/*
  Copyright (C) 2005-2012 Steven L. Scott

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
*/

#ifndef BOOM_BETA_POSTERIOR_SAMPLER_HPP_
#define BOOM_BETA_POSTERIOR_SAMPLER_HPP_

#include <Models/DoubleModel.hpp>
#include <Models/BetaModel.hpp>
#include <Models/PosteriorSamplers/PosteriorSampler.hpp>
#include <Samplers/ScalarSliceSampler.hpp>
#include <stdexcept>

namespace BOOM {

  // BetaPosteriorSampler assumes an independent prior on a/(a+b) and
  // a+b.  If priors with support outside (0, 1) and (0, infinity) are
  // given, then support is truncated to those intervals.
  class BetaPosteriorSampler : public PosteriorSampler {
   public:
    BetaPosteriorSampler(BetaModel *model,
                         Ptr<DoubleModel> mean_prior,
                         Ptr<DoubleModel> sample_size_prior);
    virtual void draw();
    virtual double logpri()const;

   private:
    BetaModel *model_;
    Ptr<DoubleModel> mean_prior_;
    Ptr<DoubleModel> sample_size_prior_;
    ScalarSliceSampler mean_sampler_;
    ScalarSliceSampler sample_size_sampler_;

    // If an exception is encountered in a call to the slice sampler,
    // generate a message containing the state of the sampler.  If *e
    // is non-NULL then print the exception message as part of the
    // error message.
    std::string error_message(
        const char *thing_being_drawn, const std::exception *e)const;
  };

} // namespace BOOM

#endif // BOOM_BETA_POSTERIOR_SAMPLER_HPP_
