module CryptoFileTests.Tests

open System.IO
open CryptoFile

let doSomeTests () =
    printfn "===== Unit tests"
    CryptoFile.UnitTests.runAllUnitTests ()
    printfn "===== Unit tests OK"

    printfn "===== API tests"
    let plainFilename = "test.txt"
    let cipherFilename = "test.cipher"
    let fileContent = "Screw the NSA"

    File.WriteAllText (plainFilename, fileContent)

    let keyCryptPub, keyCryptPriv = API.generatKeysPair
    let keySigPub, keySigPriv = API.generatKeysPair

    let encrypt () = 
        API.encryptFile plainFilename cipherFilename keySigPriv keyCryptPub

    let decrypt () = 
        API.decryptFile cipherFilename "." keySigPub keyCryptPriv

    let incrementByteCipherFileAt position = 
        using (new FileStream (cipherFilename, FileMode.Open, FileAccess.ReadWrite))
              (fun fs -> fs.Position <- position
                         let byte = fs.ReadByte () |> byte
                         fs.Position <- position
                         fs.Write ([| byte + 1uy |], 0, 1)) // Automatically modulo 256.

    encrypt ()
    File.Delete plainFilename
    decrypt ()
    assert (File.ReadAllText plainFilename = fileContent)

    printfn "== Altering the MAC..."
    incrementByteCipherFileAt 0L
    try
        decrypt ()
        assert false
    with 
        | error -> assert (error :? IntegrityError)

    printfn "== Altering the signature..."
    encrypt ()
    incrementByteCipherFileAt 32L
    try
        decrypt ()
        assert false
    with
        | error -> assert (error :? SignatureMismatch)

    printfn "== Altering the keys..."
    encrypt ()
    incrementByteCipherFileAt (32L + 256L)
    try
        decrypt ()
        assert false
    with
        | error -> assert (error :? UnableToDecryptAESKeys)

    printfn "== Altering the cyphertext..."
    encrypt ()
    incrementByteCipherFileAt (32L + 256L + 256L)
    try
        decrypt ()
        assert false
    with 
        | error -> assert (error :? IntegrityError)

    File.Delete cipherFilename
    File.Delete plainFilename

    printfn "===== API tests OK"