[BOOK-112] refactor: derivedStateOf로 전체 동의 및 시작 버튼 상태 계산 로직 변경

Author: seoyoon513

feature/login/src/main/kotlin/com/ninecraft/booket/feature/login/TermsAgreementPresenter.kt

@@ -1,10 +1,10 @@
 package com.ninecraft.booket.feature.login
 
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateListOf
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.setValue
+import androidx.compose.runtime.remember
 import com.ninecraft.booket.feature.home.HomeScreen
 import com.slack.circuit.codegen.annotations.CircuitInject
 import com.slack.circuit.retained.rememberRetained
@@ -21,39 +21,41 @@ class TermsAgreementPresenter @AssistedInject constructor(
 
     @Composable
     override fun present(): TermsAgreementScreen.State {
-        var isAllAgreed by rememberRetained { mutableStateOf(false) }
         val agreedTerms = rememberRetained { mutableStateListOf(false, false, false) }
-        var isStartButtonEnabled by rememberRetained { mutableStateOf(false) }
+
+        val isAllAgreed by remember {
+            derivedStateOf {
+                agreedTerms.all { it }
+            }
+        }
+
+        val isStartButtonEnabled by remember {
+            derivedStateOf {
+                isAllAgreed
+            }
+        }
 
         fun handleEvent(event: TermsAgreementScreen.Event) {
             when (event) {
                 is TermsAgreementScreen.Event.OnAllTermsAgreedClick -> {
-                    isAllAgreed = !isAllAgreed
-                    isStartButtonEnabled = isAllAgreed
-
+                    val toggleAgreed = !isAllAgreed
                     for (i in agreedTerms.indices) {
-                        agreedTerms[i] = isAllAgreed
+                        agreedTerms[i] = toggleAgreed
                     }
                 }
+
                 is TermsAgreementScreen.Event.OnTermItemClick -> {
                     agreedTerms[event.index] = !agreedTerms[event.index]
-
-                    val allIndividualAgreed = agreedTerms.all { it }
-
-                    if (allIndividualAgreed) {
-                        isAllAgreed = true
-                        isStartButtonEnabled = true
-                    } else {
-                        isAllAgreed = false
-                        isStartButtonEnabled = false
-                    }
                 }
+
                 is TermsAgreementScreen.Event.OnBackClick -> {
                     navigator.pop()
                 }
+
                 is TermsAgreementScreen.Event.OnTermDetailClick -> {
                     // TODO: 웹뷰 화면으로 이동
                 }
+
                 is TermsAgreementScreen.Event.OnStartButtonClick -> {
                     navigator.resetRoot(HomeScreen)
                 }