package services

import (
	"context"
	"errors"
	"git.aiterp.net/rpdata/api/internal/auth"
	"git.aiterp.net/rpdata/api/models"
	"git.aiterp.net/rpdata/api/repositories"
	"github.com/h2non/filetype"
	"io"
)

var ErrPrivateNoAuthor = errors.New("cannot search for private files without an author")
var ErrInvalidName = errors.New("invalid name")
var ErrInvalidFileSize = errors.New("file is not of a correct size (min: 320B, max: 16MB)")
var ErrCouldNotReadHead = errors.New("could not read file head")
var ErrInvalidFileType = errors.New("file type could not be recognized or is not allowed")
var ErrCouldNotUploadFile = errors.New("could not upload file")

// FileService is a service for files.
type FileService struct {
	files repositories.FileRepository
}

func (s *FileService) Find(ctx context.Context, id string) (*models.File, error) {
	file, err := s.files.Find(ctx, id)
	if err != nil {
		return nil, err
	}

	if !file.Public {
		err := auth.CheckPermission(ctx, "view", file)
		if err != nil {
			return nil, repositories.ErrNotFound
		}
	}

	return file, nil
}

func (s *FileService) List(ctx context.Context, filter models.FileFilter) ([]*models.File, error) {
	token := auth.TokenFromContext(ctx)

	if filter.Public != nil {
		if *filter.Public == false {
			if filter.Author == nil || *filter.Author == "" {
				return nil, ErrPrivateNoAuthor
			}

			if !token.PermittedUser(*filter.Author, "member", "file.list") {
				return nil, auth.ErrUnauthorized
			}
		}
	}

	return s.files.List(ctx, filter)
}

func (s *FileService) Upload(ctx context.Context, reader io.Reader, name string, size int64) (*models.File, error) {
	if name == "" {
		return nil, ErrInvalidName
	} else if size < 320 || size > 16777216 {
		return nil, ErrInvalidFileSize
	}

	head := make([]byte, 320)
	n, err := reader.Read(head)
	if err != nil || n < 320 {
		return nil, ErrCouldNotReadHead
	}

	fileType, err := filetype.Match(head)
	if err != nil || !allowedMimeTypes[fileType.MIME.Value] {
		return nil, ErrInvalidFileType
	}

	panic("implement rest of me")
}

func (s *FileService) Edit(ctx context.Context, id string, name *string, public *bool) (*models.File, error) {
	file, err := s.files.Find(ctx, id)
	if err != nil {
		return nil, err
	}

	err = auth.CheckPermission(ctx, "edit", file)
	if err != nil {
		if !file.Public {
			return nil, repositories.ErrNotFound
		}

		return nil, err
	}

	return s.files.Update(ctx, *file, models.FileUpdate{
		Name:   name,
		Public: public,
	})
}

// concatReader is a quick and dirty reader for reading the head and the file.
type concatReader struct {
	head    []byte
	headPos int
	body    io.Reader
}

func (r *concatReader) Read(p []byte) (n int, err error) {
	if len(p) == 0 {
		return 0, io.ErrShortBuffer
	}

	if r.headPos < len(r.head) {
		remainder := r.head[r.headPos:]
		if len(p) < len(remainder) {
			r.headPos += len(p)
			copy(p, remainder)

			return len(p), nil
		}

		r.headPos = len(r.head)
		copy(p, remainder)

		return len(p), nil
	}

	return r.body.Read(p)
}

var allowedMimeTypes = map[string]bool{
	"":                    false,
	"image/jpeg":          true,
	"image/png":           true,
	"image/gif":           true,
	"image/tiff":          true,
	"image/tga":           true,
	"text/plain":          true,
	"application/json":    true,
	"application/pdf":     false,
	"binary/octet-stream": false,
	"video/mp4":           false,
	"audio/mp3":           false,
}