package calls

import (
	"testing"
	"time"
)

// Task 5 review minor 5: unit coverage for ratelimit.go's own behaviour,
// independent of the signal endpoint that happens to be its only caller.

func TestRateLimiterAllowsUpToBurstThenRefuses(t *testing.T) {
	now := time.Date(2026, 9, 10, 9, 0, 0, 0, time.UTC)
	l := newRateLimiter(30, 3, 0)
	for i := 0; i < 3; i++ {
		if ok, _ := l.allow("k", now); !ok {
			t.Fatalf("call %d within burst was refused", i)
		}
	}
	ok, retry := l.allow("k", now)
	if ok {
		t.Fatal("a call past the burst, with no time elapsed, was allowed")
	}
	if retry <= 0 {
		t.Fatalf("retryAfter %v, want > 0", retry)
	}
}

func TestRateLimiterRefillsAfterAnExplicitElapsedDuration(t *testing.T) {
	now := time.Date(2026, 9, 10, 9, 0, 0, 0, time.UTC)
	l := newRateLimiter(30, 1, 0)
	if ok, _ := l.allow("k", now); !ok {
		t.Fatal("the first call, at burst, was refused")
	}
	if ok, _ := l.allow("k", now); ok {
		t.Fatal("a second call at the same instant was allowed with an empty bucket")
	}
	// One token at 30/s refills in 1/30 s ≈ 33 ms; 40 ms is comfortably
	// past that.
	later := now.Add(40 * time.Millisecond)
	if ok, _ := l.allow("k", later); !ok {
		t.Fatal("a call after the refill window was still refused")
	}
}

func TestRateLimiterRetryAfterIsBoundedByOneTokensRefillTime(t *testing.T) {
	now := time.Date(2026, 9, 10, 9, 0, 0, 0, time.UTC)
	l := newRateLimiter(30, 1, 0)
	l.allow("k", now)
	_, retry := l.allow("k", now)
	oneToken := time.Second / 30
	if retry <= 0 || retry > oneToken+time.Millisecond {
		t.Fatalf("retryAfter %v, want in (0, %v]", retry, oneToken)
	}
}

func TestRateLimiterEvictsABucketIdleOverAMinute(t *testing.T) {
	now := time.Date(2026, 9, 10, 9, 0, 0, 0, time.UTC)
	l := newRateLimiter(30, 60, 0)
	l.allow("k", now)

	l.mu.Lock()
	l.sweepLocked(now.Add(59 * time.Second))
	_, stillThereAt59s := l.buckets["k"]
	l.sweepLocked(now.Add(61 * time.Second))
	_, stillThereAt61s := l.buckets["k"]
	l.mu.Unlock()

	if !stillThereAt59s {
		t.Fatal("a bucket under a minute idle was swept early")
	}
	if stillThereAt61s {
		t.Fatal("a bucket over a minute idle was not swept")
	}
}

func TestRateLimiterCapEvictsTheLeastRecentlyTouchedBucket(t *testing.T) {
	now := time.Date(2026, 9, 10, 9, 0, 0, 0, time.UTC)
	l := newRateLimiter(30, 60, 2)
	l.allow("a", now)
	l.allow("b", now.Add(time.Second))

	l.mu.Lock()
	n := len(l.buckets)
	l.mu.Unlock()
	if n != 2 {
		t.Fatalf("buckets after two distinct keys: %d, want 2", n)
	}

	// A third key must not grow the map past the cap: "a", the oldest,
	// is evicted to make room.
	l.allow("c", now.Add(2*time.Second))

	l.mu.Lock()
	_, aStillThere := l.buckets["a"]
	_, bStillThere := l.buckets["b"]
	_, cThere := l.buckets["c"]
	size := len(l.buckets)
	l.mu.Unlock()

	if size > 2 {
		t.Fatalf("bucket count %d exceeds the cap of 2", size)
	}
	if aStillThere {
		t.Fatal("the least recently touched bucket ('a') was not evicted to make room")
	}
	if !bStillThere || !cThere {
		t.Fatal("a bucket newer than the one evicted was lost instead")
	}
}