use rpki::data_model::roa::{RoaDecodeError, RoaEContent};

fn len_bytes(len: usize) -> Vec<u8> {
    if len < 128 {
        vec![len as u8]
    } else {
        let mut tmp = Vec::new();
        let mut n = len;
        while n > 0 {
            tmp.push((n & 0xFF) as u8);
            n >>= 8;
        }
        tmp.reverse();
        let mut out = vec![0x80 | (tmp.len() as u8)];
        out.extend(tmp);
        out
    }
}

fn tlv(tag: u8, content: &[u8]) -> Vec<u8> {
    let mut out = vec![tag];
    out.extend(len_bytes(content.len()));
    out.extend_from_slice(content);
    out
}

fn der_integer_u64(v: u64) -> Vec<u8> {
    let mut bytes = Vec::new();
    let mut n = v;
    if n == 0 {
        bytes.push(0);
    } else {
        while n > 0 {
            bytes.push((n & 0xFF) as u8);
            n >>= 8;
        }
        bytes.reverse();
        if bytes[0] & 0x80 != 0 {
            bytes.insert(0, 0);
        }
    }
    tlv(0x02, &bytes)
}

fn der_octet_string(bytes: &[u8]) -> Vec<u8> {
    tlv(0x04, bytes)
}

fn der_bit_string(unused: u8, bytes: &[u8]) -> Vec<u8> {
    let mut content = vec![unused];
    content.extend_from_slice(bytes);
    tlv(0x03, &content)
}

fn der_sequence(children: Vec<Vec<u8>>) -> Vec<u8> {
    let mut content = Vec::new();
    for c in children {
        content.extend(c);
    }
    tlv(0x30, &content)
}

fn cs_explicit(tag_no: u8, inner_der: Vec<u8>) -> Vec<u8> {
    tlv(0xA0 | (tag_no & 0x1F), &inner_der)
}

fn roa_ip_address(prefix_bs: Vec<u8>, max_len: Option<u64>) -> Vec<u8> {
    let mut fields = vec![prefix_bs];
    if let Some(m) = max_len {
        fields.push(der_integer_u64(m));
    }
    der_sequence(fields)
}

fn roa_ip_family(afi: [u8; 2], addresses: Vec<Vec<u8>>) -> Vec<u8> {
    der_sequence(vec![der_octet_string(&afi), der_sequence(addresses)])
}

fn roa_attestation(version: Option<u64>, as_id: u64, families: Vec<Vec<u8>>) -> Vec<u8> {
    let mut fields = Vec::new();
    if let Some(v) = version {
        fields.push(cs_explicit(0, der_integer_u64(v)));
    }
    fields.push(der_integer_u64(as_id));
    fields.push(der_sequence(families));
    der_sequence(fields)
}

#[test]
fn version_must_be_zero_when_present() {
    let der = roa_attestation(
        Some(1),
        64496,
        vec![roa_ip_family([0, 1], vec![roa_ip_address(der_bit_string(0, &[]), None)])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::InvalidVersion(1)));
}

#[test]
fn as_id_out_of_range_is_rejected() {
    let der = roa_attestation(
        None,
        (u32::MAX as u64) + 1,
        vec![roa_ip_family([0, 1], vec![roa_ip_address(der_bit_string(0, &[]), None)])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::AsIdOutOfRange(_)));
}

#[test]
fn ip_addr_blocks_len_is_validated() {
    let der = roa_attestation(None, 64496, vec![]);
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::InvalidIpAddrBlocksLen(0)));

    let families = vec![
        roa_ip_family([0, 1], vec![roa_ip_address(der_bit_string(0, &[]), None)]),
        roa_ip_family([0, 2], vec![roa_ip_address(der_bit_string(0, &[]), None)]),
        roa_ip_family([0, 1], vec![roa_ip_address(der_bit_string(0, &[]), None)]),
    ];
    let der = roa_attestation(None, 64496, families);
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::InvalidIpAddrBlocksLen(3)));
}

#[test]
fn duplicate_afi_is_rejected() {
    let families = vec![
        roa_ip_family([0, 1], vec![roa_ip_address(der_bit_string(0, &[]), None)]),
        roa_ip_family([0, 1], vec![roa_ip_address(der_bit_string(0, &[]), None)]),
    ];
    let der = roa_attestation(None, 64496, families);
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::DuplicateAfi(_)));
}

#[test]
fn unsupported_afi_is_rejected() {
    let der = roa_attestation(
        None,
        64496,
        vec![roa_ip_family([0x12, 0x34], vec![roa_ip_address(der_bit_string(0, &[]), None)])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::UnsupportedAfi(_)));
}

#[test]
fn empty_address_list_is_rejected() {
    let der = roa_attestation(None, 64496, vec![roa_ip_family([0, 1], vec![])]);
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::EmptyAddressList));
}

#[test]
fn prefix_unused_bits_must_be_zeroed() {
    // prefix_len=1 => unused_bits=7, last byte must have lower 7 bits zero.
    // Use 0b1000_0001 which has a non-zero unused bit.
    let bs = der_bit_string(7, &[0b1000_0001]);
    let der = roa_attestation(
        None,
        64496,
        vec![roa_ip_family([0, 1], vec![roa_ip_address(bs, None)])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::InvalidPrefixUnusedBits));
}

#[test]
fn prefix_len_out_of_range_is_rejected() {
    // IPv4 ub=32, encode 33 bits: 5 bytes with unused_bits=7 => 40-7=33.
    let bs = der_bit_string(7, &[0u8; 5]);
    let der = roa_attestation(
        None,
        64496,
        vec![roa_ip_family([0, 1], vec![roa_ip_address(bs, None)])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::PrefixLenOutOfRange { .. }));
}

#[test]
fn max_length_range_and_relation_are_validated() {
    // IPv4, prefix_len=8
    let bs = der_bit_string(0, &[0x0A]);
    // maxLength < prefix_len
    let der = roa_attestation(
        None,
        64496,
        vec![roa_ip_family([0, 1], vec![roa_ip_address(bs.clone(), Some(7))])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::InvalidMaxLength { .. }));

    // maxLength > ub
    let der = roa_attestation(
        None,
        64496,
        vec![roa_ip_family([0, 1], vec![roa_ip_address(bs, Some(33))])],
    );
    let err = RoaEContent::decode_der(&der).unwrap_err();
    assert!(matches!(err, RoaDecodeError::InvalidMaxLength { .. }));
}