module CryptoFileTests.Tests

open System.IO
open CryptoFile

let doSomeTests () =
    printfn "===== Unit tests"
    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 = 
        use fs = new FileStream (cipherFilename, FileMode.Open, FileAccess.ReadWrite)
        fs.Position <- position
        let byte = fs.ReadByte () |> byte
        fs.Position <- position
        fs.Write ([| byte + 1uy |], 0, 1) // Modulo 256.

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

    printfn "== Altering the MAC... (%d bytes)" (API.hmacSize - 1)
    for i in 0 .. API.hmacSize - 1 do
        printf "."
        encrypt ()
        incrementByteCipherFileAt (int64 i)
        try
            decrypt ()
            assert false
        with
            | error -> assert (error :? IntegrityError)
    printfn ""

    printfn "== Altering the signature... (%d bytes)" (API.signatureSize - 1)
    for i in 0 .. API.signatureSize - 1 do
        printf "."
        encrypt ()
        incrementByteCipherFileAt (int64 <| API.hmacSize + i)
        try
            decrypt ()
            assert false
        with
            | error -> assert (error :? SignatureMismatch)
    printfn ""

    printfn "== Altering the keys... (%d bytes)" (API.keysSize - 1)
    for i in 0 .. API.keysSize - 1 do
        printf "."
        encrypt ()
        incrementByteCipherFileAt (int64 <| API.hmacSize + API.signatureSize + i)
        try
            decrypt ()
            assert false
        with
            | error -> assert (error :? UnableToDecryptKeys)
    printfn ""

    let cyphertextLength = (int (FileInfo (cipherFilename)).Length) + API.hmacSize + API.signatureSize + API.keysSize
    printfn "== Altering the cyphertext... (%d bytes)" cyphertextLength
    for i in 0 .. cyphertextLength do 
        printf "."
        encrypt ()
        incrementByteCipherFileAt (int64 <| API.hmacSize + API.signatureSize + API.keysSize + i)
        try
            decrypt ()
            assert false
        with
            | error -> assert (error :? IntegrityError)
    printfn ""

    File.Delete cipherFilename
    File.Delete plainFilename

    printfn "===== API tests OK"