package calc

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

type staticProvider struct {
	rate Rate
}

func (p staticProvider) RateFor(country string, day time.Time) (Rate, error) {
	if p.rate.Country != country {
		return Rate{}, errors.New("country mismatch")
	}
	return p.rate, nil
}

func d(s string) time.Time {
	t, err := time.Parse("2006-01-02", s)
	if err != nil {
		panic(err)
	}
	return t
}

func TestCompute_SingleDay_PartialRate(t *testing.T) {
	legs := []Leg{{Country: "DE", FromDate: d("2026-10-02"), ToDate: d("2026-10-02")}}
	rate := Rate{RateID: "PDR-42", Country: "DE", Currency: "EUR",
		FullDay: "28.00", PartialDayMin8h: "14.00",
		ArrivalDay: "14.00", DepartureDay: "14.00",
	}
	got, err := Compute(legs, staticProvider{rate: rate})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	want := []Item{{Type: PerDiemPartial, Amount: "14.00", IncurredOn: d("2026-10-02"), RateID: "PDR-42"}}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("got %+v want %+v", got, want)
	}
}

func TestCompute_ThreeDayTrip_ArrivalFullDeparture(t *testing.T) {
	legs := []Leg{{Country: "DE", FromDate: d("2026-10-01"), ToDate: d("2026-10-03")}}
	rate := Rate{RateID: "PDR-42", Country: "DE", Currency: "EUR",
		FullDay: "28.00", PartialDayMin8h: "14.00",
		ArrivalDay: "14.00", DepartureDay: "14.00",
	}
	got, err := Compute(legs, staticProvider{rate: rate})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	want := []Item{
		{Type: PerDiemArrival, Amount: "14.00", IncurredOn: d("2026-10-01"), RateID: "PDR-42"},
		{Type: PerDiemFull, Amount: "28.00", IncurredOn: d("2026-10-02"), RateID: "PDR-42"},
		{Type: PerDiemDeparture, Amount: "14.00", IncurredOn: d("2026-10-03"), RateID: "PDR-42"},
	}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("got %+v want %+v", got, want)
	}
}

func TestCompute_InvertedDates_Rejected(t *testing.T) {
	legs := []Leg{{Country: "DE", FromDate: d("2026-10-05"), ToDate: d("2026-10-03")}}
	_, err := Compute(legs, staticProvider{rate: Rate{Country: "DE"}})
	if err == nil {
		t.Fatal("expected error for inverted dates")
	}
}

func TestCompute_EmptyLegs_Rejected(t *testing.T) {
	_, err := Compute(nil, staticProvider{rate: Rate{Country: "DE"}})
	if err == nil {
		t.Fatal("expected error for empty legs")
	}
}

func TestCompute_NilProvider_Rejected(t *testing.T) {
	legs := []Leg{{Country: "DE", FromDate: d("2026-10-01"), ToDate: d("2026-10-03")}}
	_, err := Compute(legs, nil)
	if err == nil {
		t.Fatal("expected error for nil provider")
	}
}