use crate::block::Block;
use crate::cache::Cache;
use crate::cmp::{Cmp, DefaultCmp};
use crate::compressor::Compressor;
use crate::disk_env;
use crate::env::Env;
use crate::filter;
use crate::infolog::{self, Logger};
use crate::mem_env::MemEnv;
use crate::types::{share, Shared};

use std::default::Default;
use std::rc::Rc;

const KB: usize = 1 << 10;
const MB: usize = KB * KB;

const BLOCK_MAX_SIZE: usize = 4 * KB;
const BLOCK_CACHE_CAPACITY: usize = 8 * MB;
const WRITE_BUFFER_SIZE: usize = 4 * MB;
const DEFAULT_BITS_PER_KEY: u32 = 10; // NOTE: This may need to be optimized.

/// Options contains general parameters for a LevelDB instance. Most of the names are
/// self-explanatory; the defaults are defined in the `Default` implementation.
#[derive(Clone)]
pub struct Options {
    pub cmp: Rc<Box<dyn Cmp>>,
    pub env: Rc<Box<dyn Env>>,
    pub log: Option<Shared<Logger>>,
    pub create_if_missing: bool,
    pub error_if_exists: bool,
    pub paranoid_checks: bool,
    pub write_buffer_size: usize,
    pub max_open_files: usize,
    pub max_file_size: usize,
    pub block_cache: Shared<Cache<Block>>,
    pub block_size: usize,
    pub block_restart_interval: usize,
    /// Note: you have to open a database with the same compression type as it was written to, in
    /// order to not lose data! (this is a bug and will be fixed)
    pub compressor: u8,

    pub compressor_list: Rc<[Option<Box<dyn Compressor>>; 256]>,
    pub reuse_logs: bool,
    pub reuse_manifest: bool,
    pub filter_policy: filter::BoxedFilterPolicy,
}

impl Default for Options {
    fn default() -> Options {
        const INIT: Option<Box<dyn Compressor>> = None;
        let mut compressor_list = [INIT; 256];
        compressor_list[0] = Some(crate::compressor::NoneCompressor::new());
        compressor_list[1] = Some(crate::compressor::SnappyCompressor::new());

        Options {
            cmp: Rc::new(Box::new(DefaultCmp)),
            env: Rc::new(Box::new(disk_env::PosixDiskEnv::new())),
            log: None,
            create_if_missing: true,
            error_if_exists: false,
            paranoid_checks: false,
            write_buffer_size: WRITE_BUFFER_SIZE,
            max_open_files: 1 << 10,
            max_file_size: 2 << 20,
            // 2000 elements by default
            block_cache: share(Cache::new(BLOCK_CACHE_CAPACITY / BLOCK_MAX_SIZE)),
            block_size: BLOCK_MAX_SIZE,
            block_restart_interval: 16,
            reuse_logs: true,
            reuse_manifest: true,
            compressor: 0,
            compressor_list: Rc::new(compressor_list),
            filter_policy: Rc::new(Box::new(filter::BloomPolicy::new(DEFAULT_BITS_PER_KEY))),
        }
    }
}

/// Returns Options that will cause a database to exist purely in-memory instead of being stored on
/// disk. This is useful for testing or ephemeral databases.
pub fn in_memory() -> Options {
    let mut opt = Options::default();
    opt.env = Rc::new(Box::new(MemEnv::new()));
    opt
}

pub fn for_test() -> Options {
    let mut o = Options::default();
    o.env = Rc::new(Box::new(MemEnv::new()));
    o.log = Some(share(infolog::stderr()));
    o
}