//
//  AddressValidator.swift
//  OS Vault
//
//  Author: Simon-Pierre Boucher
//  Mail: contact@spboucher.ai
//

import Foundation
import Web3Core

/// Recipient address validation: hex shape + EIP-55 checksum.
/// All-lowercase (or all-uppercase) addresses carry no checksum information —
/// they are accepted with a warning, per the project security rules.
public enum AddressValidator {

    public enum Verdict: Equatable {
        /// Mixed-case address whose EIP-55 checksum matches.
        case valid(checksummed: String)
        /// Well-formed but caseless — no checksum to verify. Warn, don't block.
        case validNoChecksum(checksummed: String)
        case invalid
    }

    public static func validate(_ input: String) -> Verdict {
        let candidate = input.trimmingCharacters(in: .whitespacesAndNewlines)
        guard candidate.count == 42, candidate.hasPrefix("0x") else { return .invalid }
        let body = String(candidate.dropFirst(2))
        guard body.allSatisfy({ $0.isHexDigit }) else { return .invalid }
        guard let checksummed = EthereumAddress.toChecksumAddress(candidate) else { return .invalid }

        // An exact checksum match is valid even when it happens to be all one
        // case (some EIP-55 checksums are, e.g. 0x529084…9EE7).
        if candidate == checksummed {
            return .valid(checksummed: checksummed)
        }
        let letters = body.filter { $0.isLetter }
        let caseless = letters.isEmpty
            || letters.allSatisfy { $0.isLowercase }
            || letters.allSatisfy { $0.isUppercase }
        return caseless ? .validNoChecksum(checksummed: checksummed) : .invalid
    }
}