From 4c319e8ba084afeeb6957543109e3ca726fda6f4 Mon Sep 17 00:00:00 2001
From: qowevisa <qowevisa@gmail.com>
Date: Fri, 2 Aug 2024 00:03:01 +0300
Subject: [PATCH] Create tokens package

---
 tokens/dispatcher.go | 126 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 tokens/dispatcher.go

diff --git a/tokens/dispatcher.go b/tokens/dispatcher.go
new file mode 100644
index 0000000..dc4067a
--- /dev/null
+++ b/tokens/dispatcher.go
@@ -0,0 +1,126 @@
+package tokens
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"log"
+	"sync"
+	"time"
+)
+
+type Token struct {
+	Val        string
+	LastActive time.Time
+}
+
+var (
+	ActiveDur = time.Duration(time.Hour)
+)
+
+func (t Token) IsExpired() bool {
+	return time.Now().Sub(t.LastActive) >= ActiveDur
+}
+
+type TokensMapMu struct {
+	Initialized bool
+	Tokmap      map[uint]Token
+	TokmapRev   map[string]Token
+	Mu          sync.RWMutex
+}
+
+var toks TokensMapMu
+
+// NOTE: should be launch with a goroutine
+// NOTE: it cannot die
+func StartTokens() {
+	if toks.Initialized {
+		return
+	}
+	toks.Tokmap = make(map[uint]Token)
+	toks.TokmapRev = make(map[string]Token)
+	toks.Initialized = true
+	for {
+		//
+		toks.Mu.Lock()
+		for id, token := range toks.Tokmap {
+			if token.IsExpired() {
+				delete(toks.Tokmap, id)
+			}
+		}
+		toks.Mu.Unlock()
+		//
+		time.Sleep(time.Minute)
+	}
+}
+
+var (
+	ERROR_DONT_HAVE_TOKEN    = errors.New("Don't have token for this user")
+	ERROR_ALREADY_HAVE_TOKEN = errors.New("Already have token")
+)
+
+func GetToken(id uint) (Token, error) {
+	toks.Mu.RLock()
+	val, exists := toks.Tokmap[id]
+	toks.Mu.RUnlock()
+	if !exists {
+		return Token{}, ERROR_DONT_HAVE_TOKEN
+	}
+	return val, nil
+}
+
+func haveToken(id uint) bool {
+	toks.Mu.RLock()
+	_, exists := toks.Tokmap[id]
+	toks.Mu.RUnlock()
+	return exists
+}
+
+func UpdateLastActive(id uint) error {
+	if !haveToken(id) {
+		return ERROR_DONT_HAVE_TOKEN
+	}
+	toks.Mu.Lock()
+	val := toks.Tokmap[id]
+	val.LastActive = time.Now()
+	toks.Tokmap[id] = val
+	toks.Mu.Unlock()
+	return nil
+}
+
+func haveTokenVal(val string) bool {
+	toks.Mu.RLock()
+	_, exists := toks.TokmapRev[val]
+	toks.Mu.RUnlock()
+	return exists
+}
+
+func generateRandomString(length int) string {
+	bytes := make([]byte, length)
+	if _, err := rand.Read(bytes); err != nil {
+		log.Printf("generateRandomString: %v", err)
+	}
+	return base64.URLEncoding.EncodeToString(bytes)
+}
+
+func generateTokenVal() string {
+	for {
+		tok := generateRandomString(32)
+		if !haveTokenVal(tok) {
+			return tok
+		}
+	}
+}
+
+func AddToken(id uint) (Token, error) {
+	toks.Mu.RLock()
+	_, exists := toks.Tokmap[id]
+	toks.Mu.RUnlock()
+	if exists {
+		return Token{}, ERROR_ALREADY_HAVE_TOKEN
+	}
+	return Token{
+		Val:        generateTokenVal(),
+		LastActive: time.Now(),
+	}, nil
+}