package storage

import (
	"errors"
	"sort"
	"sync"

	"go-mod.ewintr.nl/planner/item"
)

type Memory struct {
	events   map[string]item.Event
	localIDs map[int]string
	mutex    sync.RWMutex
}

func NewMemory() *Memory {
	return &Memory{
		events:   make(map[string]item.Event),
		localIDs: make(map[int]string),
	}
}

func (r *Memory) Find(id string) (item.Event, error) {
	r.mutex.RLock()
	defer r.mutex.RUnlock()

	event, exists := r.events[id]
	if !exists {
		return item.Event{}, errors.New("event not found")
	}
	return event, nil
}

func (r *Memory) FindByLocal(localID int) (item.Event, error) {
	r.mutex.RLock()
	defer r.mutex.RUnlock()

	id, exists := r.localIDs[localID]
	if !exists {
		return item.Event{}, errors.New("event not found")
	}

	event, exists := r.events[id]
	if !exists {
		return item.Event{}, errors.New("id an localid mismatch")
	}
	return event, nil
}

func (r *Memory) FindAll() (map[int]string, []item.Event, error) {
	r.mutex.RLock()
	defer r.mutex.RUnlock()

	events := make([]item.Event, 0, len(r.events))
	for _, event := range r.events {
		events = append(events, event)
	}
	sort.Slice(events, func(i, j int) bool {
		return events[i].ID < events[j].ID
	})

	return r.localIDs, events, nil
}

func (r *Memory) Store(e item.Event) error {
	r.mutex.Lock()
	defer r.mutex.Unlock()

	if _, exists := r.events[e.ID]; !exists {
		cur := make([]int, 0, len(r.localIDs))
		for i := range r.localIDs {
			cur = append(cur, i)
		}
		localID := NextLocalID(cur)
		r.localIDs[localID] = e.ID
	}

	r.events[e.ID] = e

	return nil
}

func (r *Memory) Delete(id string) error {
	r.mutex.Lock()
	defer r.mutex.Unlock()

	if _, exists := r.events[id]; !exists {
		return errors.New("event not found")
	}
	delete(r.events, id)

	for localID, eventID := range r.localIDs {
		if id == eventID {
			delete(r.localIDs, localID)
		}
	}

	return nil
}