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package router
import (
"database/sql"
"encoding/base64"
"fmt"
"log/slog"
"strings"
"sync"
"golang.org/x/crypto/argon2"
)
type ClientCache struct {
hashMap map[string]string
hashMapMutex sync.RWMutex
likePageMap map[string]map[string]struct{}
pageMutexMap map[string]*sync.RWMutex
pageMutexMapMutex sync.Mutex
salt []byte
db *sql.DB
}
var CCache *ClientCache
func NewClientCache(db *sql.DB, salt []byte) (*ClientCache, error) {
tx, err := db.Begin()
if err != nil {
return nil, fmt.Errorf("fail to init transaction with db to fill cache: %w", err)
}
rows, err := tx.Query("select * from blog_likes;")
if err != nil {
tx.Rollback()
return nil, fmt.Errorf("fail to query db for blog_likes to fill cache: %w", err)
}
likePageMap := make(map[string]map[string]struct{})
pageMutexMap := make(map[string]*sync.RWMutex)
for rows.Next() {
var pageRef string
var userId []byte
if err = rows.Scan(&pageRef, &userId); err != nil {
tx.Rollback()
return nil, fmt.Errorf("fail scanning blog_likes to fill cache: %w", err)
}
userIdString := base64.RawStdEncoding.EncodeToString(userId)
if _, ok := likePageMap[pageRef]; !ok {
likePageMap[pageRef] = make(map[string]struct{})
pageMutexMap[pageRef] = &sync.RWMutex{}
}
likePageMap[pageRef][userIdString] = struct{}{}
}
if err = tx.Commit(); err != nil {
return nil, fmt.Errorf("fail to commit transaction in db: %w", err)
}
return &ClientCache{
hashMap: make(map[string]string),
likePageMap: likePageMap,
pageMutexMap: pageMutexMap,
salt: salt,
db: db,
}, nil
}
func (c *ClientCache) Close() error {
tx, err := c.db.Begin()
if err != nil {
return fmt.Errorf("fail to init transaction with db to dump cache: %w", err)
}
if _, err = tx.Exec("delete from blog_likes;"); err != nil {
tx.Rollback()
return fmt.Errorf("fail to truncate table blog_likes: %w", err)
}
userIdBytes := make(map[string][]byte)
sqlStatement := fmt.Sprintf(`
INSERT OR IGNORE INTO blog_likes (page_ref, user_id)
VALUES %s(?, ?);
`, strings.Repeat("(?, ?), ", 99))
sqlStatementVars := make([]any, 0, 200)
for pageRef, userSet := range c.likePageMap {
for userId := range userSet {
if _, ok := userIdBytes[userId]; !ok {
userIdBytes[userId], err = base64.RawStdEncoding.DecodeString(userId)
if err != nil {
slog.Warn("couldn't parse one of user hashes into bytes back", slog.String("hash", userId), slog.String("error", err.Error()))
continue
}
}
sqlStatementVars = append(sqlStatementVars, any(pageRef), any(userIdBytes[userId]))
if len(sqlStatementVars) < 200 {
continue
}
if _, err := tx.Exec(sqlStatement, sqlStatementVars...); err != nil {
slog.Warn("couldn't insert blog like pairs into db", slog.String("error", err.Error()))
}
sqlStatementVars = make([]any, 0, 200)
}
}
if len(sqlStatementVars) > 0 {
sqlStatement = fmt.Sprintf(`
INSERT OR IGNORE INTO blog_likes (page_ref, user_id)
VALUES %s(?, ?);
`, strings.Repeat("(?, ?), ", len(sqlStatementVars)/2-1))
if _, err := tx.Exec(sqlStatement, sqlStatementVars...); err != nil {
slog.Warn("couldn't insert blog like pairs into db", slog.String("error", err.Error()))
}
}
return tx.Commit()
}
func (c *ClientCache) GetHash(id string) string {
c.hashMapMutex.RLock()
if val, ok := c.hashMap[id]; ok {
c.hashMapMutex.RUnlock()
slog.Debug("gave an old hash", slog.String("hash", val))
return val
}
c.hashMapMutex.RUnlock()
c.hashMapMutex.Lock()
defer c.hashMapMutex.Unlock()
if val, ok := c.hashMap[id]; ok {
slog.Debug("gave a newly generated hash", slog.String("hash", val))
return val
}
c.hashMap[id] = base64.RawStdEncoding.EncodeToString(argon2.IDKey([]byte(id), c.salt, 1, 64*1024, 4, 32))
slog.Debug("generated hash", slog.String("hash", c.hashMap[id]))
return c.hashMap[id]
}
func (c *ClientCache) getPageMutex(page string) *sync.RWMutex {
c.pageMutexMapMutex.Lock()
defer c.pageMutexMapMutex.Unlock()
if mutex, ok := c.pageMutexMap[page]; ok {
return mutex
}
c.pageMutexMap[page] = &sync.RWMutex{}
return c.pageMutexMap[page]
}
func (c *ClientCache) GetLikeStatus(id string, page string) bool {
page = strings.Clone(page)
mutex := c.getPageMutex(page)
mutex.RLock()
defer mutex.RUnlock()
if _, ok := c.likePageMap[page]; !ok {
return false
}
_, ok := c.likePageMap[page][c.GetHash(id)]
return ok
}
func (c *ClientCache) GetLikeCount(page string) int {
page = strings.Clone(page)
mutex := c.getPageMutex(page)
mutex.RLock()
defer mutex.RUnlock()
if userSet, ok := c.likePageMap[page]; ok {
return len(userSet)
}
return 0
}
func (c *ClientCache) LikeOn(id string, page string) (alreadyLiked bool) {
page = strings.Clone(page)
hash := c.GetHash(id)
mutex := c.getPageMutex(page)
mutex.Lock()
defer mutex.Unlock()
if userSet, ok := c.likePageMap[page]; ok {
_, alreadyLiked = userSet[hash]
c.likePageMap[page][hash] = struct{}{}
return
}
c.likePageMap[page] = make(map[string]struct{})
c.likePageMap[page][hash] = struct{}{}
return
}
func (c *ClientCache) LikeOff(id string, page string) (alreadyUnliked bool) {
page = strings.Clone(page)
hash := c.GetHash(id)
mutex := c.getPageMutex(page)
mutex.Lock()
defer mutex.Unlock()
if _, ok := c.likePageMap[page]; !ok {
return true
}
if _, ok := c.likePageMap[page][hash]; !ok {
return true
}
delete(c.likePageMap[page], hash)
return false
}
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