extern crate libc;
use self::libc::{c_void, size_t};
use std::io::{IoError};
use std::c_vec::CVec;
use std::c_str::CString;
use std::str::from_utf8;

use rocksdb_ffi;

pub struct Rocksdb {
  inner: rocksdb_ffi::RocksdbInstance,
}

impl Rocksdb {
  pub fn put(&self, key: &[u8], value: &[u8]) -> Result<(), String> {
    unsafe {
      let writeopts = rocksdb_ffi::rocksdb_writeoptions_create();
      let err = 0 as *mut i8;
      rocksdb_ffi::rocksdb_put(self.inner, writeopts, key.as_ptr(),
            key.len() as size_t, value.as_ptr(),
            value.len() as size_t, err);
      if err.is_not_null() {
        let cs = CString::new(err as *const i8, true);
        match cs.as_str() {
          Some(error_string) =>
            return Err(error_string.to_string()),
          None => {
            let ie = IoError::last_error();
            return Err(format!(
                "ERROR: desc:{}, details:{}",
                ie.desc,
                ie.detail.unwrap_or_else(
                  || {"none provided by OS".to_string()})))
          }
        }
      }
      return Ok(())
    }
  }

  pub fn get<'a>(&self, key: &[u8]) -> RocksdbResult<'a, RocksdbVector, String> {
    unsafe {
      let readopts = rocksdb_ffi::rocksdb_readoptions_create();
      let rocksdb_ffi::RocksdbReadOptions(read_opts_ptr) = readopts;
      if read_opts_ptr.is_null() {
        return RocksdbResult::Error("Unable to create rocksdb read \
          options.  This is a fairly trivial call, and its failure \
          may be indicative of a mis-compiled or mis-loaded rocksdb \
          library.".to_string());
      }

      let val_len: size_t = 0;
      let val_len_ptr = &val_len as *const size_t;
      let err = 0 as *mut i8;
      let val = rocksdb_ffi::rocksdb_get(self.inner, readopts, key.as_ptr(),
                  key.len() as size_t, val_len_ptr, err) as *mut u8;
      if err.is_not_null() {
        let cs = CString::new(err as *const i8, true);
        match cs.as_str() {
          Some(error_string) =>
            return RocksdbResult::Error(error_string.to_string()),
          None =>
            return RocksdbResult::Error("Unable to get value from \
              rocksdb. (non-utf8 error received from underlying \
              library)".to_string()),
        }
      }
      match val.is_null() {
        true =>  RocksdbResult::None,
        false => {
          RocksdbResult::Some(RocksdbVector::from_c(val, val_len))
        }
      }
    }
  }

  pub fn delete(&self, key: &[u8]) -> Result<(),String> {
    unsafe {
      let writeopts = rocksdb_ffi::rocksdb_writeoptions_create();
      let err = 0 as *mut i8;
      rocksdb_ffi::rocksdb_delete(self.inner, writeopts, key.as_ptr(),
            key.len() as size_t, err);
      if err.is_not_null() {
        let cs = CString::new(err as *const i8, true);
        match cs.as_str() {
          Some(error_string) =>
            return Err(error_string.to_string()),
          None => {
            let ie = IoError::last_error();
            return Err(format!(
                "ERROR: desc:{}, details:{}",
                ie.desc,
                ie.detail.unwrap_or_else(
                  || {"none provided by OS".to_string()})))
          }
        }
      }
      return Ok(())
    }
  }

  pub fn close(&self) {
    unsafe { rocksdb_ffi::rocksdb_close(self.inner); }
  }

}

pub struct RocksdbVector {
  inner: CVec<u8>,
}

impl RocksdbVector {
  pub fn from_c(val: *mut u8, val_len: size_t) -> RocksdbVector {
    unsafe {
      RocksdbVector {
        inner:
          CVec::new_with_dtor(val, val_len as uint,
            proc(){ libc::free(val as *mut c_void); })
      }
    }
  }

  pub fn as_slice<'a>(&'a self) -> &'a [u8] {
    self.inner.as_slice()
  }

  pub fn to_utf8<'a>(&'a self) -> Option<&'a str> {
    from_utf8(self.inner.as_slice())
  }
}

// RocksdbResult exists because of the inherent difference between
// an operational failure and the absence of a possible result.
#[deriving(Clone, PartialEq, PartialOrd, Eq, Ord, Show)]
pub enum RocksdbResult<'a,T,E> {
  Some(T),
  None,
  Error(E),
}

impl <'a,T,E> RocksdbResult<'a,T,E> {
  #[unstable = "waiting for unboxed closures"]
  pub fn map<U>(self, f: |T| -> U) -> RocksdbResult<U,E> {
    match self {
      RocksdbResult::Some(x) => RocksdbResult::Some(f(x)),
      RocksdbResult::None => RocksdbResult::None,
      RocksdbResult::Error(e) => RocksdbResult::Error(e),
    }
  }

  pub fn unwrap(self) -> T {
    match self {
      RocksdbResult::Some(x) => x,
      RocksdbResult::None => panic!("Attempted unwrap on RocksdbResult::None"),
      RocksdbResult::Error(_) => panic!("Attempted unwrap on RocksdbResult::Error"),
    }
  }

  #[unstable = "waiting for unboxed closures"]
  pub fn on_error<U>(self, f: |E| -> U) -> RocksdbResult<T,U> {
    match self {
      RocksdbResult::Some(x) => RocksdbResult::Some(x),
      RocksdbResult::None => RocksdbResult::None,
      RocksdbResult::Error(e) => RocksdbResult::Error(f(e)),
    }
  }

  #[unstable = "waiting for unboxed closures"]
  pub fn on_absent(self, f: || -> ()) -> RocksdbResult<T,E> {
    match self {
      RocksdbResult::Some(x) => RocksdbResult::Some(x),
      RocksdbResult::None => {
        f();
        RocksdbResult::None
      },
      RocksdbResult::Error(e) => RocksdbResult::Error(e),
    }
  }

  pub fn is_some(self) -> bool {
    match self {
      RocksdbResult::Some(_) => true,
      RocksdbResult::None => false,
      RocksdbResult::Error(_) => false,
    }
  }
  pub fn is_none(self) -> bool {
    match self {
      RocksdbResult::Some(_) => false,
      RocksdbResult::None => true,
      RocksdbResult::Error(_) => false,
    }
  }
  pub fn is_error(self) -> bool {
    match self {
      RocksdbResult::Some(_) => false,
      RocksdbResult::None => false,
      RocksdbResult::Error(_) => true,
    }
  }
}

pub fn create_or_open(path: String) -> Result<Rocksdb, String> {
  open(path, true)
}

pub fn open(path: String, create_if_missing: bool) -> Result<Rocksdb, String> {
  unsafe {
    let opts = rocksdb_ffi::rocksdb_options_create();
    let rocksdb_ffi::RocksdbOptions(opt_ptr) = opts;
    if opt_ptr.is_null() {
      return Err("Could not create options".to_string());
    }

    //rocksdb_ffi::rocksdb_options_increase_parallelism(opts, 2);
    //rocksdb_ffi::rocksdb_options_optimize_level_style_compaction(opts, 0);

    match create_if_missing {
      true => rocksdb_ffi::rocksdb_options_set_create_if_missing(opts, 1),
      false => rocksdb_ffi::rocksdb_options_set_create_if_missing(opts, 0),
    }

    let cpath = path.to_c_str();
    let cpath_ptr = cpath.as_ptr();

    //TODO test path here, as if rocksdb fails it will just crash the
    //     process currently

    let err = 0 as *mut i8;
    let db = rocksdb_ffi::rocksdb_open(opts, cpath_ptr, err);
    let rocksdb_ffi::RocksdbInstance(db_ptr) = db;
    if err.is_not_null() {
      let cs = CString::new(err as *const i8, true);
      match cs.as_str() {
        Some(error_string) =>
          return Err(error_string.to_string()),
        None =>
          return Err("Could not initialize database.".to_string()),
      }
    }
    if db_ptr.is_null() {
      return Err("Could not initialize database.".to_string());
    }
    Ok(Rocksdb{inner: db})
  }
}

#[allow(dead_code)]
#[test]
fn external() {
  let db = open("externaltest".to_string(), true).unwrap();
  let p = db.put(b"k1", b"v1111");
  assert!(p.is_ok());
  let r: RocksdbResult<RocksdbVector, String> = db.get(b"k1");
  assert!(r.unwrap().to_utf8().unwrap() == "v1111");
  assert!(db.delete(b"k1").is_ok());
  assert!(db.get(b"k1").is_none());
  db.close();
}