//! The revset query language

//!

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

use crate::repo::Repo;

use crate::revlog::changelog::Changelog;

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

use crate::revlog::NodePrefix;

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

/// 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 = Changelog::open(repo)?;

    match resolve_rev_number_or_hex_prefix(input, &changelog.revlog) {

        Err(RevlogError::InvalidRevision) => {} // Try other syntax

        result => return result,

    }

    if input == "null" {

        return Ok(NULL_REVISION);

    }

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

}

/// 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> {

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

        if integer >= 0 && revlog.has_rev(integer) {

            return Ok(integer);

        }

    }

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

        return revlog.get_node_rev(prefix);

    }

    Err(RevlogError::InvalidRevision)

}