package server

import (
	"os"
	"bufio"
	"encoding/json"
	"git.citrons.xyz/metronode/phony"
)

var dataManager struct {
	phony.Inbox
	errHand interface {
		OnSaveError(from phony.Actor, err error)
		OnLoadError(from phony.Actor, err error)
	}
}

type atomicWriter struct {
	from phony.Actor
	name string
	tmpFile *os.File
}

func createAtomic(from phony.Actor, name string) (atomicWriter, error) {
	os.Mkdir("world", 0777)
	f, err := os.CreateTemp("world", "*.tmp")
	if err != nil {
		dataManager.errHand.OnSaveError(from, err)
		return atomicWriter {}, err
	}
	return atomicWriter {from, name, f}, nil
}

func (f atomicWriter) Write(b []byte) (n int, err error) {
	return f.tmpFile.Write(b)
}

func (f atomicWriter) Close() error {
	if f.tmpFile == nil {
		return nil
	}
	dataManager.Act(f.from, func() {
		f.tmpFile.Sync()
		err := f.tmpFile.Close()
		if err != nil {
			dataManager.errHand.OnSaveError(&dataManager, err)
			return
		}
		err = os.Rename(f.tmpFile.Name(), f.name)
		if err != nil {
			dataManager.errHand.OnSaveError(&dataManager, err)
		}
	})
	return nil
}

func saveDataFile[T any](from phony.Actor, name string, data T) {
	f, err := createAtomic(from, "world/" + name + ".json")
	if err != nil {
		dataManager.errHand.OnSaveError(from, err)
		return
	}
	defer f.Close()
	enc := json.NewEncoder(f)
	err = enc.Encode(data)
	if err != nil {
		dataManager.errHand.OnSaveError(from, err)
	}
}

func loadDataFile[T any](
		from phony.Actor, name string, reply func(data T, ok bool)) {
	dataManager.Act(from, func() {
		var (
			data T
			f *os.File
			err error
		)
		defer from.Act(nil, func() {reply(data, err == nil)})

		f, err = os.Open("world/" + name + ".json")
		if err != nil {
			if !os.IsNotExist(err) {
				dataManager.errHand.OnLoadError(&dataManager, err)
			}
			return
		}
		defer f.Close()

		dec := json.NewDecoder(f)
		err = dec.Decode(&data)
		if err != nil {
			dataManager.errHand.OnLoadError(&dataManager, err)
			return
		}
	})
}

func readDataField(rd *bufio.Reader, data any) error {
	line, err := rd.ReadBytes('\n')
	if err != nil {
		return err
	}
	return json.Unmarshal(line, data)
}

func writeDataField(wr *bufio.Writer, data any) error {
	enc := json.NewEncoder(wr)
	return enc.Encode(data)
}