package file

import (
	"context"
	"crypto/rand"
	"encoding/binary"
	"errors"
	"io"
	"strconv"
	"time"

	"git.aiterp.net/rpdata/api/internal/store"
	"github.com/globalsign/mgo"
	"github.com/globalsign/mgo/bson"
)

var fileCollection *mgo.Collection

// A File is a record of a file stored in the Space.
type File struct {
	ID       string    `bson:"_id" json:"id"`
	Time     time.Time `bson:"time" json:"time"`
	Kind     string    `bson:"kind" json:"kind"`
	Public   bool      `bson:"public" json:"public"`
	Name     string    `bson:"name" json:"name"`
	MimeType string    `bson:"mimeType" json:"mimeType"`
	Size     int64     `bson:"size" json:"size"`
	Author   string    `bson:"author" json:"author"`
	URL      string    `bson:"url,omitempty" json:"url,omitempty"`
}

// Edit edits the file, changing up to both the two mutable properties
func (file *File) Edit(name *string, public *bool) error {
	changes := bson.M{}
	changedFile := *file

	if name != nil && *name != file.Name {
		changes["name"] = *name
		changedFile.Name = *name
	}
	if public != nil && *public != file.Public {
		changes["public"] = *public
		changedFile.Public = *public
	}

	if len(changes) == 0 {
		return nil
	}

	err := fileCollection.UpdateId(file.ID, bson.M{"$set": changes})
	if err != nil {
		return err
	}

	*file = changedFile

	return nil
}

// Delete removes the file information from the database, and deletes the file.
func (file *File) Delete() error {
	err := fileCollection.RemoveId(file.ID)
	if err != nil {
		return err
	}

	if file.Kind == "upload" {
		err = store.RemoveFile("files", file.ID)
		if err != nil {
			return err
		}
	}

	file.URL = ""

	return nil
}

// Upload adds a file to the space.
func Upload(ctx context.Context, name, mimeType, author string, size int64, input io.Reader) (File, error) {
	if name == "" {
		date := time.Now().UTC().Format("Jan 02 2006 15:04:05 MST")
		name = "Unnamed file (" + date + ")"
	}

	if mimeType == "" {
		mimeType = "binary/octet-stream"
	}

	id := makeFileID()

	path, err := store.UploadFile(ctx, "files", id, mimeType, input, size)
	if err != nil {
		return File{}, err
	}

	file := File{
		ID:       id,
		Kind:     "upload",
		Time:     time.Now(),
		Public:   false,
		Author:   author,
		Name:     name,
		MimeType: mimeType,
		Size:     size,
		URL:      store.URLFromPath(path),
	}

	err = fileCollection.Insert(file)
	if err != nil {
		return File{}, err
	}

	return file, nil
}

// FindID finds a file by ID
func FindID(id string) (File, error) {
	file := File{}

	err := fileCollection.FindId(id).One(&file)
	if err != nil {
		return File{}, err
	}

	return file, nil
}

// List lists files according to the standard lookup. By default it's just the author's own files,
// but if `public` is true it will alos include files made public by other authors. If `mimeTypes` contains
// any, it will limit the results to that. If `author` is empty, it will only list public files
func List(author string, public bool, mimeTypes []string) ([]File, error) {
	query := bson.M{}

	if author != "" {
		if public {
			query["$or"] = []bson.M{
				bson.M{"author": author},
				bson.M{"public": true},
			}
		} else {
			query["author"] = author
		}
	} else {
		if !public {
			return nil, errors.New("No author specified, and public is unset")
		}

		query["public"] = true
	}

	if len(mimeTypes) > 0 {
		query["mimeTypes"] = bson.M{"$in": mimeTypes}
	}

	return listFiles(query)
}

func listFiles(query interface{}) ([]File, error) {
	list := make([]File, 0, 32)

	err := fileCollection.Find(query).All(&list)
	if err != nil {
		return nil, err
	}

	return list, nil
}

// makeFileID makes a random file ID that's 32 characters long
func makeFileID() string {
	result := "F" + strconv.FormatInt(time.Now().UnixNano(), 36)
	offset := 0
	data := make([]byte, 32)

	rand.Read(data)
	for len(result) < 32 {
		result += strconv.FormatUint(binary.LittleEndian.Uint64(data[offset:]), 36)
		offset += 8

		if offset >= 32 {
			rand.Read(data)
			offset = 0
		}
	}

	return result[:32]
}

func init() {
	store.HandleInit(func(db *mgo.Database) {
		fileCollection = db.C("file.headers")

		fileCollection.EnsureIndexKey("author")
		fileCollection.EnsureIndexKey("public")
		fileCollection.EnsureIndexKey("author", "public")
		fileCollection.EnsureIndexKey("kind")
	})
}