satbd-explorer/album_database.go

package main

import (
	"encoding/json"
	"fmt"
	"reflect"
	"sort"
	"sync"

	"github.com/peterbourgon/diskv"
)

type AlbumDatabase struct {
	dv *diskv.Diskv

	consolidated bool

	byID           map[AlbumID]*Album
	byPurchaseDate []AlbumID
	byCollection   map[string][]AlbumID
	byAuthor       map[string][]AlbumID

	lock *sync.RWMutex
}

func OpenAlbumDatabase(basepath string) *AlbumDatabase {

	return &AlbumDatabase{
		dv: diskv.New(diskv.Options{
			BasePath:     basepath,
			CacheSizeMax: 50 * 1024 * 1024, // 50 MB
			Compression:  diskv.NewGzipCompression(),
		}),
		consolidated:   false,
		byID:           make(map[AlbumID]*Album),
		byPurchaseDate: make([]AlbumID, 0, 10),
		byCollection:   make(map[string][]AlbumID),
		byAuthor:       make(map[string][]AlbumID),
		lock:           &sync.RWMutex{},
	}

}

func (db *AlbumDatabase) AddOrUpdate(a *Album) error {

	aInDb, err := db.Get(a.ID)
	dbNeedUpdate := true
	if err == nil {
		dbNeedUpdate = (a.PurchaseDate != aInDb.PurchaseDate ||
			!reflect.DeepEqual(a.Designers, aInDb.Designers) ||
			!reflect.DeepEqual(a.Scenarists, aInDb.Scenarists) ||
			!reflect.DeepEqual(a.Colorists, aInDb.Colorists) ||
			a.Collection != aInDb.Collection)
	}

	data, err := json.Marshal(a)
	if err != nil {
		return fmt.Errorf("json encoding: %s", err)
	}

	db.lock.Lock()
	err = db.dv.Write(AlbumIDString(a.ID), data)
	if err == nil {
		db.consolidated = !dbNeedUpdate
		db.byID[a.ID] = a
	}
	db.lock.Unlock()
	return err
}

func deleteFromList(list []AlbumID, idToDelete AlbumID) []AlbumID {
	toDeleteIdx := len(list)
	for i, aID := range list {
		if aID == idToDelete {
			toDeleteIdx = i
			break
		}
	}

	if toDeleteIdx == len(list) {
		return list
	}
	return append(list[:toDeleteIdx], list[toDeleteIdx+1:]...)
}

func (db *AlbumDatabase) Delete(ID AlbumID) error {
	inDB, err := db.Get(ID)
	if err != nil {
		return fmt.Errorf("Album %d not found", ID)
	}

	db.lock.Lock()
	defer db.lock.Unlock()
	delete(db.byID, ID)
	db.byPurchaseDate = deleteFromList(db.byPurchaseDate, ID)

	for _, a := range inDB.Authors() {
		db.byAuthor[a] = deleteFromList(db.byAuthor[a], ID)
	}

	if len(inDB.Collection) > 0 {
		db.byCollection[inDB.Collection] = deleteFromList(db.byCollection[inDB.Collection], ID)
	}
	return db.dv.Erase(AlbumIDString(ID))
}

func (db *AlbumDatabase) get(ID string) (*Album, error) {
	res := &Album{}

	r, err := db.dv.ReadStream(ID, false)
	if err != nil {
		return nil, fmt.Errorf("Album %s not found: %s", ID, err)
	}
	dec := json.NewDecoder(r)
	defer closeOrPanic(r, "db record "+ID)
	return res, dec.Decode(res)
}

func (db *AlbumDatabase) Get(ID AlbumID) (*Album, error) {
	db.lock.RLock()
	defer db.lock.RUnlock()

	a, ok := db.byID[ID]
	if ok == true {
		return a, nil
	}
	return db.get(AlbumIDString(ID))
}

type ListOfAlbum []*Album

func (l ListOfAlbum) Len() int {
	return len(l)
}

func (l ListOfAlbum) Less(i, j int) bool {
	return l[i].PurchaseDate.Before(l[j].PurchaseDate)
}

func (l ListOfAlbum) Swap(i, j int) {
	l[i], l[j] = l[j], l[i]
}

func maxOfInt(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func (db *AlbumDatabase) ensureConsolidated() error {
	db.lock.RLock()
	if db.consolidated == true {
		db.lock.RUnlock()
		return nil
	}
	db.lock.RUnlock()

	db.lock.Lock()
	defer db.lock.Unlock()

	allAlbums := make([]*Album, 0, maxOfInt(len(db.byID), len(db.byPurchaseDate)))
	db.byPurchaseDate = make([]AlbumID, 0, maxOfInt(len(db.byID), len(db.byPurchaseDate)))
	db.byID = make(map[AlbumID]*Album)
	db.byAuthor = make(map[string][]AlbumID)
	db.byCollection = make(map[string][]AlbumID)
	for aIDStr := range db.dv.Keys(nil) {
		a, err := db.get(aIDStr)
		if err != nil {
			return err
		}
		allAlbums = append(allAlbums, a)
		db.byID[a.ID] = a
	}

	sort.Sort(sort.Reverse(ListOfAlbum(allAlbums)))

	for _, album := range allAlbums {
		db.byPurchaseDate = append(db.byPurchaseDate, album.ID)
	}

	for aID, album := range db.byID {
		if len(album.Collection) > 0 {
			db.byCollection[album.Collection] = append(db.byCollection[album.Collection], aID)
		}

		for _, author := range album.Authors() {
			db.byAuthor[author] = append(db.byAuthor[author], aID)
		}
	}

	db.consolidated = true
	return nil
}

func (db *AlbumDatabase) ByPurchaseDate() ([]AlbumID, error) {
	err := db.ensureConsolidated()
	if err != nil {
		return nil, err
	}

	db.lock.RLock()
	defer db.lock.RUnlock()
	res := make([]AlbumID, len(db.byPurchaseDate))
	copy(res, db.byPurchaseDate)
	return res, nil
}