use std::collections::BTreeMap;
use std::path::PathBuf;
use std::time::Duration;

use super::path_with_basename::WithBasename;

use crate::dirstate::parsers::parse_dirstate_entries;
use crate::matchers::Matcher;
use crate::revlog::node::NULL_NODE;
use crate::utils::hg_path::{HgPath, HgPathBuf};
use crate::CopyMapIter;
use crate::DirstateEntry;
use crate::DirstateError;
use crate::DirstateMapError;
use crate::DirstateParents;
use crate::DirstateStatus;
use crate::EntryState;
use crate::FastHashMap;
use crate::HgPathCow;
use crate::PatternFileWarning;
use crate::StateMapIter;
use crate::StatusError;
use crate::StatusOptions;

pub struct DirstateMap {
    parents: Option<DirstateParents>,
    dirty_parents: bool,
    root: ChildNodes,
}

/// Using a plain `HgPathBuf` of the full path from the repository root as a
/// map key would also work: all paths in a given map have the same parent
/// path, so comparing full paths gives the same result as comparing base
/// names. However `BTreeMap` would waste time always re-comparing the same
/// string prefix.
type ChildNodes = BTreeMap<WithBasename<HgPathBuf>, Node>;

#[derive(Default)]
struct Node {
    entry: Option<DirstateEntry>,
    copy_source: Option<HgPathBuf>,
    children: ChildNodes,
}

impl DirstateMap {
    pub fn new() -> Self {
        Self {
            parents: None,
            dirty_parents: false,
            root: ChildNodes::new(),
        }
    }

    fn get_or_insert_node(&mut self, path: &HgPath) -> &mut Node {
        let mut child_nodes = &mut self.root;
        let mut inclusive_ancestor_paths =
            WithBasename::inclusive_ancestors_of(path);
        let mut ancestor_path = inclusive_ancestor_paths
            .next()
            .expect("expected at least one inclusive ancestor");
        loop {
            // TODO: can we avoid double lookup in all cases without allocating
            // an owned key in cases where the map already contains that key?
            let child_node =
                if child_nodes.contains_key(ancestor_path.base_name()) {
                    child_nodes.get_mut(ancestor_path.base_name()).unwrap()
                } else {
                    // This is always a vacant entry, using `.entry()` lets us
                    // return a `&mut Node` of the newly-inserted node without
                    // yet another lookup. `BTreeMap::insert` doesn’t do this.
                    child_nodes.entry(ancestor_path.to_owned()).or_default()
                };
            if let Some(next) = inclusive_ancestor_paths.next() {
                ancestor_path = next;
                child_nodes = &mut child_node.children;
            } else {
                return child_node;
            }
        }
    }
}

impl super::dispatch::DirstateMapMethods for DirstateMap {
    fn clear(&mut self) {
        self.set_parents(&DirstateParents {
            p1: NULL_NODE,
            p2: NULL_NODE,
        });
        self.root.clear()
    }

    fn add_file(
        &mut self,
        _filename: &HgPath,
        _old_state: EntryState,
        _entry: DirstateEntry,
    ) -> Result<(), DirstateMapError> {
        todo!()
    }

    fn remove_file(
        &mut self,
        _filename: &HgPath,
        _old_state: EntryState,
        _size: i32,
    ) -> Result<(), DirstateMapError> {
        todo!()
    }

    fn drop_file(
        &mut self,
        _filename: &HgPath,
        _old_state: EntryState,
    ) -> Result<bool, DirstateMapError> {
        todo!()
    }

    fn clear_ambiguous_times(
        &mut self,
        _filenames: Vec<HgPathBuf>,
        _now: i32,
    ) {
        todo!()
    }

    fn non_normal_entries_contains(&mut self, _key: &HgPath) -> bool {
        todo!()
    }

    fn non_normal_entries_remove(&mut self, _key: &HgPath) -> bool {
        todo!()
    }

    fn non_normal_or_other_parent_paths(
        &mut self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + '_> {
        todo!()
    }

    fn set_non_normal_other_parent_entries(&mut self, _force: bool) {
        todo!()
    }

    fn iter_non_normal_paths(
        &mut self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + Send + '_> {
        todo!()
    }

    fn iter_non_normal_paths_panic(
        &self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + Send + '_> {
        todo!()
    }

    fn iter_other_parent_paths(
        &mut self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + Send + '_> {
        todo!()
    }

    fn has_tracked_dir(
        &mut self,
        _directory: &HgPath,
    ) -> Result<bool, DirstateMapError> {
        todo!()
    }

    fn has_dir(
        &mut self,
        _directory: &HgPath,
    ) -> Result<bool, DirstateMapError> {
        todo!()
    }

    fn parents(
        &mut self,
        _file_contents: &[u8],
    ) -> Result<&DirstateParents, DirstateError> {
        todo!()
    }

    fn set_parents(&mut self, parents: &DirstateParents) {
        self.parents = Some(parents.clone());
        self.dirty_parents = true;
    }

    fn read<'a>(
        &mut self,
        file_contents: &'a [u8],
    ) -> Result<Option<&'a DirstateParents>, DirstateError> {
        if file_contents.is_empty() {
            return Ok(None);
        }

        let parents = parse_dirstate_entries(
            file_contents,
            |path, entry, copy_source| {
                let node = self.get_or_insert_node(path);
                node.entry = Some(*entry);
                node.copy_source = copy_source.map(HgPath::to_owned);
            },
        )?;

        if !self.dirty_parents {
            self.set_parents(parents);
        }

        Ok(Some(parents))
    }

    fn pack(
        &mut self,
        _parents: DirstateParents,
        _now: Duration,
    ) -> Result<Vec<u8>, DirstateError> {
        todo!()
    }

    fn build_file_fold_map(&mut self) -> &FastHashMap<HgPathBuf, HgPathBuf> {
        todo!()
    }

    fn set_all_dirs(&mut self) -> Result<(), DirstateMapError> {
        todo!()
    }

    fn set_dirs(&mut self) -> Result<(), DirstateMapError> {
        todo!()
    }

    fn status<'a>(
        &'a self,
        _matcher: &'a (dyn Matcher + Sync),
        _root_dir: PathBuf,
        _ignore_files: Vec<PathBuf>,
        _options: StatusOptions,
    ) -> Result<
        (
            (Vec<HgPathCow<'a>>, DirstateStatus<'a>),
            Vec<PatternFileWarning>,
        ),
        StatusError,
    > {
        todo!()
    }

    fn copy_map_len(&self) -> usize {
        todo!()
    }

    fn copy_map_iter(&self) -> CopyMapIter<'_> {
        todo!()
    }

    fn copy_map_contains_key(&self, _key: &HgPath) -> bool {
        todo!()
    }

    fn copy_map_get(&self, _key: &HgPath) -> Option<&HgPathBuf> {
        todo!()
    }

    fn copy_map_remove(&mut self, _key: &HgPath) -> Option<HgPathBuf> {
        todo!()
    }

    fn copy_map_insert(
        &mut self,
        _key: HgPathBuf,
        _value: HgPathBuf,
    ) -> Option<HgPathBuf> {
        todo!()
    }

    fn len(&self) -> usize {
        todo!()
    }

    fn contains_key(&self, _key: &HgPath) -> bool {
        todo!()
    }

    fn get(&self, _key: &HgPath) -> Option<&DirstateEntry> {
        todo!()
    }

    fn iter(&self) -> StateMapIter<'_> {
        todo!()
    }
}