Adds stash/use/save/load actions for episode progress

src/lib/context/progress.ts

@@ -0,0 +1,77 @@
+import { browser } from '$app/environment';
+import { audio, type AudioLoadOptions } from '$lib/context/audio';
+import { error, info, warn } from '$lib/utility/package/log';
+
+export type EpisodeProgress = {
+	current_time: number;
+};
+
+const episode_progress_map = new Map<string, EpisodeProgress>();
+
+function stash_episode() {
+	return audio.subscribe((state) => {
+		info('saving progress: ', state.src);
+		if (!state.src) return;
+		episode_progress_map.set(state.src, { current_time: state.current_time });
+	})();
+}
+
+function use_episode(src: string): Pick<AudioLoadOptions, 'start_at'> | null {
+	const progress = episode_progress_map.get(src);
+
+	if (!progress) return null;
+
+	info('found saved progress: ', progress);
+
+	return { start_at: progress.current_time };
+}
+
+type SavedEpisodeProgress = EpisodeProgress & { src: string };
+const EPISODE_PROGRESS_KEY = 'EPISODE_PROGRESS' as const;
+
+function save_all() {
+	if (!browser || !localStorage) {
+		warn('localStorage not available, skipping save');
+		return;
+	}
+	const items = [...episode_progress_map];
+
+	const episodes = items.reduce((prev, [src, progress]) => {
+		return [...prev, { src, ...progress }];
+	}, [] as SavedEpisodeProgress[]);
+
+	info(`Saving progress for ${episodes.length} episodes to localStorage`, episodes);
+	localStorage.setItem(EPISODE_PROGRESS_KEY, JSON.stringify(episodes));
+}
+
+function load_all() {
+	if (!browser || !localStorage) {
+		warn('localStorage not available, skipping load');
+		return;
+	}
+	const data = localStorage.getItem(EPISODE_PROGRESS_KEY);
+
+	if (!data) {
+		info('No saved episode progress found');
+		return;
+	}
+
+	const episodes = JSON.parse(data) as SavedEpisodeProgress[];
+
+	try {
+		episodes.forEach(({ src, ...progress }) => {
+			episode_progress_map.set(src, progress);
+		});
+		info(`Loaded ${episode_progress_map.size} episodes progress from localStorage`);
+	} catch (e) {
+		error('Error loading episode progress', e);
+		return;
+	}
+}
+
+export const episode_progress = {
+	stash: stash_episode,
+	use: use_episode,
+	save_all,
+	load_all,
+};