path: root/crates/tor-netdoc/src/parse2.rs

//! New netdoc parsing arrangements, with `derive`
//!
//! # Parsing principles
//!
//! A parseable network document is a type implementing [`NetdocParseable`].
//! usually via the
//! [`NetdocParseable` derive=deftly macro`](crate::derive_deftly_template_NetdocParseable).
//!
//! A document type is responsible for recognising its own heading item.
//! Its parser will also be told other of structural items that it should not consume.
//! The structural lines can then be used to pass control to the appropriate parser.
//!
//! A "structural item" is a netdoc item that is defines the structure of the document.
//! This includes the intro items for whole documents,
//! the items that introduce document sections
//! (which we model by treating the section as a sub-document)
//! and signature items (which introduce the signatures at the end of the document,
//! and after which no non-signature items may appear).
//!
//! # Ordering
//!
//! We don't always parse things into a sorted order.
//! Sorting will be done when assembling documents, before outputting.
// TODO we don't implement deriving output yet.
//!
//! # Types, and signature handling
//!
//! Most top-level network documents are signed somehow.
//! In this case there are three types:
//!
//!   * **`FooUnverified`**: a signed `Foo`, with its signatures, not yet verified.
//!     Implements [`NetdocUnverified`],
//!     typically by invoking the
//!     [`NetdocUParseablenverified` derive macro](crate::derive_deftly_template_NetdocParseableUnverified)
//!     on `Foo`.
//!
//!     Type-specific methods are provided for verification,
//!     to obtain a `Foo`.
//!
//!   * **`Foo`**: the body data for the document.
//!     This doesn't contain any signatures.
//!     Having one of these to play with means signatures have already been validated.
//!     Can be parsed as part of the signed document,
//!     via the `NetdocParseable` implementation on `FooUnverified`,
//!     and then obtained via `.verify_...` method(s) on `FooUnverified`,
//!
//!   * **`FooSignatures`**: the signatures for a `Foo`.
//!     Implements `NetdocParseableSignatures`, via
//!     [derive](crate::derive_deftly_template_NetdocParseableSignatures),
//!     with `#[deftly(netdoc(signatures))]`.
//!
//! # Relationship to tor_netdoc::parse
//!
//! This is a completely new parsing approach, based on different principles.
//! The key principle is the recognition of "structural keywords",
//! recursively within a parsing stack, via the p`NetdocParseable`] trait.
//!
//! This allows the parser to be derived.  We have type-driven parsing
//! of whole Documents, Items, and their Arguments and Objects,
//! including of their multiplicity.
//!
//! The different keyword handling means we can't use most of the existing lexer,
//! and need new item parsing API:
//!
//!  * [`NetdocParseable`] trait.
//!  * [`KeywordRef`] type.
//!  * [`ItemStream`], [`UnparsedItem`], [`ArgumentStream`], [`UnparsedObject`].
//!
//! The different error handling means we have our own error types.
//! (The crate's existing parse errors have information that we don't track,
//! and is also a portmanteau error for parsing, writing, and other functions.)
//!
//! Document signing is handled in a more abstract way.
//!
//! Some old netdoc constructs are not supported.
//! For example, the obsolete `opt` prefix on safe-to-ignore Items.
//! The parser may make different decisions about netdocs with anomalous item ordering.

#[doc(hidden)]
#[macro_use]
pub mod internal_prelude;

#[macro_use]
mod structural;

#[macro_use]
mod derive;

mod error;
mod impls;
pub mod keyword;
mod lex;
mod lines;
pub mod multiplicity;
mod signatures;
mod traits;

#[cfg(feature = "incomplete")]
pub mod poc;

use internal_prelude::*;

pub use error::{ArgumentError, ErrorProblem, ParseError, UnexpectedArgument, VerifyFailed};
pub use impls::times::NdaSystemTimeDeprecatedSyntax;
pub use keyword::KeywordRef;
pub use lex::{ArgumentStream, ItemStream, NoFurtherArguments, UnparsedItem, UnparsedObject};
pub use lines::{Lines, Peeked, StrExt};
pub use signatures::{
    HasUnverifiedParsedBody, NetdocParseableSignatures, NetdocUnverified, SignatureHashInputs,
    SignatureHashesAccumulator, SignatureItemParseable, SignaturesData, check_validity_time,
    check_validity_time_tolerance, sig_hashes,
};
pub use structural::{StopAt, StopPredicate};
pub use traits::{
    IsStructural, ItemArgumentParseable, ItemObjectParseable, ItemValueParseable, NetdocParseable,
    NetdocParseableFields,
};

#[doc(hidden)]
pub use derive::netdoc_parseable_derive_debug;

pub(crate) use internal_prelude::EP;

//---------- input ----------

/// Options for parsing
///
/// Specific document and type parsing methods may use these parameters
/// to control their parsing behaviour at run-time.
#[derive(educe::Educe, Debug, Clone)]
#[allow(clippy::manual_non_exhaustive)]
#[educe(Default)]
pub struct ParseOptions {
    /// Retain unknown values?
    ///
    /// Some field types, especially for flags fields, have the capability to retain
    /// unknown flags.  But, whereas known flags can be represented as single bits,
    /// representing unknown flags involves allocating and copying strings.
    /// Unless the document is to be reproduced, this is a waste of effort.
    ///
    /// Each document field type affected by this option should store the unknowns
    /// as `Unknown<HashSet<String>>` or similar.
    ///
    /// This feature should only be used where performance is important.
    /// For example, it is useful for types that appear in md consensus routerdescs,
    /// but less useful for types that appear only in a netstatus preamble.
    ///
    /// This is currently used for router flags.
    #[educe(Default(expression = "Unknown::new_discard()"))]
    pub retain_unknown_values: Unknown<()>,

    // Like `#[non_exhaustive]`, but doesn't prevent use of struct display syntax with `..`
    #[doc(hidden)]
    _private_non_exhaustive: (),
}

/// Input to a network document top-level parsing operation
pub struct ParseInput<'s> {
    /// The actual document text
    input: &'s str,
    /// Filename (for error reporting)
    file: &'s str,
    /// Parsing options
    options: ParseOptions,
}

impl<'s> ParseInput<'s> {
    /// Prepare to parse an input string
    pub fn new(input: &'s str, file: &'s str) -> Self {
        ParseInput {
            input,
            file,
            options: ParseOptions::default(),
        }
    }
}

//---------- parser ----------

/// Common code for `parse_netdoc` and `parse_netdoc_multiple`
///
/// Creates the `ItemStream`, calls `parse_completely`, and handles errors.
fn parse_internal<T, D: NetdocParseable>(
    input: &ParseInput<'_>,
    parse_completely: impl FnOnce(&mut ItemStream) -> Result<T, ErrorProblem>,
) -> Result<T, ParseError> {
    let mut items = ItemStream::new(input)?;
    parse_completely(&mut items).map_err(|problem| ParseError {
        problem,
        doctype: D::doctype_for_error(),
        file: input.file.to_owned(),
        lno: items.lno_for_error(),
        column: problem.column(),
    })
}

/// Parse a network document - **toplevel entrypoint**
pub fn parse_netdoc<D: NetdocParseable>(input: &ParseInput<'_>) -> Result<D, ParseError> {
    parse_internal::<_, D>(input, |items| {
        let doc = D::from_items(items, StopAt(false))?;
        if let Some(_kw) = items.peek_keyword()? {
            return Err(EP::MultipleDocuments);
        }
        Ok(doc)
    })
}

/// Parse multiple concatenated network documents - **toplevel entrypoint**
pub fn parse_netdoc_multiple<D: NetdocParseable>(
    input: &ParseInput<'_>,
) -> Result<Vec<D>, ParseError> {
    parse_internal::<_, D>(input, |items| {
        let mut docs = vec![];
        while items.peek_keyword()?.is_some() {
            let doc = D::from_items(items, StopAt(false))?;
            docs.push(doc);
        }
        Ok(docs)
    })
}

/// Parse multiple network documents, also returning their offsets  - **toplevel entrypoint**
///
/// Each returned document is accompanied by the byte offsets of its start and end.
///
/// (The netdoc metaformat does not allow anything in between subsequent documents in a file,
/// so the end of one document is the start of the next.)
///
/// This returns byte offsets rather than string slices,
/// because the caller can always convert the offsets into string slices,
/// but it is not straightforward to convert string slices borrowed from some input string
/// into offsets, in a way that is obviously correct without nightly `str::substr_range`.
///
/// Interfacing code can assume that slicing the input string with the returned
/// [`usize`] values will not cause an out-of-bounds error, meaning runtime
/// checks are not necessary there.
pub fn parse_netdoc_multiple_with_offsets<D: NetdocParseable>(
    input: &ParseInput<'_>,
) -> Result<Vec<(D, usize, usize)>, ParseError> {
    parse_internal::<_, D>(input, |items| {
        let mut docs = vec![];
        while items.peek_keyword()?.is_some() {
            let start_pos = items.byte_position();
            let doc = D::from_items(items, StopAt(false))?;
            let end_pos = items.byte_position();

            // Check start_pos and end_pos are in range.
            if input.input.get(start_pos..end_pos).is_none() {
                return Err(ErrorProblem::Internal("out-of-bounds bug?"));
            }

            docs.push((doc, start_pos, end_pos));
        }
        Ok(docs)
    })
}