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// Copyright 2015-2018 Capital One Services, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! # Key-Value Store
//! 
//! This module contains the key-value store through which guest modules access
//! the currently bound `wascap:keyvalue` capability provider

use std::rc::Rc;
use super::SOURCE_GUEST;
use crate::HostRuntimeInterface;
use crate::Result;
use codec::keyvalue::{
    AddRequest, AddResponse, DelRequest, GetRequest, GetResponse, ListPushRequest,
    ListRangeRequest, ListRangeResponse, ListResponse, SetRequest, SetResponse,
};
use prost::Message;
use wascap_codec as codec;
use wascap_codec::AsCommand;

const TARGET_KEYVALUE: &'static str = "wascap:keyvalue";


/// An abstraction around a host runtime capability for a key-value store
pub struct KeyValueStore {
    hri: Rc<&'static dyn HostRuntimeInterface>,
}

impl KeyValueStore {
    pub(crate) fn new(hri: Rc<&'static dyn HostRuntimeInterface>) -> KeyValueStore {
        KeyValueStore {
            hri,
        }
    }

    /// Retrieves the value for a given key, returning the value and whether or not 
    /// it existed.
    pub fn get(&self, key: &str) -> Result<(String, bool)> {
        let cmd = GetRequest {
            key: key.to_string(),
        }
        .as_command(SOURCE_GUEST, TARGET_KEYVALUE);
        self.hri.do_host_call(&cmd).map(|evt| {
            let resp = GetResponse::decode(&evt.payload.unwrap().value).unwrap();
            (resp.value, resp.exists)
        })
    }

    /// Sets the value for a given key
    pub fn set(&self, key: &str, value: &str) -> Result<()> {
        let cmd = SetRequest {
            key: key.to_string(),
            value: value.to_string(),
        }
        .as_command(SOURCE_GUEST, TARGET_KEYVALUE);
        self.hri.do_host_call(&cmd).map(|_evt| ())
    }

    /// Performs an atomic add operation, returning the new value
    pub fn atomic_add(&self, key: &str, value: i32) -> Result<i32> {
        let cmd = AddRequest {
            key: key.to_string(),
            value: value,
        }
        .as_command(SOURCE_GUEST, TARGET_KEYVALUE);
        self.hri.do_host_call(&cmd).map(|evt| {
            let resp = AddResponse::decode(&evt.payload.unwrap().value).unwrap();
            resp.value
        })
    }

    /// Adds a string value to a list stored within a given key
    pub fn list_add(&self, key: &str, item: &str) -> Result<usize> {
        let cmd = ListPushRequest {
            key: key.to_string(),
            value: item.to_string(),
        }
        .as_command(SOURCE_GUEST, TARGET_KEYVALUE);
        self.hri.do_host_call(&cmd).map(|evt| {
            let resp = ListResponse::decode(&evt.payload.unwrap().value).unwrap();
            resp.new_count as usize
        })
    }

    /// Deletes the given key
    pub fn del_key(&self, key: &str) -> Result<()> {
        let cmd = DelRequest {
            key: key.to_string(),
        }
        .as_command(SOURCE_GUEST, TARGET_KEYVALUE);
        self.hri.do_host_call(&cmd).map(|_evt| ())
    }

    /// Requests a list of values contained within a given key
    pub fn list_range(&self, key: &str, start: isize, stop_inclusive: isize) -> Result<Vec<String>> {
        let cmd = ListRangeRequest {
            key: key.to_string(),
            start: start as i32,
            stop: stop_inclusive as i32,
        }
        .as_command(SOURCE_GUEST, TARGET_KEYVALUE);
        self.hri.do_host_call(&cmd).map(|evt| {
            let resp = ListRangeResponse::decode(&evt.payload.unwrap().value).unwrap();
            resp.values
        })
    }
}