use super::*;


pub struct DirectoryListing {
    children: Vec<BedrockFilePath>,
    length: u32,
    selected: Option<u32>,
    name_buffer: CircularPathBuffer,
}


impl DirectoryListing {
    pub fn from_path(path: &BedrockFilePath) -> Option<Self> {
        macro_rules! unres {
            ($result:expr) => { match $result { Ok(v) => v, Err(_) => continue} };
        }
        macro_rules! unopt {
            ($option:expr) => { match $option { Some(v) => v, None => continue} };
        }

        #[cfg(target_family = "windows")] {
            if path.as_path().components().count() == 0 {
                return Some(Self::construct_virtual_root())
            }
        }

        let mut children = Vec::new();
        if let Ok(dir_listing) = std::fs::read_dir(path.as_path()) {
            for (i, entry_result) in dir_listing.enumerate() {
                // Firebreak to prevent emulator from consuming an absurd amount
                // of memory when opening too large of a directory.
                if i == (u16::MAX as usize) {
                    break;
                }

                let entry = unres!(entry_result);
                let entry_path = unopt!(BedrockFilePath::from_path(&entry.path(), path.base()));
                if entry_path.is_hidden() {
                    continue;
                }

                children.push(entry_path);
            }
        }

        children.sort();
        let length = u32::try_from(children.len()).ok()?;
        let selected = None;
        let name_buffer = CircularPathBuffer::new();
        Some( Self { children, length, selected, name_buffer } )
    }

    /// Generate entries for a virtual root directory.
    #[cfg(target_family = "windows")]
    fn construct_virtual_root() -> Self {
        let mut children = Vec::new();
        let base = PathBuf::from("");
        let drive_bits = unsafe {
            windows::Win32::Storage::FileSystem::GetLogicalDrives()
        };
        for i in 0..26 {
            if drive_bits & (0x1 << i) != 0 {
                let letter: char = (b'A' + i).into();
                let path = PathBuf::from(format!("{letter}:/"));
                if let Some(drive) = BedrockFilePath::from_path(&path, &base) {
                    children.push(drive);
                }
            }
        }

        let length = children.len() as u32;
        let selected = None;
        let name_buffer = CircularPathBuffer::new();
        Self { children, length, selected, name_buffer }
    }

    /// Attempts to return a directory child by index.
    pub fn get(&self, index: u32) -> Option<&BedrockFilePath> {
        self.children.get(index as usize)
    }

    pub fn length(&self) -> u32 {
        self.length
    }

    /// Returns the index of the selected child, or zero if no child is selected.
    pub fn selected(&self) -> u32 {
        self.selected.unwrap_or(0)
    }

    /// Attempts to select a child by index.
    pub fn set_selected(&mut self, index: u32) {
        if let Some(child) = self.get(index) {
            let buffer = child.as_buffer();
            self.name_buffer.populate(buffer);
            self.selected = Some(index);
        } else {
            self.name_buffer.clear();
            self.selected = None;
        }
    }

    pub fn child_name(&mut self) -> &mut CircularPathBuffer {
        &mut self.name_buffer
    }

    pub fn child_type(&self) -> Option<EntryType> {
        self.selected.and_then(|s| self.get(s).and_then(|i| i.entry_type()))
    }

    pub fn child_path(&self) -> Option<BedrockFilePath> {
        self.selected.and_then(|s| self.get(s).and_then(|i| Some(i.clone())))
    }
}