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// =============================================================================
// Copyright (c) 2026 Haixing Hu.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Structured serialization for maps with explicitly sensitive keys.
use std::borrow::Cow;
use std::collections::BTreeMap;
use std::collections::HashMap;
use std::collections::HashSet;
use serde::Serialize;
use serde::Serializer;
use serde::ser::Error as _;
use serde::ser::SerializeMap;
use super::RedactLevelSerialize;
use super::RedactedLevelSerializeRef;
use super::budget_serialize::BudgetSerialize;
use super::key_payload::KeyPayload;
use super::redact_serialize_scope::admit_collection_items;
use super::redact_serialize_scope::admit_input;
use super::redact_serialize_scope::remaining_payload_bytes;
use crate::RedactionPolicy;
use crate::Sensitivity;
/// Internal structured serialization capability for sensitive map keys.
#[doc(hidden)]
pub trait RedactMapKeySerialize {
/// Serializes masked keys and rejects collisions introduced by masking.
///
/// `Some(value_level)` applies that explicit level to values; `None`
/// preserves their ordinary representation under the shared budget.
///
/// # Errors
///
/// Returns key collision, admission, or downstream serialization errors.
///
/// # Type Parameters
///
/// - `S`: Downstream serializer defining the success and error types.
///
/// # Parameters
///
/// - `serializer`: Destination receiving the map with admitted,
/// collision-free keys.
/// - `policy`: Immutable policy controlling redaction and resource limits.
/// - `key_level`: Explicit sensitivity applied to each map key.
/// - `value_level`: Some level applies explicit leaf masking; None uses
/// ordinary budgeted serialization.
///
/// # Returns
///
/// The destination result after all emitted data passes shared admission.
fn serialize_redacted_map_keys<S>(
&self,
serializer: S,
policy: &RedactionPolicy,
key_level: Sensitivity,
value_level: Option<Sensitivity>,
) -> Result<S::Ok, S::Error>
where
S: Serializer;
}
/// Generates sensitive-key serialization with payload admission and collision
/// checks.
macro_rules! map_key_serialize {
($map:ty) => {
impl<K, V> RedactMapKeySerialize for $map
where
K: AsRef<str>,
V: Serialize + RedactLevelSerialize,
{
/// Masks admitted keys, rejects collisions, and serializes values
/// under one scope.
///
/// # Errors
///
/// Returns key collision, admission, or downstream serializer
/// errors.
///
/// # Type Parameters
///
/// - `S`: Downstream serializer defining the success and error types.
///
/// # Parameters
///
/// - `serializer`: Destination receiving the map with admitted,
/// collision-free keys.
/// - `policy`: Immutable policy controlling redaction and resource limits.
/// - `key_level`: Explicit sensitivity applied to each map key.
/// - `value_level`: Some level applies explicit leaf masking; None uses
/// ordinary budgeted serialization.
///
/// # Returns
///
/// The destination result after all emitted data passes shared
/// admission.
fn serialize_redacted_map_keys<S>(
&self,
serializer: S,
policy: &RedactionPolicy,
key_level: Sensitivity,
value_level: Option<Sensitivity>,
) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
if !admit_collection_items(self.len()) {
return super::redact_serialize_scope::serialize_payload(
serializer,
policy.masking().mask_opaque(Sensitivity::Secret).as_ref(),
);
}
let mut output = serializer.serialize_map(Some(self.len()))?;
let mut emitted = HashSet::new();
for (key, value) in self {
let key = if !policy.is_disabled() && key_level >= Sensitivity::High {
Cow::Borrowed(policy.masking().mask_opaque(key_level))
} else {
let raw = key.as_ref();
if !admit_input(raw.len()) {
return Err(S::Error::custom("redaction map key input budget exceeded"));
}
if policy.is_disabled() {
Cow::Borrowed(raw)
} else {
let (masked, truncated) = policy.masking().mask_bounded_with_truncation(
key_level,
raw,
remaining_payload_bytes(),
);
if truncated {
return Err(S::Error::custom("redaction map key payload budget exceeded"));
}
masked
}
};
if key.len() > remaining_payload_bytes() {
return Err(S::Error::custom("redaction map key payload budget exceeded"));
}
if !emitted.insert(key.to_string()) {
return Err(S::Error::custom("redacted map keys collide"));
}
if let Some(level) = value_level {
output.serialize_entry(
&KeyPayload(&key),
&RedactedLevelSerializeRef::new(value, policy, level),
)?;
} else {
output.serialize_entry(&KeyPayload(&key), &BudgetSerialize::new(value))?;
}
}
output.end()
}
}
};
}
map_key_serialize!(HashMap<K, V>);
map_key_serialize!(BTreeMap<K, V>);