t.Errorf("allowed=%v remaining=%d, want false/0", res.Allowed, res.Remaining)
		}
	})

	t.Run("exactly at limit is allowed", func(t *testing.T) {
		r := NewRedis(&fakeRunner{ret: []any{int64(10), int64(1000)}})
		if res, _ := r.Allow(ctx, "k", 10, time.Minute); !res.Allowed {
			t.Error("request at exactly the limit was rejected")
		}
	})

	t.Run("plain int accepted", func(t *testing.T) {
		r := NewRedis(&fakeRunner{ret: []any{1, 1000}})
		if _, err := r.Allow(ctx, "k", 10, time.Minute); err != nil {
			t.Errorf("int result rejected: %v", err)
		}
	})

	t.Run("missing ttl falls back to the window", func(t *testing.T) {
		r := NewRedis(&fakeRunner{ret: []any{int64(11), int64(-1)}})
		res, _ := r.Allow(ctx, "k", 10, time.Minute)
		if res.RetryAfter != time.Minute {
			t.Errorf("RetryAfter %v, want 1m", res.RetryAfter)
		}
	})

	t.Run("eval error propagates", func(t *testing.T) {
		r := NewRedis(&fakeRunner{err: errors.New("nope")})
		if _, err := r.Allow(ctx, "k", 10, time.Minute); err == nil {
			t.Error("expected an error so the caller can fail open")
		}
	})

	t.Run("garbage result is an error not a panic", func(t *testing.T) {
		r := NewRedis(&fakeRunner{ret: "not a list"})
		if _, err := r.Allow(ctx, "k", 10, time.Minute); err == nil {
			t.Error("expected an error")
		}
	})

	t.Run("zero limit skips redis entirely", func(t *testing.T) {
		f := &fakeRunner{ret: []any{int64(1), int64(1)}}
		r := NewRedis(f)
		res, _ := r.Allow(ctx, "k", 0, time.Minute)
		if !res.Allowed {
			t.Error("zero limit rejected")
		}
		if f.keys != nil {
			t.Error("redis was called for an unlimited tier")
		}
	})
}