package models

import (
	"fmt"
	"strings"
	"time"
	_ "time/tzdata" // Europe/Warsaw must resolve on hosts without zoneinfo.

	"git.golem15.com/golem15/summercms/modules/lagoon"
)

// Location is the time zone the programme runs in. Timestamps are stored in
// UTC (TIMESTAMPTZ) and shown in this zone; a date or time typed without an
// offset is read in it.
var Location = mustLoadLocation("Europe/Warsaw")

func mustLoadLocation(name string) *time.Location {
	loc, err := time.LoadLocation(name)
	if err != nil {
		panic(fmt.Sprintf("jz.bm: load location %s: %v", name, err))
	}
	return loc
}

// dateTimeLayouts are the forms ParseDateTime accepts. RFC 3339 carries its
// own offset; the others are wall-clock times in Location.
var dateTimeLayouts = []string{
	"2006-01-02T15:04",
	"2006-01-02 15:04",
	"2006-01-02T15:04:05",
	"2006-01-02 15:04:05",
}

// ParseDateTime reads an RFC 3339 timestamp, or a wall-clock time
// ("2026-10-03 08:00") in Location. The seed file uses these forms.
func ParseDateTime(s string) (time.Time, error) {
	s = strings.TrimSpace(s)
	if t, err := time.Parse(time.RFC3339, s); err == nil {
		return t, nil
	}
	for _, layout := range dateTimeLayouts {
		if t, err := time.ParseInLocation(layout, s, Location); err == nil {
			return t, nil
		}
	}
	return time.Time{}, fmt.Errorf("jz.bm: %q is not a date and time", s)
}

// ParseDate reads a YYYY-MM-DD calendar date.
func ParseDate(s string) (lagoon.Date, error) {
	d, err := lagoon.ParseDate(strings.TrimSpace(s))
	if err != nil {
		return lagoon.Date{}, fmt.Errorf("jz.bm: %q is not a YYYY-MM-DD date", s)
	}
	return d, nil
}

// FormatDateTime is the API form of a timestamp: RFC 3339 in Location
// ("2026-10-03T08:00:00+02:00").
func FormatDateTime(t time.Time) string { return t.In(Location).Format(time.RFC3339) }