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import fs from "fs/promises";
import path from "path";
import * as f from "fp-ts";
import * as t from "io-ts";
import * as tr from "io-ts/PathReporter";
export const PostDatabaseEntryC = t.type({
provider: t.literal("e926"),
id: t.number,
});
export type PostDatabaseEntry = t.TypeOf<typeof PostDatabaseEntryC>;
export class PostDatabase {
private entries: PostDatabaseEntry[] = [];
private readonly filePath: string;
private isLoaded = false;
constructor(filename: string, private max?: number) {
this.filePath = path.join(process.cwd(), filename);
}
private async load() {
if (this.isLoaded) {
return;
}
this.isLoaded = true;
try {
await fs.stat(this.filePath);
} catch {
await this.save();
}
const fileContent = await fs.readFile(this.filePath, "utf8");
const entries = f.function.pipe(
fileContent,
f.json.parse,
f.either.mapLeft(() => []),
f.either.chain(t.array(PostDatabaseEntryC).decode)
);
if (f.either.isRight(entries)) {
this.entries = this.max ? entries.right.slice(-1 * this.max) : entries.right;
} else {
throw new Error(tr.failure(entries.left).join("\n\n"));
}
}
private async save() {
await fs.writeFile(this.filePath, JSON.stringify(this.entries), "utf8");
}
async insertIfNotExists(entry: PostDatabaseEntry): Promise<boolean> {
await this.load();
const has = !!this.entries.find((e) => e.provider === entry.provider && e.id === entry.id);
if (!has) {
this.entries.push(entry);
await this.save();
}
return has;
}
async takeFirst(): Promise<PostDatabaseEntry | undefined> {
await this.load();
const entry = this.entries.shift();
await this.save();
return entry;
}
async remove(entry: PostDatabaseEntry): Promise<boolean> {
await this.load();
const i = this.entries.findIndex((e) => e.provider === entry.provider && e.id === entry.id);
if (i === -1) {
return false;
}
this.entries.splice(i, 1);
await this.save();
return true;
}
}
export default PostDatabase;
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