//! A read-only, high-level, virtual file API for the RuneScape cache.
//!
//! This crate provides high performant data reads into the [Oldschool RuneScape] and [RuneScape 3] cache file systems.
//! It can read the necessary data to synchronize the client's cache with the server. There are also some
//! [loaders](#loaders) that give access to definitions from the cache such as items or npcs.
//!
//! For read-heavy workloads, a writer can be used to prevent continuous buffer allocations.
//! By default every read will allocate a writer with the correct capacity.
//!
//! RuneScape's chat system uses huffman coding to compress messages. In order to decompress them this library has
//! a [`Huffman`] implementation.
//!
//! When a RuneScape client sends game packets the id's are encoded and can be decoded with the [`IsaacRand`]
//! implementation. These id's are encoded by the client in a predictable random order which can be reversed if
//! the server has its own `IsaacRand` with the same encoder/decoder keys. These keys are sent by the client
//! on login and are user specific. It will only send encoded packet id's if the packets are game packets.
//!
//! Note that this crate is still evolving; both OSRS & RS3 are not fully supported/implemented and
//! will probably contain bugs or miss core features. If you require features or find bugs consider [opening
//! an issue].
//!
//! # Safety
//!
//! In order to read bytes in a high performant way the cache uses [memmap2]. This can be unsafe because of its potential for
//! _Undefined Behaviour_ when the underlying file is subsequently modified, in or out of process.
//! Using `Mmap` here is safe because the RuneScape cache is a read-only binary file system. The map will remain valid even
//! after the `File` is dropped, it's completely independent of the `File` used to create it. Therefore, the use of unsafe is
//! not propagated outwards. When the `Cache` is dropped memory will be subsequently unmapped.
//!
//! # Features
//!
//! The cache's protocol defaults to OSRS. In order to use the RS3 protocol you can enable the `rs3` feature flag.
//! A lot of types derive [serde]'s `Serialize` and `Deserialize`. The `serde-derive` feature flag can be used to
//! enable (de)serialization on any compatible types.
//!
//! # Quick Start
//!
//! ```
//! use rscache::Cache;
//!
//! # fn main() -> Result<(), rscache::Error> {
//! let cache = Cache::new("./data/osrs_cache")?;
//!
//! let index_id = 2; // Config index.
//! let archive_id = 10; // Archive containing item definitions.
//!
//! let buffer = cache.read(index_id, archive_id)?;
//! # Ok(())
//! # }
//! ```
//!
//! # Loaders
//!
//! In order to get [definitions](crate::definition) you can look at the [loaders](crate::loader) this library provides.
//! The loaders use the cache as a dependency to parse in their data and cache the relevant definitions internally.
//! The loader module also tells you how to make a loader if this crate doesn't (yet) provide it.
//!
//! Note: Some loaders cache these definitions lazily because of either the size of the data or the
//! performance. The map loader for example is both slow and large so caching is by default lazy.
//! Lazy loaders require mutability.
//!
//! [Oldschool RuneScape]: https://oldschool.runescape.com/
//! [RuneScape 3]: https://www.runescape.com/
//! [opening an issue]: https://github.com/jimvdl/rs-cache/issues/new
//! [serde]: https://crates.io/crates/serde
//! [memmap2]: https://crates.io/crates/memmap2
//! [`Huffman`]: crate::util::Huffman
//! [`IsaacRand`]: crate::util::IsaacRand
#![cfg_attr(docsrs, feature(doc_cfg))]
#![deny(
    clippy::all,
    clippy::correctness,
    clippy::suspicious,
    clippy::style,
    clippy::complexity,
    clippy::perf
)]

#[macro_use]
pub mod util;
pub mod checksum;
pub mod definition;
pub mod error;
pub mod extension;
pub mod loader;

#[doc(inline)]
pub use error::Error;
use error::Result;

use checksum::Checksum;
#[cfg(feature = "rs3")]
use checksum::{RsaChecksum, RsaKeys};
use runefs::codec::{Buffer, Decoded, Encoded};
use runefs::error::{Error as RuneFsError, ReadError};
use runefs::{ArchiveRef, Dat2, Indices, MAIN_DATA};
use std::{io::Write, path::Path};

/// A complete virtual representation of the RuneScape cache file system.
#[derive(Debug)]
pub struct Cache {
    data: Dat2,
    pub(crate) indices: Indices,
}

impl Cache {
    /// Creates a high level virtual memory map over the cache directory.
    /// 
    /// All files are isolated on allocation by keeping them as in-memory files.
    ///
    /// # Errors
    ///
    /// The bulk of the errors which might occur are mostely I/O related due to acquiring 
    /// file handles.
    /// 
    /// Other errors might include protocol changes in newer caches.
    /// Any error unrelated to I/O at this stage should be considered a bug.
    pub fn new<P: AsRef<Path>>(path: P) -> crate::Result<Self> {
        Ok(Self {
            data: Dat2::new(path.as_ref().join(MAIN_DATA))?,
            indices: Indices::new(path)?,
        })
    }

    /// Generate a checksum based on the current cache.
    /// 
    /// The `Checksum` acts as a validator for individual cache files.
    /// Any RuneScape client will request a list of crc's to check the validity
    /// of all of the file data that was transferred.
    pub fn checksum(&self) -> crate::Result<Checksum> {
        Checksum::new(self)
    }

    /// Generate a checksum based on the current cache with RSA encryption.
    /// 
    /// `RsaChecksum` wraps a regular `Checksum` with the added benefit of encrypting
    /// the whirlpool hash into the checksum buffer.
    #[cfg(feature = "rs3")]
    #[cfg_attr(docsrs, doc(cfg(feature = "rs3")))]
    pub fn checksum_with<'a>(&self, keys: RsaKeys<'a>) -> crate::Result<RsaChecksum<'a>> {
        RsaChecksum::with_keys(self, keys)
    }

    /// Retrieves and constructs data corresponding to the given index and archive.
    ///
    /// # Errors
    ///
    /// When trying to retrieve data from an index or an archive that does not exist 
    /// the `IndexNotFound` or `ArchiveNotFound` errors are returned, respectively.
    /// 
    /// Any other errors such as sector validation failures or failed parsers should
    /// be considered a bug.
    pub fn read(&self, index_id: u8, archive_id: u32) -> crate::Result<Buffer<Encoded>> {
        let index = self
            .indices
            .get(&index_id)
            .ok_or(RuneFsError::Read(ReadError::IndexNotFound(index_id)))?;

        let archive = index
            .archive_refs
            .get(&archive_id)
            .ok_or(RuneFsError::Read(ReadError::ArchiveNotFound {
                idx: index_id,
                arc: archive_id,
            }))?;

        let buffer = self.data.read(archive)?;

        assert_eq!(buffer.len(), archive.length);

        Ok(buffer)
    }

    pub(crate) fn read_archive(&self, archive: &ArchiveRef) -> crate::Result<Buffer<Encoded>> {
        self.read(archive.index_id, archive.id)
    }

    /// Retrieves and writes data corresponding to the given index and archive into `W`.
    ///
    /// # Errors
    ///
    /// See the error section on [`read`](Cache::read) for more details.
    pub fn read_into_writer<W: Write>(
        &self,
        index_id: u8,
        archive_id: u32,
        writer: &mut W,
    ) -> crate::Result<()> {
        let index = self
            .indices
            .get(&index_id)
            .ok_or(RuneFsError::Read(ReadError::IndexNotFound(index_id)))?;

        let archive = index
            .archive_refs
            .get(&archive_id)
            .ok_or(RuneFsError::Read(ReadError::ArchiveNotFound {
                idx: index_id,
                arc: archive_id,
            }))?;
        Ok(self.data.read_into_writer(archive, writer)?)
    }

    /// Retrieves the huffman table.
    ///
    /// Required when decompressing chat messages, see [`Huffman`](crate::util::Huffman).
    pub fn huffman_table(&self) -> crate::Result<Buffer<Decoded>> {
        let index_id = 10;

        let archive = self.archive_by_name(index_id, "huffman")?;
        let buffer = self.read_archive(archive)?;

        assert_eq!(buffer.len(), archive.length);

        Ok(buffer.decode()?)
    }

    pub(crate) fn archive_by_name<T: AsRef<str>>(
        &self,
        index_id: u8,
        name: T,
    ) -> crate::Result<&ArchiveRef> {
        let index = self
            .indices
            .get(&index_id)
            .ok_or(RuneFsError::Read(ReadError::IndexNotFound(index_id)))?;
        let hash = util::djd2::hash(&name);

        let archive = index
            .metadata
            .iter()
            .find(|archive| archive.name_hash == hash)
            .ok_or_else(|| crate::error::NameHashMismatch {
                hash,
                name: name.as_ref().into(),
                idx: index_id,
            })?;

        let archive_ref = index
            .archive_refs
            .get(&archive.id)
            .ok_or(RuneFsError::Read(ReadError::ArchiveNotFound {
                idx: index_id,
                arc: archive.id,
            }))?;

        Ok(archive_ref)
    }
}

#[cfg(test)]
mod test_util {
    use super::Cache;
    use sha1::Sha1;

    fn is_normal<T: Send + Sync + Sized + Unpin>() {}

    #[test]
    fn normal_types() {
        is_normal::<super::Cache>();
    }

    pub fn osrs_cache() -> crate::Result<Cache> {
        Cache::new("./data/osrs_cache")
    }

    #[cfg(all(test, feature = "rs3"))]
    pub fn rs3_cache() -> crate::Result<Cache> {
        Cache::new("./data/rs3_cache")
    }

    pub fn hash(buffer: &[u8]) -> String {
        let mut m = Sha1::new();

        m.update(buffer);
        m.digest().to_string()
    }
}

#[cfg(test)]
mod read {
    mod osrs {
        use crate::test_util;

        #[test]
        fn ref_table() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            let buffer = cache.read(255, 10)?;
            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "64fb9fcf381a547bb7beafbc3b7ba4fd847f21ef");
            assert_eq!(buffer.len(), 77);
            Ok(())
        }
        #[test]
        fn random_read() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            let buffer = cache.read(0, 191)?;
            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "cd459f6ccfbd81c1e3bfadf899624f2519e207a9");
            assert_eq!(buffer.len(), 2055);
            Ok(())
        }
        #[test]
        fn large_read() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            let buffer = cache.read(2, 10)?;
            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "c6ee1518e9a39a42ecaf946c6c84a942cb3102f4");
            assert_eq!(buffer.len(), 260_537);
            Ok(())
        }
        #[test]
        fn deep_archive() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            let buffer = cache.read(7, 24918)?;
            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "fe91e9e9170a5a05ed2684c1db1169aa7ef4906e");
            assert_eq!(buffer.len(), 803);
            Ok(())
        }

        #[test]
        fn single_data_len() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            let buffer = cache.read(3, 278)?;

            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "036abb64d3f1734d892f69b1253a87639b7bcb44");
            assert_eq!(buffer.len(), 512);
            Ok(())
        }

        #[test]
        fn double_data_len() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            let buffer = cache.read(0, 1077)?;

            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "fbe9d365cf0c3efa94e0d4a2c5e607b28a1279b9");
            assert_eq!(buffer.len(), 1024);
            Ok(())
        }

        #[test]
        fn fails() -> crate::Result<()> {
            let cache = test_util::osrs_cache()?;
            assert!(cache.read(2, 25_000).is_err());
            Ok(())
        }
    }

    #[cfg(feature = "rs3")]
    mod rs3 {
        use crate::test_util;

        #[test]
        fn random_0_read() -> crate::Result<()> {
            let cache = test_util::rs3_cache()?;
            let buffer = cache.read(0, 25)?;
            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "81e455fc58fe5ac98fee4df5b78600bbf43e83f7");
            assert_eq!(buffer.len(), 1576);
            Ok(())
        }

        #[test]
        fn between_single_double() -> crate::Result<()> {
            let cache = test_util::rs3_cache()?;
            let buffer = cache.read(7, 0)?;

            let hash = test_util::hash(&buffer);
            assert_eq!(&hash, "b33919c6e4677abc6ec1c0bdd9557f820a163559");
            assert_eq!(buffer.len(), 529);
            Ok(())
        }

        #[test]
        fn fails() -> crate::Result<()> {
            let cache = test_util::rs3_cache()?;
            assert!(cache.read(2, 25_000).is_err());
            Ok(())
        }
    }
}

#[cfg(test)]
mod osrs {
    use super::test_util;
    use super::Cache;

    #[test]
    fn new() {
        assert!(Cache::new("./data/osrs_cache").is_ok());
    }

    #[test]
    fn new_wrong_path() {
        assert!(Cache::new("./wrong/path").is_err());
    }

    #[test]
    fn huffman_table() -> crate::Result<()> {
        let cache = test_util::osrs_cache()?;
        let buffer = cache.huffman_table()?;

        let hash = test_util::hash(&buffer);
        assert_eq!(&hash, "664e89cf25a0af7da138dd0f3904ca79cd1fe767");
        assert_eq!(buffer.len(), 256);

        Ok(())
    }
}

#[cfg(all(test, feature = "rs3"))]
mod rs3 {
    use super::test_util;
    use super::Cache;

    #[test]
    fn new() {
        assert!(Cache::new("./data/rs3_cache").is_ok());
    }

    #[test]
    fn new_wrong_path() {
        assert!(Cache::new("./wrong/path").is_err());
    }

    #[test]
    fn huffman_table() -> crate::Result<()> {
        let cache = test_util::rs3_cache()?;
        let buffer = cache.huffman_table()?;

        let hash = test_util::hash(&buffer);
        assert_eq!(&hash, "664e89cf25a0af7da138dd0f3904ca79cd1fe767");
        assert_eq!(buffer.len(), 256);

        Ok(())
    }
}