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 // This file is part of the Acts project.
 //
 // Copyright (C) 2022 CERN for the benefit of the Acts project
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 #include "ActsExamples/Io/Csv/CsvBFieldWriter.hpp"
 
 #include "Acts/Definitions/Algebra.hpp"
 #include "Acts/Definitions/Units.hpp"
 #include "Acts/MagneticField/InterpolatedBFieldMap.hpp"
 #include "Acts/MagneticField/MagneticFieldContext.hpp"
 #include "Acts/Utilities/Logger.hpp"
 #include "Acts/Utilities/Result.hpp"
 #include "Acts/Utilities/VectorHelpers.hpp"
 
 #include <iomanip>
 #include <ostream>
 #include <stdexcept>
 #include <vector>
 
 #include <dfe/dfe_io_dsv.hpp>
 
 namespace ActsExamples {
 template <CsvBFieldWriter::CoordinateType Coord, bool Grid>
 void CsvBFieldWriter::run(const Config<Coord, Grid>& config,
                           Acts::Logging::Level level) {
   ACTS_LOCAL_LOGGER(Acts::getDefaultLogger("CsvBFieldWriter", level));
 
   // Some helper typedefs, which will make our life easier down the line.
   using ConfigType = std::decay_t<decltype(config)>;
   using FieldType = typename decltype(ConfigType::bField)::element_type;
   using Vector = Acts::ActsVector<ConfigType::NDims>;
 
   FieldType& field = *config.bField;
 
   // Determine the columns to write to the CSV file. For Cartesian coordinates,
   // we give the x, y, and z coordinates for both the position and the field
   // vector. For cylindrical coordinates, we give r and z.
   std::vector<std::string> fields;
 
   if constexpr (Coord == CoordinateType::XYZ) {
     fields = {"x", "y", "z", "Bx", "By", "Bz"};
   } else {
     fields = {"r", "z", "Br", "Bz"};
   }
 
   // Initialize a CSV writer to the specified filename using the specified
   // column names.
   dfe::io_dsv_impl::DsvWriter<','> writer(fields, config.fileName);
 
   // We proceed by finding the number of bins, as well as the minimum and
   // maximum coordinates. This process depends quite heavily on the structure
   // of the magnetic field, so we need some compile-time conditionals.
   std::array<std::size_t, ConfigType::NDims> bins{};
   Vector min, max;
 
   if constexpr (Grid) {
     // First, we should check whether the Bfield actually has a
     // three-dimensional bin count and size.
     if (bins.size() != ConfigType::NDims ||
         field.getMin().size() != ConfigType::NDims ||
         field.getMax().size() != ConfigType::NDims) {
       throw std::invalid_argument("Incorrect input B-field dimensionality.");
     }
 
     // If our magnetic field is grid-like, we know that it has a built-in size
     // and bin count. We can use these, but the user may want to override the
     // values with custom values.
     for (std::size_t i = 0; i < ConfigType::NDims; ++i) {
       // For each dimension, we first get the corresponding value from the
       // grid-based vector field...
       bins[i] = field.getNBins()[i];
       min[i] = field.getMin()[i];
       max[i] = field.getMax()[i];
 
       // ...and then we override them with the optional user-supplied values.
       if (config.bins[i]) {
         bins[i] = *config.bins[i];
       }
 
       if (config.range[i][0]) {
         min[i] = *config.range[i][0];
       }
 
       if (config.range[i][1]) {
         max[i] = *config.range[i][1];
       }
     }
   } else {
     // If the vector field is not grid based, then there is no side and we are
     // forced to use the user-supplied data. Remember that in this case, the
     // values are not optional.
     for (std::size_t i = 0; i < ConfigType::NDims; ++i) {
       bins[i] = config.bins[i];
       min[i] = config.range[i][0];
       max[i] = config.range[i][1];
     }
   }
 
   // Next, we calculate the size (in physical space) of each bin.
   Vector delta;
 
   for (std::size_t i = 0; i < ConfigType::NDims; ++i) {
     delta[i] = (max[i] - min[i]) / (bins[i] - 1);
   }
 
   // Create the appropriate magnetic field context and cache to interact with
   // the B fields.
   Acts::MagneticFieldContext mctx{};
   typename FieldType::Cache cache = field.makeCache(mctx);
 
   // Finally, we can begin to fill the output file with data from our B field.
   // Again, the procedure is slightly different depending on whether we are
   // working with Cartesian or cylindrical coordinates.
   if constexpr (Coord == CoordinateType::XYZ) {
     ACTS_INFO("Writing XYZ field of size " << bins[0] << " x " << bins[1]
                                            << " x " << bins[2] << " to file "
                                            << config.fileName << "...");
 
     std::size_t total_items = bins[0] * bins[1] * bins[2];
 
     // For Cartesian coordinates, iterate over bins in the x, y, and z
     // directions. Note that we iterate one additional time because we are
     // writing the _edges_ of the bins, and the final bin needs to be closed.
     for (std::size_t x = 0; x < bins[0]; ++x) {
       for (std::size_t y = 0; y < bins[1]; ++y) {
         for (std::size_t z = 0; z < bins[2]; ++z) {
           // Compute the geometric position of this bin, then request the
           // magnetic field vector at that position.
           Acts::Vector3 pos = {x * delta[0] + min[0], y * delta[1] + min[1],
                                z * delta[2] + min[2]};
 
           Acts::Vector3 bField;
           if (auto fieldMap =
                   dynamic_cast<const Acts::InterpolatedMagneticField*>(
                       &field)) {
             // InterpolatedMagneticField::getField() returns an error for the
             // final point (upper edge), which is just outside the field volume.
             // So we use getFieldUnchecked instead.
             bField = fieldMap->getFieldUnchecked(pos);
           } else {
             Acts::Result<Acts::Vector3> flx = field.getField(pos, cache);
 
             // The aforementioned method is not guaranteed to succeed, so we
             // must check for a valid result, and then write it to disk. If the
             // result is invalid, throw an exception.
             if (flx.ok()) {
               bField = *flx;
             } else {
               throw std::runtime_error("B-field returned a non-extant value!");
             }
           }
 
           writer.append(pos[0] / Acts::UnitConstants::mm,
                         pos[1] / Acts::UnitConstants::mm,
                         pos[2] / Acts::UnitConstants::mm,
                         bField[0] / Acts::UnitConstants::T,
                         bField[1] / Acts::UnitConstants::T,
                         bField[2] / Acts::UnitConstants::T);
 
           // This final part is some diagnostic to convince the user that the
           // program is still running. We periodically provide the user with
           // some useful data.
           std::size_t idx = (x * bins[1] * bins[2]) + (y * bins[2]) + z + 1;
 
           if (idx % 10000 == 0 || idx == total_items) {
             ACTS_VERBOSE("Wrote " << idx << " out of " << total_items
                                   << " items (" << std::setprecision(3)
                                   << ((100.f * idx) / total_items) << "%).");
           }
         }
       }
     }
   } else {
     ACTS_INFO("Writing RZ field of size " << bins[0] << " x " << bins[1]
                                           << " to file " << config.fileName
                                           << "...");
 
     std::size_t total_items = bins[0] * bins[1];
 
     // For cylindrical coordinates, we only need to iterate over the r and z
     // coordinates, because we assume rotational cylindrical symmetry. This
     // makes the procedure quite a bit faster, too. Great!
     for (std::size_t r = 0; r < bins[0]; ++r) {
       for (std::size_t z = 0; z < bins[1]; ++z) {
         // Calculate the position (still in three dimensions), assuming that
         // the phi coordinate is zero. Then grab the field.
         Acts::Vector3 pos(min[0] + r * delta[0], 0.f, min[1] + z * delta[1]);
 
         Acts::Vector3 bField;
         if (auto fieldMap =
                 dynamic_cast<const Acts::InterpolatedMagneticField*>(&field)) {
           // InterpolatedMagneticField::getField() returns an error for the
           // final point (upper edge), which is just outside the field volume.
           // So we use getFieldUnchecked instead.
           bField = fieldMap->getFieldUnchecked(pos);
         } else {
           Acts::Result<Acts::Vector3> flx = field.getField(pos, cache);
 
           // Check the result, then write to disk. We write the r and z
           // positions as they are, then we write the z component of the result
           // vector as is, and we compute the r-value from the other components
           // of the vector.
           if (flx.ok()) {
             bField = *flx;
           } else {
             throw std::runtime_error("B-field returned a non-extant value!");
           }
         }
 
         writer.append(
             pos[0] / Acts::UnitConstants::mm, pos[2] / Acts::UnitConstants::mm,
             Acts::VectorHelpers::perp(bField) / Acts::UnitConstants::T,
             bField[2] / Acts::UnitConstants::T);
 
         // As before, print some progress reports for the user to enjoy while
         // they wait.
         std::size_t idx = (r * bins[1]) + z + 1;
 
         if (idx % 10000 == 0 || idx == total_items) {
           ACTS_VERBOSE("Wrote " << idx << " out of " << total_items
                                 << " items (" << std::setprecision(3)
                                 << ((100.f * idx) / total_items) << "%).");
         }
       }
     }
   }
 }
 
 // Note that this is a C++ source file, and not a header file. The reason for
 // this is that we can easily enumerate the different template parameter
 // combinations for the function above, and so we want to speed up compilation
 // times by just compiling these symbols once into the object file
 // corresponding to this TU.
 template void CsvBFieldWriter::run<CsvBFieldWriter::CoordinateType::XYZ, true>(
     const Config<CoordinateType::XYZ, true>&, Acts::Logging::Level);
 template void CsvBFieldWriter::run<CsvBFieldWriter::CoordinateType::RZ, true>(
     const Config<CoordinateType::RZ, true>&, Acts::Logging::Level);
 template void CsvBFieldWriter::run<CsvBFieldWriter::CoordinateType::XYZ, false>(
     const Config<CoordinateType::XYZ, false>&, Acts::Logging::Level);
 template void CsvBFieldWriter::run<CsvBFieldWriter::CoordinateType::RZ, false>(
     const Config<CoordinateType::RZ, false>&, Acts::Logging::Level);
 }  // namespace ActsExamples

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