use crate::config::{Config, ConfigError, ConfigParseError};

use crate::errors::{HgError, IoErrorContext, IoResultExt};

use crate::requirements;

use crate::utils::current_dir;

use crate::utils::files::get_path_from_bytes;

use memmap::{Mmap, MmapOptions};

use std::collections::HashSet;

use std::path::{Path, PathBuf};

/// A repository on disk

pub struct Repo {

    working_directory: PathBuf,

    dot_hg: PathBuf,

    store: PathBuf,

    requirements: HashSet<String>,

    config: Config,

}

#[derive(Debug, derive_more::From)]

pub enum RepoError {

    NotFound {

        at: PathBuf,

    },

    #[from]

    ConfigParseError(ConfigParseError),

    #[from]

    Other(HgError),

}

impl From<ConfigError> for RepoError {

    fn from(error: ConfigError) -> Self {

        match error {

            ConfigError::Parse(error) => error.into(),

            ConfigError::Other(error) => error.into(),

        }

    }

}

/// Filesystem access abstraction for the contents of a given "base" diretory

#[derive(Clone, Copy)]

pub struct Vfs<'a> {

    pub(crate) base: &'a Path,

}

impl Repo {

    /// Find a repository, either at the given path (which must contain a `.hg`

    /// sub-directory) or by searching the current directory and its

    /// ancestors.

    ///

    /// A method with two very different "modes" like this usually a code smell

    /// to make two methods instead, but in this case an `Option` is what rhg

    /// sub-commands get from Clap for the `-R` / `--repository` CLI argument.

    /// Having two methods would just move that `if` to almost all callers.

    pub fn find(

        config: &Config,

        explicit_path: Option<&Path>,

    ) -> Result<Self, RepoError> {

        if let Some(root) = explicit_path {

            // Having an absolute path isn’t necessary here but can help code

            // elsewhere

            let root = current_dir()?.join(root);

            if root.join(".hg").is_dir() {

                Self::new_at_path(root, config)

            } else {

                Err(RepoError::NotFound {

                    at: root.to_owned(),

                })

            }

        } else {

            let current_directory = crate::utils::current_dir()?;

            // ancestors() is inclusive: it first yields `current_directory`

            // as-is.

            for ancestor in current_directory.ancestors() {

                if ancestor.join(".hg").is_dir() {

                    return Self::new_at_path(ancestor.to_owned(), config);

                }

            }

            Err(RepoError::NotFound {

                at: current_directory,

            })

        }

    }

    /// To be called after checking that `.hg` is a sub-directory

    fn new_at_path(

        working_directory: PathBuf,

        config: &Config,

    ) -> Result<Self, RepoError> {

        let dot_hg = working_directory.join(".hg");

        let mut repo_config_files = Vec::new();

        repo_config_files.push(dot_hg.join("hgrc"));

        repo_config_files.push(dot_hg.join("hgrc-not-shared"));

        let hg_vfs = Vfs { base: &dot_hg };

        let mut reqs = requirements::load_if_exists(hg_vfs)?;

        let relative =

            reqs.contains(requirements::RELATIVE_SHARED_REQUIREMENT);

        let shared =

            reqs.contains(requirements::SHARED_REQUIREMENT) || relative;

        // From `mercurial/localrepo.py`:

        //

        // if .hg/requires contains the sharesafe requirement, it means

        // there exists a `.hg/store/requires` too and we should read it

        // NOTE: presence of SHARESAFE_REQUIREMENT imply that store requirement

        // is present. We never write SHARESAFE_REQUIREMENT for a repo if store

        // is not present, refer checkrequirementscompat() for that

        //

        // However, if SHARESAFE_REQUIREMENT is not present, it means that the

        // repository was shared the old way. We check the share source

        // .hg/requires for SHARESAFE_REQUIREMENT to detect whether the

        // current repository needs to be reshared

        let share_safe = reqs.contains(requirements::SHARESAFE_REQUIREMENT);

        let store_path;

        if !shared {

            store_path = dot_hg.join("store");

            if share_safe {

                reqs.extend(requirements::load(Vfs { base: &store_path })?);

            }

        } else {

            let bytes = hg_vfs.read("sharedpath")?;

            let mut shared_path = get_path_from_bytes(&bytes).to_owned();

            if relative {

                shared_path = dot_hg.join(shared_path)

            }

            if !shared_path.is_dir() {

                return Err(HgError::corrupted(format!(

                    ".hg/sharedpath points to nonexistent directory {}",

                    shared_path.display()

                ))

                .into());

            }

            store_path = shared_path.join("store");

            let source_is_share_safe =

                requirements::load(Vfs { base: &shared_path })?

                    .contains(requirements::SHARESAFE_REQUIREMENT);

            if share_safe && !source_is_share_safe {

                return Err(match config

                    .get(b"safe-mismatch", b"source-not-safe")

                {

                    Some(b"abort") | None => HgError::abort(

                        "share source does not support share-safe requirement",

                    ),

                    _ => HgError::unsupported("share-safe downgrade"),

                }

                .into());

            } else if source_is_share_safe && !share_safe {

                return Err(

                    match config.get(b"safe-mismatch", b"source-safe") {

                        Some(b"abort") | None => HgError::abort(

                            "version mismatch: source uses share-safe \

                            functionality while the current share does not",

                        ),

                        _ => HgError::unsupported("share-safe upgrade"),

                    }

                    .into(),

                );

            }

            if share_safe {

                repo_config_files.insert(0, shared_path.join("hgrc"))

            }

        }

        let repo_config = config.combine_with_repo(&repo_config_files)?;

        let repo = Self {

            requirements: reqs,

            working_directory,

            store: store_path,

            dot_hg,

            config: repo_config,

        };

        requirements::check(&repo)?;

        Ok(repo)

    }

    pub fn working_directory_path(&self) -> &Path {

        &self.working_directory

    }

    pub fn requirements(&self) -> &HashSet<String> {

        &self.requirements

    }

    pub fn config(&self) -> &Config {

        &self.config

    }

    /// For accessing repository files (in `.hg`), except for the store

    /// (`.hg/store`).

    pub fn hg_vfs(&self) -> Vfs<'_> {

        Vfs { base: &self.dot_hg }

    }

    /// For accessing repository store files (in `.hg/store`)

    pub fn store_vfs(&self) -> Vfs<'_> {

        Vfs { base: &self.store }

    }

    /// For accessing the working copy

    // The undescore prefix silences the "never used" warning. Remove before

    // using.

    pub fn _working_directory_vfs(&self) -> Vfs<'_> {

        Vfs {

            base: &self.working_directory,

        }

    }

}

impl Vfs<'_> {

    pub fn join(&self, relative_path: impl AsRef<Path>) -> PathBuf {

        self.base.join(relative_path)

    }

    pub fn read(

        &self,

        relative_path: impl AsRef<Path>,

    ) -> Result<Vec<u8>, HgError> {

        let path = self.join(relative_path);

        std::fs::read(&path).when_reading_file(&path)

    }

    pub fn mmap_open(

        &self,

        relative_path: impl AsRef<Path>,

    ) -> Result<Mmap, HgError> {

        let path = self.base.join(relative_path);

        let file = std::fs::File::open(&path).when_reading_file(&path)?;

        // TODO: what are the safety requirements here?

        let mmap = unsafe { MmapOptions::new().map(&file) }

            .when_reading_file(&path)?;

        Ok(mmap)

    }

    pub fn rename(

        &self,

        relative_from: impl AsRef<Path>,

        relative_to: impl AsRef<Path>,

    ) -> Result<(), HgError> {

        let from = self.join(relative_from);

        let to = self.join(relative_to);

        std::fs::rename(&from, &to)

            .with_context(|| IoErrorContext::RenamingFile { from, to })

    }

}