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//! Key-Value semantics.

use super::Database;

use options::{WriteOptions, ReadOptions, c_writeoptions, c_readoptions};
use super::error::Error;
use std::ptr;
use std::slice::from_raw_parts;
use libc::{c_char, size_t, c_void};
use leveldb_sys::*;

/// Key-Value-Access to the leveldb database, providing
/// a basic interface.
pub trait KV {
    /// get a value from the database.
    ///
    /// The passed key will be compared using the comparator.
    fn get<K: AsRef<[u8]>>(&self,
                               options: ReadOptions,
                               key: K)
                               -> Result<Option<Vec<u8>>, Error>;
    /// put a binary value into the database.
    ///
    /// If the key is already present in the database, it will be overwritten.
    ///
    /// The passed key will be compared using the comparator.
    ///
    /// The database will be synced to disc if `options.sync == true`. This is
    /// NOT the default.
    fn put<K: AsRef<[u8]>>(&self,
                           options: WriteOptions,
                           key: K,
                           value: &[u8])
                           -> Result<(), Error>;
    /// delete a value from the database.
    ///
    /// The passed key will be compared using the comparator.
    ///
    /// The database will be synced to disc if `options.sync == true`. This is
    /// NOT the default.
    fn delete<K: AsRef<[u8]>>(&self, options: WriteOptions, key: K) -> Result<(), Error>;
}

impl KV for Database {
    /// put a binary value into the database.
    ///
    /// If the key is already present in the database, it will be overwritten.
    ///
    /// The passed key will be compared using the comparator.
    ///
    /// The database will be synced to disc if `options.sync == true`. This is
    /// NOT the default.
    fn put<K: AsRef<[u8]>>(&self,
                           options: WriteOptions,
                           key: K,
                           value: &[u8])
                           -> Result<(), Error> {
        unsafe {
            let k = key.as_ref();
            let mut error = ptr::null_mut();
            let c_writeoptions = c_writeoptions(options);
            leveldb_put(self.database.ptr,
                        c_writeoptions,
                        k.as_ptr() as *mut c_char,
                        k.len() as size_t,
                        value.as_ptr() as *mut c_char,
                        value.len() as size_t,
                        &mut error);
            leveldb_writeoptions_destroy(c_writeoptions);

            if error == ptr::null_mut() {
                Ok(())
            } else {
                Err(Error::new_from_i8(error))
            }
        }
    }

    /// delete a value from the database.
    ///
    /// The passed key will be compared using the comparator.
    ///
    /// The database will be synced to disc if `options.sync == true`. This is
    /// NOT the default.
    fn delete<K: AsRef<[u8]>>(&self, options: WriteOptions, key: K) -> Result<(), Error> {
        unsafe {
            let k = key.as_ref();
            let mut error = ptr::null_mut();
            let c_writeoptions = c_writeoptions(options);
            leveldb_delete(self.database.ptr,
                           c_writeoptions,
                           k.as_ptr() as *mut c_char,
                           k.len() as size_t,
                           &mut error);
            leveldb_writeoptions_destroy(c_writeoptions);
            if error == ptr::null_mut() {
                Ok(())
            } else {
                Err(Error::new_from_i8(error))
            }
        }
    }

    /// get a value from the database.
    ///
    /// The passed key will be compared using the comparator.
    fn get<K: AsRef<[u8]>>(&self,
                               options: ReadOptions,
                               key: K)
                               -> Result<Option<Vec<u8>>, Error> {
        unsafe {
            let k = key.as_ref();
            let mut error = ptr::null_mut();
            let mut length: size_t = 0;
            let c_readoptions = c_readoptions(&options);
            let result = leveldb_get(self.database.ptr,
                                     c_readoptions,
                                     k.as_ptr() as *mut c_char,
                                     k.len() as size_t,
                                     &mut length,
                                     &mut error);
            leveldb_readoptions_destroy(c_readoptions);

            if error == ptr::null_mut() {
                if result == ptr::null_mut() {
                    Ok(None)
                } else {
                    let vec = from_raw_parts(result as *mut u8, length as usize).to_vec();
                    leveldb_free(result as *mut c_void);
                    Ok(Some(vec))
                }
            } else {
                Err(Error::new_from_i8(error))
            }
        }
    }
}