use super::Version;
use std::io;

#[derive(Debug)]
pub struct Pak<R: io::Read + io::Seek> {
    version: Version,
    mount_point: String,
    key: Option<aes::Aes256Dec>,
    entries: hashbrown::HashMap<String, super::Entry>,
    reader: R,
}

impl<R: io::Read + io::Seek> Pak<R> {
    pub fn new(
        mut reader: R,
        version: super::Version,
        key_hash: Option<&[u8]>,
    ) -> Result<Self, super::Error> {
        use super::ReadExt;
        use byteorder::{ReadBytesExt, LE};
        // read footer to get index, encryption & compression info
        reader.seek(io::SeekFrom::End(-version.size()))?;
        let footer = super::Footer::new(&mut reader, version)?;
        // read index to get all the entry info
        reader.seek(io::SeekFrom::Start(footer.index_offset))?;
        let mut index = reader.read_len(footer.index_size as usize)?;
        let mut key = None;
        // decrypt index if needed
        if footer.encrypted {
            if let Some(hash) = key_hash {
                use aes::cipher::{BlockDecrypt, KeyInit};
                match aes::Aes256Dec::new_from_slice(hash) {
                    Ok(decrypter) => {
                        for chunk in index.chunks_mut(16) {
                            decrypter.decrypt_block(aes::Block::from_mut_slice(chunk))
                        }
                        key = Some(decrypter);
                    }
                    Err(_) => return Err(super::Error::Aes),
                }
            }
        }
        let mut index = io::Cursor::new(index);
        let mount_point = index.read_string()?;
        let len = index.read_u32::<LE>()? as usize;
        let mut entries = hashbrown::HashMap::with_capacity(len);
        for _ in 0..len {
            entries.insert(
                index.read_string()?,
                super::Entry::new(&mut index, version)?,
            );
        }
        Ok(Self {
            version,
            mount_point,
            key,
            entries,
            reader,
        })
    }

    pub fn version(&self) -> super::Version {
        self.version
    }

    pub fn mount_point(&self) -> &str {
        &self.mount_point
    }

    pub fn get(&mut self, path: &str) -> Option<Result<Vec<u8>, super::Error>> {
        self.entries
            .get(path)
            .map(|entry| entry.read(&mut self.reader, self.version, self.key.as_ref()))
    }
}