//! Cardholder Unique Identifier (CHUID) Support

// Adapted from yubico-piv-tool:
// <https://github.com/Yubico/yubico-piv-tool/>
//
// Copyright (c) 2014-2016 Yubico AB
// All rights reserved.
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// modification, are permitted provided that the following conditions are
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//
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//     copyright notice, this list of conditions and the following
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use crate::{consts::*, error::Error, yubikey::YubiKey};
use getrandom::getrandom;

/// Cardholder Unique Identifier (CHUID) Template
///
/// Format defined in SP-800-73-4, Appendix A, Table 9
///
/// FASC-N containing S9999F9999F999999F0F1F0000000000300001E encoded in
/// 4-bit BCD with 1 bit parity. run through the tools/fasc.pl script to get
/// bytes. This CHUID has an expiry of 2030-01-01.
///
/// Defined fields:
///
/// - 0x30: FASC-N (hard-coded)
/// - 0x34: Card UUID / GUID (settable)
/// - 0x35: Exp. Date (hard-coded)
/// - 0x3e: Signature (hard-coded, empty)
/// - 0xfe: Error Detection Code (hard-coded)
const CHUID_TMPL: &[u8] = &[
    0x30, 0x19, 0xd4, 0xe7, 0x39, 0xda, 0x73, 0x9c, 0xed, 0x39, 0xce, 0x73, 0x9d, 0x83, 0x68, 0x58,
    0x21, 0x08, 0x42, 0x10, 0x84, 0x21, 0xc8, 0x42, 0x10, 0xc3, 0xeb, 0x34, 0x10, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x35, 0x08, 0x32,
    0x30, 0x33, 0x30, 0x30, 0x31, 0x30, 0x31, 0x3e, 0x00, 0xfe, 0x00,
];

/// Cardholder Unique Identifier (CHUID)
#[derive(Copy, Clone, Debug)]
pub struct CHUID([u8; YKPIV_CARDID_SIZE]);

impl CHUID {
    /// Generate a random Cardholder Unique Identifier (CHUID)
    pub fn generate() -> Result<Self, Error> {
        let mut id = [0u8; YKPIV_CARDID_SIZE];
        getrandom(&mut id).map_err(|_| Error::RandomnessError)?;
        Ok(CHUID(id))
    }

    /// Get Cardholder Unique Identifier (CHUID)
    pub fn get(yubikey: &mut YubiKey) -> Result<Self, Error> {
        let txn = yubikey.begin_transaction()?;
        let response = txn.fetch_object(YKPIV_OBJ_CHUID)?;

        if response.len() != CHUID_TMPL.len() {
            return Err(Error::GenericError);
        }

        let mut cardid = [0u8; YKPIV_CARDID_SIZE];
        cardid.copy_from_slice(&response[CHUID_GUID_OFFS..(CHUID_GUID_OFFS + YKPIV_CARDID_SIZE)]);
        Ok(CHUID(cardid))
    }

    /// Set Cardholder Unique Identifier (CHUID)
    pub fn set(&self, yubikey: &mut YubiKey) -> Result<(), Error> {
        let mut buf = CHUID_TMPL.to_vec();
        buf[CHUID_GUID_OFFS..(CHUID_GUID_OFFS + self.0.len())].copy_from_slice(&self.0);

        let txn = yubikey.begin_transaction()?;
        txn.save_object(YKPIV_OBJ_CHUID, &buf)
    }
}