package uploads

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"io"
	"os"
	"path/filepath"
	"time"

	"emperror.dev/errors"
	"lmika.dev/lmika/weiro/models"
)

type NewPendingRequest struct {
	FileSize int64  `json:"size"`
	Filename string `json:"name"`
	MIMEType string `json:"type"`
}

func (s *Service) NewPending(ctx context.Context, req NewPendingRequest) (models.PendingUpload, error) {
	site, user, err := s.fetchSiteAndUser(ctx)
	if err != nil {
		return models.PendingUpload{}, err
	}

	pending := models.PendingUpload{
		GUID:          models.NewNanoID(),
		SiteID:        site.ID,
		UserID:        user.ID,
		FileSize:      req.FileSize,
		Filename:      req.Filename,
		MIMEType:      req.MIMEType,
		UploadStarted: time.Now(),
	}
	if err := s.db.SavePendingUpload(ctx, &pending); err != nil {
		return models.PendingUpload{}, err
	}

	if err := os.MkdirAll(s.pendingDir, 0755); err != nil {
		return models.PendingUpload{}, err
	}

	pendingDataFile, err := os.Create(filepath.Join(s.pendingDir, pending.GUID+".upload"))
	if err != nil {
		return models.PendingUpload{}, err
	}
	return pending, pendingDataFile.Close()
}

func (s *Service) WriteToPending(ctx context.Context, pendingGUID string, data []byte) error {
	site, user, err := s.fetchSiteAndUser(ctx)
	if err != nil {
		return err
	}

	pu, err := s.db.SelectPendingUploadByGUID(ctx, pendingGUID)
	if err != nil {
		return err
	} else if pu.SiteID != site.ID || pu.UserID != user.ID {
		return errors.New("invalid pending upload")
	}

	pendingDataFilename := filepath.Join(s.pendingDir, pu.GUID+".upload")
	if _, err := os.Stat(pendingDataFilename); err != nil {
		return err
	}

	pendingDataFile, err := os.OpenFile(pendingDataFilename, os.O_WRONLY|os.O_APPEND, 0644)
	if err != nil {
		return err
	}
	defer pendingDataFile.Close()

	pendingDataFile.Seek(0, io.SeekEnd)
	if _, err := pendingDataFile.Write(data); err != nil {
		return err
	}

	return nil
}

func (s *Service) FinalizePending(ctx context.Context, pendingGUID string, expectedHash string) error {
	site, user, err := s.fetchSiteAndUser(ctx)
	if err != nil {
		return err
	}

	pu, err := s.db.SelectPendingUploadByGUID(ctx, pendingGUID)
	if err != nil {
		return err
	} else if pu.SiteID != site.ID || pu.UserID != user.ID {
		return errors.New("invalid pending upload")
	}

	expectedHashBytes, err := hex.DecodeString(expectedHash)
	if err != nil {
		return err
	}

	pendingDataFilename := filepath.Join(s.pendingDir, pu.GUID+".upload")
	if _, err := os.Stat(pendingDataFilename); err != nil {
		return err
	}

	pendingDataFile, err := os.Open(pendingDataFilename)
	if err != nil {
		return err
	}
	defer pendingDataFile.Close()

	shaSum := sha256.New()
	if _, err := io.Copy(shaSum, pendingDataFile); err != nil {
		return err
	}

	if !bytes.Equal(shaSum.Sum(nil), expectedHashBytes) {
		return errors.New("hash mismatch")
	}

	return nil
}