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

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

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

pub(crate) mod syntax {
	use anyhow::{bail, Result};
	use serde::Deserialize;

	use crate::{Content, ContentBuildContext, EffectHandle};
	// Raw serde syntax structs.
	// These are never seen by code outside this crate.

	#[derive(Debug, Deserialize)]
	pub struct Effect {
		pub sprite: String,
		pub lifetime: EffectLifetime,
		pub inherit_velocity: super::ImpactInheritVelocity,
		pub size: f32,
	}

	// We implement building here instead of in super::Effect because
	// effects may be defined inline (see EffectReference).
	impl Effect {
		pub fn add_to(
			self,
			_build_context: &mut ContentBuildContext,
			content: &mut Content,
		) -> Result<EffectHandle> {
			let sprite = match content.sprite_index.get(&self.sprite) {
				None => bail!("sprite `{}` doesn't exist", self.sprite),
				Some(t) => *t,
			};

			let lifetime = match self.lifetime {
				EffectLifetime::Seconds(s) => s,
				EffectLifetime::Inherit(s) => {
					if s == "inherit" {
						let sprite = content.get_sprite(sprite);
						sprite.fps * sprite.frames.len() as f32
					} else {
						bail!("bad effect lifetime, must be float or \"inherit\"",)
					}
				}
			};

			let handle = EffectHandle {
				index: content.effects.len(),
			};
			content.effects.push(super::Effect {
				sprite,
				lifetime,
				handle,
				inherit_velocity: self.inherit_velocity,
				size: self.size,
			});

			return Ok(handle);
		}
	}

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

	// This isn't used here, but is pulled in by other content items.
	/// A reference to an effect by name, or an inline definition.
	#[derive(Debug, Deserialize)]
	#[serde(untagged)]
	pub enum EffectReference {
		Label(String),
		Effect(Effect),
	}

	impl EffectReference {
		pub fn to_handle(
			self,
			build_context: &mut ContentBuildContext,
			content: &mut Content,
		) -> Result<EffectHandle> {
			// We do not insert anything into build_context here,
			// since inline effects cannot be referenced by name.
			Ok(match self {
				Self::Effect(e) => e.add_to(build_context, content)?,
				Self::Label(l) => match build_context.effect_index.get(&l) {
					Some(h) => *h,
					None => bail!("no effect named `{}`", l),
				},
			})
		}
	}
}

/// How we should set an effect'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,
}

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

	/// This effect's handle
	pub handle: EffectHandle,

	/// 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,
}

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

	fn build(
		effects: Self::InputSyntaxType,
		build_context: &mut ContentBuildContext,
		content: &mut Content,
	) -> Result<()> {
		for (effect_name, effect) in effects {
			let h = effect
				.add_to(build_context, content)
				.with_context(|| format!("while evaluating effect `{}`", effect_name))?;
			build_context.effect_index.insert(effect_name, h);
		}

		return Ok(());
	}
}