// 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.

#![allow(non_snake_case)]

use pyo3::buffer::PyBuffer;

use pyo3::prelude::*;

use pyo3_sharedref::PyShareable;

use std::sync::{

    atomic::{AtomicUsize, Ordering},

    RwLock, RwLockReadGuard, RwLockWriteGuard,

};

use hg::{

    revlog::{

        index::Index,

        inner_revlog::InnerRevlog as CoreInnerRevlog,

        options::RevlogOpenOptions,

        RevlogIndex, RevlogType,

    },

    utils::files::get_path_from_bytes,

    vfs::FnCacheVfs,

};

use crate::{

    exceptions::{

        map_lock_error, map_try_lock_error, nodemap_error, revlog_error_bare,

        revlog_error_from_msg,

    },

    node::{node_from_py_bytes, node_prefix_from_py_bytes, py_node_for_rev},

    revision::PyRevision,

    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),

        })

    }

    //

    // -- forwarded index methods --

    //

    fn _index_get_rev(

        slf: &Bound<'_, Self>,

        node: &Bound<'_, PyBytes>,

    ) -> PyResult<Option<PyRevision>> {

        let node = node_from_py_bytes(node)?;

        // Do not rewrite this with `Self::with_index_nt_read`: it makes

        // inconditionally a volatile nodetree, and that is not the intent

        // here: the code below specifically avoids that.

        Self::with_core_read(slf, |self_ref, irl| {

            let idx = &irl.index;

            let prev_queries =

                self_ref.nodemap_queries.fetch_add(1, Ordering::Relaxed);

            // Filelogs have no persistent nodemaps and are often small,

            // use a brute force lookup from the end

            // backwards. If there is a very large filelog

            // (automation file that changes every

            // commit etc.), it also seems to work quite well for

            // all measured purposes so far.

            if !self_ref.use_persistent_nodemap && prev_queries <= 3 {

                return Ok(idx

                    .rev_from_node_no_persistent_nodemap(node.into())

                    .ok()

                    .map(Into::into));

            }

            let opt =

                self_ref.get_nodetree(idx)?.read().map_err(map_lock_error)?;

            let nt = opt.as_ref().expect("nodetree should be set");

            let rust_rev =

                nt.find_bin(idx, node.into()).map_err(nodemap_error)?;

            Ok(rust_rev.map(Into::into))

        })

    }

    /// same as `_index_get_rev()` but raises a bare `error.RevlogError` if

    /// node is not found.

    ///

    /// No need to repeat `node` in the exception, `mercurial/revlog.py`

    /// will catch and rewrap with it

    fn _index_rev(

        slf: &Bound<'_, Self>,

        node: &Bound<'_, PyBytes>,

    ) -> PyResult<PyRevision> {

        Self::_index_get_rev(slf, node)?.ok_or_else(revlog_error_bare)

    }

    /// return True if the node exist in the index

    fn _index_has_node(

        slf: &Bound<'_, Self>,

        node: &Bound<'_, PyBytes>,

    ) -> PyResult<bool> {

        Self::_index_get_rev(slf, node).map(|opt| opt.is_some())

    }

    /// find length of shortest hex nodeid of a binary ID

    fn _index_shortest(

        slf: &Bound<'_, Self>,

        node: &Bound<'_, PyBytes>,

    ) -> PyResult<usize> {

        Self::with_index_nt_read(slf, |idx, nt| {

            match nt.unique_prefix_len_node(idx, &node_from_py_bytes(node)?) {

                Ok(Some(l)) => Ok(l),

                Ok(None) => Err(revlog_error_bare()),

                Err(e) => Err(nodemap_error(e)),

            }

        })

    }

    fn _index_partialmatch<'py>(

        slf: &Bound<'py, Self>,

        node: &Bound<'py, PyBytes>,

    ) -> PyResult<Option<Bound<'py, PyBytes>>> {

        Self::with_index_nt_read(slf, |idx, nt| {

            Ok(nt

                .find_bin(idx, node_prefix_from_py_bytes(node)?)

                .map_err(nodemap_error)?

                .map(|rev| py_node_for_rev(slf.py(), idx, rev)))

        })

    }

    fn _index___len__(slf: &Bound<'_, Self>) -> PyResult<usize> {

        Self::with_index_read(slf, |idx| Ok(idx.len()))

    }

}

impl InnerRevlog {

    /// Take the lock on `slf.irl` for reading and call a closure.

    ///

    /// This serves the purpose to keep the needed intermediate [`PyRef`]

    /// that must be obtained to access the data from the [`Bound`] reference

    /// and of which the locked [`CoreInnerRevlog`] depends.

    /// This also provides releasing of the [`PyRef`] as soon as the closure

    /// is done, which is crucial if the caller needs to obtain a [`PyRefMut`]

    /// later on.

    ///

    /// In the closure, we hand back the intermediate [`PyRef`] that

    /// has been generated so that the closure can access more attributes.

    fn with_core_read<'py, T>(

        slf: &Bound<'py, Self>,

        f: impl FnOnce(

            &PyRef<'py, Self>,

            RwLockReadGuard<CoreInnerRevlog>,

        ) -> PyResult<T>,

    ) -> PyResult<T> {

        let self_ref = slf.borrow();

        // Safety: the owner is the right one. We will anyway

        // not actually `share` it. Perhaps pyo3-sharedref should provide

        // something less scary for this kind of usage.

        let shareable_ref = unsafe { self_ref.irl.borrow_with_owner(slf) };

        let guard = shareable_ref.try_read().map_err(map_try_lock_error)?;

        f(&self_ref, guard)

    }

    /// Take the lock on `slf.irl` for writing and call a closure.

    ///

    /// See [`Self::with_core_read`] for more explanations.

    fn with_core_write<'py, T>(

        slf: &Bound<'py, Self>,

        f: impl FnOnce(

            &PyRef<'py, Self>,

            RwLockWriteGuard<CoreInnerRevlog>,

        ) -> PyResult<T>,

    ) -> PyResult<T> {

        let self_ref = slf.borrow();

        // Safety: the owner is the right one. We will anyway

        // not actually `share` it. Perhaps pyo3-sharedref should provide

        // something less scary for this kind of usage.

        let shareable_ref = unsafe { self_ref.irl.borrow_with_owner(slf) };

        let guard = shareable_ref.try_write().map_err(map_try_lock_error)?;

        f(&self_ref, guard)

    }

    fn with_index_read<T>(

        slf: &Bound<'_, Self>,

        f: impl FnOnce(&Index) -> PyResult<T>,

    ) -> PyResult<T> {

        Self::with_core_read(slf, |_, guard| f(&guard.index))

    }

    #[allow(dead_code)]

    fn with_index_write<T>(

        slf: &Bound<'_, Self>,

        f: impl FnOnce(&mut Index) -> PyResult<T>,

    ) -> PyResult<T> {

        Self::with_core_write(slf, |_, mut guard| f(&mut guard.index))

    }

    /// Lock `slf` for reading and execute a closure on its [`Index`] and

    /// [`NodeTree`]

    ///

    /// The [`NodeTree`] is initialized an filled before hand if needed.

    fn with_index_nt_read<T>(

        slf: &Bound<'_, Self>,

        f: impl FnOnce(&Index, &CoreNodeTree) -> PyResult<T>,

    ) -> PyResult<T> {

        Self::with_core_read(slf, |self_ref, guard| {

            let idx = &guard.index;

            let nt =

                self_ref.get_nodetree(idx)?.read().map_err(map_lock_error)?;

            let nt = nt.as_ref().expect("nodetree should be set");

            f(idx, nt)

        })

    }

    fn with_index_nt_write<T>(

        slf: &Bound<'_, Self>,

        f: impl FnOnce(&mut Index, &mut CoreNodeTree) -> PyResult<T>,

    ) -> PyResult<T> {

        Self::with_core_write(slf, |self_ref, mut guard| {

            let idx = &mut guard.index;

            let mut nt = self_ref

                .get_nodetree(idx)?

                .write()

                .map_err(map_lock_error)?;

            let nt = nt.as_mut().expect("nodetree should be set");

            f(idx, nt)

        })

    }

    /// 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.

    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)

}