using Dino.Entities;

using Signal;

namespace Dino.Plugins.Omemo {

public class OmemoHttpFileReceiveData : HttpFileReceiveData {
    public string original_url;
}

public class OmemoFileDecryptor : FileDecryptor, Object {

    private Regex url_regex = /^aesgcm:\/\/(.*)#(([A-Fa-f0-9]{2}){48}|([A-Fa-f0-9]{2}){44})$/;

    public FileReceiveData prepare_get_meta_info(Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data) {
        HttpFileReceiveData? http_receive_data = receive_data as HttpFileReceiveData;
        if (http_receive_data == null) assert(false);
        if ((receive_data as OmemoHttpFileReceiveData) != null) return receive_data;

        var omemo_http_receive_data = new OmemoHttpFileReceiveData();
        omemo_http_receive_data.url = aesgcm_to_https_link(http_receive_data.url);
        omemo_http_receive_data.original_url = http_receive_data.url;

        return omemo_http_receive_data;
    }

    public FileMeta prepare_download_file(Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data, FileMeta file_meta) {
        if (file_meta.file_name != null) {
            file_meta.file_name = file_meta.file_name.split("#")[0];
        }
        return file_meta;
    }

    public bool can_decrypt_file(Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data) {
        HttpFileReceiveData? http_file_receive = receive_data as HttpFileReceiveData;
        if (http_file_receive == null) return false;

        return this.url_regex.match(http_file_receive.url) || (receive_data as OmemoHttpFileReceiveData) != null;
    }

    public async InputStream decrypt_file(InputStream encrypted_stream, Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data) {
        OmemoHttpFileReceiveData? omemo_http_receive_data = receive_data as OmemoHttpFileReceiveData;
        if (omemo_http_receive_data == null) assert(false);

        // Decode IV and key
        MatchInfo match_info;
        this.url_regex.match(omemo_http_receive_data.original_url, 0, out match_info);
        uint8[] iv_and_key = hex_to_bin(match_info.fetch(2).up());
        uint8[] iv, key;
        if (iv_and_key.length == 44) {
            iv = iv_and_key[0:12];
            key = iv_and_key[12:44];
        } else {
            iv = iv_and_key[0:16];
            key = iv_and_key[16:48];
        }

        // Read data
        uint8[] buf = new uint8[256];
        Array<uint8> data = new Array<uint8>(false, true, 0);
        size_t len = -1;
        do {
            len = yield encrypted_stream.read_async(buf);
            data.append_vals(buf, (uint) len);
        } while(len > 0);

        // Decrypt
        uint8[] cleartext = Signal.aes_decrypt(Cipher.AES_GCM_NOPADDING, key, iv, data.data);
        file_transfer.encryption = Encryption.OMEMO;
        return new MemoryInputStream.from_data(cleartext);
    }

    private uint8[] hex_to_bin(string hex) {
        uint8[] bin = new uint8[hex.length / 2];
        const string HEX = "0123456789ABCDEF";
        for (int i = 0; i < hex.length / 2; i++) {
            bin[i] = (uint8) (HEX.index_of_char(hex[i*2]) << 4) | HEX.index_of_char(hex[i*2+1]);
        }
        return bin;
    }

    private string aesgcm_to_https_link(string aesgcm_link) {
        MatchInfo match_info;
        this.url_regex.match(aesgcm_link, 0, out match_info);
        return "https://" + match_info.fetch(1);
    }
}

}