use bevy::prelude::*;

use crate::{
    game::{grid::*, tetris::*},
    util::Vector2I,
};

pub fn apply_gravity(
    mut piece_query: Query<(&mut Gravity, &PieceControls, &ChildOf)>,
    time: Res<Time>,
    game_gravity_query: Query<&GameGravity>,
) {
    const SOFT_DROP_SPEED: f32 = 10.0;
    for (mut piece_gravity, controls, parent) in piece_query.iter_mut() {
        if let Ok(game_gravity) = game_gravity_query.get(parent.0) {
            piece_gravity.cumulated += game_gravity.current * time.delta_secs();
        }
        if controls.fast_drop {
            piece_gravity.cumulated += SOFT_DROP_SPEED * time.delta_secs();
        }
    }
}

pub fn apply_piece_movement(
    mut piece_query: Query<(
        &PieceControls,
        Option<&mut Gravity>,
        Entity,
        &ChildOf,
        &Children,
    )>,
    game_query: Query<(&BlockSet, &GameArea)>,
    mut transform_query: Query<(&mut GridTransform, Has<Block>)>,
    mut commands: Commands,
) {
    for (controls, maybe_gravity, entity, parent, children) in piece_query.iter_mut() {
        let game_entity = parent.parent();
        let (collisions, game_area) = game_query.get(game_entity).unwrap();

        let blocks: Vec<Vector2I> = {
            let mut blocks = vec![];
            for child in children.iter() {
                let block = transform_query
                    .get(child)
                    .iter()
                    .filter_map(|(transform, has_block)| {
                        if *has_block {
                            Some(transform.translation)
                        } else {
                            None
                        }
                    })
                    .next();
                if let Some(pos) = block {
                    blocks.push(pos);
                }
            }
            blocks
        };

        let cast_shape =
            |pos| collisions.cast_shape(pos, &blocks) || !game_area.is_shape_inside(pos, &blocks);

        let piece_pos = &mut transform_query.get_mut(entity).unwrap().0.translation;

        if controls.instant_drop {
            let mut drop_pos = *piece_pos;
            while !cast_shape(drop_pos + Vector2I::DOWN) {
                drop_pos = drop_pos + Vector2I::DOWN;
            }
            *piece_pos = drop_pos;
            commands.trigger_targets(OnPiecePlaced { piece: entity }, game_entity);
            continue;
        }

        let can_move_down = !cast_shape(*piece_pos + Vector2I::DOWN);

        if let Some(mut gravity) = maybe_gravity {
            if gravity.cumulated >= 1.0 && can_move_down {
                gravity.cumulated -= 1.0;
                *piece_pos = *piece_pos + Vector2I::DOWN;
            }
            if gravity.cumulated >= 3.0 && !can_move_down {
                commands.trigger_targets(OnPiecePlaced { piece: entity }, game_entity);
                continue;
            }
        }

        if let Some(movement) = controls.movement {
            let dir = match movement {
                input::Move::Left => Vector2I::LEFT,
                input::Move::Right => Vector2I::RIGHT,
            };
            if !cast_shape(*piece_pos + dir) {
                *piece_pos = *piece_pos + dir;
            }
        }
    }
}