namespace CryptoFile
open System.IO

type internal Metadata (d : (string * string) list) =
    new (stream : Stream, size: int) =
        let binaryReader = new BinaryReader (stream)
        new Metadata ([])
    member this.WriteTo (stream : Stream) =
        let binaryWriter = new BinaryWriter (stream)
        List.iter (fun (key : string, value : string) -> binaryWriter.Write key; binaryWriter.Write value) d

module API =
    let internal filename = "filename"
    let internal creationTimeKey = "file-creation-time"

    let generatKeysPair : Key * Key = Crypto.generateRSAKeysPair

    let encryptFile (inputFilePath : string) (outputFilePath : string) (signaturePrivKey: Key) (cryptPubKey : Key)  =
        let keyAES, keyMAC, iv = Crypto.rand 32, Crypto.rand 32, Crypto.rand 16
        let fileInfo = new FileInfo (inputFilePath)
        use inputStream = new FileStream (inputFilePath, FileMode.Open, FileAccess.Read)
        use outputStream = new FileStream (outputFilePath, FileMode.Create, FileAccess.Write)
        let writer = new BinaryWriter (outputStream)

        ignore <| writer.Seek (8 + 32 + 256, SeekOrigin.Current) // Skips file-content-size, mac and signature. They will be written later.

        Crypto.encryptRSA cryptPubKey (Array.append keyAES <| Array.append keyMAC iv) |> writer.Write

        printfn "pos: %A" outputStream.Position

        use cryptoStream = Crypto.encryptAES keyAES iv outputStream
        let cryptoWriter = new BinaryWriter (cryptoStream)

        // Write metadata.
        let metaData = new Metadata ([filename, fileInfo.Name; creationTimeKey, fileInfo.CreationTimeUtc.Ticks.ToString ()])
        let metaDataStream = new MemoryStream ()
        metaData.WriteTo metaDataStream
        cryptoWriter.Write (int metaDataStream.Length)
        printfn "meta size: %A" (int metaDataStream.Length)
        metaDataStream.Position <- 0L
        metaDataStream.CopyTo cryptoStream
        ()

    let decryptFile (sourceFilePath : string) (targetDirPath : string) (signaturePubKey: Key) (decryptPrivKey : Key) =
        ()