import { existsSync, promises as fs, readFileSync, writeFileSync } from "fs";
import { validate } from "jsonschema";

export class ConfigManager<T> {
    path: string;
    default_config: T;
    config: T | null;
    schema: object;
    constructor(path: string, default_config: T, schema: object) {
        this.path = path;
        this.default_config = default_config;
        this.config = null;
        this.schema = schema;
    }
    get_config_file(): T {
        if (this.config !== null) return this.config;
        this.config = { ...this.read_config_file() };
        return this.config;
    }
    private emptyToDefault(target: T) {
        let occur = false;
        for (const key in this.default_config) {
            if (key === undefined || key in target) {
                continue;
            }
            target[key] = this.default_config[key];
            occur = true;
        }
        return occur;
    }
    read_config_file(): T {
        if (!existsSync(this.path)) {
            writeFileSync(this.path, JSON.stringify(this.default_config));
            return this.default_config;
        }
        const ret = JSON.parse(readFileSync(this.path, { encoding: "utf8" }));
        if (this.emptyToDefault(ret)) {
            writeFileSync(this.path, JSON.stringify(ret));
        }
        const result = validate(ret, this.schema);
        if (!result.valid) {
            throw new Error(result.toString());
        }
        return ret;
    }
    async write_config_file(new_config: T) {
        this.config = new_config;
        await fs.writeFile(`${this.path}.temp`, JSON.stringify(new_config));
        await fs.rename(`${this.path}.temp`, this.path);
    }
}