use geom::Polygon;
use map_model::PermanentMapEdits;
use widgetry::{
    hotkeys, Btn, Canvas, Choice, Drawable, EventCtx, GeomBatch, GfxCtx, HorizontalAlignment, Key,
    Line, Menu, Outcome, Panel, ScreenRectangle, Text, VerticalAlignment, Widget, GUI,
};

use crate::app::{App, Flags, ShowEverything};
use crate::options::Options;
use crate::pregame::TitleScreen;
use crate::render::DrawOptions;
use crate::sandbox::{GameplayMode, SandboxMode};

// This is the top-level of the GUI logic. This module should just manage interactions between the
// top-level game states.
pub struct Game {
    // A stack of states
    states: Vec<Box<dyn State>>,
    app: App,
}

impl Game {
    pub fn new(
        flags: Flags,
        opts: Options,
        start_with_edits: Option<String>,
        maybe_mode: Option<GameplayMode>,
        ctx: &mut EventCtx,
    ) -> Game {
        let title = !opts.dev
            && !flags.sim_flags.load.contains("player/save")
            && !flags.sim_flags.load.contains("system/scenarios")
            && maybe_mode.is_none();
        let mut app = App::new(flags, opts, ctx, title);

        // Handle savestates
        let savestate = if app
            .primary
            .current_flags
            .sim_flags
            .load
            .contains("player/saves/")
        {
            assert!(maybe_mode.is_none());
            Some(app.primary.clear_sim())
        } else {
            None
        };

        // Just apply this here, don't plumb to SimFlags or anything else. We recreate things using
        // these flags later, but we don't want to keep applying the same edits.
        if let Some(edits_name) = start_with_edits {
            // TODO Maybe loading screen
            let mut timer = abstutil::Timer::new("apply initial edits");
            let edits = map_model::MapEdits::load(
                &app.primary.map,
                abstutil::path_edits(app.primary.map.get_name(), &edits_name),
                &mut timer,
            )
            .unwrap();
            crate::edit::apply_map_edits(ctx, &mut app, edits);
            app.primary
                .map
                .recalculate_pathfinding_after_edits(&mut timer);
            app.primary.clear_sim();
        }

        let states: Vec<Box<dyn State>> = if title {
            vec![Box::new(TitleScreen::new(ctx, &mut app))]
        } else {
            let mode = maybe_mode
                .unwrap_or_else(|| GameplayMode::Freeform(app.primary.map.get_name().clone()));
            vec![SandboxMode::new(ctx, &mut app, mode)]
        };
        if let Some(ss) = savestate {
            // TODO This is weird, we're left in Freeform mode with the wrong UI. Can't instantiate
            // PlayScenario without clobbering.
            app.primary.sim = ss;
        }
        Game { states, app }
    }

    // If true, then the top-most state on the stack needs to be "woken up" with a fake mouseover
    // event.
    fn execute_transition(&mut self, ctx: &mut EventCtx, transition: Transition) -> bool {
        match transition {
            Transition::Keep => false,
            Transition::KeepWithMouseover => true,
            Transition::Pop => {
                self.states.pop().unwrap().on_destroy(ctx, &mut self.app);
                if self.states.is_empty() {
                    self.before_quit(ctx.canvas);
                    std::process::exit(0);
                }
                true
            }
            Transition::ModifyState(cb) => {
                cb(self.states.last_mut().unwrap(), ctx, &mut self.app);
                true
            }
            Transition::ReplaceWithData(cb) => {
                let mut last = self.states.pop().unwrap();
                last.on_destroy(ctx, &mut self.app);
                let new_states = cb(last, ctx, &mut self.app);
                self.states.extend(new_states);
                true
            }
            Transition::Push(state) => {
                self.states.push(state);
                true
            }
            Transition::Replace(state) => {
                self.states.pop().unwrap().on_destroy(ctx, &mut self.app);
                self.states.push(state);
                true
            }
            Transition::Clear(states) => {
                while !self.states.is_empty() {
                    self.states.pop().unwrap().on_destroy(ctx, &mut self.app);
                }
                self.states.extend(states);
                true
            }
            Transition::Multi(list) => {
                // Always wake-up just the last state remaining after the sequence
                for t in list {
                    self.execute_transition(ctx, t);
                }
                true
            }
        }
    }
}

impl GUI for Game {
    fn event(&mut self, ctx: &mut EventCtx) {
        self.app.per_obj.reset();

        let transition = self.states.last_mut().unwrap().event(ctx, &mut self.app);
        if self.execute_transition(ctx, transition) {
            // Let the new state initialize with a fake event. Usually these just return
            // Transition::Keep, but nothing stops them from doing whatever. (For example, entering
            // tutorial mode immediately pushes on a Warper.) So just recurse.
            ctx.no_op_event(true, |ctx| self.event(ctx));
        }
    }

    fn draw(&self, g: &mut GfxCtx) {
        let state = self.states.last().unwrap();

        match state.draw_baselayer() {
            DrawBaselayer::DefaultMap => {
                self.app.draw(
                    g,
                    DrawOptions::new(),
                    &self.app.primary.sim,
                    &ShowEverything::new(),
                );
            }
            DrawBaselayer::Custom => {}
            DrawBaselayer::PreviousState => {
                match self.states[self.states.len() - 2].draw_baselayer() {
                    DrawBaselayer::DefaultMap => {
                        self.app.draw(
                            g,
                            DrawOptions::new(),
                            &self.app.primary.sim,
                            &ShowEverything::new(),
                        );
                    }
                    DrawBaselayer::Custom => {}
                    // Nope, don't recurse
                    DrawBaselayer::PreviousState => {}
                }

                self.states[self.states.len() - 2].draw(g, &self.app);
            }
        }
        state.draw(g, &self.app);
    }

    fn dump_before_abort(&self, canvas: &Canvas) {
        println!();
        println!(
            "********************************************************************************"
        );
        canvas.save_camera_state(self.app.primary.map.get_name());
        println!(
            "Crash! Please report to https://github.com/dabreegster/abstreet/issues/ and include \
             all output.txt; at least everything starting from the stack trace above!"
        );

        println!();
        self.app.primary.sim.dump_before_abort();

        println!();
        println!("Camera:");
        println!(
            r#"{{ "cam_x": {}, "cam_y": {}, "cam_zoom": {} }}"#,
            canvas.cam_x, canvas.cam_y, canvas.cam_zoom
        );

        println!();
        if self.app.primary.map.get_edits().commands.is_empty() {
            println!("No edits");
        } else {
            abstutil::write_json(
                "edits_during_crash.json".to_string(),
                &PermanentMapEdits::to_permanent(
                    self.app.primary.map.get_edits(),
                    &self.app.primary.map,
                ),
            );
            println!("Please include edits_during_crash.json in your bug report.");
        }

        // Repeat, because it can be hard to see the top of the report if it's long
        println!();
        println!(
            "Crash! Please report to https://github.com/dabreegster/abstreet/issues/ and include \
             all output.txt; at least everything above here until the start of the report!"
        );
        println!(
            "********************************************************************************"
        );
    }

    fn before_quit(&self, canvas: &Canvas) {
        canvas.save_camera_state(self.app.primary.map.get_name());
    }
}

pub enum DrawBaselayer {
    DefaultMap,
    Custom,
    PreviousState,
}

pub trait State: downcast_rs::Downcast {
    fn event(&mut self, ctx: &mut EventCtx, app: &mut App) -> Transition;
    fn draw(&self, g: &mut GfxCtx, app: &App);

    fn draw_baselayer(&self) -> DrawBaselayer {
        DrawBaselayer::DefaultMap
    }

    // Before this state is popped or replaced, call this.
    fn on_destroy(&mut self, _: &mut EventCtx, _: &mut App) {}
    // We don't need an on_enter -- the constructor for the state can just do it.
}

impl dyn State {
    pub fn grey_out_map(g: &mut GfxCtx, app: &App) {
        // Make it clear the map can't be interacted with right now.
        g.fork_screenspace();
        // TODO - OSD height
        g.draw_polygon(
            app.cs.fade_map_dark,
            Polygon::rectangle(g.canvas.window_width, g.canvas.window_height),
        );
        g.unfork();
    }
}

downcast_rs::impl_downcast!(State);

pub enum Transition {
    Keep,
    KeepWithMouseover,
    Pop,
    // If a state needs to pass data back to the parent, use this. Sadly, runtime type casting.
    ModifyState(Box<dyn FnOnce(&mut Box<dyn State>, &mut EventCtx, &mut App)>),
    // TODO This is like Replace + ModifyState, then returning a few Push's from the callback. Not
    // sure how to express it in terms of the others without complicating ModifyState everywhere.
    ReplaceWithData(
        Box<dyn FnOnce(Box<dyn State>, &mut EventCtx, &mut App) -> Vec<Box<dyn State>>>,
    ),
    Push(Box<dyn State>),
    Replace(Box<dyn State>),
    Clear(Vec<Box<dyn State>>),
    Multi(Vec<Transition>),
}

pub struct ChooseSomething<T> {
    panel: Panel,
    cb: Box<dyn Fn(T, &mut EventCtx, &mut App) -> Transition>,
}

impl<T: 'static> ChooseSomething<T> {
    pub fn new(
        ctx: &mut EventCtx,
        query: &str,
        choices: Vec<Choice<T>>,
        cb: Box<dyn Fn(T, &mut EventCtx, &mut App) -> Transition>,
    ) -> Box<dyn State> {
        Box::new(ChooseSomething {
            panel: Panel::new(Widget::col(vec![
                Widget::row(vec![
                    Line(query).small_heading().draw(ctx),
                    Btn::plaintext("X")
                        .build(ctx, "close", Key::Escape)
                        .align_right(),
                ]),
                Menu::new(ctx, choices).named("menu"),
            ]))
            .build(ctx),
            cb,
        })
    }

    pub fn new_below(
        ctx: &mut EventCtx,
        rect: &ScreenRectangle,
        choices: Vec<Choice<T>>,
        cb: Box<dyn Fn(T, &mut EventCtx, &mut App) -> Transition>,
    ) -> Box<dyn State> {
        Box::new(ChooseSomething {
            panel: Panel::new(Menu::new(ctx, choices).named("menu").container())
                .aligned(
                    HorizontalAlignment::Centered(rect.center().x),
                    VerticalAlignment::Below(rect.y2 + 15.0),
                )
                .build(ctx),
            cb,
        })
    }
}

impl<T: 'static> State for ChooseSomething<T> {
    fn event(&mut self, ctx: &mut EventCtx, app: &mut App) -> Transition {
        match self.panel.event(ctx) {
            Outcome::Clicked(x) => match x.as_ref() {
                "close" => Transition::Pop,
                _ => {
                    let data = self.panel.take_menu_choice::<T>("menu");
                    (self.cb)(data, ctx, app)
                }
            },
            _ => {
                if ctx.normal_left_click() && ctx.canvas.get_cursor_in_screen_space().is_none() {
                    return Transition::Pop;
                }
                // new_below doesn't make an X button
                if ctx.input.pressed(Key::Escape) {
                    return Transition::Pop;
                }
                Transition::Keep
            }
        }
    }

    fn draw_baselayer(&self) -> DrawBaselayer {
        DrawBaselayer::PreviousState
    }

    fn draw(&self, g: &mut GfxCtx, app: &App) {
        State::grey_out_map(g, app);
        self.panel.draw(g);
    }
}

pub struct PromptInput {
    panel: Panel,
    cb: Box<dyn Fn(String, &mut EventCtx, &mut App) -> Transition>,
}

impl PromptInput {
    pub fn new(
        ctx: &mut EventCtx,
        query: &str,
        cb: Box<dyn Fn(String, &mut EventCtx, &mut App) -> Transition>,
    ) -> Box<dyn State> {
        Box::new(PromptInput {
            panel: Panel::new(Widget::col(vec![
                Widget::row(vec![
                    Line(query).small_heading().draw(ctx),
                    Btn::plaintext("X")
                        .build(ctx, "close", Key::Escape)
                        .align_right(),
                ]),
                Widget::text_entry(ctx, String::new(), true).named("input"),
                Btn::text_fg("confirm").build_def(ctx, Key::Enter),
            ]))
            .build(ctx),
            cb,
        })
    }
}

impl State for PromptInput {
    fn event(&mut self, ctx: &mut EventCtx, app: &mut App) -> Transition {
        match self.panel.event(ctx) {
            Outcome::Clicked(x) => match x.as_ref() {
                "close" => Transition::Pop,
                "confirm" => {
                    let data = self.panel.text_box("input");
                    (self.cb)(data, ctx, app)
                }
                _ => unreachable!(),
            },
            _ => {
                if ctx.normal_left_click() && ctx.canvas.get_cursor_in_screen_space().is_none() {
                    return Transition::Pop;
                }
                Transition::Keep
            }
        }
    }

    fn draw_baselayer(&self) -> DrawBaselayer {
        DrawBaselayer::PreviousState
    }

    fn draw(&self, g: &mut GfxCtx, app: &App) {
        State::grey_out_map(g, app);
        self.panel.draw(g);
    }
}

pub struct PopupMsg {
    panel: Panel,
    unzoomed: Drawable,
    zoomed: Drawable,
}

impl PopupMsg {
    pub fn new<I: Into<String>>(ctx: &mut EventCtx, title: &str, lines: Vec<I>) -> Box<dyn State> {
        PopupMsg::also_draw(
            ctx,
            title,
            lines,
            ctx.upload(GeomBatch::new()),
            ctx.upload(GeomBatch::new()),
        )
    }

    pub fn also_draw<I: Into<String>>(
        ctx: &mut EventCtx,
        title: &str,
        lines: Vec<I>,
        unzoomed: Drawable,
        zoomed: Drawable,
    ) -> Box<dyn State> {
        let mut txt = Text::new();
        txt.add(Line(title).small_heading());
        for l in lines {
            txt.add(Line(l));
        }
        Box::new(PopupMsg {
            panel: Panel::new(Widget::col(vec![
                txt.draw(ctx),
                Btn::text_bg2("OK").build_def(ctx, hotkeys(vec![Key::Enter, Key::Escape])),
            ]))
            .build(ctx),
            unzoomed,
            zoomed,
        })
    }
}

impl State for PopupMsg {
    fn event(&mut self, ctx: &mut EventCtx, _: &mut App) -> Transition {
        match self.panel.event(ctx) {
            Outcome::Clicked(x) => match x.as_ref() {
                "OK" => Transition::Pop,
                _ => unreachable!(),
            },
            _ => {
                if ctx.normal_left_click() && ctx.canvas.get_cursor_in_screen_space().is_none() {
                    return Transition::Pop;
                }
                Transition::Keep
            }
        }
    }

    fn draw_baselayer(&self) -> DrawBaselayer {
        DrawBaselayer::PreviousState
    }

    fn draw(&self, g: &mut GfxCtx, app: &App) {
        State::grey_out_map(g, app);
        self.panel.draw(g);
        if g.canvas.cam_zoom < app.opts.min_zoom_for_detail {
            g.redraw(&self.unzoomed);
        } else {
            g.redraw(&self.zoomed);
        }
    }
}