package nws

import (
	"fmt"
	"strings"
	"time"
)

// ParseTime parses NWS timestamps.
//
// NWS observation timestamps are typically RFC3339, sometimes with fractional seconds.
// We accept RFC3339Nano first, then RFC3339.
func ParseTime(s string) (time.Time, error) {
	s = strings.TrimSpace(s)
	if s == "" {
		return time.Time{}, fmt.Errorf("empty time")
	}

	if t, err := time.Parse(time.RFC3339Nano, s); err == nil {
		return t, nil
	}
	if t, err := time.Parse(time.RFC3339, s); err == nil {
		return t, nil
	}

	return time.Time{}, fmt.Errorf("unsupported NWS timestamp format: %q", s)
}

// ParseTimeBestEffort parses an NWS timestamp and returns it in UTC.
//
// This is a convenience for normalizers that want "best effort" parsing:
// invalid/empty strings do not fail the entire normalization; they return zero time.
func ParseTimeBestEffort(s string) time.Time {
	t, err := ParseTime(s)
	if err != nil {
		return time.Time{}
	}
	return t.UTC()
}

// ParseTimePtr parses an NWS timestamp and returns a UTC *time.Time.
//
// Empty/unparseable input returns nil. This is useful for optional CAP fields.
func ParseTimePtr(s string) *time.Time {
	t := ParseTimeBestEffort(s)
	if t.IsZero() {
		return nil
	}
	return &t
}