package calls

import (
	"bytes"
	"context"
	"encoding/base64"
	"io"
	"log/slog"
	"net/http/httptest"
	"net/url"
	"path/filepath"
	"sync"
	"testing"
	"time"

	"amadan.net/rastrillo/rastrillo/db"
)

// blockingMailer holds every Send until release is closed — an SMTP
// relay that takes as long as the test likes.
type blockingMailer struct {
	release chan struct{}
	mu      sync.Mutex
	to      []string
}

func (m *blockingMailer) Send(_ context.Context, to, _, _ string) error {
	<-m.release
	m.mu.Lock()
	m.to = append(m.to, to)
	m.mu.Unlock()
	return nil
}

func (m *blockingMailer) sent() []string {
	m.mu.Lock()
	defer m.mu.Unlock()
	return append([]string(nil), m.to...)
}

// TestSigninNeverWaitsForTheMailer: when the send ran inside the
// request, a member waited for SMTP before its ?sent=1 and a stranger
// did not (Astra measured 252 ms against 0.35 ms on Slides, which had
// the same shape). With the mailer blocked, every POST — member,
// stranger, and both with force=1 — must answer, and the member's
// links must then go out.
func TestSigninNeverWaitsForTheMailer(t *testing.T) {
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	d, err := db.Open(filepath.Join(t.TempDir(), "calls.db"), logger)
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { d.Close() })
	bm := &blockingMailer{release: make(chan struct{})}
	var once sync.Once
	free := func() { once.Do(func() { close(bm.release) }) }
	t.Cleanup(free)
	mux, _, err := buildForTest(t, d, Config{Origin: keymailOrigin, InstanceKey: "test-only-instance",
		DEK: base64.StdEncoding.EncodeToString(bytes.Repeat([]byte{3}, 32)), AllowedAddresses: []string{plainMember}, Mailer: bm, Logger: logger})
	if err != nil {
		t.Fatal(err)
	}
	f := &keymailFixture{handler: mux}

	for _, form := range []url.Values{
		{"address": {plainMember}},
		{"address": {"someone@else.test"}},
		{"address": {plainMember}, "force": {"1"}},
		{"address": {"someone@else.test"}, "force": {"1"}},
	} {
		done := make(chan *httptest.ResponseRecorder, 1)
		go func() { done <- f.post(form) }()
		select {
		case rec := <-done:
			if rec.Code != 303 || rec.Header().Get("Location") != "/signin?sent=1" {
				t.Errorf("POST %v: %d %q, want 303 /signin?sent=1", form, rec.Code, rec.Header().Get("Location"))
			}
		case <-time.After(2 * time.Second):
			t.Errorf("POST %v waited on the mailer: the response time says the address is a member", form)
			free()
			<-done
		}
	}

	free()
	deadline := time.Now().Add(5 * time.Second)
	for len(bm.sent()) < 2 && time.Now().Before(deadline) {
		time.Sleep(10 * time.Millisecond)
	}
	time.Sleep(50 * time.Millisecond)
	if got := bm.sent(); len(got) != 2 || got[0] != plainMember || got[1] != plainMember {
		t.Fatalf("mail sent = %v, want two links, both to %s", got, plainMember)
	}
}