package gfs

import "fmt"

// Family is the dataset family ("gfs" or "gefs"). Variants of different
// families have different URL layouts but share the cube format.
type Family int

const (
	FamilyGFS Family = iota
	FamilyGEFS
)

func (f Family) String() string {
	switch f {
	case FamilyGEFS:
		return "gefs"
	default:
		return "gfs"
	}
}

// HasMember reports whether the family requires a member index in URLs.
func (f Family) HasMember() bool { return f == FamilyGEFS }

// GEFS variant constants.
//
// The 21-member ensemble is gec00 (control) + gep01..gep20 (perturbations).
// NOAA publishes more members today but 21 matches the historical Tawhiri
// configuration and is what the phase 2 spec calls for.
const GEFSMembers = 21

// GefsMemberName returns the file-name token for a GEFS member.
// member=0 → "gec00", member=1..20 → "gep01".."gep20".
func GefsMemberName(member int) string {
	if member == 0 {
		return "gec00"
	}
	return fmt.Sprintf("gep%02d", member)
}

// GEFS S3 mirror.
const GEFSS3BaseURL = "https://noaa-gefs-pds.s3.amazonaws.com"

// GefsGribURL returns the S3 URL for a GEFS primary GRIB file.
func GefsGribURL(date string, runHour, member, forecastStep int, resToken string) string {
	return fmt.Sprintf("%s/gefs.%s/%02d/atmos/pgrb2ap5/%s.t%02dz.pgrb2a.%s.f%03d",
		GEFSS3BaseURL, date, runHour, GefsMemberName(member), runHour, resToken, forecastStep)
}

// GefsGribURLB returns the S3 URL for a GEFS secondary GRIB file.
func GefsGribURLB(date string, runHour, member, forecastStep int, resToken string) string {
	return fmt.Sprintf("%s/gefs.%s/%02d/atmos/pgrb2bp5/%s.t%02dz.pgrb2b.%s.f%03d",
		GEFSS3BaseURL, date, runHour, GefsMemberName(member), runHour, resToken, forecastStep)
}

// GEFS variants — 0.5° resolution, 3-hour cadence, 192h horizon.
var GEFS0p50_3h = &Variant{
	ID:              "gefs-0p50-3h",
	Family:          FamilyGEFS,
	ResToken:        "0p50",
	Resolution:      0.5,
	HourStep:        3,
	MaxHour:         192,
	Pressures:       GFS0p50_3h.Pressures,
	PressuresPgrb2:  GFS0p50_3h.PressuresPgrb2,
	PressuresPgrb2b: GFS0p50_3h.PressuresPgrb2b,
}