package goroutineinstance

import (
	"encoding/json"
	"fmt"
	"time"

	"gfx.cafe/util/go/generic"
	"github.com/DataDog/gostackparse"
	"github.com/rs/xid"
	"github.com/spf13/afero"
)

type InstanceStore interface {
	NewInstance(xs []*gostackparse.Goroutine) (*Instance, error)
	GetInstance(id xid.ID) (*Instance, error)
}

type fileBasedInstanceStore struct {
	expiry time.Duration
	fs     afero.Fs

	cache generic.Map[xid.ID, *Instance]
}

func NewFileBasedInstanceStore(fs afero.Fs, expiry time.Duration) *fileBasedInstanceStore {
	return &fileBasedInstanceStore{
		fs:     fs,
		expiry: expiry,
	}
}

func (o *fileBasedInstanceStore) NewInstance(dat []*gostackparse.Goroutine) (*Instance, error) {
	// save instance
	id := xid.New()
	i := &Instance{
		id:  id,
		dat: dat,
	}

	jsonDat, err := json.Marshal(dat)
	if err != nil {
		return nil, err
	}

	file, err := o.fs.Create(id.String())
	if err != nil {
		return nil, err
	}
	_, err = file.Write(jsonDat)
	if err != nil {
		file.Close()
		return nil, err
	}
	err = file.Close()
	if err != nil {
		return nil, err
	}
	o.cache.Store(id, i)
	return i, nil
}

func (o *fileBasedInstanceStore) GetInstance(id xid.ID) (*Instance, error) {
	if i, ok := o.cache.Load(id); ok {
		return i, nil
	}
	if o.expiry > 0 {
		if id.Time().After(time.Now().Add(o.expiry)) {
			o.fs.Remove(id.String())
			return nil, fmt.Errorf("goroutine expired")
		}
	}
	bts, err := afero.ReadFile(o.fs, id.String())
	if err != nil {
		return nil, err
	}
	i := &Instance{id: id}
	err = json.Unmarshal(bts, &i.dat)
	if err != nil {
		return nil, err
	}
	o.cache.Store(id, i)
	return i, nil
}