// Copyright (c) 2018-2019, The Monero Project
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#pragma once

#include <cstdint>
#include <functional>
#include <vector>

#include "common/expect.h"            // monero/src
#include "rpc/message_data_structs.h" // monero/src
#include "span.h"                     // monero/src
#include "util/fwd.h"

namespace lws
{
    using histogram = cryptonote::rpc::output_amount_count;
    using output_ref = cryptonote::rpc::output_amount_and_index;
    using output_keys = cryptonote::rpc::output_key_mask_unlocked;

    struct random_output
    {
        output_keys keys;
        std::uint64_t index;
    };

    struct random_ring
    {
        std::vector<random_output> ring;
        std::uint64_t amount;
    };

    using key_fetcher = expect<std::vector<output_keys>>(std::vector<output_ref>);

    /*!
        Selects random outputs for use in a ring signature. `amounts` of `0`
        use a gamma distribution algorithm and all other amounts use a
        triangular distribution.

        \param mixin The number of dummy outputs per ring.
        \param amounts The amounts that need dummy outputs to be selected.
        \param pick_rct Ring-ct distribution from the daemon
        \param histograms A histogram from the daemon foreach non-zero value
            in `amounts`.
        \param fetch A function that can retrieve the keys for the randomly
            selected outputs.

        \note `histograms` is modified - the list is sorted by amount.

        \note This currenty leaks the real outputs to `fetch`, because the
            real output is not provided alongside the dummy outputs. This is a
            limitation of the current openmonero/mymonero API. When this is
            resolved, this function can possibly be moved outside of the `lws`
            namespace for use by simple wallet.

        \return Randomly selected outputs in rings of size `mixin`, one for
            each element in `amounts`. Amounts with less than `mixin` available
            are not returned. All outputs are unlocked.
    */
    expect<std::vector<random_ring>> pick_random_outputs(
        std::uint32_t mixin,
        epee::span<const std::uint64_t> amounts,
        gamma_picker& pick_rct,
        epee::span<histogram> histograms,
        std::function<key_fetcher> fetch
    );
}