package aplicare

import (
	"encoding/json"
	"os"
	"time"
)

// RoomSnapshot adalah snapshot nilai per ruangan
type RoomSnapshot struct {
	Kapasitas          int `json:"kapasitas"`
	Tersedia           int `json:"tersedia"`
	TersediaPria       int `json:"tersedia_pria"`
	TersediaWanita     int `json:"tersedia_wanita"`
	TersediaPriaWanita int `json:"tersedia_pria_wanita"`
}

// RoomState adalah state per ruangan dengan perbandingan old vs new
type RoomState struct {
	KodeRuang  string       `json:"kode_ruang"`
	KodeKelas  string       `json:"kodekelas"`
	NamaRuang  string       `json:"nama_ruang"`
	OldValue   RoomSnapshot `json:"old_value"`
	NewValue   RoomSnapshot `json:"new_value"`
	Changed    bool         `json:"changed"`
	LastSynced string       `json:"last_synced"`
}

// State adalah struktur utama state.json
type State struct {
	LastUpdated string               `json:"last_updated"`
	Rooms       map[string]RoomState `json:"rooms"` // key: kode_ruang
}

// LoadState membaca state.json dari disk
// Mengembalikan empty State (bukan error) jika file belum ada
func LoadState(path string) (*State, error) {
	data, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return &State{Rooms: make(map[string]RoomState)}, nil
	}
	if err != nil {
		return nil, err
	}

	var state State
	if err := json.Unmarshal(data, &state); err != nil {
		return nil, err
	}

	if state.Rooms == nil {
		state.Rooms = make(map[string]RoomState)
	}

	return &state, nil
}

// SaveState menulis state ke disk
func SaveState(path string, state *State) error {
	state.LastUpdated = time.Now().Format(time.RFC3339)

	data, err := json.MarshalIndent(state, "", "  ")
	if err != nil {
		return err
	}

	return os.WriteFile(path, data, 0644)
}

// ComputeDiff membandingkan data SIMRS terbaru dengan state lama.
// Mengembalikan state baru dengan field Changed=true hanya untuk yang berubah.
func ComputeDiff(old *State, current []BedData) *State {
	newState := &State{
		Rooms: make(map[string]RoomState),
	}

	now := time.Now().Format(time.RFC3339)

	for _, bed := range current {
		newSnap := RoomSnapshot{
			Kapasitas:          bed.Kapasitas,
			Tersedia:           bed.Tersedia,
			TersediaPria:       bed.TersediaPria,
			TersediaWanita:     bed.TersediaWanita,
			TersediaPriaWanita: bed.TersediaPriaWanita,
		}

		oldRoom, exists := old.Rooms[bed.KodeRuang]
		oldSnap := oldRoom.NewValue
		if !exists {

			oldSnap = RoomSnapshot{}
		}

		changed := !snapshotEqual(oldSnap, newSnap)

		// Kalau sebelumnya sudah ada lastSynced, pertahankan
		lastSynced := oldRoom.LastSynced
		if changed {
			lastSynced = now
		}

		newState.Rooms[bed.KodeRuang] = RoomState{
			KodeRuang:  bed.KodeRuang,
			KodeKelas:  bed.KodeKelas,
			NamaRuang:  bed.NamaRuang,
			OldValue:   oldSnap,
			NewValue:   newSnap,
			Changed:    changed,
			LastSynced: lastSynced,
		}
	}

	return newState
}

// GetChangedBeds mengembalikan hanya BedData yang berubah dari state
func GetChangedBeds(state *State, allBeds []BedData) []BedData {
	changedMap := make(map[string]bool)
	for kode, room := range state.Rooms {
		if room.Changed {
			changedMap[kode] = true
		}
	}

	var changed []BedData
	for _, bed := range allBeds {
		if changedMap[bed.KodeRuang] {
			changed = append(changed, bed)
		}
	}
	return changed
}

func snapshotEqual(a, b RoomSnapshot) bool {
	return a.Kapasitas == b.Kapasitas &&
		a.Tersedia == b.Tersedia &&
		a.TersediaPria == b.TersediaPria &&
		a.TersediaWanita == b.TersediaWanita &&
		a.TersediaPriaWanita == b.TersediaPriaWanita
}