[+] Separate user validator

src/main/java/icu/samnyan/aqua/net/db/AquaNetUser.kt

@@ -1,10 +1,18 @@
 package icu.samnyan.aqua.net.db
 
+import ext.Str
+import ext.isValidEmail
+import ext.minus
 import icu.samnyan.aqua.sega.general.model.Card
 import jakarta.persistence.*
 import org.springframework.data.jpa.repository.JpaRepository
+import org.springframework.security.crypto.password.PasswordEncoder
 import org.springframework.stereotype.Repository
+import org.springframework.stereotype.Service
 import java.io.Serializable
+import kotlin.reflect.KFunction
+import kotlin.reflect.KMutableProperty
+import kotlin.reflect.full.functions
 
 @Entity(name = "AquaNetUser")
 @Table(name = "aqua_net_user")
@@ -57,4 +65,77 @@ interface AquaNetUserRepo : JpaRepository<AquaNetUser, Long> {
     fun findByAuId(auId: Long): AquaNetUser?
     fun findByEmailIgnoreCase(email: String): AquaNetUser?
     fun findByUsernameIgnoreCase(username: String): AquaNetUser?
+}
+
+data class SettingField(
+    val name: Str,
+    val checker: KFunction<*>,
+    val setter: KMutableProperty.Setter<*>,
+)
+
+/**
+ * This class is a validator for user fields. It will return the parsed value if the field is valid, or
+ * throw an ApiException if the field is invalid.
+ */
+@Service
+class AquaUserValidator(
+    val userRepo: AquaNetUserRepo,
+    val hasher: PasswordEncoder,
+) {
+    companion object {
+        val SETTING_FIELDS = AquaUserValidator::class.functions
+            .filter { it.name.startsWith("check") }
+            .map {
+                val name = it.name.removePrefix("check").replaceFirstChar { c -> c.lowercase() }
+                val prop = AquaNetUser::class.members.find { m -> m.name == name } as KMutableProperty<*>
+                SettingField(name, it, prop.setter)
+            }
+    }
+
+    fun checkUsername(username: Str) = username.apply {
+        // Check if username is valid
+        if (length < 2) 400 - "Username must be at least 2 letters"
+        if (length > 32) 400 - "Username too long (max 32 letters)"
+        if (contains(" ")) 400 - "Username cannot contain spaces"
+
+        // Check if username is within A-Za-z0-9_-~.
+        find { !it.isLetterOrDigit() && it != '_' && it != '-' && it != '~' && it != '.' }?.let {
+            400 - "Username cannot contain `$it`. Please only use letters (A-Z), numbers (0-9), and `_-~.` characters. You can set a display name later."
+        }
+
+        // Check if user with the same username exists
+        if (userRepo.findByUsernameIgnoreCase(this) != null)
+            400 - "User with username `$this` already exists"
+    }
+
+    fun checkEmail(email: Str) = email.apply {
+        // Check if email is valid
+        if (!isValidEmail()) 400 - "Invalid email"
+
+        // Check if user with the same email exists
+        if (userRepo.findByEmailIgnoreCase(email) != null)
+            400 - "User with email `$email` already exists"
+    }
+
+    fun checkPwHash(password: Str) = password.run {
+        // Validate password
+        if (length < 8) 400 - "Password must be at least 8 characters"
+
+        hasher.encode(this)
+    }
+
+    fun checkDisplayName(displayName: Str) = displayName.apply {
+        // Check if display name is valid
+        if (length > 32) 400 - "Display name too long (max 32 letters)"
+    }
+
+    fun checkProfileLocation(profileLocation: Str) = profileLocation.apply {
+        // Check if profile location is valid
+        if (length > 64) 400 - "Profile location too long (max 64 letters)"
+    }
+
+    fun checkProfileBio(profileBio: Str) = profileBio.apply {
+        // Check if profile bio is valid
+        if (length > 255) 400 - "Profile bio too long (max 255 letters)"
+    }
 }