// Copyright (c) 2024-present, fjall-rs
// This source code is licensed under both the Apache 2.0 and MIT License
// (found in the LICENSE-* files in the repository)

use crate::{
    CompressionType, journal::error::RecoveryError as JournalRecoveryError, version::FormatVersion,
};

/// Errors that may occur in the storage engine
#[derive(Debug)]
#[non_exhaustive]
pub enum Error {
    /// Error inside LSM-tree
    Storage(lsm_tree::Error),

    /// I/O error
    Io(std::io::Error),

    /// Error during journal recovery
    JournalRecovery(JournalRecoveryError),

    /// Invalid or unparsable data format version
    InvalidVersion(Option<FormatVersion>),

    /// Decompression failed
    Decompress(CompressionType),

    /// Invalid journal trailer detected
    InvalidTrailer,

    /// Invalid tag detected during decoding
    InvalidTag((&'static str, u8)),

    /// A previous flush / commit operation failed, indicating a hardware-related failure
    ///
    /// Future writes will not be accepted as consistency cannot be guaranteed.
    ///
    /// **At this point, it's best to let the application crash and try to recover.**
    ///
    /// More info: <https://www.usenix.org/system/files/atc20-rebello.pdf>
    Poisoned,

    /// Keyspace is deleted
    KeyspaceDeleted,

    /// Database is locked.
    Locked,

    /// Database is unrecoverable, see logs for details
    Unrecoverable,
}

impl std::fmt::Display for Error {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "FjallError: {self:?}")
    }
}

impl From<std::io::Error> for Error {
    fn from(inner: std::io::Error) -> Self {
        Self::Io(inner)
    }
}

impl From<lsm_tree::Error> for Error {
    fn from(inner: lsm_tree::Error) -> Self {
        Self::Storage(inner)
    }
}

impl std::error::Error for Error {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            Self::Storage(inner) => Some(inner),
            Self::Io(inner) => Some(inner),
            Self::JournalRecovery(inner) => Some(inner),
            _ => None,
        }
    }
}

/// Result helper type
pub type Result<T> = std::result::Result<T, Error>;
