package main

import (
	e "codeberg.org/pebbe/errors"

	"encoding/json"
	"fmt"
	"os"
	"slices"
	"strconv"
	"strings"
	"time"
)

type Date struct {
	Week  string `json:"week"`
	First string `json:"first"`
	Last  string `json:"last"`
}

var (
	x = e.ExitErr

	dates = make([]Date, 0)
)

func main() {

	files, err := os.ReadDir("/net/corpora/nlnieuws/data")
	x(err)

	for _, file := range files {
		filename := file.Name()
		if strings.HasPrefix(filename, "DATA-") && strings.HasSuffix(filename, "-4.json") {
			addWeek(filename[5:12])
		}
	}

	slices.Reverse(dates)
	b, err := json.Marshal(dates)
	x(err)
	fmt.Println(string(b))

}

func addWeek(s string) {

	week, err := strconv.Atoi(s[5:])
	x(err)
	year, err := strconv.Atoi(s[:4])
	x(err)

	// 15 januari van het jaar
	t := time.Date(year, 1, 15, 12, 0, 0, 0, time.UTC)

	// eerste gok
	t = t.AddDate(0, 0, 7*week-14)

	// zoek juiste week
	var y, w int
	for {
		y, _ = t.ISOWeek()
		if y < year {
			t = t.AddDate(0, 12, 0)
			continue
		}
		if y > year {
			t = t.AddDate(0, -12, 0)
			continue
		}
		break
	}
	for {
		y, w = t.ISOWeek()
		if w < week {
			t = t.AddDate(0, 0, 7)
			continue
		}
		if w > week {
			t = t.AddDate(0, 0, -7)
		}
		break
	}
	if y != year {
		x(fmt.Errorf("ongeldige combinatie van week/jaar: %d/%d", week, year))
	}

	// zoek begin van de week
	d := int(t.Weekday())
	if d == 0 {
		d = 7
	}
	tFirst := t.AddDate(0, 0, 1-d)
	tLast := tFirst.AddDate(0, 0, 6)

	dates = append(dates, Date{
		Week:  s,
		First: makeDate(tFirst),
		Last:  makeDate(tLast),
	})
}

func makeDate(d time.Time) string {
	return fmt.Sprintf("%d-%02d-%02d", d.Year(), int(d.Month()), d.Day())
}