use std::collections::{BTreeMap, HashMap};

use abstutil::MultiMap;
use geom::{Distance, FindClosest, Line, PolyLine};
use kml::{ExtraShape, ExtraShapes};

use crate::{Direction, OriginalRoad, RawMap};

const DEBUG_OUTPUT: bool = true;

/// Snap separately mapped cycleways to main roads.
pub fn snap_cycleways(map: &mut RawMap) {
    if true {
        return;
    }

    let mut cycleways = Vec::new();
    for (id, road) in &map.roads {
        // Because there are so many false positives with snapping, only start with cycleways
        // explicitly tagged with
        // https://wiki.openstreetmap.org/wiki/Proposed_features/cycleway:separation
        if road.is_cycleway()
            && (road.osm_tags.contains_key("separation:left")
                || road.osm_tags.contains_key("separation:right"))
        {
            let (center, total_width) = road.untrimmed_road_geometry();
            cycleways.push(Cycleway {
                id: *id,
                center,
                total_width,
                layer: road.osm_tags.get("layer").cloned(),
            });
        }
    }

    let mut road_edges: HashMap<(OriginalRoad, Direction), PolyLine> = HashMap::new();
    for (id, r) in &map.roads {
        if r.is_light_rail() || r.is_footway() || r.is_service() || r.is_cycleway() {
            continue;
        }
        let (pl, total_width) = r.untrimmed_road_geometry();
        road_edges.insert(
            (*id, Direction::Fwd),
            pl.must_shift_right(total_width / 2.0),
        );
        road_edges.insert(
            (*id, Direction::Back),
            pl.must_shift_left(total_width / 2.0),
        );
    }

    let matches = v1(map, &cycleways, &road_edges);

    // Go apply the matches!
    let mut snapped_ids = Vec::new();
    for (cycleway_id, roads) in matches.consume() {
        snapped_ids.push(cycleway_id);

        // Remove the separate cycleway
        let deleted_cycleway = map.roads.remove(&cycleway_id).unwrap();

        // Add it as an attribute to the roads instead
        for (road_id, dir) in roads {
            let dir = if dir == Direction::Fwd {
                "right"
            } else {
                "left"
            };
            let tags = &mut map.roads.get_mut(&road_id).unwrap().osm_tags;
            tags.insert(format!("cycleway:{}", dir), "track");
            if !deleted_cycleway.osm_tags.is("oneway", "yes") {
                tags.insert(format!("cycleway:{}:oneway", dir), "no");
            }

            // Copy over the separation tags from the separate way. Since we're only attempting to
            // snap cycleways with these tags, at least one should exist.
            for traffic_side in ["left", "right"] {
                if let Some(value) = deleted_cycleway
                    .osm_tags
                    .get(&format!("separation:{}", traffic_side))
                {
                    tags.insert(
                        format!("cycleway:{}:separation:{}", dir, traffic_side),
                        value,
                    );
                }
            }

            if DEBUG_OUTPUT {
                tags.insert(
                    format!("abst:cycleway_snap:{}", dir),
                    cycleway_id.osm_way_id.0.to_string(),
                );
            }
        }
    }

    for r in snapped_ids {
        // After removing the separate cycleway, likely its two intersections become degenerate and
        // will be super close to a "real" intersection. Collapse the intersection.
        //
        // Do all of these in one batch after snapping everything. Otherwise, some cycleway IDs
        // totally disappear.
        for i in [r.i1, r.i2] {
            if map.roads_per_intersection(i).len() == 2 {
                crate::transform::collapse_intersections::collapse_intersection(map, i);
            }
        }
    }
}

struct Cycleway {
    id: OriginalRoad,
    center: PolyLine,
    total_width: Distance,
    layer: Option<String>,
}

// Walk along every cycleway, form a perpendicular line, and mark all road edges that it hits.
// Returns (cycleway ID, every directed road hit).
//
// TODO Inverse idea: Walk every road, project perpendicular from each of the 4 corners and see what
// cycleways hit.
// TODO Or look for cycleway polygons strictly overlapping thick road polygons
fn v1(
    map: &RawMap,
    cycleways: &[Cycleway],
    road_edges: &HashMap<(OriginalRoad, Direction), PolyLine>,
) -> MultiMap<OriginalRoad, (OriginalRoad, Direction)> {
    let mut matches = MultiMap::new();

    let mut closest: FindClosest<(OriginalRoad, Direction)> =
        FindClosest::new(&map.gps_bounds.to_bounds());
    for (id, pl) in road_edges {
        closest.add(*id, pl.points());
    }

    // TODO If this is too large, we might miss some intermediate pieces of the road.
    let step_size = Distance::meters(5.0);
    // This gives the length of the perpendicular test line
    let buffer_from_cycleway = Distance::meters(3.0);
    // How many degrees difference to consider parallel ways
    let parallel_threshold = 30.0;

    let mut debug_shapes = Vec::new();

    for cycleway in cycleways {
        let cycleway_half_width = (cycleway.total_width / 2.0) + buffer_from_cycleway;
        // Walk along the cycleway's center line
        let mut dist = Distance::ZERO;
        let mut matches_here = Vec::new();
        loop {
            let (pt, cycleway_angle) = cycleway.center.must_dist_along(dist);
            // TODO In the common case, only the separation between the cyclepath and main traffic
            // will be tagged. So we could just look in that direction...
            let perp_line = Line::must_new(
                pt.project_away(cycleway_half_width, cycleway_angle.rotate_degs(90.0)),
                pt.project_away(cycleway_half_width, cycleway_angle.rotate_degs(-90.0)),
            );
            let mut matched = None;
            for (road_pair, _, _) in closest.all_close_pts(pt, cycleway_half_width) {
                // A cycleway can't snap to a road at a different height
                if map.roads[&road_pair.0].osm_tags.get("layer") != cycleway.layer.as_ref() {
                    continue;
                }

                if let Some((_, road_angle)) =
                    road_edges[&road_pair].intersection(&perp_line.to_polyline())
                {
                    if road_angle.approx_parallel(cycleway_angle, parallel_threshold) {
                        matched = Some(road_pair);
                        // Just stop at the first, closest hit. One point along a cycleway might be
                        // close to multiple road edges, but we want the closest hit.
                        break;
                    }
                }
            }
            let mut attributes = BTreeMap::new();
            if let Some(road_pair) = matched {
                attributes.insert(
                    "hit".to_string(),
                    format!("way {}, {}", road_pair.0.osm_way_id, road_pair.1),
                );
                matches_here.push(road_pair);
            }
            debug_shapes.push(ExtraShape {
                points: map.gps_bounds.convert_back(&perp_line.points()),
                attributes,
            });

            if dist == cycleway.center.length() {
                break;
            }
            dist += step_size;
            dist = dist.min(cycleway.center.length());
        }

        // If only part of this cyclepath snapped to a parallel road, just keep it separate.
        let pct_snapped = (matches_here.len() as f64) / (cycleway.center.length() / step_size);
        info!(
            "Only {}% of {} snapped to a road",
            (pct_snapped * 100.0).round(),
            cycleway.id
        );
        if pct_snapped >= 0.8 {
            for pair in matches_here {
                matches.insert(cycleway.id, pair);
            }

            let mut attributes = BTreeMap::new();
            attributes.insert("pct_snapped".to_string(), pct_snapped.to_string());
            attributes.insert(
                "num_segments_modified".to_string(),
                matches.get(cycleway.id).len().to_string(),
            );
            debug_shapes.push(ExtraShape {
                points: map.gps_bounds.convert_back(cycleway.center.points()),
                attributes,
            });
        }
    }

    if DEBUG_OUTPUT {
        abstio::write_binary(
            map.name
                .city
                .input_path(format!("{}_snapping.bin", map.name.map)),
            &ExtraShapes {
                shapes: debug_shapes,
            },
        );
    }

    matches
}