kverify

// Define rules once
val nicknameRule = RuleList(
    StringRules.notBlank(),
    StringRules.lengthBetween(3..20),
    StringRules.alphanumeric(),
)

// Compose with +
val userRule = nicknameRule + emailRule + ageRule

// Type safety guaranteed at compile time
user.nickname verifyWith nicknameRule  // ✅ Works
user.age verifyWith nicknameRule       // ❌ Compile error

// Collect all errors (for forms, DTOs, APIs)
val result = verifyCollecting {
    user.nickname verifyWith nicknameRule
    user.email verifyWith emailRule
    user.age verifyWith ageRule
}
// Returns: Valid or Invalid(List<Violation>)

// Throw on first error (for business logic, use cases)
verifyThrowing {
    order.total verifyWith minimumAmountRule
    order.items verifyWith notEmptyRule
}
// Throws: ValidationException on first failure

data class PasswordTooShortViolation(
    val actualLength: Int,
    val minimumLength: Int,
) : Violation {
    override val reason =
        "Password must be at least $minimumLength characters, but is $actualLength"
}

// Handle errors by type
when (val violation = result.violations.first()) {
    is PasswordTooShortViolation ->
        "Try a longer password (min: ${violation.minimumLength})"
    is EmailInvalidViolation ->
        "Please check your email format"
    else -> violation.reason
}

dependencies {
    implementation("io.github.kverify:kverify-core:2.0.0")
    implementation("io.github.kverify:kverify-rule-set:2.0.0")
    implementation("io.github.kverify:kverify-named-value:2.0.0")
    implementation("io.github.kverify:kverify-named-rule-set:2.0.0")
}

import io.github.kverify.core.context.verifyCollecting
import io.github.kverify.rule.set.provider.*

object StringRules : StringRuleProvider by DefaultStringRuleProvider()

data class SignUpRequest(
    val username: String,
    val email: String,
    val age: Int,
)

fun validateSignUp(request: SignUpRequest): ValidationResult = verifyCollecting {
    request.username withName "username" verifyWith RuleList(
        NamedStringRules.namedNotBlank(),
        NamedStringRules.namedLengthBetween(3..20),
        NamedStringRules.namedAlphanumeric(),
    )

    request.email withName "email" verifyWith emailRule
    request.age withName "age" verifyWith ageRule
}

// Use the result
val result = validateSignUp(request)

result.fold(
    ifValid = { createUser(request) },
    ifInvalid = { violations ->
        violations.forEach { println(it.reason) }
        // 'username' must be alphanumeric
        // 'email' must contain @
        // 'age' must be at least 13
    }
)