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

use anyhow::Result;

use abstutil::{Parallelism, Timer};
use geom::{Angle, Distance, FindClosest, HashablePt2D, Line, PolyLine, Polygon, Pt2D, Ring};

use crate::make::{match_points_to_lanes, trim_path};
use crate::raw::RawParkingLot;
use crate::{
    osm, Map, ParkingLot, ParkingLotID, PathConstraints, Position, NORMAL_LANE_THICKNESS,
    PARKING_LOT_SPOT_LENGTH,
};

/// Take in parking lots from OSM and all parking aisle roads. Match parking lots to the nearest
/// sidewalk + driving lane, then automatically generate individual parking spots perpendicular to
/// the aisles.
pub fn make_all_parking_lots(
    input: &[RawParkingLot],
    aisles: &[(osm::WayID, Vec<Pt2D>)],
    map: &Map,
    timer: &mut Timer,
) -> Vec<ParkingLot> {
    timer.start("convert parking lots");
    let mut center_per_lot: Vec<HashablePt2D> = Vec::new();
    let mut query: HashSet<HashablePt2D> = HashSet::new();
    for lot in input {
        let center = lot.polygon.center().to_hashable();
        center_per_lot.push(center);
        query.insert(center);
    }

    let sidewalk_buffer = Distance::meters(7.5);
    let sidewalk_pts = match_points_to_lanes(
        map.get_bounds(),
        query,
        map.all_lanes(),
        |l| l.is_walkable(),
        sidewalk_buffer,
        Distance::meters(1000.0),
        timer,
    );

    let mut results = Vec::new();
    timer.start_iter("create parking lot driveways", center_per_lot.len());
    for (lot_center, orig) in center_per_lot.into_iter().zip(input.iter()) {
        timer.next();
        match snap_driveway(lot_center, &orig.polygon, &sidewalk_pts, map) {
            Ok((driveway_line, driving_pos, sidewalk_line, sidewalk_pos)) => {
                let id = ParkingLotID(results.len());
                results.push(ParkingLot {
                    id,
                    polygon: orig.polygon.clone(),
                    aisles: Vec::new(),
                    osm_id: orig.osm_id,
                    spots: Vec::new(),
                    extra_spots: 0,

                    driveway_line,
                    driving_pos,
                    sidewalk_line,
                    sidewalk_pos,
                });
            }
            Err(err) => {
                warn!("Skipping parking lot {}: {}", orig.osm_id, err);
            }
        }
    }
    info!(
        "Discarded {} parking lots that weren't close enough to a sidewalk",
        input.len() - results.len()
    );

    let mut closest: FindClosest<ParkingLotID> = FindClosest::new(map.get_bounds());
    for lot in &results {
        closest.add(lot.id, lot.polygon.points());
    }
    timer.start_iter("match parking aisles", aisles.len());
    for (aisle_id, pts) in aisles {
        timer.next();
        // Use the center of all the aisle points to match it to lots
        let candidates: Vec<ParkingLotID> = closest
            .all_close_pts(Pt2D::center(&pts), Distance::meters(500.0))
            .into_iter()
            .map(|(id, _, _)| id)
            .collect();

        match Ring::split_points(pts) {
            Ok((polylines, rings)) => {
                for pl in polylines {
                    for id in &candidates {
                        let lot = &mut results[id.0];
                        if let Some(segment) = lot.polygon.clip_polyline(&pl) {
                            lot.aisles.push(segment);
                            // A single aisle sometimes covers two adjacent parking lots -- like
                            // https://www.openstreetmap.org/way/688540935. So allow for all
                            // possible matches.
                        }
                    }
                }
                for ring in rings {
                    for id in &candidates {
                        let lot = &mut results[id.0];
                        if let Some(segment) = lot.polygon.clip_ring(&ring) {
                            lot.aisles.push(segment);
                        }
                    }
                }
            }
            Err(err) => {
                warn!("Parking aisle {} has weird geometry: {}", aisle_id, err);
            }
        }
    }

    let results = timer.parallelize(
        "generate parking lot spots",
        Parallelism::Fastest,
        results,
        |mut lot| {
            lot.spots = infer_spots(&lot.polygon, &lot.aisles);

            // Guess how many extra spots are available, that maybe aren't renderable.
            if lot.spots.is_empty() {
                // No parking aisles. Just guess based on the area. One spot per 30m^2 is a quick
                // guess from looking at examples with aisles.
                lot.extra_spots = (lot.polygon.area() / 30.0) as usize;
            }

            lot
        },
    );
    timer.stop("convert parking lots");
    results
}

/// Returns (driveway_line, driving_pos, sidewalk_line, sidewalk_pos)
pub fn snap_driveway(
    center: HashablePt2D,
    polygon: &Polygon,
    sidewalk_pts: &HashMap<HashablePt2D, Position>,
    map: &Map,
) -> Result<(PolyLine, Position, Line, Position)> {
    let driveway_buffer = Distance::meters(7.0);

    let sidewalk_pos = sidewalk_pts
        .get(&center)
        .ok_or_else(|| anyhow!("parking lot center didn't snap to a sidewalk"))?;
    let sidewalk_line = match Line::new(center.to_pt2d(), sidewalk_pos.pt(map)) {
        Some(l) => trim_path(polygon, l),
        None => {
            bail!("front path has 0 length");
        }
    };

    // Can this lot have a driveway? If it's not next to a driving lane, then no.
    let mut driveway: Option<(PolyLine, Position)> = None;
    let sidewalk_lane = sidewalk_pos.lane();
    if let Some(driving_pos) = map
        .get_parent(sidewalk_lane)
        .find_closest_lane(sidewalk_lane, |l| PathConstraints::Car.can_use(l, map), map)
        .and_then(|l| {
            sidewalk_pos
                .equiv_pos(l, map)
                .buffer_dist(driveway_buffer, map)
        })
    {
        if let Ok(pl) = PolyLine::new(vec![
            sidewalk_line.pt1(),
            sidewalk_line.pt2(),
            driving_pos.pt(map),
        ]) {
            driveway = Some((pl, driving_pos));
        }
    }
    let (driveway_line, driving_pos) = driveway.ok_or_else(|| {
        anyhow!(
            "snapped to sidewalk {}, but no driving connection",
            sidewalk_pos.lane()
        )
    })?;
    Ok((driveway_line, driving_pos, sidewalk_line, *sidewalk_pos))
}

fn infer_spots(lot_polygon: &Polygon, aisles: &[Vec<Pt2D>]) -> Vec<(Pt2D, Angle)> {
    let mut spots = Vec::new();
    let mut finalized_lines = Vec::new();

    for aisle in aisles {
        let aisle_thickness = NORMAL_LANE_THICKNESS / 2.0;
        let pl = PolyLine::unchecked_new(aisle.clone());

        for &rotate in &[90.0, -90.0] {
            // Blindly generate all of the lines
            let lines = {
                let mut lines = Vec::new();
                let mut start = Distance::ZERO;
                while start + NORMAL_LANE_THICKNESS < pl.length() {
                    let (pt, angle) = pl.must_dist_along(start);
                    start += NORMAL_LANE_THICKNESS;
                    let theta = angle.rotate_degs(rotate);
                    lines.push(Line::must_new(
                        pt.project_away(aisle_thickness / 2.0, theta),
                        pt.project_away(aisle_thickness / 2.0 + PARKING_LOT_SPOT_LENGTH, theta),
                    ));
                }
                lines
            };

            for pair in lines.windows(2) {
                let l1 = &pair[0];
                let l2 = &pair[1];
                if let Some(back) = Line::new(l1.pt2(), l2.pt2()) {
                    if l1.intersection(&l2).is_none()
                        && l1.angle().approx_eq(l2.angle(), 5.0)
                        && line_valid(lot_polygon, aisles, l1, &finalized_lines)
                        && line_valid(lot_polygon, aisles, l2, &finalized_lines)
                        && line_valid(lot_polygon, aisles, &back, &finalized_lines)
                    {
                        let avg_angle = (l1.angle() + l2.angle()) / 2.0;
                        spots.push((back.middle().unwrap(), avg_angle.opposite()));
                        finalized_lines.push(l1.clone());
                        finalized_lines.push(l2.clone());
                        finalized_lines.push(back);
                    }
                }
            }
        }
    }
    spots
}

fn line_valid(
    lot_polygon: &Polygon,
    aisles: &[Vec<Pt2D>],
    line: &Line,
    finalized_lines: &[Line],
) -> bool {
    // Don't leak out of the parking lot
    // TODO Entire line
    if !lot_polygon.contains_pt(line.pt1()) || !lot_polygon.contains_pt(line.pt2()) {
        return false;
    }

    // Don't let this line hit another line
    if finalized_lines.iter().any(|other| line.crosses(other)) {
        return false;
    }

    // Don't hit an aisle
    if aisles.iter().any(|pts| {
        PolyLine::unchecked_new(pts.clone())
            .intersection(&line.to_polyline())
            .is_some()
    }) {
        return false;
    }

    true
}