package insight

import "time"

type Freshness string

const (
	FreshnessFresh   Freshness = "FRESH"
	FreshnessLagging Freshness = "LAGGING"
	FreshnessStale   Freshness = "STALE"
)

type TimeContext struct {
	AsOfDate          string    `json:"asOfDate"`
	DataThroughDate   string    `json:"dataThroughDate"`
	ForecastStartDate string    `json:"forecastStartDate"`
	Freshness         Freshness `json:"freshness"`
	DataLagDays       int       `json:"dataLagDays"`
}

func BuildTimeContext(now, dataThrough time.Time) TimeContext {
	location, err := time.LoadLocation("Asia/Tehran")
	if err != nil {
		location = time.FixedZone("Asia/Tehran", 3*60*60+30*60)
	}
	today := dateOnly(now.In(location), location)
	through := dateOnly(dataThrough.In(location), location)
	lag := max(0, int(today.Sub(through).Hours()/24))
	return TimeContext{
		AsOfDate: today.Format(time.DateOnly), DataThroughDate: through.Format(time.DateOnly),
		ForecastStartDate: today.Format(time.DateOnly), Freshness: ClassifyFreshness(lag), DataLagDays: lag,
	}
}

func ClassifyFreshness(lagDays int) Freshness {
	switch {
	case lagDays <= 1:
		return FreshnessFresh
	case lagDays <= 7:
		return FreshnessLagging
	default:
		return FreshnessStale
	}
}

func dateOnly(value time.Time, location *time.Location) time.Time {
	year, month, day := value.In(location).Date()
	return time.Date(year, month, day, 0, 0, 0, 0, location)
}