package common

import (
	"encoding/json"
	"fmt"
	"os"
	"reflect"
	"sync"
)

var persistentWriteMu sync.Mutex

func ReadPersistent() (*Persistent, error) {
	raw, err := os.ReadFile("persistent")
	if err != nil {
		return nil, err
	}
	var p Persistent
	if err := json.Unmarshal(raw, &p); err != nil {
		return nil, fmt.Errorf("parse persistent: %w", err)
	}
	return &p, nil
}

func jsonObject(value any) (map[string]any, error) {
	raw, err := json.Marshal(value)
	if err != nil {
		return nil, err
	}
	var object map[string]any
	err = json.Unmarshal(raw, &object)
	return object, err
}

func (f *FreesrData) persistentSnapshot() Persistent {
	ex := make(map[uint32]bool)
	for id := range AvatarExRankMap {
		if avatar := f.Avatars[id]; avatar != nil {
			ex[id] = avatar.ExRankUnlocked
		}
	}
	return Persistent{TeamPresets: f.TeamPresets, ActiveTeamPreset: f.ActiveTeamPreset, TierceProgress: f.TierceProgress, TechniqueFoodStock: f.TechniqueFoodStock, AutoTechniqueFood: f.AutoTechniqueFood, Lineups: f.Lineups, Position: f.Position, Scene: f.Scene,
		MainCharacter: f.MainCharacter, MarchType: f.MarchType,
		EnableSWGlobal: f.EnableSWGlobal, EnableCastoriceGlobal: f.EnableCastoriceGlobal,
		EnableAhaGlobal: f.EnableAhaGlobal, DressedSkins: f.DressedSkins, ExRanksUnlocked: ex}
}

// Apply only locally changed fields. A stale game session saving its position
// must not undo an EX switch written by the SDK process. Nested maps are merged
// per key so different avatars' switches do not overwrite one another.
func mergePersistentChanges(existing, baseline, next map[string]any) {
	for key, value := range next {
		old, known := baseline[key]
		if known && reflect.DeepEqual(old, value) {
			continue
		}
		newMap, newOK := value.(map[string]any)
		oldMap, oldOK := old.(map[string]any)
		if newOK && oldOK {
			dest, ok := existing[key].(map[string]any)
			if !ok {
				dest = make(map[string]any)
			}
			mergePersistentChanges(dest, oldMap, newMap)
			for removed := range oldMap {
				if _, present := newMap[removed]; !present {
					delete(dest, removed)
				}
			}
			existing[key] = dest
		} else {
			existing[key] = value
		}
	}
}

func writeJSONAtomic(path string, value any) error {
	raw, err := json.MarshalIndent(value, "", "  ")
	if err != nil {
		return err
	}
	file, err := os.CreateTemp(".", ".gac-save-*.tmp")
	if err != nil {
		return err
	}
	name := file.Name()
	defer os.Remove(name)
	if _, err := file.Write(raw); err != nil {
		file.Close()
		return err
	}
	if err := file.Close(); err != nil {
		return err
	}
	return os.Rename(name, path)
}

func (f *FreesrData) SavePersistentChecked() error {
	persistentWriteMu.Lock()
	defer persistentWriteMu.Unlock()
	unlock, err := lockPersistentFile()
	if err != nil {
		return err
	}
	defer unlock()
	next, err := jsonObject(f.persistentSnapshot())
	if err != nil {
		return err
	}
	existing := make(map[string]any)
	if raw, err := os.ReadFile("persistent"); err == nil {
		if err := json.Unmarshal(raw, &existing); err != nil {
			return fmt.Errorf("refuse to overwrite invalid persistent: %w", err)
		}
	} else if !os.IsNotExist(err) {
		return err
	}
	mergePersistentChanges(existing, f.persistentBaseline, next)
	if err := writeJSONAtomic("persistent", existing); err != nil {
		return err
	}
	// Track our own observed snapshot, not external changes we have not loaded.
	f.persistentBaseline = next
	return nil
}

// RefreshExRanks imports persisted switches without replacing inventory,
// lineup, scene or the configured battle. Call under the session state lock.
func (f *FreesrData) RefreshExRanks(p *Persistent) []uint32 {
	var changed []uint32
	for id := range AvatarExRankMap {
		avatar := f.Avatars[id]
		if avatar == nil {
			continue
		}
		unlocked := p.ExRanksUnlocked[id]
		if avatar.ExRankUnlocked != unlocked {
			avatar.ExRankUnlocked = unlocked
			changed = append(changed, id)
		}
	}
	if current, err := jsonObject(f.persistentSnapshot()); err == nil {
		if f.persistentBaseline == nil {
			f.persistentBaseline = make(map[string]any)
		}
		f.persistentBaseline["ex_ranks_unlocked"] = current["ex_ranks_unlocked"]
	}
	return changed
}

// Patch only the selected avatar's rank in the latest import. Unknown FreeSR
// fields and all inventory IDs/affixes retain their original JSON values.
func SaveAvatarRank(id, rank uint32) error {
	persistentWriteMu.Lock()
	defer persistentWriteMu.Unlock()
	unlock, err := lockPersistentFile()
	if err != nil {
		return err
	}
	defer unlock()
	raw, err := os.ReadFile("freesr-data.json")
	if err != nil {
		return err
	}
	var root map[string]json.RawMessage
	if err := json.Unmarshal(raw, &root); err != nil {
		return err
	}
	var avatars map[uint32]json.RawMessage
	if err := json.Unmarshal(root["avatars"], &avatars); err != nil {
		return err
	}
	var avatar map[string]json.RawMessage
	if err := json.Unmarshal(avatars[id], &avatar); err != nil {
		return err
	}
	var data map[string]json.RawMessage
	if err := json.Unmarshal(avatar["data"], &data); err != nil {
		return err
	}
	data["rank"], err = json.Marshal(rank)
	if err != nil {
		return err
	}
	avatar["data"], err = json.Marshal(data)
	if err != nil {
		return err
	}
	avatars[id], err = json.Marshal(avatar)
	if err != nil {
		return err
	}
	root["avatars"], err = json.Marshal(avatars)
	if err != nil {
		return err
	}
	return writeJSONAtomic("freesr-data.json", root)
}