FinaleBot_CheckRevision.swift

gistfile1.txt

import Foundation
import CryptoSwift

enum CheckRevision {

    enum CheckRevisionError: Error {
        case formulaNotBase64
        case formulaTooShort
        case unparseableVersion
    }

    static func execute(formula: String, versionString: String = "1.14.3.71") throws -> (UInt32, UInt32, String) {
        guard let formulaData = Data(base64Encoded: formula, options: []) else {
            throw CheckRevisionError.formulaNotBase64
        }
        guard formulaData.count > 4 else {
            throw CheckRevisionError.formulaTooShort
        }

        let versionComponents = versionString.split(separator: ".").compactMap({ UInt32($0) })
        guard versionComponents.count == 4 else { throw CheckRevisionError.unparseableVersion }
        let version = versionComponents[3] << 24 | versionComponents[2] << 16 | versionComponents[1] << 8 | versionComponents[0]

        var hashComposer = RawMessageComposer()
        var formulaConsumer = RawMessageConsumer(message: formulaData)
        hashComposer.write(formulaConsumer.readUInt32())
        hashComposer.write(":\(versionString):", withNullTerminator: false)
        hashComposer.write(1 as UInt8)

        var hashConsumer = RawMessageConsumer(message: hashComposer.build().sha1().base64EncodedData(options: []))
        let hash = hashConsumer.readUInt32()
        let info = hashConsumer.readString(length: hashConsumer.message.count - 4)

        return (version, hash, info)
    }

}