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// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2026 Praxis Contributors
//! Reserved internal header prefixes for proxy-owned routing metadata.
// -----------------------------------------------------------------------------
// Constants
// -----------------------------------------------------------------------------
/// Built-in reserved header prefixes for Praxis routing metadata.
///
/// Headers with these prefixes are proxy-internal metadata used for
/// body-derived routing decisions. Clients must not be able to inject
/// them directly, and they should not be forwarded to upstream
/// backends or mutated by external processors.
///
/// The `x-ext-protocol-*` and `x-ext-agent-*` prefixes are reserved
/// for the AI extension package (`praxis-ai`). They are stripped to
/// prevent clients from spoofing internal AI routing headers even
/// when the AI filters are not loaded.
///
/// ```
/// use praxis_core::reserved_headers::RESERVED_HEADER_PREFIXES;
///
/// assert!(
/// RESERVED_HEADER_PREFIXES
/// .iter()
/// .any(|p| "x-praxis-foo".starts_with(p))
/// );
/// assert!(
/// !RESERVED_HEADER_PREFIXES
/// .iter()
/// .any(|p| "x-custom-foo".starts_with(p))
/// );
/// ```
// TODO(#186) Spike: consider additive operator-managed reserved prefixes
// once the broader config model defines global vs listener/filter-chain
// scope and additive vs override semantics.
pub const RESERVED_HEADER_PREFIXES: & = &;
/// Return whether a header name matches any reserved prefix.
///
/// The comparison is ASCII case-insensitive. Every current caller passes an
/// [`http::HeaderName`] string, which is already lowercase, but matching
/// case-insensitively means a future caller handing this a raw config or user
/// string (e.g. `"X-Praxis-Route"`) cannot slip a reserved header past the
/// check.
///
/// ```
/// assert!(praxis_core::reserved_headers::is_reserved("x-praxis-route"));
/// assert!(praxis_core::reserved_headers::is_reserved("X-Praxis-Route"));
/// assert!(praxis_core::reserved_headers::is_reserved(
/// "x-ext-agent-task"
/// ));
/// assert!(!praxis_core::reserved_headers::is_reserved("authorization"));
/// ```
/// [RFC 9110] hop-by-hop headers: connection-specific headers that apply to a
/// single transport hop and must not be forwarded across a proxy boundary.
///
/// This is the canonical set shared by sub-request stripping in `praxis-core`
/// and the protocol request handlers in `praxis-protocol`, so the two cannot
/// drift. Response stripping uses this set minus `proxy-authorization`, which
/// is a request-only credential header.
///
/// [RFC 9110]: https://datatracker.ietf.org/doc/html/rfc9110
pub const HOP_BY_HOP_HEADERS: & = &;