opentdf-protocol 0.16.0

//! TDF Manifest structures
//!
//! This module contains the data structures for TDF manifests, including:
//! - Payload information
//! - Encryption configuration
//! - Key access objects
//! - Integrity information (segments and root signature)
//! - Assertions (statement + binding)
//!
//! Note: Cryptographic operations (HMAC, policy binding generation) are in the crypto crate.

use serde::{Deserialize, Serialize};

/// The TDF spec version written into `schemaVersion` by every writer.
pub const TDF_SPEC_VERSION: &str = "4.3.0";

/// TDF manifest structure
#[derive(Debug, Serialize, Deserialize)]
pub struct TdfManifest {
    pub payload: Payload,
    #[serde(rename = "encryptionInformation")]
    pub encryption_information: EncryptionInformation,
    #[serde(rename = "schemaVersion", skip_serializing_if = "Option::is_none")]
    pub schema_version: Option<String>,
    /// OpenTDF specification version. Omitted by default so existing
    /// manifests serialize unchanged; the `gguf-tdf/1` writer sets it.
    #[serde(rename = "tdf_spec_version", skip_serializing_if = "Option::is_none")]
    pub tdf_spec_version: Option<String>,
    /// `gguf-tdf/1` hybrid index. Absent for every other TDF profile.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub gguf: Option<crate::GgufIndex>,
    /// Optional top-level `assertions` array (spec: assertion.md). Empty
    /// when absent; omitted from JSON when empty so existing manifests
    /// serialize unchanged.
    #[serde(
        default,
        deserialize_with = "null_as_empty_vec",
        skip_serializing_if = "Vec::is_empty"
    )]
    pub assertions: Vec<Assertion>,
}

/// Accept `"assertions": null` (Jackson-style writers emit it for an empty
/// list) as an empty vector. `#[serde(default)]` alone covers only a missing key.
fn null_as_empty_vec<'de, D>(deserializer: D) -> Result<Vec<Assertion>, D::Error>
where
    D: serde::Deserializer<'de>,
{
    Ok(Option::<Vec<Assertion>>::deserialize(deserializer)?.unwrap_or_default())
}

/// A verifiable statement about the TDF or its payload (spec: assertion.md).
///
/// Field names and JSON shape match the OpenTDF spec and the Go SDK
/// (`sdk/assertion.go`).
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct Assertion {
    /// Unique identifier for this assertion within the manifest.
    pub id: String,
    /// Categorizes the assertion's purpose, e.g. `handling` or `other`.
    #[serde(rename = "type")]
    pub assertion_type: String,
    /// What the assertion applies to: `tdo` or `payload`.
    pub scope: String,
    /// Whether the statement applies to `encrypted` or `unencrypted` data.
    /// Optional in the spec (default `encrypted`); omitted when unset.
    #[serde(rename = "appliesToState", skip_serializing_if = "Option::is_none")]
    pub applies_to_state: Option<String>,
    /// The assertion content (spec: assertion_statement.md).
    pub statement: AssertionStatement,
    /// Cryptographic binding of the assertion to this TDF
    /// (spec: assertion_binding.md). Omitted when unsigned.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub binding: Option<AssertionBinding>,
}

/// The `statement` object of an assertion (spec: assertion_statement.md).
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct AssertionStatement {
    /// How `value` is encoded: `json-structured`, `base64binary`, `string`, ...
    #[serde(default, skip_serializing_if = "String::is_empty")]
    pub format: String,
    /// Optional URI identifying the schema of `value`.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub schema: Option<String>,
    /// The assertion content. Kept as raw JSON (string *or* structured
    /// object/array/number/bool) so it round-trips byte-for-byte for
    /// JCS hashing and never gets re-typed.
    #[serde(default, skip_serializing_if = "serde_json::Value::is_null")]
    pub value: serde_json::Value,
}

/// The `binding` object of an assertion (spec: assertion_binding.md).
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
///
/// Both fields default to empty so that `"binding": {}`, which the Go SDK
/// emits for an unsigned assertion (non-pointer struct with `omitempty`
/// string fields), parses and re-serializes unchanged.
pub struct AssertionBinding {
    /// Signature method, e.g. `jws`.
    #[serde(default, skip_serializing_if = "String::is_empty")]
    pub method: String,
    /// The Base64URL-encoded signature (e.g. a JWS compact serialization).
    #[serde(default, skip_serializing_if = "String::is_empty")]
    pub signature: String,
}

/// Payload reference in TDF manifest
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Payload {
    #[serde(rename = "type")]
    pub payload_type: String,
    pub url: String,
    pub protocol: String,
    #[serde(rename = "isEncrypted")]
    pub is_encrypted: bool,
    #[serde(rename = "mimeType", skip_serializing_if = "Option::is_none")]
    pub mime_type: Option<String>,
    #[serde(rename = "tdf_spec_version", skip_serializing_if = "Option::is_none")]
    pub tdf_spec_version: Option<String>,
}

impl Default for Payload {
    fn default() -> Self {
        Self {
            payload_type: "reference".to_string(),
            url: "0.payload".to_string(),
            protocol: "zip".to_string(),
            is_encrypted: true,
            mime_type: Some("application/octet-stream".to_string()),
            // Match go/Swift: version lives on root `schemaVersion`, not payload.
            // Emitting payload.tdf_spec_version breaks strict readers (e.g. otdf-python
            // ManifestPayload, which has no such field).
            tdf_spec_version: None,
        }
    }
}

/// Encryption information in TDF manifest
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct EncryptionInformation {
    #[serde(rename = "type")]
    pub encryption_type: String,
    #[serde(rename = "keyAccess")]
    pub key_access: Vec<KeyAccess>,
    pub method: EncryptionMethod,
    #[serde(rename = "integrityInformation")]
    pub integrity_information: IntegrityInformation,
    pub policy: String,
}

/// Policy binding structure
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct PolicyBinding {
    pub alg: String,
    pub hash: String,
}

/// Key access type constants for TDF3
pub mod key_access_type {
    /// Standard RSA-wrapped key (RSA-OAEP)
    pub const WRAPPED: &str = "wrapped";
    /// EC-wrapped key (ECIES: ECDH + HKDF + AES-GCM)
    pub const EC_WRAPPED: &str = "ec-wrapped";
    /// Remote key access (key stored on KAS)
    pub const REMOTE: &str = "remote";
    /// Remote wrapped key access
    pub const REMOTE_WRAPPED: &str = "remoteWrapped";
}

/// Key access object in manifest
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct KeyAccess {
    #[serde(rename = "type")]
    pub access_type: String,
    pub url: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub kid: Option<String>,
    /// Optional key split (share) identifier (spec: key_access_object.md `sid`).
    #[serde(skip_serializing_if = "Option::is_none")]
    pub sid: Option<String>,
    pub protocol: String,
    #[serde(rename = "wrappedKey")]
    pub wrapped_key: String,
    #[serde(rename = "policyBinding")]
    pub policy_binding: PolicyBinding,
    #[serde(rename = "encryptedMetadata", skip_serializing_if = "Option::is_none")]
    pub encrypted_metadata: Option<String>,
    #[serde(rename = "schemaVersion", skip_serializing_if = "Option::is_none")]
    pub schema_version: Option<String>,
    /// Ephemeral public key for EC-wrapped keys (PEM format)
    #[serde(rename = "ephemeralPublicKey", skip_serializing_if = "Option::is_none")]
    pub ephemeral_public_key: Option<String>,
}

impl KeyAccess {
    /// Creates a new KeyAccess object with default values (RSA-wrapped)
    pub fn new(url: String) -> Self {
        KeyAccess {
            access_type: key_access_type::WRAPPED.to_string(),
            url,
            kid: None,
            sid: None,
            protocol: "kas".to_string(),
            wrapped_key: String::new(),
            policy_binding: PolicyBinding {
                alg: "HS256".to_string(),
                hash: String::new(),
            },
            encrypted_metadata: None,
            schema_version: Some("1.0".to_string()),
            ephemeral_public_key: None,
        }
    }

    /// Creates a new KeyAccess object for EC-wrapped keys
    pub fn new_ec_wrapped(url: String) -> Self {
        KeyAccess {
            access_type: key_access_type::EC_WRAPPED.to_string(),
            url,
            kid: None,
            sid: None,
            protocol: "kas".to_string(),
            wrapped_key: String::new(),
            policy_binding: PolicyBinding {
                alg: "HS256".to_string(),
                hash: String::new(),
            },
            encrypted_metadata: None,
            schema_version: Some("1.0".to_string()),
            ephemeral_public_key: None,
        }
    }

    /// Check if this key access uses EC wrapping
    pub fn is_ec_wrapped(&self) -> bool {
        self.access_type == key_access_type::EC_WRAPPED
    }

    /// Check if this key access uses RSA wrapping
    pub fn is_rsa_wrapped(&self) -> bool {
        self.access_type == key_access_type::WRAPPED
    }

    /// Set the ephemeral public key (for EC-wrapped keys)
    pub fn set_ephemeral_public_key(&mut self, pem: String) {
        self.ephemeral_public_key = Some(pem);
    }
}

/// Encryption method configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct EncryptionMethod {
    pub algorithm: String,
    /// Spec: required. Pre-4.3.0 Java manifests omit it; default false.
    #[serde(rename = "isStreamable", default)]
    pub is_streamable: bool,
    /// Spec prose: required. Every streaming SDK carries per-segment IVs in
    /// the payload and writes `""` or omits the field (Java), so it defaults
    /// to empty on read.
    #[serde(default)]
    pub iv: String,
}

impl Default for EncryptionMethod {
    fn default() -> Self {
        Self {
            algorithm: "AES-256-GCM".to_string(),
            is_streamable: true,
            iv: String::new(),
        }
    }
}

/// Integrity information including segments and root signature
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct IntegrityInformation {
    #[serde(rename = "rootSignature")]
    pub root_signature: RootSignature,
    #[serde(rename = "segmentHashAlg")]
    pub segment_hash_alg: String,
    pub segments: Vec<Segment>,
    #[serde(rename = "segmentSizeDefault")]
    pub segment_size_default: u64,
    #[serde(rename = "encryptedSegmentSizeDefault")]
    pub encrypted_segment_size_default: u64,
}

impl Default for IntegrityInformation {
    fn default() -> Self {
        Self {
            root_signature: RootSignature::default(),
            segment_hash_alg: "GMAC".to_string(),
            segments: Vec::new(),
            segment_size_default: 1024 * 1024,                // 1MB
            encrypted_segment_size_default: 1024 * 1024 + 28, // +IV+tag
        }
    }
}

impl IntegrityInformation {
    /// Resolve every segment's `(plaintext_size, encrypted_size)`.
    ///
    /// Spec (integrity_information.md): `segmentSize` and
    /// `encryptedSegmentSize` are optional on a segment and are inferred from
    /// `segmentSizeDefault` / `encryptedSegmentSizeDefault` when omitted.
    pub fn segment_sizes(&self) -> Vec<(u64, u64)> {
        self.segments
            .iter()
            .map(|s| {
                (
                    s.segment_size.unwrap_or(self.segment_size_default),
                    s.encrypted_segment_size
                        .unwrap_or(self.encrypted_segment_size_default),
                )
            })
            .collect()
    }
}

/// Root signature for integrity verification
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RootSignature {
    pub alg: String,
    pub sig: String,
}

impl Default for RootSignature {
    fn default() -> Self {
        Self {
            alg: "HS256".to_string(),
            sig: String::new(),
        }
    }
}

/// Segment information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Segment {
    pub hash: String,
    #[serde(rename = "segmentSize", skip_serializing_if = "Option::is_none")]
    pub segment_size: Option<u64>,
    #[serde(
        rename = "encryptedSegmentSize",
        skip_serializing_if = "Option::is_none"
    )]
    pub encrypted_segment_size: Option<u64>,
}

impl TdfManifest {
    /// Creates a new TDF manifest with basic structure
    pub fn new(payload_url: String, kas_url: String) -> Self {
        TdfManifest {
            payload: Payload {
                payload_type: "reference".to_string(),
                url: payload_url,
                protocol: "zip".to_string(),
                is_encrypted: true,
                mime_type: Some("application/octet-stream".to_string()),
                // Omit by default — go/Swift only set root schemaVersion.
                tdf_spec_version: None,
            },
            encryption_information: EncryptionInformation {
                encryption_type: "split".to_string(),
                key_access: vec![KeyAccess::new(kas_url)],
                method: EncryptionMethod {
                    algorithm: "AES-256-GCM".to_string(),
                    is_streamable: true,
                    iv: String::new(),
                },
                integrity_information: IntegrityInformation {
                    root_signature: RootSignature {
                        alg: "HS256".to_string(),
                        sig: String::new(),
                    },
                    segment_hash_alg: "GMAC".to_string(),
                    segments: Vec::new(),
                    segment_size_default: 1024 * 1024, // 1MB default
                    encrypted_segment_size_default: 1024 * 1024 + 28, // +IV+tag
                },
                policy: String::new(),
            },
            schema_version: Some(TDF_SPEC_VERSION.to_string()),
            tdf_spec_version: None,
            gguf: None,
            assertions: Vec::new(),
        }
    }

    /// Resolve the spec version a peer wrote, in priority order:
    /// root `schemaVersion` (what every SDK writes), then root `tdf_spec_version`
    /// (spec prose), then `payload.tdf_spec_version` (spec JSON schema).
    pub fn spec_version(&self) -> Option<&str> {
        [
            self.schema_version.as_deref(),
            self.tdf_spec_version.as_deref(),
            self.payload.tdf_spec_version.as_deref(),
        ]
        .into_iter()
        .flatten()
        .find(|v| !v.is_empty())
    }

    /// Set the policy for the manifest using a raw string
    pub fn set_policy_raw(&mut self, policy: &str) {
        use base64::{Engine as _, engine::general_purpose::STANDARD as BASE64};
        self.encryption_information.policy = BASE64.encode(policy);
    }

    /// Get the decoded policy from the manifest as a raw string
    pub fn get_policy_raw(&self) -> Result<String, base64::DecodeError> {
        use base64::{Engine as _, engine::general_purpose::STANDARD as BASE64};
        let bytes = BASE64.decode(&self.encryption_information.policy)?;
        String::from_utf8(bytes)
            .map_err(|err| base64::DecodeError::InvalidByte(err.utf8_error().valid_up_to(), 0))
    }

    /// Add a segment to the manifest
    pub fn add_segment(
        &mut self,
        hash: String,
        segment_size: Option<u64>,
        encrypted_segment_size: Option<u64>,
    ) {
        self.encryption_information
            .integrity_information
            .segments
            .push(Segment {
                hash,
                segment_size,
                encrypted_segment_size,
            });
    }

    /// Serialize to JSON
    pub fn to_json(&self) -> Result<String, serde_json::Error> {
        serde_json::to_string(self)
    }

    /// Deserialize from JSON
    pub fn from_json(json: &str) -> Result<Self, serde_json::Error> {
        serde_json::from_str(json)
    }
}

impl KeyAccess {
    /// Set encrypted metadata
    pub fn set_encrypted_metadata(&mut self, metadata: &str) {
        use base64::{Engine as _, engine::general_purpose::STANDARD as BASE64};
        self.encrypted_metadata = Some(BASE64.encode(metadata));
    }

    /// Clear encrypted metadata
    pub fn clear_encrypted_metadata(&mut self) {
        self.encrypted_metadata = None;
    }
}

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

    #[test]
    fn gguf_index_round_trips_and_stays_absent_by_default() {
        // Existing manifests must serialize unchanged: no new keys appear.
        let plain = TdfManifest::new(
            "0.payload".to_string(),
            "https://kas.example.com".to_string(),
        );
        let value: serde_json::Value = serde_json::from_str(&plain.to_json().unwrap()).unwrap();
        assert!(
            value.get("gguf").is_none(),
            "gguf must be absent when unset: {value}"
        );
        assert!(
            value.get("tdf_spec_version").is_none(),
            "tdf_spec_version must be absent when unset: {value}"
        );

        // The gguf-tdf/1 writer sets both and they round-trip.
        let mut m = TdfManifest::new("header".to_string(), "https://kas.example.com".to_string());
        m.tdf_spec_version = Some("4.3.0".to_string());
        m.gguf = Some(crate::GgufIndex {
            profile: crate::GGUF_TDF_PROFILE_V1.to_string(),
            alignment: 32,
            header_bytes: 64,
            virtual_size: 352,
            max_segment: 128,
            tensors: vec![crate::GgufTensor {
                name: "token_embd.weight".to_string(),
                offset: 64,
                size: 256,
                segments: [1, 3],
            }],
            segments: vec![crate::GgufSegment {
                id: 0,
                kind: crate::GgufSegmentKind::Header,
                plain: 64,
                entry: "header".to_string(),
            }],
        });

        let json = m.to_json().unwrap();
        let value: serde_json::Value = serde_json::from_str(&json).unwrap();
        assert_eq!(value["tdf_spec_version"], "4.3.0");
        assert_eq!(value["gguf"]["profile"], "gguf-tdf/1");
        assert_eq!(value["gguf"]["headerBytes"], 64);
        assert_eq!(value["gguf"]["maxSegment"], 128);
        assert_eq!(value["gguf"]["segments"][0]["kind"], "header");
        assert_eq!(value["gguf"]["tensors"][0]["segments"][1], 3);

        let back = TdfManifest::from_json(&json).unwrap();
        assert_eq!(back.gguf.as_ref().unwrap().virtual_size, 352);
        assert_eq!(back.tdf_spec_version.as_deref(), Some("4.3.0"));
    }
}

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

    fn minimal_json(top: &str, payload_extra: &str) -> String {
        format!(
            r#"{{
            "payload": {{"type":"reference","url":"0.payload","protocol":"zip","isEncrypted":true{payload_extra}}},
            "encryptionInformation": {{
                "type":"split","keyAccess":[],
                "method":{{"algorithm":"AES-256-GCM","isStreamable":true,"iv":""}},
                "integrityInformation":{{"rootSignature":{{"alg":"HS256","sig":""}},"segmentHashAlg":"GMAC","segments":[],"segmentSizeDefault":0,"encryptedSegmentSizeDefault":0}},
                "policy":""
            }}{top}
        }}"#
        )
    }

    #[test]
    fn spec_version_prefers_schema_version() {
        let m = TdfManifest::from_json(&minimal_json(
            r#","schemaVersion":"4.3.0","tdf_spec_version":"9.9.9""#,
            r#","tdf_spec_version":"8.8.8""#,
        ))
        .unwrap();
        assert_eq!(m.spec_version(), Some("4.3.0"));
    }

    #[test]
    fn spec_version_then_top_level_tdf_spec_version() {
        let m = TdfManifest::from_json(&minimal_json(
            r#","tdf_spec_version":"9.9.9""#,
            r#","tdf_spec_version":"8.8.8""#,
        ))
        .unwrap();
        assert_eq!(m.spec_version(), Some("9.9.9"));
    }

    #[test]
    fn spec_version_then_payload_tdf_spec_version() {
        let m =
            TdfManifest::from_json(&minimal_json("", r#","tdf_spec_version":"8.8.8""#)).unwrap();
        assert_eq!(m.spec_version(), Some("8.8.8"));
    }

    #[test]
    fn spec_version_absent_is_none() {
        let m = TdfManifest::from_json(&minimal_json("", "")).unwrap();
        assert_eq!(m.spec_version(), None);
    }

    #[test]
    fn new_manifest_writes_schema_version_4_3_0_and_no_tdf_spec_version() {
        let m = TdfManifest::new(
            "0.payload".to_string(),
            "https://kas.example.com".to_string(),
        );
        let v: serde_json::Value = serde_json::from_str(&m.to_json().unwrap()).unwrap();
        assert_eq!(v["schemaVersion"], TDF_SPEC_VERSION);
        assert_eq!(v["schemaVersion"], "4.3.0");
        assert!(v.get("tdf_spec_version").is_none());
        assert!(v["payload"].get("tdf_spec_version").is_none());
    }
}

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

    /// Java SDK manifests omit `method.iv` (and the oldest omit `isStreamable`).
    #[test]
    fn method_without_iv_or_is_streamable_parses() {
        let m: EncryptionMethod = serde_json::from_str(r#"{"algorithm":"AES-256-GCM"}"#).unwrap();
        assert_eq!(m.algorithm, "AES-256-GCM");
        assert!(!m.is_streamable);
        assert_eq!(m.iv, "");

        let m: EncryptionMethod =
            serde_json::from_str(r#"{"algorithm":"AES-256-GCM","isStreamable":true}"#).unwrap();
        assert!(m.is_streamable);
        assert_eq!(m.iv, "");
    }
}

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

    /// Manifest carrying `keyAccess[].sid` and one assertion whose
    /// `statement.value` is a structured JSON object (spec: assertion_statement.md).
    const MANIFEST_WITH_SID_AND_ASSERTION: &str = r#"{
        "payload": {"type":"reference","url":"0.payload","protocol":"zip","isEncrypted":true,"mimeType":"text/plain"},
        "encryptionInformation": {
            "type":"split",
            "keyAccess":[{
                "type":"wrapped",
                "url":"https://kas.example.com",
                "kid":"r1",
                "sid":"split-id-1",
                "protocol":"kas",
                "wrappedKey":"AAAA",
                "policyBinding":{"alg":"HS256","hash":"BBBB"}
            }],
            "method":{"algorithm":"AES-256-GCM","isStreamable":true,"iv":""},
            "integrityInformation":{"rootSignature":{"alg":"HS256","sig":""},"segmentHashAlg":"GMAC","segments":[],"segmentSizeDefault":0,"encryptedSegmentSizeDefault":0},
            "policy":""
        },
        "assertions":[{
            "id":"nato-label-1",
            "type":"handling",
            "scope":"payload",
            "appliesToState":"encrypted",
            "statement":{
                "schema":"urn:nato:stanag:4774:confidentialitymetadatalabel:1:0",
                "format":"json-structured",
                "value":{
                    "Xmlns":"urn:nato:stanag:4774:confidentialitymetadatalabel:1:0",
                    "CreationTime":"2015-08-29T16:15:00Z",
                    "ConfidentialityInformation":{"PolicyIdentifier":"NATO","Classification":"SECRET","nested":[1,true,null,{"k":"v"}]}
                }
            },
            "binding":{"method":"jws","signature":"eyJhbGciOiJSUzI1NiJ9.e30.sig"}
        }],
        "schemaVersion":"4.3.0"
    }"#;

    #[test]
    fn manifest_round_trips_key_access_sid_and_assertions() {
        let input: serde_json::Value =
            serde_json::from_str(MANIFEST_WITH_SID_AND_ASSERTION).unwrap();

        let m = TdfManifest::from_json(MANIFEST_WITH_SID_AND_ASSERTION).unwrap();

        // Typed access documents the intent, not just Value equality.
        assert_eq!(
            m.encryption_information.key_access[0].sid.as_deref(),
            Some("split-id-1")
        );
        assert_eq!(m.assertions.len(), 1);
        let a = &m.assertions[0];
        assert_eq!(a.id, "nato-label-1");
        assert_eq!(a.assertion_type, "handling");
        assert_eq!(a.scope, "payload");
        assert_eq!(a.applies_to_state.as_deref(), Some("encrypted"));
        assert_eq!(a.statement.format, "json-structured");
        assert_eq!(
            a.statement.schema.as_deref(),
            Some("urn:nato:stanag:4774:confidentialitymetadatalabel:1:0")
        );
        assert!(
            a.statement.value.is_object(),
            "statement.value must stay structured JSON: {:?}",
            a.statement.value
        );
        let b = a.binding.as_ref().expect("binding present");
        assert_eq!(b.method, "jws");
        assert_eq!(b.signature, "eyJhbGciOiJSUzI1NiJ9.e30.sig");

        // Re-serialize: nothing dropped, nothing invented.
        let output: serde_json::Value = serde_json::from_str(&m.to_json().unwrap()).unwrap();
        assert_eq!(output, input);
    }

    #[test]
    fn manifest_with_string_statement_value_round_trips() {
        let json = MANIFEST_WITH_SID_AND_ASSERTION
            .replace(r#""format":"json-structured","#, r#""format":"string","#);
        // Swap the object value for a plain string value.
        let mut input: serde_json::Value = serde_json::from_str(&json).unwrap();
        input["assertions"][0]["statement"]["value"] =
            serde_json::Value::String("plain text".into());

        let m: TdfManifest = serde_json::from_value(input.clone()).unwrap();
        assert_eq!(
            m.assertions[0].statement.value,
            serde_json::json!("plain text")
        );

        let output = serde_json::to_value(&m).unwrap();
        assert_eq!(output, input);
    }

    #[test]
    fn manifest_without_sid_or_assertions_serializes_unchanged() {
        // Existing manifests (no sid, no assertions) must not grow new keys.
        let m = TdfManifest::new(
            "0.payload".to_string(),
            "https://kas.example.com".to_string(),
        );
        assert!(m.encryption_information.key_access[0].sid.is_none());
        assert!(m.assertions.is_empty());

        let v: serde_json::Value = serde_json::from_str(&m.to_json().unwrap()).unwrap();
        assert!(v.get("assertions").is_none(), "{v}");
        assert!(
            v["encryptionInformation"]["keyAccess"][0]
                .get("sid")
                .is_none(),
            "{v}"
        );

        // And a peer manifest that omits both still parses (serde default).
        let json = MANIFEST_WITH_SID_AND_ASSERTION.replace(r#""sid":"split-id-1","#, "");
        let mut without: serde_json::Value = serde_json::from_str(&json).unwrap();
        without.as_object_mut().unwrap().remove("assertions");
        let m: TdfManifest = serde_json::from_value(without).unwrap();
        assert!(m.assertions.is_empty());
        assert!(m.encryption_information.key_access[0].sid.is_none());
    }

    /// Jackson-style writers serialize an empty list as `null`. serde's
    /// `default` covers only a missing key, so this must be handled explicitly.
    #[test]
    fn assertions_null_parses_as_empty() {
        let json = r#"{
            "payload": {"type":"reference","url":"0.payload","protocol":"zip","isEncrypted":true},
            "encryptionInformation": {
                "type":"split",
                "keyAccess":[],
                "method":{"algorithm":"AES-256-GCM","isStreamable":true,"iv":""},
                "integrityInformation":{"rootSignature":{"alg":"HS256","sig":""},"segmentHashAlg":"GMAC","segments":[],"segmentSizeDefault":0,"encryptedSegmentSizeDefault":0},
                "policy":""
            },
            "assertions": null
        }"#;
        let m = TdfManifest::from_json(json).expect("null assertions must parse");
        assert!(m.assertions.is_empty());
    }

    /// Go's `Assertion.Binding` is a non-pointer struct with `omitempty` on its
    /// string fields, so an unsigned assertion serializes as `"binding": {}`.
    #[test]
    fn unsigned_assertion_with_empty_binding_object_parses_and_round_trips() {
        let json = r#"{"id":"a1","type":"handling","scope":"payload","statement":{"format":"string","value":"x"},"binding":{}}"#;
        let a: Assertion = serde_json::from_str(json).expect("empty binding object must parse");
        let binding = a.binding.as_ref().expect("binding object is present");
        assert_eq!(binding.method, "");
        assert_eq!(binding.signature, "");

        let out = serde_json::to_value(&a).unwrap();
        assert_eq!(
            out,
            serde_json::from_str::<serde_json::Value>(json).unwrap()
        );
    }
}

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

    #[test]
    fn segment_sizes_fall_back_to_integrity_defaults_when_omitted() {
        let mut info = IntegrityInformation {
            segment_size_default: 1000,
            encrypted_segment_size_default: 1028,
            ..IntegrityInformation::default()
        };
        // Spec (integrity_information.md): segmentSize / encryptedSegmentSize are
        // optional and inferred from the *Default values when omitted.
        info.segments.push(Segment {
            hash: "a".into(),
            segment_size: None,
            encrypted_segment_size: None,
        });
        // Explicit values always win (a re-encrypted or short tail segment).
        info.segments.push(Segment {
            hash: "b".into(),
            segment_size: Some(7),
            encrypted_segment_size: Some(35),
        });
        // Mixed: only one side omitted.
        info.segments.push(Segment {
            hash: "c".into(),
            segment_size: Some(1000),
            encrypted_segment_size: None,
        });

        assert_eq!(
            info.segment_sizes(),
            vec![(1000, 1028), (7, 35), (1000, 1028)]
        );
    }
}