import Globals from './globals';

import { Resource, ShouldNeverHappenError } from './data-types';

export default class ResourceRAMCache {
	private data = new Map<string, { resource: Resource, lastUsed: Date }>(); // (guildId, resourceId) -> { resource, lastUsed }
	private size = 0;

	public putResource(guildId: number, resource: Resource): void {
		if (resource.data.length > Globals.MAX_RESOURCE_SIZE) { // skip resources if they would flood the cache
			return;
		}
		let id = `s#${guildId}/r#${resource.id}`;
		this.data.set(id, { resource: resource, lastUsed: new Date() });
		this.size += resource.data.length;
		if (this.size > Globals.MAX_GUILD_RESOURCE_CACHE_SIZE) { // TODO: this feature needs to be tested
			let entries = Array.from(this.data.entries())
				.map(([ key, value ]) => { return { id: key, value: value }; })
				.sort((a, b) => b.value.lastUsed.getTime() - a.value.lastUsed.getTime()); // oldest last (for pop)
			while (this.size > Globals.MAX_GUILD_RESOURCE_CACHE_SIZE) {
				let entry = entries.pop();
				if (entry === undefined) throw new ShouldNeverHappenError('No entry in the array but the ram cache still has a size...');
				this.data.delete(entry.id);
				this.size -= entry.value.resource.data.length;
			}
		}
	}

	public getResource(guildId: number, resourceId: string): Resource | null {
		let id = `s#${guildId}/r#${resourceId}`;
		let v = this.data.get(id);
		if (!v) return null;
		v.lastUsed = new Date();
		return v.resource;
	}
}