osrm-backend/include/engine/guidance/assemble_leg.hpp

#ifndef ENGINE_GUIDANCE_ASSEMBLE_LEG_HPP_
#define ENGINE_GUIDANCE_ASSEMBLE_LEG_HPP_

#include "engine/datafacade/datafacade_base.hpp"
#include "engine/guidance/leg_geometry.hpp"
#include "engine/guidance/route_leg.hpp"
#include "engine/guidance/route_step.hpp"
#include "engine/internal_route_result.hpp"
#include "util/typedefs.hpp"

#include <boost/algorithm/string/join.hpp>
#include <boost/range/adaptor/filtered.hpp>
#include <boost/range/adaptor/transformed.hpp>

#include <cstddef>
#include <cstdint>

#include <algorithm>
#include <array>
#include <numeric>
#include <string>
#include <utility>
#include <vector>

namespace osrm
{
namespace engine
{
namespace guidance
{
namespace detail
{
const constexpr std::size_t MAX_USED_SEGMENTS = 2;
struct NamedSegment
{
    EdgeWeight duration;
    std::uint32_t position;
    std::uint32_t name_id;
};

template <std::size_t SegmentNumber>

std::array<std::uint32_t, SegmentNumber> summarizeRoute(const std::vector<PathData> &route_data,
                                                        const PhantomNode &target_node,
                                                        const bool target_traversed_in_reverse)
{
    // merges segments with same name id
    const auto collapse_segments = [](std::vector<NamedSegment> &segments) {
        auto out = segments.begin();
        auto end = segments.end();

        // Do nothing if we were given an empty array
        if (out == end)
        {
            return end;
        }

        for (auto in = std::next(out); in != end; ++in)
        {
            if (in->name_id == out->name_id)
            {
                out->duration += in->duration;
            }
            else
            {
                ++out;
                BOOST_ASSERT(out != end);
                *out = *in;
            }
        }
        BOOST_ASSERT(out != end);
        return ++out;
    };

    std::vector<NamedSegment> segments(route_data.size());
    std::uint32_t index = 0;
    std::transform(
        route_data.begin(), route_data.end(), segments.begin(), [&index](const PathData &point) {
            return NamedSegment{point.duration_until_turn, index++, point.name_id};
        });
    const auto target_duration =
        target_traversed_in_reverse ? target_node.reverse_weight : target_node.forward_weight;
    if (target_duration > 1)
        segments.push_back({target_duration, index++, target_node.name_id});
    // this makes sure that the segment with the lowest position comes first
    std::sort(
        segments.begin(), segments.end(), [](const NamedSegment &lhs, const NamedSegment &rhs) {
            return lhs.name_id < rhs.name_id ||
                   (lhs.name_id == rhs.name_id && lhs.position < rhs.position);
        });
    auto new_end = collapse_segments(segments);
    segments.resize(new_end - segments.begin());

    // Filter out segments with an empty name (name_id == 0)
    new_end = std::remove_if(segments.begin(), segments.end(), [](const NamedSegment &segment) {
        return segment.name_id == 0;
    });
    segments.resize(new_end - segments.begin());

    // sort descending
    std::sort(
        segments.begin(), segments.end(), [](const NamedSegment &lhs, const NamedSegment &rhs) {
            return lhs.duration > rhs.duration ||
                   (lhs.duration == rhs.duration && lhs.position < rhs.position);
        });

    // make sure the segments are sorted by position
    segments.resize(std::min(segments.size(), SegmentNumber));
    std::sort(
        segments.begin(), segments.end(), [](const NamedSegment &lhs, const NamedSegment &rhs) {
            return lhs.position < rhs.position;
        });

    std::array<std::uint32_t, SegmentNumber> summary;
    std::fill(summary.begin(), summary.end(), EMPTY_NAMEID);
    std::transform(segments.begin(),
                   segments.end(),
                   summary.begin(),
                   [](const NamedSegment &segment) { return segment.name_id; });
    return summary;
}
}

inline RouteLeg assembleLeg(const datafacade::BaseDataFacade &facade,
                            const std::vector<PathData> &route_data,
                            const LegGeometry &leg_geometry,
                            const PhantomNode &source_node,
                            const PhantomNode &target_node,
                            const bool target_traversed_in_reverse,
                            const bool needs_summary)
{
    const auto target_duration =
        (target_traversed_in_reverse ? target_node.reverse_weight : target_node.forward_weight) /
        10.;

    auto distance = std::accumulate(
        leg_geometry.segment_distances.begin(), leg_geometry.segment_distances.end(), 0.);
    auto duration = std::accumulate(route_data.begin(),
                                    route_data.end(),
                                    0.,
                                    [](const double sum, const PathData &data) {
                                        return sum + data.duration_until_turn;
                                    }) /
                    10.;

    //                 s
    //                 |
    // Given a route a---b---c  where there is a right turn at c.
    //                       |
    //                       d
    //                       |--t
    //                       e
    // (a, b, c) gets compressed to (a,c)
    // (c, d, e) gets compressed to (c,e)
    // The duration of the turn (a,c) -> (c,e) will be the duration of (a,c) (e.g. the duration
    // of (a,b,c)).
    // The phantom node of s will contain:
    // `forward_weight`: duration of (a,s)
    // `forward_offset`: 0 (its the first segment)
    // The phantom node of t will contain:
    // `forward_weight`: duration of (d,t)
    // `forward_offset`: duration of (c, d)
    // path_data will have entries for (s,b), (b, c), (c, d) but (d, t) is only
    // caputed by the phantom node. So we need to add the target duration here.
    // On local segments, the target duration is already part of the duration, however.

    duration = duration + target_duration;
    if (route_data.empty())
    {
        duration -= (target_traversed_in_reverse ? source_node.reverse_weight
                                                 : source_node.forward_weight) /
                    10.0;
    }

    std::string summary;
    if (needs_summary)
    {
        auto summary_array = detail::summarizeRoute<detail::MAX_USED_SEGMENTS>(
            route_data, target_node, target_traversed_in_reverse);

        BOOST_ASSERT(detail::MAX_USED_SEGMENTS > 0);
        BOOST_ASSERT(summary_array.begin() != summary_array.end());

        // transform a name_id into a string containing either the name, or -if the name is empty-
        // the reference.
        const auto name_id_to_string = [&](const NameID name_id) {
            const auto name = facade.GetNameForID(name_id);
            if (!name.empty())
                return name;
            else
            {
                const auto ref = facade.GetRefForID(name_id);
                return ref;
            }
        };

        const auto not_empty = [&](const std::string &name) { return !name.empty(); };

        const auto summary_names = summary_array | boost::adaptors::transformed(name_id_to_string) |
                                   boost::adaptors::filtered(not_empty);
        summary = boost::algorithm::join(summary_names, ", ");
    }

    return RouteLeg{duration, distance, summary, {}};
}

} // namespace guidance
} // namespace engine
} // namespace osrm

#endif // ENGINE_GUIDANCE_SEGMENT_LIST_HPP_