Galactica/crates/content/src/part/gun.rs

use anyhow::{bail, Context, Result};
use cgmath::{Deg, Rad};
use serde::Deserialize;
use std::collections::HashMap;

use crate::{handle::SpriteHandle, Content};

use crate::{ContentBuildContext, EffectHandle, OutfitSpace};

pub(crate) mod syntax {
	use crate::part::effect;
	use crate::part::outfitspace;
	use serde::Deserialize;
	// Raw serde syntax structs.
	// These are never seen by code outside this crate.

	#[derive(Debug, Deserialize)]
	pub struct Gun {
		pub projectile: Projectile,
		pub rate: f32,
		pub rate_rng: f32,
		pub space: outfitspace::syntax::OutfitSpace,
	}

	#[derive(Debug, Deserialize)]
	pub struct Projectile {
		pub sprite: String,
		pub size: f32,
		pub size_rng: f32,
		pub speed: f32,
		pub speed_rng: f32,
		pub lifetime: f32,
		pub lifetime_rng: f32,
		pub damage: f32,
		pub angle_rng: f32,
		pub impact_effect: Option<effect::syntax::EffectReference>,
		pub expire_effect: Option<effect::syntax::EffectReference>,
		pub collider: super::ProjectileCollider,
		pub force: f32,
	}
}

/// Defines a projectile's collider
#[derive(Debug, Deserialize, Clone)]
pub enum ProjectileCollider {
	/// A ball collider
	#[serde(rename = "ball")]
	Ball(BallCollider),
}

/// A simple ball-shaped collider, centered at the object's position
#[derive(Debug, Deserialize, Clone)]
pub struct BallCollider {
	/// The radius of this ball
	pub radius: f32,
}

/// Represents a gun outfit.
#[derive(Debug, Clone)]
pub struct Gun {
	/// The name of this gun
	pub name: String,

	/// The projectile this gun produces
	pub projectile: Projectile,

	/// Average delay between projectiles, in seconds.
	pub rate: f32,

	/// Random variation of projectile delay, in seconds.
	/// Each shot waits (rate += rate_rng).
	pub rate_rng: f32,

	/// How much space this gun uses
	pub space: OutfitSpace,
}

/// Represents a projectile that a [`Gun`] produces.
#[derive(Debug, Clone)]
pub struct Projectile {
	/// The projectile sprite
	pub sprite: SpriteHandle,

	/// The average size of this projectile
	/// (height in game units)
	pub size: f32,
	/// Random size variation
	pub size_rng: f32,

	/// The speed of this projectile, in game units / second
	pub speed: f32,
	/// Random speed variation
	pub speed_rng: f32,

	/// The lifespan of this projectile.
	/// It will vanish if it lives this long without hitting anything.
	pub lifetime: f32,
	/// Random lifetime variation
	pub lifetime_rng: f32,

	/// The damage this projectile does
	pub damage: f32,

	/// The force this projectile applies
	pub force: f32,

	/// The angle variation of this projectile.
	/// Projectiles can be off center up to
	/// `spread / 2` degrees in both directions.
	///
	/// (Forming a "fire cone" of `spread` degrees)
	pub angle_rng: Rad<f32>,

	/// The particle this projectile will spawn when it hits something
	pub impact_effect: Option<EffectHandle>,

	/// The particle this projectile will spawn when it expires
	pub expire_effect: Option<EffectHandle>,

	/// Collider parameters for this projectile
	pub collider: ProjectileCollider,
}

impl crate::Build for Gun {
	type InputSyntaxType = HashMap<String, syntax::Gun>;

	fn build(
		gun: Self::InputSyntaxType,
		build_context: &mut ContentBuildContext,
		content: &mut Content,
	) -> Result<()> {
		for (gun_name, gun) in gun {
			let projectile_sprite_handle = match content.sprite_index.get(&gun.projectile.sprite) {
				None => bail!(
					"projectile sprite `{}` doesn't exist in gun `{}`",
					gun.projectile.sprite,
					gun_name,
				),
				Some(t) => *t,
			};

			let impact_effect = match gun.projectile.impact_effect {
				Some(e) => Some(
					e.to_handle(build_context, content)
						.with_context(|| format!("while loading gun `{}`", gun_name))?,
				),
				None => None,
			};

			let expire_effect = match gun.projectile.expire_effect {
				Some(e) => Some(
					e.to_handle(build_context, content)
						.with_context(|| format!("while loading gun `{}`", gun_name))?,
				),
				None => None,
			};

			content.guns.push(Self {
				name: gun_name,
				space: gun.space.into(),
				rate: gun.rate,
				rate_rng: gun.rate_rng,
				projectile: Projectile {
					force: gun.projectile.force,
					sprite: projectile_sprite_handle,
					size: gun.projectile.size,
					size_rng: gun.projectile.size_rng,
					speed: gun.projectile.speed,
					speed_rng: gun.projectile.speed_rng,
					lifetime: gun.projectile.lifetime,
					lifetime_rng: gun.projectile.lifetime_rng,
					damage: gun.projectile.damage,

					// Divide by 2, so the angle matches the angle of the fire cone.
					// This should ALWAYS be done in the content parser.
					angle_rng: Deg(gun.projectile.angle_rng / 2.0).into(),
					impact_effect,
					expire_effect,
					collider: gun.projectile.collider,
				},
			});
		}

		return Ok(());
	}
}