use crate::{
    CarID, DrivingGoal, OrigPersonID, ParkingSpot, PersonID, SidewalkPOI, SidewalkSpot, Sim,
    TripEndpoint, TripMode, TripSpec, Vehicle, VehicleSpec, VehicleType, BIKE_LENGTH,
    MAX_CAR_LENGTH, MIN_CAR_LENGTH, SPAWN_DIST,
};
use abstutil::{prettyprint_usize, Counter, Timer};
use geom::{Distance, Duration, LonLat, Speed, Time};
use map_model::{
    BuildingID, BusRouteID, BusStopID, DirectedRoadID, Map, OffstreetParking, PathConstraints,
    Position, RoadID,
};
use rand::seq::SliceRandom;
use rand::{Rng, SeedableRng};
use rand_xorshift::XorShiftRng;
use serde::{Deserialize, Serialize};
use std::collections::{BTreeMap, BTreeSet, HashSet, VecDeque};

// How to start a simulation.
#[derive(Clone, Serialize, Deserialize, Debug)]
pub struct Scenario {
    pub scenario_name: String,
    pub map_name: String,

    pub people: Vec<PersonSpec>,
    // None means seed all buses. Otherwise the route name must be present here.
    pub only_seed_buses: Option<BTreeSet<String>>,
}

#[derive(Clone, Serialize, Deserialize, Debug)]
pub struct PersonSpec {
    pub id: PersonID,
    // Just used for debugging
    pub orig_id: Option<OrigPersonID>,
    pub trips: Vec<IndividTrip>,
}

#[derive(Clone, Serialize, Deserialize, Debug)]
pub struct IndividTrip {
    pub depart: Time,
    pub trip: SpawnTrip,
    pub cancelled: bool,
    // Did a ScenarioModifier affect this?
    pub modified: bool,
}

impl IndividTrip {
    pub fn new(depart: Time, trip: SpawnTrip) -> IndividTrip {
        IndividTrip {
            depart,
            trip,
            cancelled: false,
            modified: false,
        }
    }
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub enum SpawnTrip {
    // Only for interactive / debug trips
    VehicleAppearing {
        start: Position,
        goal: DrivingGoal,
        is_bike: bool,
    },
    FromBorder {
        dr: DirectedRoadID,
        goal: DrivingGoal,
        // For bikes starting at a border, use FromBorder. UsingBike implies a walk->bike trip.
        is_bike: bool,
        origin: Option<OffMapLocation>,
    },
    UsingParkedCar(BuildingID, DrivingGoal),
    UsingBike(BuildingID, DrivingGoal),
    JustWalking(SidewalkSpot, SidewalkSpot),
    UsingTransit(
        SidewalkSpot,
        SidewalkSpot,
        BusRouteID,
        BusStopID,
        Option<BusStopID>,
    ),
    // Completely off-map trip. Don't really simulate much of it.
    Remote {
        from: OffMapLocation,
        to: OffMapLocation,
        trip_time: Duration,
        mode: TripMode,
    },
}

#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
pub struct OffMapLocation {
    pub parcel_id: usize,
    pub gps: LonLat,
}

impl Scenario {
    // Any case where map edits could change the calls to the RNG, we have to fork.
    pub fn instantiate(&self, sim: &mut Sim, map: &Map, rng: &mut XorShiftRng, timer: &mut Timer) {
        sim.set_name(self.scenario_name.clone());

        timer.start(format!("Instantiating {}", self.scenario_name));

        if let Some(ref routes) = self.only_seed_buses {
            for route in map.all_bus_routes() {
                if routes.contains(&route.full_name) {
                    sim.seed_bus_route(route);
                }
            }
        } else {
            // All of them
            for route in map.all_bus_routes() {
                sim.seed_bus_route(route);
            }
        }

        timer.start_iter("trips for People", self.people.len());
        let mut spawner = sim.make_spawner();
        let mut parked_cars: Vec<(Vehicle, BuildingID)> = Vec::new();
        for p in &self.people {
            timer.next();

            if let Err(err) = p.check_schedule(map) {
                panic!("{}", err);
            }

            let (vehicle_specs, cars_initially_parked_at, vehicle_foreach_trip) =
                p.get_vehicles(rng);
            sim.new_person(
                p.id,
                p.orig_id,
                Scenario::rand_ped_speed(rng),
                vehicle_specs,
            );
            let person = sim.get_person(p.id);
            for (idx, b) in cars_initially_parked_at {
                parked_cars.push((person.vehicles[idx].clone(), b));
            }
            for (t, maybe_idx) in p.trips.iter().zip(vehicle_foreach_trip) {
                // The RNG call might change over edits for picking the spawning lane from a border
                // with multiple choices for a vehicle type.
                let mut tmp_rng = abstutil::fork_rng(rng);
                let spec = t.trip.clone().to_trip_spec(
                    maybe_idx.map(|idx| person.vehicles[idx].id),
                    &mut tmp_rng,
                    map,
                );
                spawner.schedule_trip(
                    person,
                    t.depart,
                    spec,
                    t.trip.start(map),
                    t.cancelled,
                    t.modified,
                    map,
                );
            }
        }

        // parked_cars is stable over map edits, so don't fork.
        parked_cars.shuffle(rng);
        seed_parked_cars(parked_cars, sim, map, rng, timer);

        sim.flush_spawner(spawner, map, timer);
        timer.stop(format!("Instantiating {}", self.scenario_name));
    }

    pub fn save(&self) {
        abstutil::write_binary(
            abstutil::path_scenario(&self.map_name, &self.scenario_name),
            self,
        );
    }

    pub fn empty(map: &Map, name: &str) -> Scenario {
        Scenario {
            scenario_name: name.to_string(),
            map_name: map.get_name().to_string(),
            people: Vec::new(),
            only_seed_buses: Some(BTreeSet::new()),
        }
    }

    pub fn rand_car(rng: &mut XorShiftRng) -> VehicleSpec {
        let length = Scenario::rand_dist(rng, MIN_CAR_LENGTH, MAX_CAR_LENGTH);
        VehicleSpec {
            vehicle_type: VehicleType::Car,
            length,
            max_speed: None,
        }
    }

    pub fn rand_bike(rng: &mut XorShiftRng) -> VehicleSpec {
        let max_speed = Some(Scenario::rand_speed(
            rng,
            Speed::miles_per_hour(8.0),
            Speed::miles_per_hour(10.0),
        ));
        VehicleSpec {
            vehicle_type: VehicleType::Bike,
            length: BIKE_LENGTH,
            max_speed,
        }
    }

    pub fn rand_dist(rng: &mut XorShiftRng, low: Distance, high: Distance) -> Distance {
        assert!(high > low);
        Distance::meters(rng.gen_range(low.inner_meters(), high.inner_meters()))
    }

    fn rand_speed(rng: &mut XorShiftRng, low: Speed, high: Speed) -> Speed {
        assert!(high > low);
        Speed::meters_per_second(rng.gen_range(
            low.inner_meters_per_second(),
            high.inner_meters_per_second(),
        ))
    }

    pub fn rand_ped_speed(rng: &mut XorShiftRng) -> Speed {
        Scenario::rand_speed(rng, Speed::miles_per_hour(2.0), Speed::miles_per_hour(3.0))
    }

    pub fn count_parked_cars_per_bldg(&self) -> Counter<BuildingID> {
        let mut per_bldg = Counter::new();
        // Pass in a dummy RNG
        let mut rng = XorShiftRng::from_seed([0; 16]);
        for p in &self.people {
            let (_, cars_initially_parked_at, _) = p.get_vehicles(&mut rng);
            for (_, b) in cars_initially_parked_at {
                per_bldg.inc(b);
            }
        }
        per_bldg
    }

    pub fn remove_weird_schedules(mut self, map: &Map) -> Scenario {
        let orig = self.people.len();
        self.people
            .retain(|person| match person.check_schedule(map) {
                Ok(()) => true,
                Err(err) => {
                    println!("{}", err);
                    false
                }
            });
        println!(
            "{} of {} people have nonsense schedules",
            prettyprint_usize(orig - self.people.len()),
            prettyprint_usize(orig)
        );
        // Fix up IDs
        for (idx, person) in self.people.iter_mut().enumerate() {
            person.id = PersonID(idx);
        }
        self
    }
}

fn seed_parked_cars(
    parked_cars: Vec<(Vehicle, BuildingID)>,
    sim: &mut Sim,
    map: &Map,
    base_rng: &mut XorShiftRng,
    timer: &mut Timer,
) {
    let mut open_spots_per_road: BTreeMap<RoadID, Vec<(ParkingSpot, Option<BuildingID>)>> =
        BTreeMap::new();
    for spot in sim.get_all_parking_spots().1 {
        let (r, restriction) = match spot {
            ParkingSpot::Onstreet(l, _) => (map.get_l(l).parent, None),
            ParkingSpot::Offstreet(b, _) => (
                map.get_l(map.get_b(b).sidewalk()).parent,
                match map.get_b(b).parking {
                    OffstreetParking::PublicGarage(_, _) => None,
                    OffstreetParking::Private(_, _) => Some(b),
                },
            ),
            ParkingSpot::Lot(pl, _) => (map.get_l(map.get_pl(pl).driving_pos.lane()).parent, None),
        };
        open_spots_per_road
            .entry(r)
            .or_insert_with(Vec::new)
            .push((spot, restriction));
    }
    // Changing parking on one road shouldn't affect far-off roads. Fork carefully.
    for r in map.all_roads() {
        let mut tmp_rng = abstutil::fork_rng(base_rng);
        if let Some(ref mut spots) = open_spots_per_road.get_mut(&r.id) {
            spots.shuffle(&mut tmp_rng);
        }
    }

    timer.start_iter("seed parked cars", parked_cars.len());
    let mut ok = true;
    let total_cars = parked_cars.len();
    let mut seeded = 0;
    for (vehicle, b) in parked_cars {
        timer.next();
        if !ok {
            continue;
        }
        if let Some(spot) = find_spot_near_building(b, &mut open_spots_per_road, map) {
            seeded += 1;
            sim.seed_parked_car(vehicle, spot);
        } else {
            timer.warn(format!(
                "Not enough room to seed parked cars. Only found spots for {} of {}",
                prettyprint_usize(seeded),
                prettyprint_usize(total_cars)
            ));
            ok = false;
        }
    }
}

// Pick a parking spot for this building. If the building's road has a free spot, use it. If not,
// start BFSing out from the road in a deterministic way until finding a nearby road with an open
// spot.
fn find_spot_near_building(
    b: BuildingID,
    open_spots_per_road: &mut BTreeMap<RoadID, Vec<(ParkingSpot, Option<BuildingID>)>>,
    map: &Map,
) -> Option<ParkingSpot> {
    let mut roads_queue: VecDeque<RoadID> = VecDeque::new();
    let mut visited: HashSet<RoadID> = HashSet::new();
    {
        let start = map.building_to_road(b).id;
        roads_queue.push_back(start);
        visited.insert(start);
    }

    loop {
        let r = roads_queue.pop_front()?;
        if let Some(spots) = open_spots_per_road.get_mut(&r) {
            // Fill in all private parking first before
            // TODO With some probability, skip this available spot and park farther away
            if let Some(idx) = spots
                .iter()
                .position(|(_, restriction)| restriction == &Some(b))
            {
                return Some(spots.remove(idx).0);
            }
            if let Some(idx) = spots
                .iter()
                .position(|(_, restriction)| restriction.is_none())
            {
                return Some(spots.remove(idx).0);
            }
        }

        for next_r in map.get_next_roads(r).into_iter() {
            if !visited.contains(&next_r) {
                roads_queue.push_back(next_r);
                visited.insert(next_r);
            }
        }
    }
}

impl SpawnTrip {
    fn to_trip_spec(
        self,
        use_vehicle: Option<CarID>,
        rng: &mut XorShiftRng,
        map: &Map,
    ) -> TripSpec {
        match self {
            SpawnTrip::VehicleAppearing { start, goal, .. } => TripSpec::VehicleAppearing {
                start_pos: start,
                goal,
                use_vehicle: use_vehicle.unwrap(),
                retry_if_no_room: true,
                origin: None,
            },
            SpawnTrip::FromBorder {
                dr,
                goal,
                is_bike,
                origin,
            } => {
                let constraints = if is_bike {
                    PathConstraints::Bike
                } else {
                    PathConstraints::Car
                };
                if let Some(l) = dr.lanes(constraints, map).choose(rng) {
                    TripSpec::VehicleAppearing {
                        start_pos: Position::new(*l, SPAWN_DIST),
                        goal,
                        use_vehicle: use_vehicle.unwrap(),
                        retry_if_no_room: true,
                        origin,
                    }
                } else {
                    TripSpec::NoRoomToSpawn {
                        i: dr.src_i(map),
                        goal,
                        use_vehicle: use_vehicle.unwrap(),
                        origin,
                        error: format!("{} has no lanes to spawn a {:?}", dr.id, constraints),
                    }
                }
            }
            SpawnTrip::UsingParkedCar(start_bldg, goal) => TripSpec::UsingParkedCar {
                start_bldg,
                goal,
                car: use_vehicle.unwrap(),
            },
            SpawnTrip::UsingBike(start, goal) => TripSpec::UsingBike {
                bike: use_vehicle.unwrap(),
                start,
                goal,
            },
            SpawnTrip::JustWalking(start, goal) => TripSpec::JustWalking { start, goal },
            SpawnTrip::UsingTransit(start, goal, route, stop1, maybe_stop2) => {
                TripSpec::UsingTransit {
                    start,
                    goal,
                    route,
                    stop1,
                    maybe_stop2,
                }
            }
            SpawnTrip::Remote {
                from,
                to,
                trip_time,
                mode,
            } => TripSpec::Remote {
                from,
                to,
                trip_time,
                mode,
            },
        }
    }

    // TODO Why do I feel like this code is sitting somewhere else already
    pub fn mode(&self) -> TripMode {
        match self {
            SpawnTrip::VehicleAppearing { is_bike, .. } => {
                if *is_bike {
                    TripMode::Bike
                } else {
                    TripMode::Drive
                }
            }
            SpawnTrip::FromBorder { is_bike, .. } => {
                if *is_bike {
                    TripMode::Bike
                } else {
                    TripMode::Drive
                }
            }
            SpawnTrip::UsingParkedCar(_, _) => TripMode::Drive,
            SpawnTrip::UsingBike(_, _) => TripMode::Bike,
            SpawnTrip::JustWalking(_, _) => TripMode::Walk,
            SpawnTrip::UsingTransit(_, _, _, _, _) => TripMode::Transit,
            // TODO Uh...
            SpawnTrip::Remote { .. } => TripMode::Drive,
        }
    }

    pub fn start(&self, map: &Map) -> TripEndpoint {
        match self {
            SpawnTrip::VehicleAppearing { ref start, .. } => {
                TripEndpoint::Border(map.get_l(start.lane()).src_i, None)
            }
            SpawnTrip::FromBorder { dr, ref origin, .. } => {
                TripEndpoint::Border(dr.src_i(map), origin.clone())
            }
            SpawnTrip::UsingParkedCar(b, _) => TripEndpoint::Bldg(*b),
            SpawnTrip::UsingBike(b, _) => TripEndpoint::Bldg(*b),
            SpawnTrip::JustWalking(ref spot, _) | SpawnTrip::UsingTransit(ref spot, _, _, _, _) => {
                match spot.connection {
                    SidewalkPOI::Building(b) => TripEndpoint::Bldg(b),
                    SidewalkPOI::Border(i, ref loc) => TripEndpoint::Border(i, loc.clone()),
                    SidewalkPOI::SuddenlyAppear => {
                        TripEndpoint::Border(map.get_l(spot.sidewalk_pos.lane()).src_i, None)
                    }
                    _ => unreachable!(),
                }
            }
            // Pick an arbitrary border
            SpawnTrip::Remote { ref from, .. } => {
                TripEndpoint::Border(map.all_outgoing_borders()[0].id, Some(from.clone()))
            }
        }
    }

    pub fn end(&self, map: &Map) -> TripEndpoint {
        match self {
            SpawnTrip::VehicleAppearing { ref goal, .. }
            | SpawnTrip::FromBorder { ref goal, .. }
            | SpawnTrip::UsingParkedCar(_, ref goal)
            | SpawnTrip::UsingBike(_, ref goal) => match goal {
                DrivingGoal::ParkNear(b) => TripEndpoint::Bldg(*b),
                DrivingGoal::Border(i, _, ref loc) => TripEndpoint::Border(*i, loc.clone()),
            },
            SpawnTrip::JustWalking(_, ref spot) | SpawnTrip::UsingTransit(_, ref spot, _, _, _) => {
                match spot.connection {
                    SidewalkPOI::Building(b) => TripEndpoint::Bldg(b),
                    SidewalkPOI::Border(i, ref loc) => TripEndpoint::Border(i, loc.clone()),
                    _ => unreachable!(),
                }
            }
            // Pick an arbitrary border
            SpawnTrip::Remote { ref to, .. } => {
                TripEndpoint::Border(map.all_incoming_borders()[0].id, Some(to.clone()))
            }
        }
    }

    pub fn new(
        from: TripEndpoint,
        to: TripEndpoint,
        mode: TripMode,
        map: &Map,
    ) -> Option<SpawnTrip> {
        Some(match mode {
            TripMode::Drive => match from {
                TripEndpoint::Bldg(b) => {
                    SpawnTrip::UsingParkedCar(b, to.driving_goal(PathConstraints::Car, map)?)
                }
                TripEndpoint::Border(i, ref origin) => SpawnTrip::FromBorder {
                    dr: map.get_i(i).some_outgoing_road(map)?,
                    goal: to.driving_goal(PathConstraints::Car, map)?,
                    is_bike: false,
                    origin: origin.clone(),
                },
            },
            TripMode::Bike => match from {
                TripEndpoint::Bldg(b) => {
                    SpawnTrip::UsingBike(b, to.driving_goal(PathConstraints::Bike, map)?)
                }
                TripEndpoint::Border(i, ref origin) => SpawnTrip::FromBorder {
                    dr: map.get_i(i).some_outgoing_road(map)?,
                    goal: to.driving_goal(PathConstraints::Bike, map)?,
                    is_bike: true,
                    origin: origin.clone(),
                },
            },
            TripMode::Walk => {
                SpawnTrip::JustWalking(from.start_sidewalk_spot(map)?, to.end_sidewalk_spot(map)?)
            }
            TripMode::Transit => {
                let start = from.start_sidewalk_spot(map)?;
                let goal = to.end_sidewalk_spot(map)?;
                if let Some((stop1, maybe_stop2, route)) =
                    map.should_use_transit(start.sidewalk_pos, goal.sidewalk_pos)
                {
                    SpawnTrip::UsingTransit(start, goal, route, stop1, maybe_stop2)
                } else {
                    //timer.warn(format!("{:?} not actually using transit, because pathfinding
                    // didn't find any useful route", trip));
                    SpawnTrip::JustWalking(start, goal)
                }
            }
        })
    }
}

impl PersonSpec {
    // Verify that the trip start/endpoints of the person match up
    fn check_schedule(&self, map: &Map) -> Result<(), String> {
        for pair in self.trips.iter().zip(self.trips.iter().skip(1)) {
            if pair.0.depart >= pair.1.depart {
                return Err(format!(
                    "{} {:?} starts two trips in the wrong order: {} then {}",
                    self.id, self.orig_id, pair.0.depart, pair.1.depart
                ));
            }

            // Once off-map, re-enter via any border node.
            let end_bldg = match pair.0.trip.end(map) {
                TripEndpoint::Bldg(b) => Some(b),
                TripEndpoint::Border(_, _) => None,
            };
            let start_bldg = match pair.1.trip.start(map) {
                TripEndpoint::Bldg(b) => Some(b),
                TripEndpoint::Border(_, _) => None,
            };

            if end_bldg != start_bldg {
                return Err(format!(
                    "At {}, {} {:?} warps between some trips, from {:?} to {:?}",
                    pair.1.depart, self.id, self.orig_id, end_bldg, start_bldg
                ));
            }

            // But actually, make sure pairs of remote trips match up.
            if let (SpawnTrip::Remote { ref to, .. }, SpawnTrip::Remote { ref from, .. }) =
                (&pair.0.trip, &pair.1.trip)
            {
                if to != from {
                    return Err(format!(
                        "At {}, {} {:?} warps between some trips, from {:?} to {:?}",
                        pair.1.depart, self.id, self.orig_id, to, from
                    ));
                }
            }
        }
        Ok(())
    }

    fn get_vehicles(
        &self,
        rng: &mut XorShiftRng,
    ) -> (
        Vec<VehicleSpec>,
        Vec<(usize, BuildingID)>,
        Vec<Option<usize>>,
    ) {
        let mut vehicle_specs = Vec::new();
        let mut cars_initially_parked_at = Vec::new();
        let mut vehicle_foreach_trip = Vec::new();

        let mut bike_idx = None;
        // For each indexed car, is it parked somewhere, or off-map?
        let mut car_locations: Vec<(usize, Option<BuildingID>)> = Vec::new();

        // TODO If the trip is cancelled, this should be affected...
        for trip in &self.trips {
            let use_for_trip = match trip.trip {
                SpawnTrip::VehicleAppearing {
                    is_bike, ref goal, ..
                }
                | SpawnTrip::FromBorder {
                    is_bike, ref goal, ..
                } => {
                    if is_bike {
                        if bike_idx.is_none() {
                            bike_idx = Some(vehicle_specs.len());
                            vehicle_specs.push(Scenario::rand_bike(rng));
                        }
                        bike_idx
                    } else {
                        // Any available cars off-map?
                        let idx = if let Some(idx) = car_locations
                            .iter()
                            .find(|(_, parked_at)| parked_at.is_none())
                            .map(|(idx, _)| *idx)
                        {
                            idx
                        } else {
                            // Need a new car, starting off-map
                            let idx = vehicle_specs.len();
                            vehicle_specs.push(Scenario::rand_car(rng));
                            idx
                        };

                        // Where does this car wind up?
                        car_locations.retain(|(i, _)| idx != *i);
                        match goal {
                            DrivingGoal::ParkNear(b) => {
                                car_locations.push((idx, Some(*b)));
                            }
                            DrivingGoal::Border(_, _, _) => {
                                car_locations.push((idx, None));
                            }
                        }

                        Some(idx)
                    }
                }
                SpawnTrip::UsingParkedCar(b, ref goal) => {
                    // Is there already a car parked here?
                    let idx = if let Some(idx) = car_locations
                        .iter()
                        .find(|(_, parked_at)| *parked_at == Some(b))
                        .map(|(idx, _)| *idx)
                    {
                        idx
                    } else {
                        // Need a new car, starting at this building
                        let idx = vehicle_specs.len();
                        vehicle_specs.push(Scenario::rand_car(rng));
                        cars_initially_parked_at.push((idx, b));
                        idx
                    };

                    // Where does this car wind up?
                    car_locations.retain(|(i, _)| idx != *i);
                    match goal {
                        DrivingGoal::ParkNear(b) => {
                            car_locations.push((idx, Some(*b)));
                        }
                        DrivingGoal::Border(_, _, _) => {
                            car_locations.push((idx, None));
                        }
                    }

                    Some(idx)
                }
                SpawnTrip::UsingBike(_, _) => {
                    if bike_idx.is_none() {
                        bike_idx = Some(vehicle_specs.len());
                        vehicle_specs.push(Scenario::rand_bike(rng));
                    }
                    bike_idx
                }
                SpawnTrip::JustWalking(_, _) | SpawnTrip::UsingTransit(_, _, _, _, _) => None,
                SpawnTrip::Remote { .. } => None,
            };
            vehicle_foreach_trip.push(use_for_trip);
        }

        // For debugging
        if false {
            let mut n = vehicle_specs.len();
            if bike_idx.is_some() {
                n -= 1;
            }
            if n > 1 {
                println!("{} needs {} cars", self.id, n);
            }
        }

        (
            vehicle_specs,
            cars_initially_parked_at,
            vehicle_foreach_trip,
        )
    }
}