// ancestors.rs

//

// Copyright 2018 Georges Racinet <gracinet@anybox.fr>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

//! Bindings for the `hg::ancestors` module provided by the

//! `hg-core` crate. From Python, this will be seen as `rustext.ancestor`

//! and can be used as replacement for the the pure `ancestor` Python module.

//!

//! # Classes visible from Python:

//! - [`LazyAncestors`] is the Rust implementation of

//!   `mercurial.ancestor.lazyancestors`. The only difference is that it is

//!   instantiated with a C `parsers.index` instance instead of a parents

//!   function.

//!

//! - [`MissingAncestors`] is the Rust implementation of

//!   `mercurial.ancestor.incrementalmissingancestors`.

//!

//!   API differences:

//!    + it is instantiated with a C `parsers.index`

//!      instance instead of a parents function.

//!    + `MissingAncestors.bases` is a method returning a tuple instead of

//!      a set-valued attribute. We could return a Python set easily if our

//!      [PySet PR](https://github.com/dgrunwald/rust-cpython/pull/165)

//!      is accepted.

//!

//! - [`AncestorsIterator`] is the Rust counterpart of the

//!   `ancestor._lazyancestorsiter` Python generator. From Python, instances of

//!   this should be mainly obtained by calling `iter()` on a [`LazyAncestors`]

//!   instance.

//!

//! [`LazyAncestors`]: struct.LazyAncestors.html

//! [`MissingAncestors`]: struct.MissingAncestors.html

//! [`AncestorsIterator`]: struct.AncestorsIterator.html

use crate::{

    cindex::Index,

    conversion::{py_set, rev_pyiter_collect},

    exceptions::GraphError,

};

use cpython::{

    ObjectProtocol, PyClone, PyDict, PyList, PyModule, PyObject, PyResult,

    Python, PythonObject, ToPyObject,

};

use hg::Revision;

use hg::{

    AncestorsIterator as CoreIterator, LazyAncestors as CoreLazy,

    MissingAncestors as CoreMissing,

};

use std::cell::RefCell;

use std::collections::HashSet;

py_class!(pub class AncestorsIterator |py| {

    data inner: RefCell<Box<CoreIterator<Index>>>;

    def __next__(&self) -> PyResult<Option<Revision>> {

        match self.inner(py).borrow_mut().next() {

            Some(Err(e)) => Err(GraphError::pynew(py, e)),

            None => Ok(None),

            Some(Ok(r)) => Ok(Some(r)),

        }

    }

    def __contains__(&self, rev: Revision) -> PyResult<bool> {

        self.inner(py).borrow_mut().contains(rev)

            .map_err(|e| GraphError::pynew(py, e))

    }

    def __iter__(&self) -> PyResult<Self> {

        Ok(self.clone_ref(py))

    }

    def __new__(_cls, index: PyObject, initrevs: PyObject, stoprev: Revision,

                inclusive: bool) -> PyResult<AncestorsIterator> {

        let initvec: Vec<Revision> = rev_pyiter_collect(py, &initrevs)?;

        let ait = CoreIterator::new(

            Index::new(py, index)?,

            initvec,

            stoprev,

            inclusive,

        )

        .map_err(|e| GraphError::pynew(py, e))?;

        AncestorsIterator::from_inner(py, ait)

    }

});

impl AncestorsIterator {

    pub fn from_inner(py: Python, ait: CoreIterator<Index>) -> PyResult<Self> {

        Self::create_instance(py, RefCell::new(Box::new(ait)))

    }

}

py_class!(pub class LazyAncestors |py| {

    data inner: RefCell<Box<CoreLazy<Index>>>;

    def __contains__(&self, rev: Revision) -> PyResult<bool> {

        self.inner(py)

            .borrow_mut()

            .contains(rev)

            .map_err(|e| GraphError::pynew(py, e))

    }

    def __iter__(&self) -> PyResult<AncestorsIterator> {

        AncestorsIterator::from_inner(py, self.inner(py).borrow().iter())

    }

    def __bool__(&self) -> PyResult<bool> {

        Ok(!self.inner(py).borrow().is_empty())

    }

    def __new__(_cls, index: PyObject, initrevs: PyObject, stoprev: Revision,

                inclusive: bool) -> PyResult<Self> {

        let initvec: Vec<Revision> = rev_pyiter_collect(py, &initrevs)?;

        let lazy =

            CoreLazy::new(Index::new(py, index)?, initvec, stoprev, inclusive)

                .map_err(|e| GraphError::pynew(py, e))?;

        Self::create_instance(py, RefCell::new(Box::new(lazy)))

        }

});

py_class!(pub class MissingAncestors |py| {

    data inner: RefCell<Box<CoreMissing<Index>>>;

    def __new__(_cls, index: PyObject, bases: PyObject) -> PyResult<MissingAncestors> {

        let bases_vec: Vec<Revision> = rev_pyiter_collect(py, &bases)?;

        let inner = CoreMissing::new(Index::new(py, index)?, bases_vec);

        MissingAncestors::create_instance(py, RefCell::new(Box::new(inner)))

    }

    def hasbases(&self) -> PyResult<bool> {

        Ok(self.inner(py).borrow().has_bases())

    }

    def addbases(&self, bases: PyObject) -> PyResult<PyObject> {

        let mut inner = self.inner(py).borrow_mut();

        let bases_vec: Vec<Revision> = rev_pyiter_collect(py, &bases)?;

        inner.add_bases(bases_vec);

        // cpython doc has examples with PyResult<()> but this gives me

        //   the trait `cpython::ToPyObject` is not implemented for `()`

        // so let's return an explicit None

        Ok(py.None())

    }

    def bases(&self) -> PyResult<PyObject> {

        py_set(py, self.inner(py).borrow().get_bases())

    }

    def basesheads(&self) -> PyResult<PyObject> {

        let inner = self.inner(py).borrow();

        py_set(py, &inner.bases_heads().map_err(|e| GraphError::pynew(py, e))?)

    }

    def removeancestorsfrom(&self, revs: PyObject) -> PyResult<PyObject> {

        let mut inner = self.inner(py).borrow_mut();

        // this is very lame: we convert to a Rust set, update it in place

        // and then convert back to Python, only to have Python remove the

        // excess (thankfully, Python is happy with a list or even an iterator)

        // Leads to improve this:

        //  - have the CoreMissing instead do something emit revisions to

        //    discard

        //  - define a trait for sets of revisions in the core and implement

        //    it for a Python set rewrapped with the GIL marker

        let mut revs_pyset: HashSet<Revision> = rev_pyiter_collect(py, &revs)?;

        inner.remove_ancestors_from(&mut revs_pyset)

            .map_err(|e| GraphError::pynew(py, e))?;

        // convert as Python list

        let mut remaining_pyint_vec: Vec<PyObject> = Vec::with_capacity(

            revs_pyset.len());

        for rev in revs_pyset {

            remaining_pyint_vec.push(rev.to_py_object(py).into_object());

        }

        let remaining_pylist = PyList::new(py, remaining_pyint_vec.as_slice());

        revs.call_method(py, "intersection_update", (remaining_pylist, ), None)

    }

    def missingancestors(&self, revs: PyObject) -> PyResult<PyList> {

        let mut inner = self.inner(py).borrow_mut();

        let revs_vec: Vec<Revision> = rev_pyiter_collect(py, &revs)?;

        let missing_vec = match inner.missing_ancestors(revs_vec) {

            Ok(missing) => missing,

            Err(e) => {

                return Err(GraphError::pynew(py, e));

            }

        };

        // convert as Python list

        let mut missing_pyint_vec: Vec<PyObject> = Vec::with_capacity(

            missing_vec.len());

        for rev in missing_vec {

            missing_pyint_vec.push(rev.to_py_object(py).into_object());

        }

        Ok(PyList::new(py, missing_pyint_vec.as_slice()))

    }

});

/// Create the module, with __package__ given from parent

pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {

    let dotted_name = &format!("{}.ancestor", package);

    let m = PyModule::new(py, dotted_name)?;

    m.add(py, "__package__", package)?;

    m.add(

        py,

        "__doc__",

        "Generic DAG ancestor algorithms - Rust implementation",

    )?;

    m.add_class::<AncestorsIterator>(py)?;

    m.add_class::<LazyAncestors>(py)?;

    m.add_class::<MissingAncestors>(py)?;

    let sys = PyModule::import(py, "sys")?;

    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;

    sys_modules.set_item(py, dotted_name, &m)?;

    // Example C code (see pyexpat.c and import.c) will "give away the

    // reference", but we won't because it will be consumed once the

    // Rust PyObject is dropped.

    Ok(m)

}