// Package storage handles reading and writing data from various sources.
package storage

import (
	"fmt"
	"os"
	"time"

	"github.com/emersion/go-ical"
	"github.com/luxick/chronological/internal/models"
)

// ICSStore handles reading and writing ICS calendar files.
type ICSStore struct {
	calendarPath string
	diaryPath    string
}

// NewICSStore creates a new ICS store with the given file paths.
func NewICSStore(calendarPath, diaryPath string) *ICSStore {
	return &ICSStore{
		calendarPath: calendarPath,
		diaryPath:    diaryPath,
	}
}

// LoadEvents loads all events from the calendar ICS file.
func (s *ICSStore) LoadEvents() ([]*models.Event, error) {
	if s.calendarPath == "" {
		return nil, nil
	}

	file, err := os.Open(s.calendarPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("failed to open calendar file: %w", err)
	}
	defer file.Close()

	dec := ical.NewDecoder(file)
	cal, err := dec.Decode()
	if err != nil {
		return nil, fmt.Errorf("failed to decode calendar: %w", err)
	}

	return parseEventsFromCalendar(cal, models.SourceLocal)
}

// LoadEventsForMonth loads events that occur within the specified month.
func (s *ICSStore) LoadEventsForMonth(year int, month time.Month) ([]*models.Event, error) {
	allEvents, err := s.LoadEvents()
	if err != nil {
		return nil, err
	}

	start := time.Date(year, month, 1, 0, 0, 0, 0, time.Local)
	end := start.AddDate(0, 1, 0)

	var monthEvents []*models.Event
	for _, event := range allEvents {
		if eventInRange(event, start, end) {
			monthEvents = append(monthEvents, event)
		}
	}

	return monthEvents, nil
}

// LoadDiaryEntries loads all diary entries from the diary ICS file.
func (s *ICSStore) LoadDiaryEntries() ([]*models.DiaryEntry, error) {
	if s.diaryPath == "" {
		return nil, nil
	}

	file, err := os.Open(s.diaryPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("failed to open diary file: %w", err)
	}
	defer file.Close()

	dec := ical.NewDecoder(file)
	cal, err := dec.Decode()
	if err != nil {
		return nil, fmt.Errorf("failed to decode diary calendar: %w", err)
	}

	return parseDiaryFromCalendar(cal)
}

// LoadDiaryEntry loads a single diary entry for a specific date.
func (s *ICSStore) LoadDiaryEntry(date time.Time) (*models.DiaryEntry, error) {
	entries, err := s.LoadDiaryEntries()
	if err != nil {
		return nil, err
	}

	targetDate := date.Truncate(24 * time.Hour)
	for _, entry := range entries {
		if entry.Date.Truncate(24 * time.Hour).Equal(targetDate) {
			return entry, nil
		}
	}

	return nil, nil
}

// SaveDiaryEntry saves or updates a diary entry for a specific date.
func (s *ICSStore) SaveDiaryEntry(entry *models.DiaryEntry) error {
	if s.diaryPath == "" {
		return fmt.Errorf("diary path not configured")
	}

	var cal *ical.Calendar

	// Try to load existing calendar
	file, err := os.Open(s.diaryPath)
	if err == nil {
		dec := ical.NewDecoder(file)
		cal, err = dec.Decode()
		file.Close()
		if err != nil {
			cal = nil
		}
	}

	// Create new calendar if none exists
	if cal == nil {
		cal = ical.NewCalendar()
		cal.Props.SetText(ical.PropVersion, "2.0")
		cal.Props.SetText(ical.PropProductID, "-//Chronological//Diary//EN")
	}

	targetDate := entry.Date.Truncate(24 * time.Hour)
	found := false

	// Update existing entry if found
	for _, child := range cal.Children {
		if child.Name != ical.CompEvent {
			continue
		}
		event := ical.Event{Component: child}
		summary, _ := event.Props.Text(ical.PropSummary)
		if summary != "Chronolog" {
			continue
		}

		dtstart, err := event.Props.DateTime(ical.PropDateTimeStart, time.Local)
		if err != nil {
			continue
		}

		if dtstart.Truncate(24 * time.Hour).Equal(targetDate) {
			event.Props.SetText(ical.PropDescription, entry.Text)
			found = true
			break
		}
	}

	// Create new entry if not found
	if !found {
		event := ical.NewEvent()
		event.Props.SetText(ical.PropUID, fmt.Sprintf("chronolog-%s@chronological", entry.DateString()))
		event.Props.SetDateTime(ical.PropDateTimeStamp, time.Now())
		event.Props.SetDate(ical.PropDateTimeStart, targetDate)
		event.Props.SetDate(ical.PropDateTimeEnd, targetDate.AddDate(0, 0, 1))
		event.Props.SetText(ical.PropSummary, "Chronolog")
		event.Props.SetText(ical.PropDescription, entry.Text)
		cal.Children = append(cal.Children, event.Component)
	}

	// Write calendar back to file
	outFile, err := os.Create(s.diaryPath)
	if err != nil {
		return fmt.Errorf("failed to create diary file: %w", err)
	}
	defer outFile.Close()

	enc := ical.NewEncoder(outFile)
	if err := enc.Encode(cal); err != nil {
		return fmt.Errorf("failed to encode diary calendar: %w", err)
	}

	return nil
}

// DeleteDiaryEntry removes a diary entry for a specific date.
func (s *ICSStore) DeleteDiaryEntry(date time.Time) error {
	if s.diaryPath == "" {
		return fmt.Errorf("diary path not configured")
	}

	file, err := os.Open(s.diaryPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("failed to open diary file: %w", err)
	}

	dec := ical.NewDecoder(file)
	cal, err := dec.Decode()
	file.Close()
	if err != nil {
		return fmt.Errorf("failed to decode diary calendar: %w", err)
	}

	targetDate := date.Truncate(24 * time.Hour)
	var newChildren []*ical.Component

	for _, child := range cal.Children {
		keep := true

		if child.Name == ical.CompEvent {
			event := ical.Event{Component: child}
			summary, _ := event.Props.Text(ical.PropSummary)
			if summary == "Chronolog" {
				dtstart, err := event.Props.DateTime(ical.PropDateTimeStart, time.Local)
				if err == nil && dtstart.Truncate(24*time.Hour).Equal(targetDate) {
					keep = false
				}
			}
		}

		if keep {
			newChildren = append(newChildren, child)
		}
	}

	cal.Children = newChildren

	outFile, err := os.Create(s.diaryPath)
	if err != nil {
		return fmt.Errorf("failed to create diary file: %w", err)
	}
	defer outFile.Close()

	enc := ical.NewEncoder(outFile)
	if err := enc.Encode(cal); err != nil {
		return fmt.Errorf("failed to encode diary calendar: %w", err)
	}

	return nil
}

func parseEventsFromCalendar(cal *ical.Calendar, source models.EventSource) ([]*models.Event, error) {
	var events []*models.Event

	for _, child := range cal.Children {
		if child.Name != ical.CompEvent {
			continue
		}

		event := ical.Event{Component: child}

		uid, _ := event.Props.Text(ical.PropUID)
		summary, _ := event.Props.Text(ical.PropSummary)
		description, _ := event.Props.Text(ical.PropDescription)
		location, _ := event.Props.Text(ical.PropLocation)

		dtstart, err := event.Props.DateTime(ical.PropDateTimeStart, time.Local)
		if err != nil {
			// Try date-only format for all-day events
			dtstart, err = event.Props.DateTime(ical.PropDateTimeStart, time.Local)
			if err != nil {
				continue
			}
		}

		dtend, err := event.Props.DateTime(ical.PropDateTimeEnd, time.Local)
		if err != nil {
			dtend = dtstart.Add(time.Hour)
		}

		// Check if all-day event (date-only, no time component)
		allDay := isAllDayEvent(&event)

		events = append(events, &models.Event{
			ID:          uid,
			Title:       summary,
			Description: description,
			Start:       dtstart,
			End:         dtend,
			AllDay:      allDay,
			Location:    location,
			Source:      source,
		})
	}

	return events, nil
}

func parseDiaryFromCalendar(cal *ical.Calendar) ([]*models.DiaryEntry, error) {
	var entries []*models.DiaryEntry

	for _, child := range cal.Children {
		if child.Name != ical.CompEvent {
			continue
		}

		event := ical.Event{Component: child}

		summary, _ := event.Props.Text(ical.PropSummary)
		if summary != "Chronolog" {
			continue
		}

		dtstart, err := event.Props.DateTime(ical.PropDateTimeStart, time.Local)
		if err != nil {
			continue
		}

		description, _ := event.Props.Text(ical.PropDescription)

		entries = append(entries, &models.DiaryEntry{
			Date: dtstart.Truncate(24 * time.Hour),
			Text: description,
		})
	}

	return entries, nil
}

func isAllDayEvent(event *ical.Event) bool {
	prop := event.Props.Get(ical.PropDateTimeStart)
	if prop == nil {
		return false
	}

	// All-day events have VALUE=DATE parameter
	valueParam := prop.Params.Get(ical.ParamValue)
	return valueParam == "DATE"
}

func eventInRange(event *models.Event, start, end time.Time) bool {
	return event.Start.Before(end) && event.End.After(start)
}