package reacquisition

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

func TestBackoffSchedule(t *testing.T) {
	s := Defaults // 6h base, 168h (one week) cap, 3 attempts

	cases := []struct {
		name     string
		attempts int32
		want     time.Duration
	}{
		// Never tried is always due — the grace window, not the backoff, is
		// what holds the first attempt back.
		{"never attempted", 0, 0},
		{"negative is treated as never", -1, 0},
		{"after one attempt", 1, 6 * time.Hour},
		{"after two", 2, 12 * time.Hour},
		{"after three", 3, 24 * time.Hour},
		{"after four", 4, 48 * time.Hour},
		{"after five", 5, 96 * time.Hour},
		// 6h * 2^5 = 192h, past the one-week cap.
		{"clamped at the cap", 6, 168 * time.Hour},
		{"still clamped far out", 20, 168 * time.Hour},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			if got := s.Backoff(c.attempts); got != c.want {
				t.Errorf("Backoff(%d) = %v, want %v", c.attempts, got, c.want)
			}
		})
	}
}

// The doubling must not be able to overflow int32 before the clamp is
// consulted — a large base with a high attempt count is the case that would
// wrap negative and make a spent album look due immediately.
func TestBackoffDoesNotOverflow(t *testing.T) {
	s := Settings{BackoffBaseHours: 168, BackoffMaxHours: 720}
	for attempts := int32(1); attempts <= 40; attempts++ {
		got := s.Backoff(attempts)
		if got <= 0 {
			t.Fatalf("Backoff(%d) = %v, want a positive duration", attempts, got)
		}
		if got > 720*time.Hour {
			t.Fatalf("Backoff(%d) = %v, want <= the 720h cap", attempts, got)
		}
	}
}

func TestBackoffRespectsCustomSettings(t *testing.T) {
	s := Settings{BackoffBaseHours: 1, BackoffMaxHours: 4}
	for attempts, want := range map[int32]time.Duration{
		1: 1 * time.Hour,
		2: 2 * time.Hour,
		3: 4 * time.Hour,
		4: 4 * time.Hour, // clamped
	} {
		if got := s.Backoff(attempts); got != want {
			t.Errorf("Backoff(%d) = %v, want %v", attempts, got, want)
		}
	}
}

func TestValidateRejectsWhatTheCheckWouldReject(t *testing.T) {
	// Each case mirrors a CHECK in migration 0056. Validating in Go as well
	// means the API answers 400 with a readable message instead of surfacing
	// a constraint violation.
	cases := []struct {
		name string
		in   Settings
	}{
		{"zero grace would fire on every transient unmount",
			mutate(func(s *Settings) { s.GraceHours = 0 })},
		{"grace beyond a month", mutate(func(s *Settings) { s.GraceHours = 721 })},
		{"zero backoff base", mutate(func(s *Settings) { s.BackoffBaseHours = 0 })},
		{"backoff base beyond a week", mutate(func(s *Settings) { s.BackoffBaseHours = 169 })},
		{"zero backoff cap", mutate(func(s *Settings) { s.BackoffMaxHours = 0 })},
		{"cap below base is incoherent", mutate(func(s *Settings) {
			s.BackoffBaseHours = 48
			s.BackoffMaxHours = 24
		})},
		{"zero attempts means never try", mutate(func(s *Settings) { s.MaxAttempts = 0 })},
		{"attempts beyond ten", mutate(func(s *Settings) { s.MaxAttempts = 11 })},
		{"zero per pass means never sweep", mutate(func(s *Settings) { s.MaxPerPass = 0 })},
		{"per pass beyond the cap", mutate(func(s *Settings) { s.MaxPerPass = 201 })},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			if err := validate(c.in); !errors.Is(err, ErrOutOfRange) {
				t.Errorf("validate() = %v, want ErrOutOfRange", err)
			}
		})
	}
}

func TestValidateAcceptsDefaults(t *testing.T) {
	if err := validate(Defaults); err != nil {
		t.Fatalf("the shipped defaults must be valid, got %v", err)
	}
}

// Equal base and cap is legal — it is how an operator asks for a flat retry
// interval rather than an escalating one.
func TestValidateAcceptsFlatBackoff(t *testing.T) {
	s := mutate(func(s *Settings) {
		s.BackoffBaseHours = 12
		s.BackoffMaxHours = 12
	})
	if err := validate(s); err != nil {
		t.Fatalf("flat backoff should be allowed, got %v", err)
	}
	if got := s.Backoff(5); got != 12*time.Hour {
		t.Errorf("flat backoff gave %v, want 12h at every attempt", got)
	}
}

func mutate(f func(*Settings)) Settings {
	s := Defaults
	f(&s)
	return s
}