// revlog.rs

//

// Copyright 2019-2020 Georges Racinet <georges.racinet@octobus.net>

//           2020-2024 Raphaël Gomès <raphael.gomes@octobus.net>

//           2024 Georges Racinet <georges.racinet@cloudcrane.io>

//

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

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

use pyo3::buffer::PyBuffer;

use pyo3::prelude::*;

use pyo3::types::{PyBytes, PyBytesMethods, PyList};

use pyo3_sharedref::PyShareable;

use hg::{

    revlog::{

        index::Index, inner_revlog::InnerRevlog as CoreInnerRevlog,

        nodemap::NodeTree as CoreNodeTree, options::RevlogOpenOptions,

        RevlogIndex, RevlogType,

    },

    utils::files::get_path_from_bytes,

    vfs::FnCacheVfs,

    BaseRevision, Revision,

};

use crate::{

    store::PyFnCache,

    util::{new_submodule, take_buffer_with_slice},

};

mod config;

use config::*;

#[pyclass]

#[allow(dead_code)]

struct InnerRevlog {

    irl: PyShareable<CoreInnerRevlog>,

    nt: RwLock<Option<CoreNodeTree>>,

    docket: Option<PyObject>,

    // Holds a reference to the mmap'ed persistent nodemap data

    nodemap_mmap: Option<PyBuffer<u8>>,

    // Holds a reference to the mmap'ed persistent index data

    index_mmap: Option<PyBuffer<u8>>,

    revision_cache: Option<PyObject>,

    head_revs_py_list: Option<Py<PyList>>,

    head_node_ids_py_list: Option<Py<PyList>>,

    use_persistent_nodemap: bool,

    nodemap_queries: AtomicUsize,

}

#[pymethods]

impl InnerRevlog {

    #[new]

    // The Python side has authority on this signature.

    #[allow(clippy::too_many_arguments)]

    fn new(

        vfs_base: &Bound<'_, PyBytes>,

        fncache: &Bound<'_, PyAny>,

        vfs_is_readonly: bool,

        index_data: &Bound<'_, PyAny>,

        index_file: &Bound<'_, PyBytes>,

        data_file: &Bound<'_, PyBytes>,

        sidedata_file: &Bound<'_, PyAny>,

        inline: bool,

        data_config: &Bound<'_, PyAny>,

        delta_config: &Bound<'_, PyAny>,

        feature_config: &Bound<'_, PyAny>,

        chunk_cache: &Bound<'_, PyAny>,

        default_compression_header: &Bound<'_, PyAny>,

        revlog_type: usize,

        use_persistent_nodemap: bool,

    ) -> PyResult<Self> {

        // Let clippy accept the unused arguments. This is a bit better than

        // a blank `allow` directive

        let _ = sidedata_file;

        let _ = chunk_cache;

        let _ = default_compression_header;

        let index_file = get_path_from_bytes(index_file.as_bytes()).to_owned();

        let data_file = get_path_from_bytes(data_file.as_bytes()).to_owned();

        let revlog_type = RevlogType::try_from(revlog_type)

            .map_err(revlog_error_from_msg)?;

        let data_config = extract_data_config(data_config, revlog_type)?;

        let delta_config = extract_delta_config(delta_config, revlog_type)?;

        let feature_config =

            extract_feature_config(feature_config, revlog_type)?;

        let options = RevlogOpenOptions::new(

            inline,

            data_config,

            delta_config,

            feature_config,

        );

        // Safety: we keep the buffer around inside the returned instance as

        // `index_mmap`

        let (buf, bytes) = unsafe { take_buffer_with_slice(index_data)? };

        let index = Index::new(bytes, options.index_header())

            .map_err(revlog_error_from_msg)?;

        let base = get_path_from_bytes(vfs_base.as_bytes()).to_owned();

        let core = CoreInnerRevlog::new(

            Box::new(FnCacheVfs::new(

                base,

                vfs_is_readonly,

                Box::new(PyFnCache::new(fncache.clone().unbind())),

            )),

            index,

            index_file,

            data_file,

            data_config,

            delta_config,

            feature_config,

        );

        Ok(Self {

            irl: core.into(),

            nt: None.into(),

            docket: None,

            nodemap_mmap: None,

            index_mmap: buf.into(),

            head_revs_py_list: None,

            head_node_ids_py_list: None,

            revision_cache: None,

            use_persistent_nodemap,

            nodemap_queries: AtomicUsize::new(0),

        })

    }

}

impl InnerRevlog {

    /// Fill a [`CoreNodeTree`] by doing a full iteration on the given

    /// [`Index`]

    ///

    /// # Python exceptions

    /// Raises `ValueError` if `nt` has existing data that is inconsistent

    /// with `idx`.

    fn fill_nodemap(idx: &Index, nt: &mut CoreNodeTree) -> PyResult<()> {

        for r in 0..idx.len() {

            let rev = Revision(r as BaseRevision);

            // in this case node() won't ever return None

            nt.insert(idx, idx.node(rev).expect("node should exist"), rev)

                .map_err(nodemap_error)?

        }

        Ok(())

    }

    /// Return a working NodeTree of this InnerRevlog

    ///

    /// In case the NodeTree has not been initialized yet (in particular

    /// not from persistent data at instantiation), it is created and

    /// filled right away from the index.

    ///

    /// Technically, the returned NodeTree is still behind the lock of

    /// the `nt` field, hence still wrapped in an [`Option`]. Callers

    /// will need to take the lock and unwrap with `expect()`.

    ///

    /// # Python exceptions

    /// The case mentioned in [`Self::fill_nodemap()`] cannot happen, as the

    /// NodeTree is empty when it is called.

    #[allow(dead_code)]

    fn get_nodetree(

        &self,

        idx: &Index,

    ) -> PyResult<&RwLock<Option<CoreNodeTree>>> {

        if self.nt.read().map_err(map_lock_error)?.is_none() {

            let readonly = Box::<Vec<_>>::default();

            let mut nt = CoreNodeTree::load_bytes(readonly, 0);

            Self::fill_nodemap(idx, &mut nt)?;

            self.nt.write().map_err(map_lock_error)?.replace(nt);

        }

        Ok(&self.nt)

    }

}

pub fn init_module<'py>(

    py: Python<'py>,

    package: &str,

) -> PyResult<Bound<'py, PyModule>> {

    let m = new_submodule(py, package, "revlog")?;

    m.add_class::<InnerRevlog>()?;

    Ok(m)

}