import { QueryResultDescription } from './types-client';

const BASE_URL: string = 'https://shikimori.one/api/graphql';
const headers: HeadersInit | undefined = { 'Content-Type': 'application/json' };

const getResultFields = <TResultDescription>(resultDescription: QueryResultDescription<TResultDescription>): string => {
    const resultParts = [];
    for (const [key, value] of Object.entries(resultDescription)) {
        if (typeof value === 'object') {
            const nestedResult = getResultFields(value as QueryResultDescription<TResultDescription>);
            resultParts.push(`${key} { ${nestedResult} }`);
        } else {
            resultParts.push(key);
        }
    }

    return resultParts.join(' ');
}

/*
 * Internal. Fetches data from the Shikimori API using GraphQL.
 */
export let internal_client_fetch = async <
    TArgs extends Record<string, unknown>,
    TResultDescription,
    TQueryResult = TResultDescription | TResultDescription[],
>(
    datatype: string,
    args: TArgs,
    resultDescription: QueryResultDescription<TResultDescription>,
): Promise<TQueryResult> => {
    const queryArgs = Object.entries(args).map(([key, value]) => `${key}: ${JSON.stringify(value)}`).join(', ');
    const queryResult = getResultFields(resultDescription);
    const query = `{ ${datatype}(${queryArgs}) { ${queryResult} } }`;

    const response = await fetch(BASE_URL, {
        method: 'POST',
        headers,
        body: JSON.stringify({ query }),
    });

    return (await response.json())['data'][datatype];
};

/*
 * Sets the 'User-Agent' header for the client.
 * Providing a proper user agent is mandatory for the API.
 */
export const client_setUserAgent = (userAgent: string): void => {
    headers['User-Agent'] = userAgent;
}

/*
 * Sets the 'Authorization' header for the client.
 */
export const client_setAuthToken = (token: string): void => {
    headers['Authorization'] = `Bearer ${token}`;
}

/*
 * Sets a custom fetch function for the client.
 */
export const client_setCustomFetch = (customFetch: typeof internal_client_fetch): void => {
    internal_client_fetch = customFetch;
};