export type UserEntry = {
    id: string,
    username: string,
    display_name?: string,
    biography?: string,
    joined_at?: string,
    age: number, // actually not just that
    badges?: string[]
    type?: 'user',
    karma?: number
};

export type GuildEntry = {
    type?: 'guild',
    id: string,
    name: string,
    display_name?: string,
    description?: string,
    created_at?: string,
    subscriber_count?: number,
    post_count?: number
};

export type PostEntry = {
    id: string,
    url: string,
    title: string,
    created_at: string,
    author?: UserEntry | null,
    content?: string | null,
    to: UserEntry | GuildEntry 
};

export type ServerHealth = {
    version: string,
    name: string,
    post_count: number,
    user_count: number,
    me: string | null,
    csrf_token?: string,
    color_theme?: number
};


// caches an oath (CSRF token)
class OathKeeper {
    lastOath : number;
    csrfToken: string | null;

    constructor () {
        this.lastOath = 0;
        this.csrfToken = null;
    }

    set (tok: string) {
        this.lastOath = +new Date;
        this.csrfToken = tok;
    }

    get () {
        if (this.lastOath === 0 || +new Date() - this.lastOath > 1800000) {
            // 30 minutes decay
            return null;
        }
        return this.csrfToken;
    }
}

const oathKeeper = new OathKeeper();

export class Backend {
    static ENDPOINT_BASE = '/v1';

    constructor () {
    }

    async fetch(url: string, options?: RequestInit) {
        return await fetch(`${Backend.ENDPOINT_BASE}/${url.replace(/^\/+/, '')}`, options);
    }

    withEvent(event: any) {
        return new EventBackend(event);
    }
}

class EventBackend extends Backend {
    event: any | null;

    constructor (event: any | null) {
        super();
        this.event = event;
    }

    async oath (): Promise<CsrfEventBackend> {
        let csrfToken = oathKeeper.get();
        if (!csrfToken) {
            const resp = await this.fetch("oath");
            if (resp.status !== 200) {
                throw new Error();
            }
            const respJ = await resp.json();
            csrfToken = respJ.csrf_token;
        }
        if (!csrfToken) {
            console.warn("csrf_token is null");
        }
        else {
            oathKeeper.set(csrfToken);
        }
        return new CsrfEventBackend(this.event, csrfToken);
    }

    async fetch(url: string, options?: RequestInit): Promise<Response> {
        console.debug(`fetch ${Backend.ENDPOINT_BASE}/${url.replace(/^\/+/, '')}`);
        return await (this.event?.fetch||fetch)(`${Backend.ENDPOINT_BASE}/${url.replace(/^\/+/, '')}`, options);
    }
}

class CsrfEventBackend extends EventBackend {
    csrfToken: string | null;

    constructor(event: EventBackend | null, csrfToken: string | null) {
        super(event);
        this.csrfToken = csrfToken;
    }

    async submitJson(url: string, data: object) {
        return await this.fetch(url, {
            method: 'POST',
            body: JSON.stringify(data),
            headers: {
                'content-type': 'application/json',
                'x-csrftoken': this.csrfToken || ""
            }
        });
    }
}

export const backend = new Backend();