use pile_config::Label;
use std::sync::OnceLock;

use super::TomlExtractor;
use crate::{
	extract::traits::ObjectExtractor,
	value::{Item, PileValue},
};

pub struct SidecarExtractor {
	item: Item,
	output: OnceLock<Option<TomlExtractor>>,
}

impl SidecarExtractor {
	pub fn new(item: &Item) -> Self {
		Self {
			item: item.clone(),
			output: OnceLock::new(),
		}
	}
}

#[async_trait::async_trait]
impl ObjectExtractor for SidecarExtractor {
	async fn field(
		&self,
		name: &Label,
		args: Option<&str>,
	) -> Result<Option<PileValue>, std::io::Error> {
		match self
			.output
			.get_or_init(|| self.item.sidecar().map(TomlExtractor::new))
		{
			Some(x) => Ok(x.field(name, args).await?),
			None => Ok(Some(PileValue::Null)),
		}
	}

	async fn fields(&self) -> Result<Vec<Label>, std::io::Error> {
		match self
			.output
			.get_or_init(|| self.item.sidecar().map(TomlExtractor::new))
		{
			Some(x) => Ok(x.fields().await?),
			None => Ok(Vec::new()),
		}
	}
}