use std::fmt::Debug;

pub use memory_fs::MemoryFileSystem;
#[cfg(feature = "os")]
pub use os::OsSystem;
use ruff_notebook::{Notebook, NotebookError};
pub use test::{DbWithTestSystem, TestSystem};
use walk_directory::WalkDirectoryBuilder;

use crate::file_revision::FileRevision;

pub use self::path::{
    deduplicate_nested_paths, DeduplicatedNestedPathsIter, SystemPath, SystemPathBuf,
    SystemVirtualPath, SystemVirtualPathBuf,
};

mod memory_fs;
#[cfg(feature = "os")]
mod os;
mod path;
mod test;
pub mod walk_directory;

pub type Result<T> = std::io::Result<T>;

/// The system on which Ruff runs.
///
/// Ruff supports running on the CLI, in a language server, and in a browser (WASM). Each of these
/// host-systems differ in what system operations they support and how they interact with the file system:
/// * Language server:
///    * Reading a file's content should take into account that it might have unsaved changes because it's open in the editor.
///    * Use structured representations for notebooks, making deserializing a notebook from a string unnecessary.
///    * Use their own file watching infrastructure.
/// * WASM (Browser):
///    * There are ways to emulate a file system in WASM but a native memory-filesystem is more efficient.
///    * Doesn't support a current working directory
///    * File watching isn't supported.
///
/// Abstracting the system also enables tests to use a more efficient in-memory file system.
pub trait System: Debug {
    /// Reads the metadata of the file or directory at `path`.
    fn path_metadata(&self, path: &SystemPath) -> Result<Metadata>;

    /// Reads the content of the file at `path` into a [`String`].
    fn read_to_string(&self, path: &SystemPath) -> Result<String>;

    /// Reads the content of the file at `path` as a Notebook.
    ///
    /// This method optimizes for the case where the system holds a structured representation of a [`Notebook`],
    /// allowing to skip the notebook deserialization. Systems that don't use a structured
    /// representation fall-back to deserializing the notebook from a string.
    fn read_to_notebook(&self, path: &SystemPath) -> std::result::Result<Notebook, NotebookError>;

    /// Reads the metadata of the virtual file at `path`.
    fn virtual_path_metadata(&self, path: &SystemVirtualPath) -> Result<Metadata>;

    /// Reads the content of the virtual file at `path` into a [`String`].
    fn read_virtual_path_to_string(&self, path: &SystemVirtualPath) -> Result<String>;

    /// Reads the content of the virtual file at `path` as a [`Notebook`].
    fn read_virtual_path_to_notebook(
        &self,
        path: &SystemVirtualPath,
    ) -> std::result::Result<Notebook, NotebookError>;

    /// Returns `true` if `path` exists.
    fn path_exists(&self, path: &SystemPath) -> bool {
        self.path_metadata(path).is_ok()
    }

    /// Returns `true` if `path` exists and is a directory.
    fn is_directory(&self, path: &SystemPath) -> bool {
        self.path_metadata(path)
            .map_or(false, |metadata| metadata.file_type.is_directory())
    }

    /// Returns `true` if `path` exists and is a file.
    fn is_file(&self, path: &SystemPath) -> bool {
        self.path_metadata(path)
            .map_or(false, |metadata| metadata.file_type.is_file())
    }

    /// Returns the current working directory
    fn current_directory(&self) -> &SystemPath;

    /// Iterate over the contents of the directory at `path`.
    ///
    /// The returned iterator must have the following properties:
    /// - It only iterates over the top level of the directory,
    ///   i.e., it does not recurse into subdirectories.
    /// - It skips the current and parent directories (`.` and `..`
    ///   respectively).
    /// - The iterator yields `std::io::Result<DirEntry>` instances.
    ///   For each instance, an `Err` variant may signify that the path
    ///   of the entry was not valid UTF8, in which case it should be an
    ///   [`std::io::Error`] with the ErrorKind set to
    ///   [`std::io::ErrorKind::InvalidData`] and the payload set to a
    ///   [`camino::FromPathBufError`]. It may also indicate that
    ///   "some sort of intermittent IO error occurred during iteration"
    ///   (language taken from the [`std::fs::read_dir`] documentation).
    ///
    /// # Errors
    /// Returns an error:
    /// - if `path` does not exist in the system,
    /// - if `path` does not point to a directory,
    /// - if the process does not have sufficient permissions to
    ///   view the contents of the directory at `path`
    /// - May also return an error in some other situations as well.
    fn read_directory<'a>(
        &'a self,
        path: &SystemPath,
    ) -> Result<Box<dyn Iterator<Item = Result<DirectoryEntry>> + 'a>>;

    /// Recursively walks the content of `path`.
    ///
    /// It is allowed to pass a `path` that points to a file. In this case, the walker
    /// yields a single entry for that file.
    fn walk_directory(&self, path: &SystemPath) -> WalkDirectoryBuilder;

    fn as_any(&self) -> &dyn std::any::Any;
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Metadata {
    revision: FileRevision,
    permissions: Option<u32>,
    file_type: FileType,
}

impl Metadata {
    pub fn revision(&self) -> FileRevision {
        self.revision
    }

    pub fn permissions(&self) -> Option<u32> {
        self.permissions
    }

    pub fn file_type(&self) -> FileType {
        self.file_type
    }
}

#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
pub enum FileType {
    File,
    Directory,
    Symlink,
}

impl FileType {
    pub const fn is_file(self) -> bool {
        matches!(self, FileType::File)
    }

    pub const fn is_directory(self) -> bool {
        matches!(self, FileType::Directory)
    }

    pub const fn is_symlink(self) -> bool {
        matches!(self, FileType::Symlink)
    }
}

#[derive(Debug, PartialEq, Eq)]
pub struct DirectoryEntry {
    path: SystemPathBuf,
    file_type: FileType,
}

impl DirectoryEntry {
    pub fn new(path: SystemPathBuf, file_type: FileType) -> Self {
        Self { path, file_type }
    }

    pub fn into_path(self) -> SystemPathBuf {
        self.path
    }

    pub fn path(&self) -> &SystemPath {
        &self.path
    }

    pub fn file_type(&self) -> FileType {
        self.file_type
    }
}