use crate::data_model::common::BigUnsigned;
use crate::data_model::oid::{OID_CT_RPKI_MANIFEST, OID_SHA256};
use crate::data_model::rc::ResourceCertificate;
use crate::data_model::signed_object::{
    RpkiSignedObject, RpkiSignedObjectParsed, SignedObjectParseError, SignedObjectValidateError,
};
use der_parser::ber::BerObjectContent;
use der_parser::der::{DerObject, Tag, parse_der};
use time::OffsetDateTime;

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ManifestObject {
    pub signed_object: RpkiSignedObject,
    pub econtent_type: String,
    pub manifest: ManifestEContent,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ManifestObjectParsed {
    pub signed_object: RpkiSignedObjectParsed,
    pub econtent_type: String,
    pub manifest: Option<ManifestEContentParsed>,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ManifestEContent {
    pub version: u32,
    pub manifest_number: BigUnsigned,
    pub this_update: OffsetDateTime,
    pub next_update: OffsetDateTime,
    pub file_hash_alg: String,
    pub files: Vec<FileAndHash>,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ManifestEContentParsed {
    der: Vec<u8>,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct FileAndHash {
    pub file_name: String,
    pub hash_bytes: Vec<u8>,
}

#[derive(Debug, thiserror::Error)]
pub enum ManifestParseError {
    #[error("signed object parse error: {0} (RFC 6488 §2-§3; RFC 9589 §4)")]
    SignedObject(#[from] SignedObjectParseError),
    #[error("DER parse error: {0} (RFC 9286 §4.2; DER)")]
    Parse(String),

    #[error("trailing bytes after DER object: {0} bytes (RFC 9286 §4.2; DER)")]
    TrailingBytes(usize),
}

#[derive(Debug, thiserror::Error)]
pub enum ManifestProfileError {
    #[error("signed object profile error: {0} (RFC 6488 §2-§3; RFC 9589 §4)")]
    SignedObject(#[from] SignedObjectValidateError),

    #[error(
        "eContentType must be id-ct-rpkiManifest ({OID_CT_RPKI_MANIFEST}), got {0} (RFC 9286 §4.1; RFC 9286 §4.4(1))"
    )]
    InvalidEContentType(String),

    #[error("manifest profile decode error: {0} (RFC 9286 §4.2; DER)")]
    ProfileDecode(String),

    #[error("Manifest must be a SEQUENCE of 5 or 6 elements, got {0} (RFC 9286 §4.2)")]
    InvalidManifestSequenceLen(usize),

    #[error("Manifest.version must be 0, got {0} (RFC 9286 §4.2.1)")]
    InvalidManifestVersion(u64),

    #[error(
        "Manifest.manifestNumber must be non-negative INTEGER (RFC 9286 §4.2; RFC 9286 §4.2.1)"
    )]
    InvalidManifestNumber,

    #[error("Manifest.manifestNumber longer than 20 octets (RFC 9286 §4.2.1)")]
    ManifestNumberTooLong,

    #[error("Manifest.thisUpdate must be GeneralizedTime (RFC 9286 §4.2)")]
    InvalidThisUpdate,

    #[error("Manifest.nextUpdate must be GeneralizedTime (RFC 9286 §4.2)")]
    InvalidNextUpdate,

    #[error("Manifest.nextUpdate must be later than thisUpdate (RFC 9286 §4.2.1)")]
    NextUpdateNotLater,

    #[error(
        "Manifest.fileHashAlg must be id-sha256 ({OID_SHA256}), got {0} (RFC 9286 §4.2.1; RFC 7935 §2)"
    )]
    InvalidFileHashAlg(String),

    #[error("Manifest.fileList must be a SEQUENCE (RFC 9286 §4.2)")]
    InvalidFileList,

    #[error("FileAndHash must be SEQUENCE of 2 (RFC 9286 §4.2)")]
    InvalidFileAndHash,

    #[error("fileList file name invalid: {0} (RFC 9286 §4.2.2)")]
    InvalidFileName(String),

    #[error("fileList hash must be BIT STRING (RFC 9286 §4.2)")]
    InvalidHashType,

    #[error(
        "fileList hash BIT STRING must be octet-aligned (unused bits=0) (RFC 9286 §4.2.1; DER BIT STRING)"
    )]
    HashNotOctetAligned,

    #[error(
        "fileList hash length invalid for sha256: got {0} bytes (RFC 9286 §4.2.1; RFC 7935 §2)"
    )]
    InvalidHashLength(usize),
}

#[derive(Debug, thiserror::Error)]
pub enum ManifestDecodeError {
    #[error("{0}")]
    Parse(#[from] ManifestParseError),

    #[error("{0}")]
    Validate(#[from] ManifestProfileError),
}

#[derive(Debug, thiserror::Error)]
pub enum ManifestValidateError {
    #[error(
        "Manifest EE certificate MUST include at least one RFC 3779 resource extension (IP or AS) (RFC 6487 §4.8.10-§4.8.11; RFC 3779; RFC 9286 §5.1)"
    )]
    EeResourcesMissing,

    #[error(
        "Manifest EE certificate IP resources MUST use inherit only (RFC 9286 §5.1; RFC 3779 §2.2.3.5)"
    )]
    EeIpResourcesNotInherit,

    #[error(
        "Manifest EE certificate AS resources MUST use inherit only (RFC 9286 §5.1; RFC 3779 §3.2.3.3)"
    )]
    EeAsResourcesNotInherit,

    #[error(
        "Manifest EE certificate AS resources rdi MUST be absent (RFC 6487 §4.8.11; RFC 3779 §3.2.3.5)"
    )]
    EeAsResourcesRdiPresent,
}

impl ManifestObject {
    /// Parse step of scheme A (`parse → validate → verify`).
    pub fn parse_der(der: &[u8]) -> Result<ManifestObjectParsed, ManifestParseError> {
        let signed_object = RpkiSignedObject::parse_der(der)?;
        let econtent_type = signed_object
            .signed_data
            .encap_content_info
            .econtent_type
            .clone();
        let manifest = signed_object
            .signed_data
            .encap_content_info
            .econtent
            .as_deref()
            .map(ManifestEContent::parse_der)
            .transpose()?;
        Ok(ManifestObjectParsed {
            signed_object,
            econtent_type,
            manifest,
        })
    }

    /// Profile validate step of scheme A (`parse → validate → verify`).
    ///
    /// `ManifestObject` is already profile-validated when constructed via `decode_der()` /
    /// `ManifestObjectParsed::validate_profile()`.
    pub fn validate_profile(&self) -> Result<(), ManifestProfileError> {
        Ok(())
    }

    pub fn decode_der(der: &[u8]) -> Result<Self, ManifestDecodeError> {
        Ok(Self::parse_der(der)?.validate_profile()?)
    }

    pub fn from_signed_object(
        signed_object: RpkiSignedObject,
    ) -> Result<Self, ManifestDecodeError> {
        let econtent_type = signed_object
            .signed_data
            .encap_content_info
            .econtent_type
            .clone();
        if econtent_type != OID_CT_RPKI_MANIFEST {
            return Err(ManifestProfileError::InvalidEContentType(econtent_type).into());
        }
        let manifest =
            ManifestEContent::decode_der(&signed_object.signed_data.encap_content_info.econtent)?;
        Ok(Self {
            signed_object,
            econtent_type: OID_CT_RPKI_MANIFEST.to_string(),
            manifest,
        })
    }

    /// Validate the embedded EE certificate resources against RFC 9286 §5.1.
    ///
    /// This does **not** perform certificate path validation. It assumes `ee` is a parsed and
    /// profile-validated RPKI EE resource certificate.
    pub fn validate_against_ee_cert(
        &self,
        ee: &ResourceCertificate,
    ) -> Result<(), ManifestValidateError> {
        let ip = ee.tbs.extensions.ip_resources.as_ref();
        let asn = ee.tbs.extensions.as_resources.as_ref();
        if ip.is_none() && asn.is_none() {
            return Err(ManifestValidateError::EeResourcesMissing);
        }

        if let Some(ip) = ip {
            if !ip.is_all_inherit() {
                return Err(ManifestValidateError::EeIpResourcesNotInherit);
            }
        }

        if let Some(asn) = asn {
            if asn.rdi.is_some() {
                return Err(ManifestValidateError::EeAsResourcesRdiPresent);
            }
            if !asn.is_asnum_inherit() {
                return Err(ManifestValidateError::EeAsResourcesNotInherit);
            }
        }

        Ok(())
    }

    /// Validate this manifest's embedded EE certificate resources.
    pub fn validate_embedded_ee_cert(&self) -> Result<(), ManifestValidateError> {
        let ee = &self.signed_object.signed_data.certificates[0].resource_cert;
        self.validate_against_ee_cert(ee)
    }
}

impl ManifestEContent {
    /// Parse step of scheme A (`parse → validate → verify`).
    pub fn parse_der(der: &[u8]) -> Result<ManifestEContentParsed, ManifestParseError> {
        let (rem, _obj) = parse_der(der).map_err(|e| ManifestParseError::Parse(e.to_string()))?;
        if !rem.is_empty() {
            return Err(ManifestParseError::TrailingBytes(rem.len()));
        }
        Ok(ManifestEContentParsed { der: der.to_vec() })
    }

    /// Profile validate step of scheme A (`parse → validate → verify`).
    ///
    /// `ManifestEContent` is already profile-validated when constructed via `decode_der()` /
    /// `ManifestEContentParsed::validate_profile()`.
    pub fn validate_profile(&self) -> Result<(), ManifestProfileError> {
        Ok(())
    }

    /// Decode the DER-encoded Manifest eContent defined in RFC 9286 §4.2 (`parse + validate`).
    pub fn decode_der(der: &[u8]) -> Result<Self, ManifestDecodeError> {
        Ok(Self::parse_der(der)?.validate_profile()?)
    }
}

impl ManifestObjectParsed {
    pub fn validate_profile(self) -> Result<ManifestObject, ManifestProfileError> {
        let signed_object = self.signed_object.validate_profile()?;
        let econtent_type = signed_object
            .signed_data
            .encap_content_info
            .econtent_type
            .clone();
        if econtent_type != OID_CT_RPKI_MANIFEST {
            return Err(ManifestProfileError::InvalidEContentType(econtent_type));
        }
        let manifest = self
            .manifest
            .ok_or_else(|| ManifestProfileError::ProfileDecode("Manifest.eContent missing".into()))?
            .validate_profile()?;
        Ok(ManifestObject {
            signed_object,
            econtent_type: OID_CT_RPKI_MANIFEST.to_string(),
            manifest,
        })
    }
}

impl ManifestEContentParsed {
    pub fn validate_profile(self) -> Result<ManifestEContent, ManifestProfileError> {
        let (_rem, obj) =
            parse_der(&self.der).map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;

        let seq = obj
            .as_sequence()
            .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;
        if seq.len() != 5 && seq.len() != 6 {
            return Err(ManifestProfileError::InvalidManifestSequenceLen(seq.len()));
        }

        let mut idx = 0;
        let mut version: u32 = 0;
        if seq.len() == 6 {
            let v_obj = &seq[0];
            if v_obj.class() != der_parser::ber::Class::ContextSpecific || v_obj.tag() != Tag(0) {
                return Err(ManifestProfileError::ProfileDecode(
                    "Manifest.version must be [0] EXPLICIT INTEGER".into(),
                ));
            }
            let inner_der = v_obj
                .as_slice()
                .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;
            let (rem, inner) = parse_der(inner_der)
                .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;
            if !rem.is_empty() {
                return Err(ManifestProfileError::ProfileDecode(
                    "trailing bytes inside Manifest.version".into(),
                ));
            }
            let v = inner
                .as_u64()
                .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;
            if v != 0 {
                return Err(ManifestProfileError::InvalidManifestVersion(v));
            }
            version = 0;
            idx = 1;
        }

        let manifest_number = parse_manifest_number(&seq[idx])?;
        idx += 1;

        let this_update =
            parse_generalized_time(&seq[idx], ManifestProfileError::InvalidThisUpdate)?;
        idx += 1;
        let next_update =
            parse_generalized_time(&seq[idx], ManifestProfileError::InvalidNextUpdate)?;
        idx += 1;
        if next_update <= this_update {
            return Err(ManifestProfileError::NextUpdateNotLater);
        }

        let file_hash_alg = oid_to_string(&seq[idx])?;
        idx += 1;
        if file_hash_alg != OID_SHA256 {
            return Err(ManifestProfileError::InvalidFileHashAlg(file_hash_alg));
        }

        let files = parse_file_list_sha256(&seq[idx])?;

        Ok(ManifestEContent {
            version,
            manifest_number,
            this_update,
            next_update,
            file_hash_alg: OID_SHA256.to_string(),
            files,
        })
    }
}

fn parse_manifest_number(obj: &DerObject<'_>) -> Result<BigUnsigned, ManifestProfileError> {
    let n = obj
        .as_biguint()
        .map_err(|_e| ManifestProfileError::InvalidManifestNumber)?;
    let out = BigUnsigned::from_biguint(&n);
    if out.bytes_be.len() > 20 {
        return Err(ManifestProfileError::ManifestNumberTooLong);
    }
    Ok(out)
}

fn parse_generalized_time(
    obj: &DerObject<'_>,
    err: ManifestProfileError,
) -> Result<OffsetDateTime, ManifestProfileError> {
    match &obj.content {
        BerObjectContent::GeneralizedTime(dt) => dt
            .to_datetime()
            .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string())),
        _ => Err(err),
    }
}

fn parse_file_list_sha256(obj: &DerObject<'_>) -> Result<Vec<FileAndHash>, ManifestProfileError> {
    let seq = obj
        .as_sequence()
        .map_err(|_e| ManifestProfileError::InvalidFileList)?;
    let mut out = Vec::with_capacity(seq.len());
    for entry in seq {
        let (file_name, hash_bytes) = parse_file_and_hash(entry)?;
        validate_file_name(&file_name)?;
        if hash_bytes.len() != 32 {
            return Err(ManifestProfileError::InvalidHashLength(hash_bytes.len()));
        }
        out.push(FileAndHash {
            file_name,
            hash_bytes,
        });
    }
    Ok(out)
}

fn parse_file_and_hash(obj: &DerObject<'_>) -> Result<(String, Vec<u8>), ManifestProfileError> {
    let seq = obj
        .as_sequence()
        .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;
    if seq.len() != 2 {
        return Err(ManifestProfileError::InvalidFileAndHash);
    }
    let file_name = seq[0]
        .as_str()
        .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?
        .to_string();
    let (unused_bits, bits) = match &seq[1].content {
        BerObjectContent::BitString(unused, bso) => (*unused, bso.data.to_vec()),
        _ => return Err(ManifestProfileError::InvalidHashType),
    };
    if unused_bits != 0 {
        return Err(ManifestProfileError::HashNotOctetAligned);
    }
    Ok((file_name, bits))
}

fn validate_file_name(name: &str) -> Result<(), ManifestProfileError> {
    // RFC 9286 §4.2.2:
    // 1+ chars from a-zA-Z0-9-_ , then '.', then 3-letter extension.
    let Some((base, ext)) = name.rsplit_once('.') else {
        return Err(ManifestProfileError::InvalidFileName(name.to_string()));
    };
    if base.is_empty() || ext.len() != 3 {
        return Err(ManifestProfileError::InvalidFileName(name.to_string()));
    }
    if !base
        .bytes()
        .all(|b| b.is_ascii_alphanumeric() || b == b'-' || b == b'_')
    {
        return Err(ManifestProfileError::InvalidFileName(name.to_string()));
    }
    if !ext.bytes().all(|b| b.is_ascii_alphabetic()) {
        return Err(ManifestProfileError::InvalidFileName(name.to_string()));
    }
    let ext_lower = ext.to_ascii_lowercase();
    if !crate::data_model::common::IANA_RPKI_REPOSITORY_FILENAME_EXTENSIONS
        .iter()
        .any(|&e| e == ext_lower)
    {
        return Err(ManifestProfileError::InvalidFileName(name.to_string()));
    }
    Ok(())
}

fn oid_to_string(obj: &DerObject<'_>) -> Result<String, ManifestProfileError> {
    let oid = obj
        .as_oid()
        .map_err(|e| ManifestProfileError::ProfileDecode(e.to_string()))?;
    Ok(oid.to_id_string())
}