package app

import (
	"strings"
	"testing"
	"time"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/weatherdata"
)

func TestEligibleDailyDatesRequiresFullOrdinaryLocalDay(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	hourly := hourlyRun(fullDayPeriods(t, "2026-05-31", location)...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location, "2026-05-31")
}

func TestEligibleDailyDatesMatchesFixedOffsetStartInstants(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	hourly := hourlyRun(fixedOffsetPeriods(t, fullDayPeriods(t, "2026-05-31", location))...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location, "2026-05-31")
}

func TestEligibleDailyDatesSkipsDayWithMissingRequiredHour(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	periods := fullDayPeriods(t, "2026-05-31", location)
	periods = append(periods[:12], periods[13:]...)
	hourly := hourlyRun(periods...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location)
}

func TestEligibleDailyDatesSkipsPartialFinalDay(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	periods := fullDayPeriods(t, "2026-05-31", location)
	periods = append(periods, partialDayPeriods(t, "2026-06-01", location, 12)...)
	hourly := hourlyRun(periods...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location, "2026-05-31")
}

func TestEligibleDailyDatesStartsAfterTomorrow(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	periods := fullDayPeriods(t, "2026-05-29", location)
	periods = append(periods, fullDayPeriods(t, "2026-05-30", location)...)
	periods = append(periods, fullDayPeriods(t, "2026-05-31", location)...)
	hourly := hourlyRun(periods...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location, "2026-05-31")
}

func TestEligibleDailyDatesReturnsMultipleFutureDatesInOrder(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	periods := fullDayPeriods(t, "2026-05-31", location)
	periods = append(periods, fullDayPeriods(t, "2026-06-01", location)...)
	hourly := hourlyRun(periods...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location, "2026-05-31", "2026-06-01")
}

func TestEligibleDailyDatesIgnoresNonHourlyAndInvalidPeriods(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	day := timeutil.CivilDay(mustParseLocalDate(t, "2026-05-31", location), location)
	periods := []weatherdata.ForecastPeriod{
		{StartTime: day.Start, EndTime: day.Start.Add(2 * time.Hour)},
		{StartTime: day.Start.Add(time.Hour), EndTime: day.Start.Add(time.Hour)},
		{StartTime: time.Time{}, EndTime: day.Start.Add(3 * time.Hour)},
	}
	periods = append(periods, fullDayPeriods(t, "2026-06-01", location)...)
	hourly := hourlyRun(periods...)

	got := eligibleDailyDates(hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
	assertLocalDates(t, got, location, "2026-06-01")
}

func TestEligibleDailyDatesUsesDSTCivilDayInstants(t *testing.T) {
	location := mustLoadTestLocation(t, "America/New_York")
	tests := []struct {
		name string
		now  string
		date string
	}{
		{
			name: "spring forward",
			now:  "2026-03-06T08:00:00-05:00",
			date: "2026-03-08",
		},
		{
			name: "fall back",
			now:  "2026-10-30T08:00:00-04:00",
			date: "2026-11-01",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			hourly := hourlyRun(fullDayPeriods(t, tt.date, location)...)

			got := eligibleDailyDates(hourly, mustParse(tt.now), location)
			assertLocalDates(t, got, location, tt.date)
		})
	}
}

func TestEligibleDailyDatesReturnsNoneWithoutHourlyForecast(t *testing.T) {
	location := mustLoadTestLocation(t, "America/Chicago")
	fullDay := fullDayPeriods(t, "2026-05-31", location)

	tests := []struct {
		name   string
		hourly *weatherdata.ForecastRun
	}{
		{name: "nil run"},
		{name: "empty periods", hourly: hourlyRun()},
		{name: "non-hourly product", hourly: forecastRun("narrative", fullDay...)},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := eligibleDailyDates(tt.hourly, mustParse("2026-05-29T08:00:00-05:00"), location)
			assertLocalDates(t, got, location)
		})
	}
}

func hourlyRun(periods ...weatherdata.ForecastPeriod) *weatherdata.ForecastRun {
	return forecastRun("hourly", periods...)
}

func forecastRun(product string, periods ...weatherdata.ForecastPeriod) *weatherdata.ForecastRun {
	return &weatherdata.ForecastRun{
		Product: product,
		Periods: periods,
	}
}

func fullDayPeriods(t *testing.T, date string, location *time.Location) []weatherdata.ForecastPeriod {
	t.Helper()
	day := timeutil.CivilDay(mustParseLocalDate(t, date, location), location)
	var periods []weatherdata.ForecastPeriod
	for start := day.Start; start.Before(day.End); start = start.Add(time.Hour) {
		periods = append(periods, weatherdata.ForecastPeriod{
			StartTime: start,
			EndTime:   start.Add(time.Hour),
		})
	}
	return periods
}

func partialDayPeriods(t *testing.T, date string, location *time.Location, count int) []weatherdata.ForecastPeriod {
	t.Helper()
	periods := fullDayPeriods(t, date, location)
	if count > len(periods) {
		count = len(periods)
	}
	return periods[:count]
}

func fixedOffsetPeriods(t *testing.T, periods []weatherdata.ForecastPeriod) []weatherdata.ForecastPeriod {
	t.Helper()
	out := make([]weatherdata.ForecastPeriod, 0, len(periods))
	for _, period := range periods {
		start, err := time.Parse(time.RFC3339, period.StartTime.Format(time.RFC3339))
		if err != nil {
			t.Fatalf("parse fixed-offset start: %v", err)
		}
		end, err := time.Parse(time.RFC3339, period.EndTime.Format(time.RFC3339))
		if err != nil {
			t.Fatalf("parse fixed-offset end: %v", err)
		}
		out = append(out, weatherdata.ForecastPeriod{StartTime: start, EndTime: end})
	}
	return out
}

func assertLocalDates(t *testing.T, got []time.Time, location *time.Location, want ...string) {
	t.Helper()
	gotDates := make([]string, 0, len(got))
	for _, date := range got {
		gotDates = append(gotDates, date.In(location).Format(timeutil.DateLayout))
	}
	if strings.Join(gotDates, ",") != strings.Join(want, ",") {
		t.Fatalf("eligibleDailyDates() = [%s], want [%s]", strings.Join(gotDates, ","), strings.Join(want, ","))
	}
	for _, date := range got {
		day := timeutil.CivilDay(date, location)
		if !date.Equal(day.Start) {
			t.Fatalf("eligible date %s is not local civil day start %s", date, day.Start)
		}
	}
}

func mustLoadTestLocation(t *testing.T, name string) *time.Location {
	t.Helper()
	location, err := time.LoadLocation(name)
	if err != nil {
		t.Fatalf("LoadLocation(%q) error = %v", name, err)
	}
	return location
}

func mustParseLocalDate(t *testing.T, value string, location *time.Location) time.Time {
	t.Helper()
	parsed, err := timeutil.ParseLocalDate(value, location)
	if err != nil {
		t.Fatalf("ParseLocalDate(%q) error = %v", value, err)
	}
	return parsed
}