synta-certificate 0.2.6

//! Fluent builders for RFC 2634 Extended Security Services (ESS) structures.
//!
//! Three builders are provided:
//!
//! | Builder | Structure | RFC §|
//! |---------|-----------|------|
//! | [`SigningCertificateBuilder`] | `SigningCertificate` | 5.4 |
//! | [`ReceiptRequestBuilder`] | `ReceiptRequest` | 2.7 |
//! | [`ESSSecurityLabelBuilder`] | `ESSSecurityLabel` | 3.2 |
//!
//! # Example — `SigningCertificate`
//!
//! ```rust,ignore
//! use synta_certificate::SigningCertificateBuilder;
//!
//! // SHA-1 hash of the signer's certificate DER
//! let cert_sha1 = [0u8; 20];
//! let sc_der = SigningCertificateBuilder::new()
//!     .add_cert_id(&cert_sha1, None)
//!     .build()
//!     .unwrap();
//! ```
//!
//! # Example — `ReceiptRequest`
//!
//! ```rust,ignore
//! use synta_certificate::ReceiptRequestBuilder;
//!
//! let rr_der = ReceiptRequestBuilder::new()
//!     .signed_content_identifier(b"\x01\x02\x03\x04")
//!     .receipts_from_all()
//!     .add_receipt_to_email("receipts@example.com")
//!     .build()
//!     .unwrap();
//! ```

use crate::ext_builder::encode_sequence;
use synta::tag::TAG_SET;
use synta::traits::Encode;

use crate::ess_types::{
    AllOrFirstTier, ESSCertID, ESSPrivacyMark, ReceiptsFrom, SecurityClassification,
    SecurityPolicyIdentifier, ALL_OR_FIRST_TIER_ALL_RECEIPTS,
    ALL_OR_FIRST_TIER_FIRST_TIER_RECIPIENTS,
};
use crate::GeneralNameSpec;

// ── SigningCertificateBuilder ─────────────────────────────────────────────────

/// Fluent builder for a `SigningCertificate` DER structure (RFC 2634 §5.4).
///
/// `SigningCertificate` is a CMS signed attribute that identifies the signer's
/// certificate by its SHA-1 hash and optionally by its issuer/serial number.
///
/// Add certificate IDs with [`add_cert_id`](Self::add_cert_id) and optional
/// certificate policies with [`add_policy`](Self::add_policy).
#[derive(Debug, Default)]
pub struct SigningCertificateBuilder {
    /// Pre-encoded `ESSCertID` TLVs accumulated as raw DER bytes.
    certs_encoded: Vec<u8>,
    /// Pre-encoded `PolicyInformation` TLVs accumulated as raw DER bytes.
    policies_encoded: Vec<u8>,
    /// First error encountered.
    error: Option<String>,
}

impl SigningCertificateBuilder {
    /// Create a new, empty `SigningCertificateBuilder`.
    pub fn new() -> Self {
        Self::default()
    }

    /// Add a certificate entry identified by its SHA-1 hash.
    ///
    /// `cert_hash` is the 20-byte SHA-1 hash of the complete DER-encoded
    /// certificate (the entire `Certificate` structure bytes).
    ///
    /// `issuer_serial_der` is an optional pre-encoded `IssuerSerial` SEQUENCE
    /// DER TLV.  Pass `None` to omit the issuer/serial field.
    pub fn add_cert_id(mut self, cert_hash: &[u8], issuer_serial_der: Option<&[u8]>) -> Self {
        if self.error.is_some() {
            return self;
        }
        let hash_ref = synta::OctetStringRef::new(cert_hash);

        // If an IssuerSerial DER blob was provided, validate it by decoding once,
        // then use the decoded value directly when building ESSCertID.
        // (Keeping the owned Vec alive so the borrowed IssuerSerial can reference it.)
        let issuer_serial_bytes = issuer_serial_der.map(|b| b.to_vec());
        let cert_id_der = {
            let issuer_serial_decoded: Option<crate::ess_types::IssuerSerial<'_>> =
                if let Some(ref bytes) = issuer_serial_bytes {
                    match synta::Decoder::new(bytes, synta::Encoding::Der)
                        .decode::<crate::ess_types::IssuerSerial<'_>>()
                    {
                        Ok(is) => Some(is),
                        Err(e) => {
                            self.error = Some(format!("IssuerSerial decode failed: {e}"));
                            return self;
                        }
                    }
                } else {
                    None
                };

            let cert_id = ESSCertID {
                cert_hash: hash_ref,
                issuer_serial: issuer_serial_decoded,
            };
            let mut enc = synta::Encoder::new(synta::Encoding::Der);
            match cert_id.encode(&mut enc).and_then(|()| enc.finish()) {
                Ok(b) => b,
                Err(e) => {
                    self.error = Some(format!("ESSCertID DER encoding failed: {e}"));
                    return self;
                }
            }
        };

        self.certs_encoded.extend_from_slice(&cert_id_der);
        self
    }

    /// Add a certificate policy OID to the optional `policies` field.
    ///
    /// `policy_oid` is the policy OID as a `&[u32]` component slice.  No
    /// qualifiers are added (pass policy OID and rely on defaults per RFC 3280).
    pub fn add_policy(mut self, policy_oid: &[u32]) -> Self {
        if self.error.is_some() {
            return self;
        }
        let oid = match synta::ObjectIdentifier::new(policy_oid) {
            Ok(o) => o,
            Err(e) => {
                self.error = Some(format!("invalid policy OID: {e}"));
                return self;
            }
        };
        let pi = crate::PolicyInformation {
            policy_identifier: oid,
            policy_qualifiers: None,
        };
        let mut enc = synta::Encoder::new(synta::Encoding::Der);
        match pi.encode(&mut enc).and_then(|()| enc.finish()) {
            Ok(bytes) => self.policies_encoded.extend_from_slice(&bytes),
            Err(e) => {
                self.error = Some(format!("PolicyInformation DER encoding failed: {e}"));
            }
        }
        self
    }

    /// Build the DER-encoded `SigningCertificate` SEQUENCE.
    ///
    /// Returns `Err` if no certificate IDs were added or if DER encoding fails.
    pub fn build(self) -> Result<Vec<u8>, String> {
        if let Some(e) = self.error {
            return Err(e);
        }
        if self.certs_encoded.is_empty() {
            return Err("at least one certificate ID is required".to_string());
        }

        // Build `SigningCertificate ::= SEQUENCE { certs SEQUENCE OF ESSCertID,
        //                                          policies SEQUENCE OF PolicyInformation OPTIONAL }`
        // by wrapping the pre-encoded TLVs in SEQUENCE containers.
        let mut content = Vec::new();
        content.extend_from_slice(&encode_sequence(self.certs_encoded));
        if !self.policies_encoded.is_empty() {
            content.extend_from_slice(&encode_sequence(self.policies_encoded));
        }
        Ok(encode_sequence(content))
    }
}

// ── ReceiptRequestBuilder ─────────────────────────────────────────────────────

/// Fluent builder for a `ReceiptRequest` DER structure (RFC 2634 §2.7).
///
/// A `ReceiptRequest` is a CMS signed attribute that requests a signed receipt.
/// Required fields: `signed_content_identifier` and one `receipts_from_*` call.
#[derive(Debug, Default)]
pub struct ReceiptRequestBuilder {
    /// `signedContentIdentifier` OCTET STRING value bytes.
    signed_content_id: Option<Vec<u8>>,
    /// Pre-encoded `ReceiptsFrom` CHOICE TLV bytes.
    receipts_from: Option<Vec<u8>>,
    /// Pre-encoded `GeneralNames` SEQUENCE TLVs for the `receiptsTo` list.
    receipts_to_encoded: Vec<u8>,
    /// First error encountered.
    error: Option<String>,
}

impl ReceiptRequestBuilder {
    /// Create a new, empty `ReceiptRequestBuilder`.
    pub fn new() -> Self {
        Self::default()
    }

    /// Set the `signedContentIdentifier` (an OCTET STRING value).
    pub fn signed_content_identifier(mut self, id: &[u8]) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.signed_content_id = Some(id.to_vec());
        self
    }

    /// Request receipts from all recipients (`allReceipts [0]`).
    pub fn receipts_from_all(self) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.encode_receipts_from(ReceiptsFrom::AllOrFirstTier(AllOrFirstTier::from(
            ALL_OR_FIRST_TIER_ALL_RECEIPTS,
        )))
    }

    /// Request receipts from first-tier recipients only (`firstTierRecipients [0]`).
    pub fn receipts_from_first_tier(self) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.encode_receipts_from(ReceiptsFrom::AllOrFirstTier(AllOrFirstTier::from(
            ALL_OR_FIRST_TIER_FIRST_TIER_RECIPIENTS,
        )))
    }

    fn encode_receipts_from(mut self, rf: ReceiptsFrom<'_>) -> Self {
        let mut enc = synta::Encoder::new(synta::Encoding::Der);
        match rf.encode(&mut enc).and_then(|()| enc.finish()) {
            Ok(bytes) => self.receipts_from = Some(bytes),
            Err(e) => self.error = Some(format!("ReceiptsFrom DER encoding failed: {e}")),
        }
        self
    }

    /// Add an email address to the `receiptsTo` list.
    ///
    /// Each entry in `receiptsTo` is a `GeneralNames` (SEQUENCE OF GeneralName).
    /// This convenience method wraps a single RFC 822 name in a `GeneralNames`
    /// SEQUENCE.
    pub fn add_receipt_to_email(mut self, email: &str) -> Self {
        if self.error.is_some() {
            return self;
        }
        let spec = GeneralNameSpec::rfc822(email);
        let gn = match spec.to_general_name() {
            Ok(gn) => gn,
            Err(e) => {
                self.error = Some(format!("GeneralName error: {e}"));
                return self;
            }
        };
        let mut enc = synta::Encoder::new(synta::Encoding::Der);
        match gn.encode(&mut enc).and_then(|()| enc.finish()) {
            Ok(gn_bytes) => {
                // Wrap in a GeneralNames SEQUENCE.
                let gn_seq = encode_sequence(gn_bytes);
                self.receipts_to_encoded.extend_from_slice(&gn_seq);
            }
            Err(e) => {
                self.error = Some(format!("GeneralName DER encoding failed: {e}"));
            }
        }
        self
    }

    /// Add a pre-encoded `GeneralNames` DER TLV to the `receiptsTo` list.
    pub fn add_receipt_to_raw(mut self, general_names_der: &[u8]) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.receipts_to_encoded
            .extend_from_slice(general_names_der);
        self
    }

    /// Build the DER-encoded `ReceiptRequest` SEQUENCE.
    ///
    /// Returns `Err` if required fields are missing or DER encoding fails.
    pub fn build(self) -> Result<Vec<u8>, String> {
        if let Some(e) = self.error {
            return Err(e);
        }

        let sci_bytes = self
            .signed_content_id
            .ok_or_else(|| "signed_content_identifier is required".to_string())?;
        let rf_bytes = self.receipts_from.ok_or_else(|| {
            "receipts_from (call receipts_from_all or receipts_from_first_tier) is required"
                .to_string()
        })?;
        if self.receipts_to_encoded.is_empty() {
            return Err(
                "at least one receiptsTo entry is required (use add_receipt_to_email or add_receipt_to_raw)"
                    .to_string(),
            );
        }

        // Encode signedContentIdentifier as OCTET STRING TLV.
        let sci_os = synta::OctetString::new(sci_bytes);
        let mut sci_enc = synta::Encoder::new(synta::Encoding::Der);
        sci_os
            .encode(&mut sci_enc)
            .map_err(|e| format!("signedContentIdentifier encode failed: {e}"))?;
        let sci_der = sci_enc
            .finish()
            .map_err(|e| format!("signedContentIdentifier finish failed: {e}"))?;

        // Build ReceiptRequest ::= SEQUENCE {
        //     signedContentIdentifier ContentIdentifier,   -- OCTET STRING
        //     receiptsFrom            ReceiptsFrom,        -- CHOICE (pre-encoded)
        //     receiptsTo              ReceiptsTo }         -- SEQUENCE OF GeneralNames
        // receipts_to_encoded contains pre-encoded GeneralNames SEQUENCE TLVs;
        // wrap them in an outer SEQUENCE to form the ReceiptsTo SEQUENCE OF.
        let receipts_to_der = encode_sequence(self.receipts_to_encoded);

        let mut content = Vec::new();
        content.extend_from_slice(&sci_der);
        content.extend_from_slice(&rf_bytes);
        content.extend_from_slice(&receipts_to_der);

        Ok(encode_sequence(content))
    }
}

// ── ESSSecurityLabelBuilder ───────────────────────────────────────────────────

/// Fluent builder for an `ESSSecurityLabel` DER SET (RFC 2634 §3.2).
///
/// An `ESSSecurityLabel` is a CMS signed attribute that carries an information
/// security label on a signed message.  The `security_policy_identifier` OID
/// is required; all other fields are optional.
#[derive(Debug, Default)]
pub struct ESSSecurityLabelBuilder {
    /// `securityPolicyIdentifier` OID components.
    policy_oid: Option<Vec<u32>>,
    /// `securityClassification` value (0..32767).
    classification: Option<u16>,
    /// `privacyMark` string value.
    privacy_mark: Option<String>,
    /// `true` if `privacy_mark` was set via `privacy_mark_printable` (PrintableString),
    /// `false` if via `privacy_mark_utf8` (UTF8String).
    privacy_mark_is_printable: bool,
    /// Pre-encoded `SecurityCategory` TLVs accumulated as raw bytes for the SET.
    categories_encoded: Vec<u8>,
    /// First error encountered.
    error: Option<String>,
}

impl ESSSecurityLabelBuilder {
    /// Create a new, empty `ESSSecurityLabelBuilder`.
    pub fn new() -> Self {
        Self::default()
    }

    /// Set the `securityPolicyIdentifier` OID.
    ///
    /// `policy_oid` is the OID as a `&[u32]` component slice.  This field is
    /// required.
    pub fn security_policy(mut self, policy_oid: &[u32]) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.policy_oid = Some(policy_oid.to_vec());
        self
    }

    /// Set the optional `securityClassification` value.
    ///
    /// Standard values (RFC 2634 §3.2):
    /// - `SecurityClassification::UNMARKED` = 0
    /// - `SecurityClassification::UNCLASSIFIED` = 1
    /// - `SecurityClassification::RESTRICTED` = 2
    /// - `SecurityClassification::CONFIDENTIAL` = 3
    /// - `SecurityClassification::SECRET` = 4
    /// - `SecurityClassification::TOP_SECRET` = 5
    ///
    /// Values above 32767 are rejected: RFC 2634 §3.2 constrains this field to
    /// `INTEGER (0..32767)`.
    pub fn classification(mut self, value: u16) -> Self {
        if self.error.is_some() {
            return self;
        }
        if value > 32767 {
            self.error = Some(format!(
                "security classification value {} exceeds RFC 2634 maximum of 32767",
                value
            ));
            return self;
        }
        self.classification = Some(value);
        self
    }

    /// Set the optional `privacyMark` as a UTF8String.
    ///
    /// The standard also allows PrintableString; use [`privacy_mark_printable`](Self::privacy_mark_printable)
    /// for that variant.
    pub fn privacy_mark_utf8(mut self, mark: &str) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.privacy_mark = Some(mark.to_string());
        self.privacy_mark_is_printable = false;
        self
    }

    /// Set the optional `privacyMark` as a PrintableString.
    ///
    /// The DER output will carry tag `0x13` (PrintableString) rather than
    /// `0x0C` (UTF8String).  The content is validated against the
    /// PrintableString character set at call time.
    pub fn privacy_mark_printable(mut self, mark: &str) -> Self {
        if self.error.is_some() {
            return self;
        }
        // Validate that the string is valid PrintableString content.
        let printable_chars = mark
            .chars()
            .all(|c| c.is_ascii_alphanumeric() || " '()+,-./:=?".contains(c));
        if !printable_chars {
            self.error = Some(format!(
                "privacy mark '{}' contains characters not allowed in PrintableString",
                mark
            ));
            return self;
        }
        self.privacy_mark = Some(mark.to_string());
        self.privacy_mark_is_printable = true;
        self
    }

    /// Add a pre-encoded `SecurityCategory` DER TLV to the security categories field.
    ///
    /// Each call appends one `SecurityCategory SEQUENCE` to the `securityCategories`
    /// `SET OF SecurityCategory` field (RFC 2634 §3.2).
    ///
    /// `security_category_der` must be a valid DER-encoded `SecurityCategory` TLV.
    pub fn add_security_category_raw(mut self, security_category_der: &[u8]) -> Self {
        if self.error.is_some() {
            return self;
        }
        self.categories_encoded
            .extend_from_slice(security_category_der);
        self
    }

    /// Build the DER-encoded `ESSSecurityLabel` SET.
    ///
    /// Returns `Err` if `security_policy` was not set or if DER encoding fails.
    pub fn build(self) -> Result<Vec<u8>, String> {
        if let Some(e) = self.error {
            return Err(e);
        }

        let policy_comps = self
            .policy_oid
            .ok_or_else(|| "security_policy (OID) is required".to_string())?;
        let policy_oid: SecurityPolicyIdentifier = synta::ObjectIdentifier::new(&policy_comps)
            .map_err(|e| format!("invalid security policy OID: {e}"))?;

        let security_classification = self
            .classification
            .map(SecurityClassification::new_unchecked);

        let privacy_mark_str = self.privacy_mark;
        let privacy_mark_is_printable = self.privacy_mark_is_printable;
        let privacy_mark: Option<ESSPrivacyMark<'_>> = if let Some(ref s) = privacy_mark_str {
            if privacy_mark_is_printable {
                // Content was validated as PrintableString in the setter.
                match synta::PrintableStringRef::new(s) {
                    Ok(ps) => Some(ESSPrivacyMark::PString(ps)),
                    Err(e) => {
                        return Err(format!("privacyMark PrintableString encoding failed: {e}"))
                    }
                }
            } else {
                Some(ESSPrivacyMark::Utf8String(synta::Utf8StringRef::new(s)))
            }
        } else {
            None
        };

        // ESSSecurityLabel is a SET. We build its content from pre-encoded
        // fields and wrap in a SET TLV (tag 0x31) rather than fighting with
        // lifetime constraints in the generated struct.

        // Encode securityPolicyIdentifier OID.
        let mut pol_enc = synta::Encoder::new(synta::Encoding::Der);
        use synta::traits::Encode;
        policy_oid
            .encode(&mut pol_enc)
            .map_err(|e| format!("securityPolicyIdentifier encode failed: {e}"))?;
        let pol_der = pol_enc
            .finish()
            .map_err(|e| format!("securityPolicyIdentifier finish failed: {e}"))?;

        // Encode optional securityClassification.
        let class_der: Option<Vec<u8>> = if let Some(c) = security_classification {
            let mut enc = synta::Encoder::new(synta::Encoding::Der);
            c.encode(&mut enc)
                .map_err(|e| format!("securityClassification encode failed: {e}"))?;
            Some(
                enc.finish()
                    .map_err(|e| format!("securityClassification finish failed: {e}"))?,
            )
        } else {
            None
        };

        // Encode optional privacyMark.
        let pm_der: Option<Vec<u8>> = if let Some(pm) = privacy_mark {
            let mut enc = synta::Encoder::new(synta::Encoding::Der);
            pm.encode(&mut enc)
                .map_err(|e| format!("privacyMark encode failed: {e}"))?;
            Some(
                enc.finish()
                    .map_err(|e| format!("privacyMark finish failed: {e}"))?,
            )
        } else {
            None
        };

        // Assemble ESSSecurityLabel SET content in ASN.1 declaration order.
        // Note: strict DER (X.690 §11.6) requires SET components to be sorted by
        // tag value (INTEGER 0x02 before OID 0x06), but the synta generated decoder
        // reads fields in declaration order.  Keeping declaration order here ensures
        // the round-trip decoder works; fix both encoder and decoder together if
        // strict canonical ordering is needed in future.
        let mut set_content = Vec::new();
        // 1. securityPolicyIdentifier OBJECT IDENTIFIER (tag 0x06) — required
        set_content.extend_from_slice(&pol_der);
        // 2. securityClassification INTEGER (tag 0x02) — optional
        if let Some(ref c) = class_der {
            set_content.extend_from_slice(c);
        }
        // 3. privacyMark: UTF8String (0x0C) or PrintableString (0x13) — optional
        if let Some(ref pm) = pm_der {
            set_content.extend_from_slice(pm);
        }
        if !self.categories_encoded.is_empty() {
            // Wrap SecurityCategory TLVs in a SET OF (tag 0x31).
            let cat_tag = synta::Tag::universal_constructed(TAG_SET);
            let mut cat_enc = synta::Encoder::new(synta::Encoding::Der);
            cat_enc
                .start_constructed_no_guard(cat_tag)
                .map_err(|e| format!("SecurityCategories SET start failed: {e}"))?;
            cat_enc.write_bytes(&self.categories_encoded);
            cat_enc
                .end_constructed()
                .map_err(|e| format!("SecurityCategories SET end failed: {e}"))?;
            let cat_der = cat_enc
                .finish()
                .map_err(|e| format!("SecurityCategories SET finish failed: {e}"))?;
            set_content.extend_from_slice(&cat_der);
        }

        // Wrap the entire SET content with the SET tag.
        let set_tag = synta::Tag::universal_constructed(TAG_SET);
        let mut enc = synta::Encoder::new(synta::Encoding::Der);
        enc.start_constructed_no_guard(set_tag)
            .map_err(|e| format!("ESSSecurityLabel SET start failed: {e}"))?;
        enc.write_bytes(&set_content);
        enc.end_constructed()
            .map_err(|e| format!("ESSSecurityLabel SET end failed: {e}"))?;
        enc.finish().map_err(|e| format!("DER finish failed: {e}"))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn signing_certificate_minimal() {
        let cert_hash = [0xabu8; 20]; // fake SHA-1 hash
        let der = SigningCertificateBuilder::new()
            .add_cert_id(&cert_hash, None)
            .build()
            .expect("build should succeed");

        let decoded =
            crate::ess_types::SigningCertificate::from_der(&der).expect("round-trip decode failed");
        assert_eq!(decoded.certs.len(), 1);
        assert!(decoded.policies.is_none());
    }

    #[test]
    fn signing_certificate_requires_at_least_one_cert() {
        let err = SigningCertificateBuilder::new().build();
        assert!(err.is_err());
    }

    #[test]
    fn receipt_request_all_receipts() {
        let der = ReceiptRequestBuilder::new()
            .signed_content_identifier(b"\x01\x02\x03\x04")
            .receipts_from_all()
            .add_receipt_to_email("receipts@example.com")
            .build()
            .expect("build should succeed");

        let decoded =
            crate::ess_types::ReceiptRequest::from_der(&der).expect("round-trip decode failed");
        assert!(!decoded.receipts_to.is_empty());
    }

    #[test]
    fn receipt_request_missing_sci_returns_error() {
        let err = ReceiptRequestBuilder::new().receipts_from_all().build();
        assert!(err.is_err());
        assert!(err.unwrap_err().contains("signed_content_identifier"));
    }

    #[test]
    fn receipt_request_missing_from_returns_error() {
        let err = ReceiptRequestBuilder::new()
            .signed_content_identifier(b"\x01\x02")
            .build();
        assert!(err.is_err());
        assert!(err.unwrap_err().contains("receipts_from"));
    }

    #[test]
    fn ess_security_label_minimal() {
        // Use a custom policy OID
        let policy = &[1u32, 3, 6, 1, 5, 5, 7, 13, 1];
        let der = ESSSecurityLabelBuilder::new()
            .security_policy(policy)
            .build()
            .expect("build should succeed");

        let decoded =
            crate::ess_types::ESSSecurityLabel::from_der(&der).expect("round-trip decode failed");
        assert!(decoded.security_classification.is_none());
        assert!(decoded.privacy_mark.is_none());
    }

    #[test]
    fn ess_security_label_with_classification() {
        let policy = &[1u32, 3, 6, 1, 5, 5, 7, 13, 1];
        let der = ESSSecurityLabelBuilder::new()
            .security_policy(policy)
            .classification(SecurityClassification::SECRET)
            .privacy_mark_utf8("SECRET")
            .build()
            .expect("build with classification should succeed");

        let decoded =
            crate::ess_types::ESSSecurityLabel::from_der(&der).expect("round-trip decode failed");
        assert_eq!(
            decoded.security_classification.map(|c| c.get()),
            Some(SecurityClassification::SECRET)
        );
    }

    #[test]
    fn receipt_request_empty_receipts_to_returns_error() {
        // M6: at least one receiptsTo entry must be present
        let err = ReceiptRequestBuilder::new()
            .signed_content_identifier(b"\x01\x02")
            .receipts_from_all()
            .build();
        assert!(err.is_err());
        assert!(err.unwrap_err().contains("receiptsTo"));
    }

    #[test]
    fn ess_security_label_requires_policy() {
        let err = ESSSecurityLabelBuilder::new().build();
        assert!(err.is_err());
        assert!(err.unwrap_err().contains("security_policy"));
    }

    #[test]
    fn ess_security_label_classification_out_of_range() {
        // M1: values above 32767 must be rejected
        let policy = &[1u32, 3, 6, 1, 5, 5, 7, 13, 1];
        let err = ESSSecurityLabelBuilder::new()
            .security_policy(policy)
            .classification(32768)
            .build();
        assert!(err.is_err());
        assert!(err.unwrap_err().contains("32767"));
    }

    #[test]
    fn ess_security_label_privacy_mark_printable_encodes_correctly() {
        // H1: privacy_mark_printable must produce a PrintableString-tagged field
        let policy = &[1u32, 3, 6, 1, 5, 5, 7, 13, 1];
        let der = ESSSecurityLabelBuilder::new()
            .security_policy(policy)
            .privacy_mark_printable("SECRET")
            .build()
            .expect("build with PrintableString mark should succeed");

        let decoded =
            crate::ess_types::ESSSecurityLabel::from_der(&der).expect("round-trip decode failed");
        assert!(
            matches!(
                decoded.privacy_mark,
                Some(crate::ess_types::ESSPrivacyMark::PString(_))
            ),
            "expected PString variant, got {:?}",
            decoded.privacy_mark
        );
    }
}