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//     Genten: Software for Generalized Tensor Decompositions
//     by Sandia National Laboratories
//
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// (NTESS). Under the terms of Contract DE-NA0003525 with NTESS, the U.S.
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#pragma once

#include <vector>
#include <ostream>
#include <iomanip>
#include <fstream>
#include "Genten_Util.hpp"

namespace Genten {

  // Captures and stores tensor decomposition performance information across
  // solver iterations
  class PerfHistory {
  public:

    // Stores performance history for a single iteration.  Not all methods
    // capture all values
    struct Entry {
      ttb_indx iteration;          // Completed solver iteration
      ttb_real residual;           // Residual of tensor approximation
      ttb_real fit;                // Tensor fit
      ttb_real grad_norm;          // Norm of gradient
      ttb_real cum_time;           // Cumulative time including this iteration
      ttb_real mttkrp_throughput;  // Floating-point throughput of MTTKRP

      Entry() : iteration(0), residual(0.0), fit(0.0), grad_norm(0.0),
                cum_time(0.0), mttkrp_throughput(0.0) {}
    };

    PerfHistory() = default;

    // Add a new entry
    void addEntry(const Entry& entry) { entries.push_back(entry); }

    // Add an empty entry
    void addEmpty() { entries.push_back(Entry()); }

    // Get a given entry
    Entry& getEntry(const ttb_indx i) { return entries[i]; }
    const Entry& getEntry(const ttb_indx i) const { return entries[i]; }
    Entry& operator[](const ttb_indx i) { return entries[i]; }
    const Entry& operator[](const ttb_indx i) const { return entries[i]; }

    // Get the last entry
    Entry& lastEntry() { return entries[entries.size()-1]; }
    const Entry& lastEntry() const { return entries[entries.size()-1]; }

    // The number of entries
    ttb_indx size() const { return entries.size(); }

    // Resize to given size
    void resize(const ttb_indx new_size) { entries.resize(new_size); }

    // Print history to stream
    void print(std::ostream& os) const {
      os << std::setw(6) << "iter" << "\t"
         << std::setw(13) << "residual" << "\t"
         << std::setw(13) << "fit" << "\t"
         << std::setw(13) << "||grad||" << "\t"
         << std::setw(9) << "time" << "\t"
         << std::setw(9) << "mttkrp" << std::endl;
      for (const auto& entry : entries)
        os << std::setw(6) << entry.iteration << " \t"
           << std::setw(13) << std::setprecision(6) << std::scientific
           << entry.residual << "\t"
           << std::setw(13) << std::setprecision(6) << std::scientific
           << entry.fit << "\t"
           << std::setw(13) << std::setprecision(6) << std::scientific
           << entry.grad_norm << "\t"
           << std::setw(9) << std::setprecision(2) << std::scientific
           << entry.cum_time << "\t"
           << std::setw(9) << std::setprecision(2) << std::scientific
           << entry.mttkrp_throughput
           << std::endl;
    }
    void print(const std::string& fname) const {
      std::ofstream fs(fname);
      print(fs);
    }

  private:
    std::vector<Entry> entries;
  };

}
