package ratewatch

import (
	"context"
	"fmt"
	"testing"
	"time"

	"github.com/google/uuid"
)

// fakeFlagger records flag calls and reports them as newly set.
type fakeFlagger struct {
	calls []uuid.UUID
}

func (f *fakeFlagger) FlagHighRate(_ context.Context, id uuid.UUID, _ time.Time) (bool, error) {
	f.calls = append(f.calls, id)
	return true, nil
}

// watchAt returns a Watch with a controllable clock.
func watchAt(cfg Config, flagger Flagger, at *time.Time) *Watch {
	w := New(cfg, flagger, nil)
	w.now = func() time.Time { return *at }
	return w
}

// TestIngestAggregatesAndRecent verifies episodes accumulate per (class, key),
// invalid entries are skipped, and Recent orders by last rejection.
func TestIngestAggregatesAndRecent(t *testing.T) {
	now := time.Date(2026, 6, 10, 12, 0, 0, 0, time.UTC)
	w := watchAt(DefaultConfig(), nil, &now)
	ctx := context.Background()

	w.Ingest(ctx, []Entry{
		{Class: "public", Key: "10.0.0.1", Rejected: 3},
		{Class: "user", Key: "u-1", Rejected: 5},
		{Class: "", Key: "x", Rejected: 1},
		{Class: "user", Key: "", Rejected: 1},
		{Class: "user", Key: "u-1", Rejected: 0},
	})
	now = now.Add(30 * time.Second)
	w.Ingest(ctx, []Entry{{Class: "public", Key: "10.0.0.1", Rejected: 4}})

	got := w.Recent()
	if len(got) != 2 {
		t.Fatalf("Recent returned %d episodes, want 2", len(got))
	}
	if got[0].Class != "public" || got[0].Key != "10.0.0.1" || got[0].Rejected != 7 {
		t.Errorf("first episode = %+v, want public/10.0.0.1 rejected=7", got[0])
	}
	if !got[0].LastSeen.After(got[0].FirstSeen) {
		t.Errorf("episode span = [%v, %v], want a positive span", got[0].FirstSeen, got[0].LastSeen)
	}
	if got[1].Class != "user" || got[1].Rejected != 5 {
		t.Errorf("second episode = %+v, want user rejected=5", got[1])
	}
}

// TestAutoFlagThreshold verifies the flag fires only for a user-class series
// crossing the threshold within the window, with a parseable account id.
func TestAutoFlagThreshold(t *testing.T) {
	now := time.Date(2026, 6, 10, 12, 0, 0, 0, time.UTC)
	flagged := &fakeFlagger{}
	id := uuid.New()
	w := watchAt(Config{FlagThreshold: 100, FlagWindow: 10 * time.Minute}, flagged, &now)
	ctx := context.Background()

	w.Ingest(ctx, []Entry{
		{Class: "user", Key: id.String(), Rejected: 99},
		{Class: "public", Key: "10.0.0.1", Rejected: 1000},
		{Class: "user", Key: "not-a-uuid", Rejected: 1000},
	})
	if len(flagged.calls) != 0 {
		t.Fatalf("flagged %v below the threshold", flagged.calls)
	}

	now = now.Add(30 * time.Second)
	w.Ingest(ctx, []Entry{{Class: "user", Key: id.String(), Rejected: 1}})
	if len(flagged.calls) != 1 || flagged.calls[0] != id {
		t.Fatalf("flag calls = %v, want exactly [%s]", flagged.calls, id)
	}
}

// TestAutoFlagWindowExpiry verifies rejections age out of the rolling window.
func TestAutoFlagWindowExpiry(t *testing.T) {
	now := time.Date(2026, 6, 10, 12, 0, 0, 0, time.UTC)
	flagged := &fakeFlagger{}
	id := uuid.New()
	w := watchAt(Config{FlagThreshold: 100, FlagWindow: 10 * time.Minute}, flagged, &now)
	ctx := context.Background()

	w.Ingest(ctx, []Entry{{Class: "user", Key: id.String(), Rejected: 60}})
	now = now.Add(11 * time.Minute)
	w.Ingest(ctx, []Entry{{Class: "user", Key: id.String(), Rejected: 60}})
	if len(flagged.calls) != 0 {
		t.Fatalf("flagged %v across an expired window", flagged.calls)
	}
	now = now.Add(time.Minute)
	w.Ingest(ctx, []Entry{{Class: "user", Key: id.String(), Rejected: 50}})
	if len(flagged.calls) != 1 {
		t.Fatalf("flag calls = %v, want one in-window crossing", flagged.calls)
	}
}

// TestSeriesBound verifies the episode map stays bounded by evicting the
// least-recently-throttled series.
func TestSeriesBound(t *testing.T) {
	now := time.Date(2026, 6, 10, 12, 0, 0, 0, time.UTC)
	w := watchAt(DefaultConfig(), nil, &now)
	ctx := context.Background()

	for i := range maxSeries + 10 {
		now = now.Add(time.Second)
		w.Ingest(ctx, []Entry{{Class: "public", Key: fmt.Sprintf("10.0.%d.%d", i/256, i%256), Rejected: 1}})
	}
	got := w.Recent()
	if len(got) != maxSeries {
		t.Fatalf("retained %d series, want %d", len(got), maxSeries)
	}
	for _, ep := range got {
		if ep.Key == "10.0.0.0" {
			t.Fatal("the least-recently-throttled series survived the bound")
		}
	}
}

// TestConfigValidate covers the tuning guards.
func TestConfigValidate(t *testing.T) {
	if err := DefaultConfig().Validate(); err != nil {
		t.Errorf("default config invalid: %v", err)
	}
	if err := (Config{FlagThreshold: 0, FlagWindow: time.Minute}).Validate(); err == nil {
		t.Error("zero threshold passed validation")
	}
	if err := (Config{FlagThreshold: 1, FlagWindow: 0}).Validate(); err == nil {
		t.Error("zero window passed validation")
	}
}