use crate::dirstate::status::IgnoreFnType;

use crate::dirstate_tree::dirstate_map::ChildNodes;

use crate::dirstate_tree::dirstate_map::DirstateMap;

use crate::dirstate_tree::dirstate_map::Node;

use crate::matchers::get_ignore_function;

use crate::matchers::Matcher;

use crate::utils::files::get_bytes_from_os_string;

use crate::utils::hg_path::HgPath;

use crate::DirstateStatus;

use crate::EntryState;

use crate::HgPathBuf;

use crate::PatternFileWarning;

use crate::StatusError;

use crate::StatusOptions;

use std::borrow::Cow;

use std::io;

use std::path::Path;

use std::path::PathBuf;

/// Returns the status of the working directory compared to its parent

/// changeset.

///

/// This algorithm is based on traversing the filesystem tree (`fs` in function

/// and variable names) and dirstate tree at the same time. The core of this

/// traversal is the recursive `traverse_fs_directory_and_dirstate` function

/// and its use of `itertools::merge_join_by`. When reaching a path that only

/// exists in one of the two trees, depending on information requested by

/// `options` we may need to traverse the remaining subtree.

pub fn status<'tree>(

    dmap: &'tree mut DirstateMap,

    matcher: &(dyn Matcher + Sync),

    root_dir: PathBuf,

    ignore_files: Vec<PathBuf>,

    options: StatusOptions,

) -> Result<(DirstateStatus<'tree>, Vec<PatternFileWarning>), StatusError> {

    let (ignore_fn, warnings): (IgnoreFnType, _) =

        if options.list_ignored || options.list_unknown {

            get_ignore_function(ignore_files, &root_dir)?

        } else {

            (Box::new(|&_| true), vec![])

        };

    let mut common = StatusCommon {

        options,

        matcher,

        ignore_fn,

        outcome: DirstateStatus::default(),

    };

    let is_at_repo_root = true;

    let hg_path = HgPath::new("");

    let has_ignored_ancestor = false;

    common.traverse_fs_directory_and_dirstate(

        has_ignored_ancestor,

        &mut dmap.root,

        hg_path,

        &root_dir,

        is_at_repo_root,

    );

    Ok((common.outcome, warnings))

}

/// Bag of random things needed by various parts of the algorithm. Reduces the

/// number of parameters passed to functions.

struct StatusCommon<'tree, 'a> {

    options: StatusOptions,

    matcher: &'a (dyn Matcher + Sync),

    ignore_fn: IgnoreFnType<'a>,

    outcome: DirstateStatus<'tree>,

}

impl<'tree, 'a> StatusCommon<'tree, 'a> {

    fn traverse_fs_directory_and_dirstate(

        &mut self,

        has_ignored_ancestor: bool,

        dirstate_nodes: &'tree mut ChildNodes,

        directory_hg_path: &HgPath,

        fs_path: &Path,

        is_at_repo_root: bool,

    ) {

        // TODO: handle I/O errors

        let mut fs_entries =

            DirEntry::read_dir(fs_path, is_at_repo_root).unwrap();

        // `merge_join_by` requires both its input iterators to be sorted:

        // * `BTreeMap` iterates according to keys’ ordering by definition

        // `sort_unstable_by_key` doesn’t allow keys borrowing from the value:

        // https://github.com/rust-lang/rust/issues/34162

        fs_entries.sort_unstable_by(|e1, e2| e1.base_name.cmp(&e2.base_name));

        for pair in itertools::merge_join_by(

            dirstate_nodes,

            &fs_entries,

            |(full_path, _node), fs_entry| {

                full_path.base_name().cmp(&fs_entry.base_name)

            },

        ) {

            use itertools::EitherOrBoth::*;

            match pair {

                Both((hg_path, dirstate_node), fs_entry) => {

                    self.traverse_fs_and_dirstate(

                        fs_entry,

                        hg_path.full_path(),

                        dirstate_node,

                        has_ignored_ancestor,

                    );

                }

                Left((hg_path, dirstate_node)) => self.traverse_dirstate_only(

                    hg_path.full_path(),

                    dirstate_node,

                ),

                Right(fs_entry) => self.traverse_fs_only(

                    has_ignored_ancestor,

                    directory_hg_path,

                    fs_entry,

                ),

            }

        }

    }

    fn traverse_fs_and_dirstate(

        &mut self,

        fs_entry: &DirEntry,

        hg_path: &'tree HgPath,

        dirstate_node: &'tree mut Node,

        has_ignored_ancestor: bool,

    ) {

            // If we previously had a file here, it was removed (with

            // `hg rm` or similar) or deleted before it could be

            self.mark_removed_or_deleted_if_file(

                hg_path,

                dirstate_node.state(),

            );

            let is_ignored = has_ignored_ancestor || (self.ignore_fn)(hg_path);

            let is_at_repo_root = false;

            self.traverse_fs_directory_and_dirstate(

                is_ignored,

                &mut dirstate_node.children,

                hg_path,

                &fs_entry.full_path,

                is_at_repo_root,

            );

        } else {

                let full_path = Cow::from(hg_path);

                if let Some(entry) = &dirstate_node.entry {

                    match entry.state {

                        EntryState::Added => {

                            self.outcome.added.push(full_path)

                        }

                        EntryState::Removed => {

                            self.outcome.removed.push(full_path)

                        }

                        EntryState::Merged => {

                            self.outcome.modified.push(full_path)

                        }

                        EntryState::Normal => {

                            self.handle_normal_file(

                                full_path,

                                dirstate_node,

                                entry,

                                fs_entry,

                            );

                        }

                        // This variant is not used in DirstateMap

                        // nodes

                        EntryState::Unknown => unreachable!(),

                    }

                } else {

                    // `node.entry.is_none()` indicates a "directory"

                    // node, but the filesystem has a file

                    self.mark_unknown_or_ignored(

                        has_ignored_ancestor,

                        full_path,

                    )

                }

            }

            for (child_hg_path, child_node) in &mut dirstate_node.children {

                self.traverse_dirstate_only(

                    child_hg_path.full_path(),

                    child_node,

                )

            }

        }

    }

    /// A file with `EntryState::Normal` in the dirstate was found in the

    /// filesystem

    fn handle_normal_file(

        &mut self,

        full_path: Cow<'tree, HgPath>,

        dirstate_node: &Node,

        entry: &crate::DirstateEntry,

        fs_entry: &DirEntry,

    ) {

        // Keep the low 31 bits

        fn truncate_u64(value: u64) -> i32 {

            (value & 0x7FFF_FFFF) as i32

        }

        fn truncate_i64(value: i64) -> i32 {

            (value & 0x7FFF_FFFF) as i32

        }

        let mode_changed = || {

            self.options.check_exec && entry.mode_changed(&fs_entry.metadata)

        };

        let size_changed = entry.size != truncate_u64(fs_entry.metadata.len());

        if entry.size >= 0

            && size_changed

            && fs_entry.metadata.file_type().is_symlink()

        {

            // issue6456: Size returned may be longer due to encryption

            // on EXT-4 fscrypt. TODO maybe only do it on EXT4?

            self.outcome.unsure.push(full_path)

        } else if dirstate_node.copy_source.is_some()

            || entry.is_from_other_parent()

            || (entry.size >= 0 && (size_changed || mode_changed()))

        {

            self.outcome.modified.push(full_path)

        } else {

            let mtime = mtime_seconds(&fs_entry.metadata);

            if truncate_i64(mtime) != entry.mtime

                || mtime == self.options.last_normal_time

            {

                self.outcome.unsure.push(full_path)

            } else if self.options.list_clean {

                self.outcome.clean.push(full_path)

            }

        }

    }

    /// A node in the dirstate tree has no corresponding filesystem entry

    fn traverse_dirstate_only(

        &mut self,

        hg_path: &'tree HgPath,

        dirstate_node: &'tree mut Node,

    ) {

        self.mark_removed_or_deleted_if_file(hg_path, dirstate_node.state());

        for (child_hg_path, child_node) in &mut dirstate_node.children {

            self.traverse_dirstate_only(child_hg_path.full_path(), child_node)

        }

    }

    /// A node in the dirstate tree has no corresponding *file* on the

    /// filesystem

    ///

    /// Does nothing on a "directory" node

    fn mark_removed_or_deleted_if_file(

        &mut self,

        hg_path: &'tree HgPath,

        dirstate_node_state: Option<EntryState>,

    ) {

        if let Some(state) = dirstate_node_state {

            if self.matcher.matches(hg_path) {

                if let EntryState::Removed = state {

                    self.outcome.removed.push(hg_path.into())

                } else {

                    self.outcome.deleted.push(hg_path.into())

                }

            }

        }

    }

    /// Something in the filesystem has no corresponding dirstate node

    fn traverse_fs_only(

        &mut self,

        has_ignored_ancestor: bool,

        directory_hg_path: &HgPath,

        fs_entry: &DirEntry,

    ) {

        let hg_path = directory_hg_path.join(&fs_entry.base_name);

            let is_ignored =

                has_ignored_ancestor || (self.ignore_fn)(&hg_path);

            let traverse_children = if is_ignored {

                // Descendants of an ignored directory are all ignored

                self.options.list_ignored

            } else {

                // Descendants of an unknown directory may be either unknown or

                // ignored

                self.options.list_unknown || self.options.list_ignored

            };

            if traverse_children {

                let is_at_repo_root = false;

                // TODO: handle I/O errors

                let children_fs_entries =

                    DirEntry::read_dir(&fs_entry.full_path, is_at_repo_root)

                        .unwrap();

                for child_fs_entry in children_fs_entries {

                    self.traverse_fs_only(

                        is_ignored,

                        &hg_path,

                        &child_fs_entry,

                    )

                }

            }

            if self.options.collect_traversed_dirs {

                self.outcome.traversed.push(hg_path.into())

            }

            self.mark_unknown_or_ignored(has_ignored_ancestor, hg_path.into())

        }

    }

    fn mark_unknown_or_ignored(

        &mut self,

        has_ignored_ancestor: bool,

        hg_path: Cow<'tree, HgPath>,

    ) {

        let is_ignored = has_ignored_ancestor || (self.ignore_fn)(&hg_path);

        if is_ignored {

            if self.options.list_ignored {

                self.outcome.ignored.push(hg_path)

            }

        } else {

            if self.options.list_unknown {

                self.outcome.unknown.push(hg_path)

            }

        }

    }

}

#[cfg(unix)] // TODO

fn mtime_seconds(metadata: &std::fs::Metadata) -> i64 {

    // Going through `Metadata::modified()` would be portable, but would take

    // care to construct a `SystemTime` value with sub-second precision just

    // for us to throw that away here.

    use std::os::unix::fs::MetadataExt;

    metadata.mtime()

}

struct DirEntry {

    base_name: HgPathBuf,

    full_path: PathBuf,

    metadata: std::fs::Metadata,