//
// Swiftfin is subject to the terms of the Mozilla Public
// License, v2.0. If a copy of the MPL was not distributed with this
// file, you can obtain one at https://mozilla.org/MPL/2.0/.
//
// Copyright (c) 2022 Jellyfin & Jellyfin Contributors
//

import Foundation

private let encodeCharacters: [String] = {
    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#$%*+,-.:;=?@[]^_{|}~".map { String($0) }
}()

private let decodeCharacters: [String: Int] = {
    var dict: [String: Int] = [:]
    for (index, character) in encodeCharacters.enumerated() {
        dict[character] = index
    }
    return dict
}()

extension BinaryInteger {
    func encode83(length: Int) -> String {
        var result = ""
        for i in 1 ... length {
            let digit = (Int(self) / pow(83, length - i)) % 83
            result += encodeCharacters[Int(digit)]
        }
        return result
    }
}

extension String {
    func decode83() -> Int {
        var value: Int = 0
        for character in self {
            if let digit = decodeCharacters[String(character)] {
                value = value * 83 + digit
            }
        }
        return value
    }
}

private func pow(_ base: Int, _ exponent: Int) -> Int {
    (0 ..< exponent).reduce(1) { value, _ in value * base }
}