//! The revset query language

//!

//! <https://www.mercurial-scm.org/repo/hg/help/revsets>

use crate::errors::HgError;

use crate::repo::Repo;

use crate::revlog::revlog::{Revlog, RevlogError};

use crate::revlog::NodePrefix;

use crate::revlog::{Revision, NULL_REVISION, WORKING_DIRECTORY_HEX};

use crate::Node;

/// Resolve a query string into a single revision.

///

/// Only some of the revset language is implemented yet.

pub fn resolve_single(

    input: &str,

    repo: &Repo,

) -> Result<Revision, RevlogError> {

    let changelog = repo.changelog()?;

    match input {

        "." => {

            let p1 = repo.dirstate_parents()?.p1;

            return Ok(changelog.revlog.rev_from_node(p1.into())?);

        }

        "null" => return Ok(NULL_REVISION),

        _ => {}

    }

    match resolve_rev_number_or_hex_prefix(input, &changelog.revlog) {

        Err(RevlogError::InvalidRevision) => {

            // TODO: support for the rest of the language here.

            let msg = format!("cannot parse revset '{}'", input);

            Err(HgError::unsupported(msg).into())

        }

        result => return result,

    }

}

/// Resolve the small subset of the language suitable for revlogs other than

/// the changelog, such as in `hg debugdata --manifest` CLI argument.

///

/// * A non-negative decimal integer for a revision number, or

/// * An hexadecimal string, for the unique node ID that starts with this

///   prefix

pub fn resolve_rev_number_or_hex_prefix(

    input: &str,

    revlog: &Revlog,

) -> Result<Revision, RevlogError> {

    // The Python equivalent of this is part of `revsymbol` in

    // `mercurial/scmutil.py`

    if let Ok(integer) = input.parse::<i32>() {

        if integer.to_string() == input

            && integer >= 0

            && revlog.has_rev(integer)

        {

            return Ok(integer);

        }

    }

    if let Ok(prefix) = NodePrefix::from_hex(input) {

        if prefix.is_prefix_of(&Node::from_hex(WORKING_DIRECTORY_HEX).unwrap())

        {

            return Err(RevlogError::WDirUnsupported);

        }

        return revlog.rev_from_node(prefix);

    }

    Err(RevlogError::InvalidRevision)

}