use std::cell::RefCell;
use std::collections::HashMap;
use std::collections::hash_map::Iter;
use std::error::Error;
use std::iter::Filter;

use cgmath::Zero;

use crate::GameState;
use crate::solar_system::body::BodyId;
use crate::solar_system::orbit::StaticOrbiter;
use crate::solar_system::{SystemId, GRAVITATIONAL_CONSTANT, Kilometers, SolarSystem, body::OrbitalBody, orbit::StaticOrbit};
use crate::timeman::{self, Second};
use crate::ui::fleet_window::NewFleet;

pub type FleetId = usize;

pub struct Fleet
{
    id: FleetId,
    name: String,

    origin: cgmath::Vector3<Kilometers>,
    offset: cgmath::Vector3<Kilometers>,
    heading: cgmath::Vector2<cgmath::Rad<f32>>,

    system: Option<SystemId>,
    baked_orbit: Option<(f64, StaticOrbit)>,
}

pub struct FleetsManager
{
    next_id: FleetId,
    fleets: HashMap<FleetId, Fleet>
}

impl StaticOrbiter for Fleet {
    fn orbit(&self) -> Option<&StaticOrbit> {
        match &self.baked_orbit {
            Some((_, orbit)) => {
                Some(orbit)
            },
            None => None
        }
    }

    fn sgp(&self) -> f64 {
        match &self.baked_orbit {
            Some((sgp, _)) => { *sgp },
            None => { 0.0 }
        }
    }
}

impl Fleet
{
    pub fn new(
        id: FleetId,
        name: String)
    -> Self
    {
        Self {
            id,
            name,
            origin: cgmath::vec3(0.0, 0.0, 0.0),
            offset: cgmath::vec3(0.0, 0.0, 0.0),
            heading: cgmath::vec2(
                cgmath::Rad::zero(), 
                cgmath::Rad::zero()),

            system: None,
            baked_orbit: None,
        }
    }

    pub fn id(&self) -> FleetId { self.id }
    pub fn name(&self) -> &String { &self.name }
    pub fn origin_position(&self) -> &cgmath::Vector3<Kilometers>
    { &self.origin }
    pub fn offset_position(&self) -> &cgmath::Vector3<Kilometers>
    { &self.offset }
    pub fn heading(&self) -> &cgmath::Vector2<cgmath::Rad<f32>>
    { &self.heading }
    pub fn system(&self) -> Option<SystemId>
    { self.system }

    pub fn make_orbit(
        &mut self,
        star_system: &SolarSystem,
        body: BodyId,
        radius: Kilometers)
    {
        let body = star_system.body(body);
        let sgp = body.mass() * GRAVITATIONAL_CONSTANT;

        self.baked_orbit = Some((sgp, StaticOrbit::new_circular(body, radius)));
        self.system = Some(star_system.id());
    }

    fn subtick(
        &mut self,
        star_systems: &[SolarSystem],
        time: Second)
    -> Result<(), ()>
    {
        if let Some((_sgp, orbit)) = &self.baked_orbit {
            let solar_system = &star_systems[self.system().unwrap()];
            let body = solar_system.body(orbit.parent());
            
            self.origin = body.absolute_position(solar_system, time);
            self.offset = orbit.calculate_position_at(self, time);
        }
        Ok(())
    }
} // impl Fleet

impl FleetsManager
{
    pub fn new()
    -> Self {
        Self {
            next_id: 0,
            fleets: HashMap::new()
        }
    }

    fn reserve_new_id(&mut self)
    -> FleetId
    {
        let new_id = self.next_id;
        self.next_id += 1;
        new_id
    }

    pub fn all(&self)
    -> Vec<usize>
    {
        self.fleets.keys().cloned().collect()
    }

    pub fn all_in_system(
        &self,
        system: SystemId)
    -> Vec<usize>
    {
        self.fleets.iter().filter_map(|v| {
            if v.1.system().is_some_and(|id| { id == system }) {
                Some(*v.0)
            }else {
                None
            }
        }).collect()
    }

    pub fn entry_mut(
        &mut self,
        id: FleetId)
    -> Option<&mut Fleet>
    { self.fleets.get_mut(&id) }

    pub fn entry(
        &self,
        id: FleetId)
    -> Option<&Fleet>
    { self.fleets.get(&id) }

    fn subtick_fleet(
        &mut self,
        star_systems: &[SolarSystem],
        time: Second)
    -> Result<(), ()>
    {
        let mut tick_interrupt = Ok(());
        for (id, fleet) in &mut self.fleets {
            let res = fleet.subtick(star_systems, time);
            if res.is_err() {
                tick_interrupt = Err(());
            }
        }
        tick_interrupt
    }

    pub fn tick(
        &mut self,
        star_systems: &[SolarSystem],
        time_then: Second,
        time_now: Second)
    -> Result<(), Second>
    {
        self.subtick_fleet(star_systems, time_now);

        Ok(())
    }
} // impl FleetsManager

impl GameState
{
    pub fn new_fleet_from_ui(
        &mut self,
        info: NewFleet)
    -> Result<FleetId, Box<dyn Error>>
    {
        let star_system = &self.solar_systems[info.system];

        let fleet_id = self.fleets.reserve_new_id();
        let mut fleet = Fleet::new(fleet_id, info.name);
        fleet.make_orbit(star_system, info.orbiting, info.sma);

        self.fleets.fleets.insert(
            fleet_id,
            fleet);

        Ok(fleet_id)
    }
}

impl SolarSystem
{
    pub fn fleets(
        &self,
        fleets_manager: &FleetsManager)
    -> Vec<usize>
    {
        fleets_manager.all_in_system(self.id())
    }
}