// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.stash;
using fuchsia.mem;

// Strings over 12 kb will be tossed. This number is chosen arbitrarily, if you
// think it should be higher just ask.
const uint64 MAX_STRING_SIZE = 12000;
const uint64 MAX_KEY_SIZE = 256;

// ValueType encodes a type for a field in the store
enum ValueType : uint8 {
    INT_VAL = 1;
    FLOAT_VAL = 2;
    BOOL_VAL = 3;
    STRING_VAL = 4;
    BYTES_VAL = 5;
};

// ListItem is returned when a series of keys are being listed.
struct ListItem {
    string:MAX_KEY_SIZE key;
    ValueType type;
};

// KeyValue is used when a series of keys are being read, or the default state
// for the store is being set.
struct KeyValue {
    string:MAX_KEY_SIZE key;
    Value val;
};

// Value holds a value for a given key.
union Value {
    int64 intval;
    float64 floatval;
    bool boolval;
    string:MAX_STRING_SIZE stringval;
    fuchsia.mem.Buffer bytesval;
};

// The iterator returned when a series of keys are being listed. Returns an
// empty vector when there are no more remaining ListItems.
protocol ListIterator {
    GetNext() -> (vector<ListItem> keys);
};

// The iterator returned when a series of keys are being read. Returns an
// empty vector when there are no more remaining KeyValues.
protocol GetIterator {
    GetNext() -> (vector<KeyValue> kvs);
};

// The interface returned when a new accessor is created.
protocol StoreAccessor {
    // Gets a single value from the store.
    GetValue(string:MAX_KEY_SIZE key) -> (Value? val);

    // Sets a single value in the store. Overwrites existing values. Commit()
    // must be called for this change to take effect.
    SetValue(string:MAX_KEY_SIZE key, Value val);

    // Deletes a single value in the store. Does nothing if the value doesn't
    // exist. Commit() must be called for this change to take effect.
    DeleteValue(string:MAX_KEY_SIZE key);

    // Lists all keys under a given prefix.
    ListPrefix(string:MAX_KEY_SIZE prefix, request<ListIterator> it);

    // Reads the values of all keys under a given prefix.
    GetPrefix(string:MAX_KEY_SIZE prefix, request<GetIterator> it);

    // Deletes the all keys under a given prefix.
    DeletePrefix(string:MAX_KEY_SIZE prefix);

    // Atomically causes all of the state modifications that happened in this
    // accessor to take place.
    Commit();
};

// Interface used to interact with a given client's key/value store
[Discoverable, FragileBase]
protocol Store {
    // Identify should be called at the beginning of a connection to identify
    // which client service's store is to be accessed. In the future this will
    // be deprecated in favor of component monikers, and each client will only
    // be able to access its own store.
    Identify(string:MAX_KEY_SIZE name);

    // Creates a accessor for interacting with the store. The resulting
    // interface can be used to inspect and modify the state of the store.
    CreateAccessor(bool read_only, request<StoreAccessor> accessor_request);
};

// Interface used to interact with a given client's key/value store. The bytes
// type is disabled in this store.
[Discoverable]
protocol SecureStore {
    compose Store;
};