package main

import (
	"fmt"
	"sort"
	"strings"
)

func buildTasksForDay(plans []Plan, month, day int) []Task {
	var tasks []Task
	for _, p := range plans {
		field := p.TargetName
		if strings.TrimSpace(field) == "" {
			field = "Unbekanntes Feld"
		}
		if p.StartMonth == month && p.StartDay == day {
			tasks = append(tasks, Task{Type: "Aussaat", Field: field, Message: fmt.Sprintf("%s auf %s aussaeen", p.CropName, field), SortOrder: 1})
		}
		if p.HarvestMonth == month && p.HarvestDay == day {
			tasks = append(tasks, Task{Type: "Ernte", Field: field, Message: fmt.Sprintf("%s auf %s ernten", p.CropName, field), SortOrder: 2})
		}
	}
	sort.Slice(tasks, func(i, j int) bool {
		if tasks[i].SortOrder == tasks[j].SortOrder {
			return tasks[i].Field < tasks[j].Field
		}
		return tasks[i].SortOrder < tasks[j].SortOrder
	})
	return tasks
}

func buildCalendar(plans []Plan, startMonth, startDay, daysPerMonth, spanMonths int) []CalendarMonth {
	tasksByKey := make(map[string][]Task)
	for _, p := range plans {
		field := p.TargetName
		if strings.TrimSpace(field) == "" {
			field = "Unbekanntes Feld"
		}
		tasksByKey[fmt.Sprintf("%d-%d", p.StartMonth, p.StartDay)] = append(tasksByKey[fmt.Sprintf("%d-%d", p.StartMonth, p.StartDay)], Task{
			Type:      "Aussaat",
			Field:     field,
			Message:   fmt.Sprintf("%s auf %s", p.CropName, field),
			SortOrder: 1,
		})
		tasksByKey[fmt.Sprintf("%d-%d", p.HarvestMonth, p.HarvestDay)] = append(tasksByKey[fmt.Sprintf("%d-%d", p.HarvestMonth, p.HarvestDay)], Task{
			Type:      "Ernte",
			Field:     field,
			Message:   fmt.Sprintf("%s auf %s", p.CropName, field),
			SortOrder: 2,
		})
	}

	var out []CalendarMonth
	for offset := 0; offset < spanMonths; offset++ {
		month := wrapMonth(startMonth + offset)
		yearOffset := (startMonth - 1 + offset) / 12
		label := monthNames[month-1]
		if yearOffset > 0 {
			label = fmt.Sprintf("%s (+%d Jahr)", label, yearOffset)
		}

		fromDay := 1
		if offset == 0 {
			fromDay = startDay
		}
		var days []CalendarDay
		for day := fromDay; day <= daysPerMonth; day++ {
			key := fmt.Sprintf("%d-%d", month, day)
			items := append([]Task(nil), tasksByKey[key]...)
			sort.Slice(items, func(i, j int) bool {
				if items[i].SortOrder == items[j].SortOrder {
					return items[i].Field < items[j].Field
				}
				return items[i].SortOrder < items[j].SortOrder
			})
			days = append(days, CalendarDay{Day: day, Tasks: items})
		}
		out = append(out, CalendarMonth{
			Offset:     offset,
			Month:      month,
			Label:      label,
			YearOffset: yearOffset,
			Days:       days,
		})
	}
	return out
}