use std::cell::OnceCell;
use std::ffi::OsString;
use std::fs::{FileType, Metadata};
use std::path::{Path, PathBuf};

use lscolors::{Colorable, LsColors, Style};

use crate::config::Config;
use crate::filesystem::strip_current_dir;

#[derive(Debug)]
enum DirEntryInner {
    Normal(ignore::DirEntry),
    // Broken symlinks reach us as walk errors rather than entries, so we carry
    // over the depth the walker recorded on the error.
    BrokenSymlink { path: PathBuf, depth: Option<usize> },
}

#[derive(Debug)]
pub struct DirEntry {
    inner: DirEntryInner,
    metadata: OnceCell<Option<Metadata>>,
    style: OnceCell<Option<Style>>,
}

impl DirEntry {
    #[inline]
    pub fn normal(e: ignore::DirEntry) -> Self {
        Self {
            inner: DirEntryInner::Normal(e),
            metadata: OnceCell::new(),
            style: OnceCell::new(),
        }
    }

    pub fn broken_symlink(path: PathBuf, depth: Option<usize>) -> Self {
        Self {
            inner: DirEntryInner::BrokenSymlink { path, depth },
            metadata: OnceCell::new(),
            style: OnceCell::new(),
        }
    }

    pub fn path(&self) -> &Path {
        match &self.inner {
            DirEntryInner::Normal(e) => e.path(),
            DirEntryInner::BrokenSymlink { path, .. } => path.as_path(),
        }
    }

    pub fn into_path(self) -> PathBuf {
        match self.inner {
            DirEntryInner::Normal(e) => e.into_path(),
            DirEntryInner::BrokenSymlink { path, .. } => path,
        }
    }

    /// Returns the path as it should be presented to the user.
    /// When stripping `./` would leave the path starting with `-`, keep the original
    /// (with `./`) so downstream tools don't interpret it as an option.
    pub fn stripped_path(&self, config: &Config) -> &Path {
        let path = self.path();
        if config.strip_cwd_prefix {
            let stripped = strip_current_dir(path);
            if starts_with_dash(stripped) {
                path
            } else {
                stripped
            }
        } else {
            path
        }
    }

    /// Returns the path as it should be presented to the user.
    pub fn into_stripped_path(self, config: &Config) -> PathBuf {
        if config.strip_cwd_prefix {
            self.stripped_path(config).to_path_buf()
        } else {
            self.into_path()
        }
    }

    pub fn file_type(&self) -> Option<FileType> {
        match &self.inner {
            DirEntryInner::Normal(e) => e.file_type(),
            DirEntryInner::BrokenSymlink { .. } => self.metadata().map(|m| m.file_type()),
        }
    }

    pub fn metadata(&self) -> Option<&Metadata> {
        self.metadata
            .get_or_init(|| match &self.inner {
                DirEntryInner::Normal(e) => e.metadata().ok(),
                DirEntryInner::BrokenSymlink { path, .. } => path.symlink_metadata().ok(),
            })
            .as_ref()
    }

    pub fn depth(&self) -> Option<usize> {
        match &self.inner {
            DirEntryInner::Normal(e) => Some(e.depth()),
            DirEntryInner::BrokenSymlink { depth, .. } => *depth,
        }
    }

    pub fn style(&self, ls_colors: &LsColors) -> Option<&Style> {
        self.style
            .get_or_init(|| ls_colors.style_for(self).cloned())
            .as_ref()
    }
}

fn starts_with_dash(path: &Path) -> bool {
    path.as_os_str().as_encoded_bytes().first() == Some(&b'-')
}

impl PartialEq for DirEntry {
    #[inline]
    fn eq(&self, other: &Self) -> bool {
        self.path() == other.path()
    }
}

impl Eq for DirEntry {}

impl PartialOrd for DirEntry {
    #[inline]
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for DirEntry {
    #[inline]
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.path().cmp(other.path())
    }
}

impl Colorable for DirEntry {
    fn path(&self) -> PathBuf {
        self.path().to_owned()
    }

    fn file_name(&self) -> OsString {
        let name = match &self.inner {
            DirEntryInner::Normal(e) => e.file_name(),
            DirEntryInner::BrokenSymlink { path, .. } => {
                // Path::file_name() only works if the last component is Normal,
                // but we want it for all component types, so we open code it.
                // Copied from LsColors::style_for_path_with_metadata().
                path.components()
                    .next_back()
                    .map(|c| c.as_os_str())
                    .unwrap_or_else(|| path.as_os_str())
            }
        };
        name.to_owned()
    }

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

    fn metadata(&self) -> Option<Metadata> {
        self.metadata().cloned()
    }
}

#[cfg(test)]
mod tests {
    use super::starts_with_dash;
    use std::path::Path;

    #[test]
    fn dash_prefixed_paths_detected() {
        assert!(starts_with_dash(Path::new("-rf")));
        assert!(starts_with_dash(Path::new("--delete")));
        assert!(starts_with_dash(Path::new("-")));
    }

    #[test]
    fn safe_paths_not_flagged() {
        assert!(!starts_with_dash(Path::new("foo")));
        assert!(!starts_with_dash(Path::new("./foo")));
        assert!(!starts_with_dash(Path::new("sub/-rf")));
        assert!(!starts_with_dash(Path::new("")));
        assert!(!starts_with_dash(Path::new(" -rf")));
    }
}