/*

  EXAMPLE osmium_filter_discussions

  Read OSM changesets with discussions from a changeset dump like the one
  you get from https://planet.osm.org/planet/discussions-latest.osm.bz2
  and write out only those changesets which have discussions (ie comments).

  DEMONSTRATES USE OF:
  * file input and output
  * setting file formats using the osmium::io::File class
  * OSM file headers
  * input and output iterators

  SIMPLER EXAMPLES you might want to understand first:
  * osmium_read
  * osmium_count

  LICENSE
  The code in this example file is released into the Public Domain.

*/

#include <algorithm> // for std::copy_if
#include <exception>
#include <iostream>  // for std::cout, std::cerr

// We want to read OSM files in XML format
// (other formats don't support full changesets, so only XML is needed here).
#include <osmium/io/xml_input.hpp>

// We want to write OSM files in XML format.
#include <osmium/io/xml_output.hpp>

// We want to use input and output iterators for easy integration with the
// algorithms of the standard library.
#include <osmium/io/input_iterator.hpp>
#include <osmium/io/output_iterator.hpp>

// We want to support any compression (none, gzip, and bzip2).
#include <osmium/io/any_compression.hpp>

int main(int argc, char* argv[]) {
    if (argc != 3) {
        std::cout << "Usage: " << argv[0] << " INFILE OUTFILE\n";
        return 1;
    }

    try {
        // The input file, deduce file format from file suffix.
        const osmium::io::File input_file{argv[1]};

        // The output file, force XML OSM file format.
        const osmium::io::File output_file{argv[2], "osm"};

        // Initialize Reader for the input file.
        // Read only changesets (will ignore nodes, ways, and
        // relations if there are any).
        osmium::io::Reader reader{input_file, osmium::osm_entity_bits::changeset};

        // Get the header from the input file.
        osmium::io::Header header = reader.header();

        // Set the "generator" on the header to ourselves.
        header.set("generator", "osmium_filter_discussions");

        // Initialize writer for the output file. Use the header from the input
        // file for the output file. This will copy over some header information.
        // The last parameter will tell the writer that it is allowed to overwrite
        // an existing file. Without it, it will refuse to do so.
        osmium::io::Writer writer{output_file, header, osmium::io::overwrite::allow};

        // Create range of input iterators that will iterator over all changesets
        // delivered from input file through the "reader".
        auto input_range = osmium::io::make_input_iterator_range<osmium::Changeset>(reader);

        // Create an output iterator writing through the "writer" object to the
        // output file.
        auto output_iterator = osmium::io::make_output_iterator(writer);

        // Copy all changesets from input to output that have at least one comment.
        std::copy_if(input_range.begin(), input_range.end(), output_iterator, [](const osmium::Changeset& changeset) {
            return changeset.num_comments() > 0;
        });

        // Explicitly close the writer and reader. Will throw an exception if
        // there is a problem. If you wait for the destructor to close the writer
        // and reader, you will not notice the problem, because destructors must
        // not throw.
        writer.close();
        reader.close();
    } catch (const std::exception& e) {
        // All exceptions used by the Osmium library derive from std::exception.
        std::cerr << e.what() << '\n';
        return 1;
    }
}

