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

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

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

use crate::OutfitSpace;

pub(crate) mod syntax {
	use crate::part::shared;
	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: shared::syntax::OutfitSpace,
	}

	#[derive(Debug, Deserialize)]
	pub struct Projectile {
		pub sprite_texture: 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: Option<ProjectileParticle>,
		pub expire: Option<ProjectileParticle>,
		pub collider: super::ProjectileCollider,
		pub force: f32,
	}

	#[derive(Debug, Deserialize)]
	pub struct ProjectileParticle {
		pub texture: String,
		pub lifetime: ParticleLifetime,
		pub inherit_velocity: super::ImpactInheritVelocity,
		pub size: f32,
	}

	#[derive(Debug, Deserialize)]
	#[serde(untagged)]
	pub enum ParticleLifetime {
		Inherit(String),
		Seconds(f32),
	}
}

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

#[derive(Debug, Deserialize, Clone)]
pub struct BallCollider {
	pub radius: f32,
}

/// How we should set an impact particle's velocity
#[derive(Debug, Deserialize, Clone)]
pub enum ImpactInheritVelocity {
	/// Don't inherit any velocity.
	/// This impact particle will be still.
	#[serde(rename = "don't")]
	Dont,

	/// Inherit target velocity.
	/// This impact particle will stick to the object it hits.
	#[serde(rename = "target")]
	Target,

	/// Inherit projectile velocity.
	/// This impact particle will continue on its projectile's path.
	#[serde(rename = "projectile")]
	Projectile,
}

/// 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_texture: TextureHandle,

	/// 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: Deg<f32>,

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

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

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

/// The particle a projectile will spawn when it hits something
#[derive(Debug, Clone)]
pub struct ProjectileParticle {
	/// The texture to use for this particle.
	/// This is most likely animated.
	pub texture: TextureHandle,

	/// How many seconds this particle should live
	pub lifetime: f32,

	/// How we should set this particle's velocity
	pub inherit_velocity: ImpactInheritVelocity,

	/// The height of this particle, in game units.
	pub size: f32,
}

fn parse_projectile_particle(
	ct: &Content,
	p: Option<syntax::ProjectileParticle>,
) -> Result<Option<ProjectileParticle>> {
	if let Some(impact) = p {
		let impact_texture = match ct.texture_index.get(&impact.texture) {
			None => bail!("impact texture `{}` doesn't exist", impact.texture),
			Some(t) => *t,
		};

		let impact_lifetime = match impact.lifetime {
			syntax::ParticleLifetime::Seconds(s) => s,
			syntax::ParticleLifetime::Inherit(s) => {
				if s == "inherit" {
					let t = ct.get_texture(impact_texture);
					t.fps * t.frames.len() as f32
				} else {
					bail!("bad impact lifetime, must be float or \"inherit\"",)
				}
			}
		};

		Ok(Some(ProjectileParticle {
			texture: impact_texture,
			lifetime: impact_lifetime,
			inherit_velocity: impact.inherit_velocity,
			size: impact.size,
		}))
	} else {
		Ok(None)
	}
}

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

	fn build(gun: Self::InputSyntax, ct: &mut Content) -> Result<()> {
		for (gun_name, gun) in gun {
			let projectile_texture = match ct.texture_index.get(&gun.projectile.sprite_texture) {
				None => bail!(
					"In gun `{}`: projectile texture `{}` doesn't exist",
					gun_name,
					gun.projectile.sprite_texture
				),
				Some(t) => *t,
			};

			let impact_particle = parse_projectile_particle(ct, gun.projectile.impact)
				.with_context(|| format!("In gun `{}`", gun_name))?;

			let expire_particle = parse_projectile_particle(ct, gun.projectile.expire)
				.with_context(|| format!("In gun `{}`", gun_name))?;

			ct.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_texture: projectile_texture,
					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,
					angle_rng: Deg(gun.projectile.angle_rng),
					impact_particle,
					expire_particle,
					collider: gun.projectile.collider,
				},
			});
		}

		return Ok(());
	}
}