use pile_config::Label;
use std::{collections::HashMap, io::BufReader, sync::OnceLock};
use tracing::debug;

use crate::{Item, PileValue, SyncReadBridge, extract::ObjectExtractor};

pub struct ExifExtractor<'a> {
	item: &'a Item,
	output: OnceLock<HashMap<Label, PileValue<'a>>>,
}

impl<'a> ExifExtractor<'a> {
	pub fn new(item: &'a Item) -> Self {
		Self {
			item,
			output: OnceLock::new(),
		}
	}

	async fn get_inner(&self) -> Result<&HashMap<Label, PileValue<'a>>, std::io::Error> {
		if let Some(x) = self.output.get() {
			return Ok(x);
		}

		let reader = SyncReadBridge::new_current(self.item.read().await?);
		let raw_fields = tokio::task::spawn_blocking(move || {
			let mut br = BufReader::new(reader);
			let exif = exif::Reader::new()
				.read_from_container(&mut br)
				.map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e.to_string()))?;

			let fields: Vec<(String, String)> = exif
				.fields()
				.map(|f| {
					(
						f.tag.to_string(),
						f.display_value().with_unit(&exif).to_string(),
					)
				})
				.collect();

			Ok::<_, std::io::Error>(fields)
		})
		.await
		.map_err(std::io::Error::other)?;

		let raw_fields = match raw_fields {
			Ok(x) => x,
			Err(error) => {
				debug!(message = "Could not process exif", ?error, key = ?self.item.key());
				return Ok(self.output.get_or_init(HashMap::new));
			}
		};

		let mut output: HashMap<Label, PileValue<'a>> = HashMap::new();

		for (tag_name, value) in raw_fields {
			let Some(label) = tag_to_label(&tag_name) else {
				continue;
			};
			// First occurrence wins (PRIMARY IFD comes before THUMBNAIL)
			output
				.entry(label)
				.or_insert_with(|| PileValue::String(value.into()));
		}

		return Ok(self.output.get_or_init(|| output));
	}
}

fn tag_to_label(tag: &str) -> Option<Label> {
	let sanitized: String = tag
		.chars()
		.map(|c| if c == ' ' { '_' } else { c })
		.filter(|c| Label::VALID_CHARS.contains(*c))
		.collect();
	Label::new(sanitized)
}

#[async_trait::async_trait]
impl ObjectExtractor for ExifExtractor<'_> {
	async fn field<'a>(
		&'a self,
		name: &Label,
	) -> Result<Option<&'a PileValue<'a>>, std::io::Error> {
		Ok(self.get_inner().await?.get(name))
	}

	async fn fields(&self) -> Result<Vec<Label>, std::io::Error> {
		Ok(self.get_inner().await?.keys().cloned().collect())
	}
}