nvda_url 0.1.3

Retrieve download URLs for the NVDA screen reader.
Documentation 
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#![warn(clippy::all, clippy::pedantic, clippy::nursery)]

use std::{
	collections::HashMap,
	time::{Duration, Instant},
};

use reqwest::Client;
use tokio::sync::Mutex;

const CACHE_TTL: Duration = Duration::from_secs(30);

/// Direct download link for NVDA 2017.3 (Windows XP).
pub const XP_URL: &str = "https://download.nvaccess.org/releases/2017.3/nvda_2017.3.exe";
/// Direct download link for NVDA 2023.3.4 (Windows 7).
pub const WIN7_URL: &str = "https://download.nvaccess.org/releases/2023.3.4/nvda_2023.3.4.exe";

/// NV Access has their own custom format for NVDA's update API, this lets us parse only the fields we care about out of it.
#[derive(Debug)]
struct UpdateInfo {
	pub launcher_url: Option<String>,
}

impl UpdateInfo {
	#[must_use]
	fn parse(data: &str) -> Self {
		let launcher_url = data.lines().find_map(|line| {
			let (key, value) = line.split_once(": ")?;
			(key == "launcherUrl").then(|| value.to_owned())
		});
		Self { launcher_url }
	}
}

/// Represents the different NVDA release channels.
#[derive(Clone, Copy, Eq, Hash, PartialEq, Debug)]
pub enum VersionType {
	/// Official stable releases.
	Stable,
	/// Pre-release beta versions.
	Beta,
	/// Snapshot alpha builds.
	Alpha,
}

impl VersionType {
	const fn as_str(self) -> &'static str {
		match self {
			Self::Alpha => "snapshot:alpha",
			Self::Beta => "beta",
			Self::Stable => "stable",
		}
	}
}

/// Fetches and caches NVDA download URLs.
#[derive(Default)]
pub struct NvdaUrl {
	client: Client,
	cache: Mutex<HashMap<VersionType, (String, Instant)>>,
}

impl NvdaUrl {
	/// Retrieves the latest download URL for the specified NVDA version type.
	///
	/// If a cached URL is still valid, it is returned. Otherwise, a new request is made.
	///
	/// # Arguments
	///
	/// * `version_type` - The type of NVDA version to fetch.
	///  
	/// # Returns
	///
	/// An `Option<String>` containing the URL if successful, or `None` if an error occurs.
	pub async fn get_url(&self, version_type: VersionType) -> Option<String> {
		let mut cache = self.cache.lock().await;
		if let Some((url, timestamp)) = cache.get(&version_type)
			&& timestamp.elapsed() < CACHE_TTL {
				return Some(url.clone());
			}
		let url = self.fetch_url(&version_type).await?;
		cache.insert(version_type, (url.clone(), Instant::now()));
		drop(cache);
		Some(url)
	}

	async fn fetch_url(&self, version_type: &VersionType) -> Option<String> {
		let url = format!("https://api.nvaccess.org/nvdaUpdateCheck?versionType={}", version_type.as_str());
		let body = self.client.get(&url).send().await.ok()?.text().await.ok()?;
		let info = UpdateInfo::parse(&body);
		info.launcher_url
	}
}