lofty 0.2.0

Unified IO for different types of audio metadata
Documentation 
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use super::constants::LIST_ID;
use crate::{Error, Result};

use byteorder::{LittleEndian, ReadBytesExt};
use std::collections::HashMap;
use std::io::{Cursor, Read, Seek};

pub(crate) fn wav<T>(mut data: T) -> Result<Option<HashMap<String, String>>>
where
	T: Read + Seek,
{
	let chunk = riff::Chunk::read(&mut data, 0)?;

	let mut lists: Vec<riff::Chunk> = Vec::new();

	for child in chunk.iter(&mut data) {
		let chunk_id = child.id();

		if &chunk_id.value == LIST_ID {
			lists.push(child)
		}
	}

	return if lists.is_empty() {
		Err(Error::Wav(
			"This file doesn't contain a LIST chunk".to_string(),
		))
	} else {
		let mut info: Option<riff::Chunk> = None;

		for child in lists {
			if &child.read_type(&mut data)?.value == b"INFO" {
				info = Some(child);
				break;
			}
		}

		if let Some(list) = info {
			let mut content = list.read_contents(&mut data)?;

			content.drain(0..4); // Get rid of the chunk ID
			let mut cursor = Cursor::new(&*content);

			let chunk_len = list.len();
			let mut metadata: HashMap<String, String> = HashMap::with_capacity(chunk_len as usize);

			let mut reading = true;

			while reading {
				if let (Ok(fourcc), Ok(size)) = (
					cursor.read_u32::<LittleEndian>(),
					cursor.read_u32::<LittleEndian>(),
				) {
					match create_wav_key(&fourcc.to_le_bytes()) {
						Some(key) => {
							let mut buf = vec![0; size as usize];
							cursor.read_exact(&mut buf)?;

							// Just skip any values that can't be converted
							match std::string::String::from_utf8(buf) {
								Ok(val) => {
									let _ = metadata
										.insert(key, val.trim_matches(char::from(0)).to_string());
								},
								Err(_) => continue,
							}
						},
						#[allow(clippy::cast_lossless)]
						None => cursor.set_position(cursor.position() + size as u64),
					}

					// Skip null byte
					if size as usize % 2 != 0 {
						cursor.set_position(cursor.position() + 1)
					}

					if cursor.position() >= cursor.get_ref().len() as u64 {
						reading = false
					}
				} else {
					reading = false
				}
			}

			Ok(Some(metadata))
		} else {
			Err(Error::Wav(
				"This file doesn't contain an INFO chunk".to_string(),
			))
		}
	};
}

fn create_wav_key(fourcc: &[u8]) -> Option<String> {
	match fourcc {
		fcc if fcc == super::constants::IART => Some("Artist".to_string()),
		fcc if fcc == super::constants::ICMT => Some("Comment".to_string()),
		fcc if fcc == super::constants::ICRD => Some("Date".to_string()),
		fcc if fcc == super::constants::INAM => Some("Title".to_string()),
		fcc if fcc == super::constants::IPRD => Some("Album".to_string()),

		// Non-standard
		fcc if fcc == super::constants::ITRK || fcc == super::constants::IPRT => {
			Some("TrackNumber".to_string())
		},
		fcc if fcc == super::constants::IFRM => Some("TrackTotal".to_string()),
		fcc if fcc == super::constants::ALBU => Some("Album".to_string()),
		fcc if fcc == super::constants::TRAC => Some("TrackNumber".to_string()),
		fcc if fcc == super::constants::DISC => Some("DiscNumber".to_string()),
		_ => None,
	}
}

pub fn key_to_fourcc(key: &str) -> Option<[u8; 4]> {
	match key {
		"Artist" => Some(super::constants::IART),
		"Comment" => Some(super::constants::ICMT),
		"Date" => Some(super::constants::ICRD),
		"Title" => Some(super::constants::INAM),
		"Album" => Some(super::constants::IPRD),
		"TrackTotal" => Some(super::constants::IFRM),
		"TrackNumber" => Some(super::constants::TRAC),
		"DiscNumber" | "DiscTotal" => Some(super::constants::DISC),
		_ => None,
	}
}