use std::cell::RefCell;
use std::collections::HashMap;

use geom::{Angle, ArrowCap, Distance, Line, PolyLine, Polygon, Pt2D};
use map_model::{
    Direction, DrivingSide, Lane, LaneID, LaneType, Map, Road, RoadID, TurnID, PARKING_SPOT_LENGTH,
};
use widgetry::{Drawable, GeomBatch, GfxCtx, Prerender, RewriteColor};

use crate::render::{DrawOptions, Renderable, OUTLINE_THICKNESS};
use crate::{AppLike, ID};

pub struct DrawLane {
    pub id: LaneID,
    pub polygon: Polygon,
    zorder: isize,

    draw_default: RefCell<Option<Drawable>>,
}

impl DrawLane {
    pub fn new(lane: &Lane, map: &Map) -> DrawLane {
        DrawLane {
            id: lane.id,
            polygon: lane.lane_center_pts.make_polygons(lane.width),
            zorder: map.get_r(lane.parent).zorder,
            draw_default: RefCell::new(None),
        }
    }

    pub fn clear_rendering(&mut self) {
        *self.draw_default.borrow_mut() = None;
    }

    pub fn render<P: AsRef<Prerender>>(&self, prerender: &P, app: &dyn AppLike) -> GeomBatch {
        let map = app.map();
        let lane = map.get_l(self.id);
        let road = map.get_r(lane.parent);
        let mut batch = GeomBatch::new();

        if !lane.is_light_rail() {
            batch.push(
                app.cs()
                    .zoomed_road_surface(lane.lane_type, road.get_rank()),
                self.polygon.clone(),
            );
        }
        let general_road_marking = app.cs().general_road_marking(road.get_rank());
        match lane.lane_type {
            LaneType::Sidewalk => {
                if let Some(c) = app.cs().sidewalk_lines {
                    batch.extend(c, calculate_sidewalk_lines(lane));
                } else {
                    // Otherwise, draw a border at both edges
                    let width = Distance::meters(0.2);
                    let shift = (lane.width - width) / 2.0;
                    batch.push(
                        general_road_marking,
                        lane.lane_center_pts
                            .must_shift_right(shift)
                            .make_polygons(width),
                    );
                    batch.push(
                        general_road_marking,
                        lane.lane_center_pts
                            .must_shift_left(shift)
                            .make_polygons(width),
                    );
                }
            }
            LaneType::Shoulder => {}
            LaneType::Parking => {
                batch.extend(general_road_marking, calculate_parking_lines(lane, map));
            }
            LaneType::Driving | LaneType::Bus => {
                batch.extend(general_road_marking, calculate_driving_lines(lane, road));
                batch.extend(general_road_marking, calculate_turn_markings(map, lane));
                batch.extend(general_road_marking, calculate_one_way_markings(lane, road));
            }
            LaneType::Biking => {}
            LaneType::SharedLeftTurn => {
                let thickness = Distance::meters(0.25);
                batch.push(
                    app.cs().road_center_line(road.get_rank()),
                    lane.lane_center_pts
                        .must_shift_right((lane.width - thickness) / 2.0)
                        .make_polygons(thickness),
                );
                batch.push(
                    app.cs().road_center_line(road.get_rank()),
                    lane.lane_center_pts
                        .must_shift_left((lane.width - thickness) / 2.0)
                        .make_polygons(thickness),
                );
            }
            LaneType::Construction => {}
            LaneType::LightRail => {
                let track_width = lane.width / 4.0;
                batch.push(
                    app.cs().light_rail_track,
                    lane.lane_center_pts
                        .must_shift_right((lane.width - track_width) / 2.5)
                        .make_polygons(track_width),
                );
                batch.push(
                    app.cs().light_rail_track,
                    lane.lane_center_pts
                        .must_shift_left((lane.width - track_width) / 2.5)
                        .make_polygons(track_width),
                );

                // Start away from the intersections
                let tile_every = Distance::meters(3.0);
                let mut dist_along = tile_every;
                while dist_along < lane.lane_center_pts.length() - tile_every {
                    let (pt, angle) = lane.lane_center_pts.must_dist_along(dist_along);
                    // Reuse perp_line. Project away an arbitrary amount
                    let pt2 = pt.project_away(Distance::meters(1.0), angle);
                    batch.push(
                        app.cs().light_rail_track,
                        perp_line(Line::must_new(pt, pt2), lane.width).make_polygons(track_width),
                    );
                    dist_along += tile_every;
                }
            }
        }

        if lane.is_bus()
            || lane.is_biking()
            || lane.lane_type == LaneType::Construction
            || lane.lane_type == LaneType::SharedLeftTurn
        {
            let buffer = Distance::meters(5.0);
            let btwn = Distance::meters(30.0);
            let len = lane.lane_center_pts.length();

            let mut dist = buffer;
            while dist + buffer <= len {
                let (pt, angle) = lane.lane_center_pts.must_dist_along(dist);
                if lane.is_bus() {
                    batch.append(
                        GeomBatch::load_svg(prerender, "system/assets/map/bus_only.svg")
                            .scale(0.06)
                            .centered_on(pt)
                            .rotate(angle.shortest_rotation_towards(Angle::degrees(-90.0))),
                    );
                } else if lane.is_biking() {
                    batch.append(
                        GeomBatch::load_svg(prerender, "system/assets/meters/bike.svg")
                            .scale(0.06)
                            .centered_on(pt)
                            .rotate(angle.shortest_rotation_towards(Angle::degrees(-90.0))),
                    );
                } else if lane.lane_type == LaneType::SharedLeftTurn {
                    batch.append(
                        GeomBatch::load_svg(prerender, "system/assets/map/shared_left_turn.svg")
                            .autocrop()
                            .scale(0.003)
                            .centered_on(pt)
                            .rotate(angle.shortest_rotation_towards(Angle::degrees(-90.0))),
                    );
                } else if lane.lane_type == LaneType::Construction {
                    // TODO Still not quite centered right, but close enough
                    batch.append(
                        GeomBatch::load_svg(prerender, "system/assets/map/under_construction.svg")
                            .scale(0.05)
                            .rotate_around_batch_center(
                                angle.shortest_rotation_towards(Angle::degrees(-90.0)),
                            )
                            .autocrop()
                            .centered_on(pt),
                    );
                }
                dist += btwn;
            }
        }

        if road.is_private() {
            batch.push(app.cs().private_road.alpha(0.5), self.polygon.clone());
        }

        if self.zorder < 0 {
            batch = batch.color(RewriteColor::ChangeAlpha(0.5));
        }

        batch
    }
}

impl Renderable for DrawLane {
    fn get_id(&self) -> ID {
        ID::Lane(self.id)
    }

    fn draw(&self, g: &mut GfxCtx, app: &dyn AppLike, _: &DrawOptions) {
        // Lazily calculate, because these are expensive to all do up-front, and most players won't
        // exhaustively see every lane during a single session
        let mut draw = self.draw_default.borrow_mut();
        if draw.is_none() {
            *draw = Some(g.upload(self.render(g, app)));
        }
        g.redraw(draw.as_ref().unwrap());
    }

    fn get_outline(&self, map: &Map) -> Polygon {
        let lane = map.get_l(self.id);
        lane.lane_center_pts
            .to_thick_boundary(lane.width, OUTLINE_THICKNESS)
            .unwrap_or_else(|| self.polygon.clone())
    }

    fn contains_pt(&self, pt: Pt2D, _: &Map) -> bool {
        self.polygon.contains_pt(pt)
    }

    fn get_zorder(&self) -> isize {
        self.zorder
    }
}

// TODO this always does it at pt1
fn perp_line(l: Line, length: Distance) -> Line {
    let pt1 = l.shift_right(length / 2.0).pt1();
    let pt2 = l.shift_left(length / 2.0).pt1();
    Line::must_new(pt1, pt2)
}

fn calculate_sidewalk_lines(lane: &Lane) -> Vec<Polygon> {
    let tile_every = lane.width;

    let length = lane.length();

    let mut result = Vec::new();
    // Start away from the intersections
    let mut dist_along = tile_every;
    while dist_along < length - tile_every {
        let (pt, angle) = lane.lane_center_pts.must_dist_along(dist_along);
        // Reuse perp_line. Project away an arbitrary amount
        let pt2 = pt.project_away(Distance::meters(1.0), angle);
        result.push(
            perp_line(Line::must_new(pt, pt2), lane.width).make_polygons(Distance::meters(0.25)),
        );
        dist_along += tile_every;
    }

    result
}

fn calculate_parking_lines(lane: &Lane, map: &Map) -> Vec<Polygon> {
    // meters, but the dims get annoying below to remove
    let leg_length = Distance::meters(1.0);

    let mut result = Vec::new();
    let num_spots = lane.number_parking_spots();
    if num_spots > 0 {
        for idx in 0..=num_spots {
            let (pt, lane_angle) = lane
                .lane_center_pts
                .must_dist_along(PARKING_SPOT_LENGTH * (1.0 + idx as f64));
            let perp_angle = if map.get_config().driving_side == DrivingSide::Right {
                lane_angle.rotate_degs(270.0)
            } else {
                lane_angle.rotate_degs(90.0)
            };
            // Find the outside of the lane. Actually, shift inside a little bit, since the line
            // will have thickness, but shouldn't really intersect the adjacent line
            // when drawn.
            let t_pt = pt.project_away(lane.width * 0.4, perp_angle);
            // The perp leg
            let p1 = t_pt.project_away(leg_length, perp_angle.opposite());
            result.push(Line::must_new(t_pt, p1).make_polygons(Distance::meters(0.25)));
            // Upper leg
            let p2 = t_pt.project_away(leg_length, lane_angle);
            result.push(Line::must_new(t_pt, p2).make_polygons(Distance::meters(0.25)));
            // Lower leg
            let p3 = t_pt.project_away(leg_length, lane_angle.opposite());
            result.push(Line::must_new(t_pt, p3).make_polygons(Distance::meters(0.25)));
        }
    }

    result
}

// Because the stripe straddles two lanes, it'll be partly hidden on one side. There are a bunch of
// ways to work around this z-order issue. The current approach is to rely on the fact that
// quadtrees return LaneIDs in order, and lanes are always created from left->right.
fn calculate_driving_lines(lane: &Lane, parent: &Road) -> Vec<Polygon> {
    let lanes = parent.lanes_ltr();
    let idx = parent.offset(lane.id);

    // If the lane to the left of us isn't in the same direction or isn't the same type, don't
    // need dashed lines.
    if idx == 0 || lanes[idx].1 != lanes[idx - 1].1 || lanes[idx].2 != lanes[idx - 1].2 {
        return Vec::new();
    }

    let lane_edge_pts = if lanes[idx].1 == Direction::Fwd {
        lane.lane_center_pts.must_shift_left(lane.width / 2.0)
    } else {
        lane.lane_center_pts.must_shift_right(lane.width / 2.0)
    };
    lane_edge_pts.dashed_lines(
        Distance::meters(0.25),
        Distance::meters(1.0),
        Distance::meters(1.5),
    )
}

fn calculate_turn_markings(map: &Map, lane: &Lane) -> Vec<Polygon> {
    if lane.length() < Distance::meters(7.0) {
        return Vec::new();
    }

    // Does this lane connect to every other possible outbound lane of the same type, excluding
    // U-turns to the same road? If so, then there's nothing unexpected to communicate.
    let i = map.get_i(lane.dst_i);
    if i.outgoing_lanes.iter().all(|l| {
        let l = map.get_l(*l);
        l.lane_type != lane.lane_type
            || l.parent == lane.parent
            || map
                .maybe_get_t(TurnID {
                    parent: i.id,
                    src: lane.id,
                    dst: l.id,
                })
                .is_some()
    }) {
        return Vec::new();
    }

    // Don't call out the strange lane-changing in intersections. Per target road, find the average
    // turn angle.
    let mut angles_per_road: HashMap<RoadID, Vec<Angle>> = HashMap::new();
    for turn in map.get_turns_from_lane(lane.id) {
        angles_per_road
            .entry(map.get_l(turn.id.dst).parent)
            .or_insert_with(Vec::new)
            .push(turn.angle());
    }

    let mut results = Vec::new();
    let thickness = Distance::meters(0.2);

    let common_base = lane.lane_center_pts.exact_slice(
        lane.length() - Distance::meters(7.0),
        lane.length() - Distance::meters(5.0),
    );
    results.push(common_base.make_polygons(thickness));

    for (_, angles) in angles_per_road.into_iter() {
        let n = angles.len() as f64;
        let avg = angles.into_iter().sum::<Angle>() / n;
        results.push(
            PolyLine::must_new(vec![
                common_base.last_pt(),
                common_base.last_pt().project_away(lane.width / 2.0, avg),
            ])
            .make_arrow(thickness, ArrowCap::Triangle),
        );
    }

    results
}

fn calculate_one_way_markings(lane: &Lane, parent: &Road) -> Vec<Polygon> {
    let mut results = Vec::new();
    let lanes = parent.lanes_ltr();
    let dir = parent.dir(lane.id);
    if lanes
        .into_iter()
        .any(|(_, d, lt)| dir != d && lt == LaneType::Driving)
    {
        // Not a one-way
        return results;
    }

    let arrow_len = Distance::meters(4.0);
    let btwn = Distance::meters(30.0);
    let thickness = Distance::meters(0.25);
    // Stop 1m before the calculate_turn_markings() stuff starts
    let len = lane.length() - Distance::meters(8.0);

    let mut dist = arrow_len;
    while dist + arrow_len <= len {
        let (pt, angle) = lane.lane_center_pts.must_dist_along(dist);
        results.push(
            PolyLine::must_new(vec![
                pt.project_away(arrow_len / 2.0, angle.opposite()),
                pt.project_away(arrow_len / 2.0, angle),
            ])
            .make_arrow(thickness, ArrowCap::Triangle),
        );
        dist += btwn;
    }
    results
}