import * as Block from 'multiformats/block';
import { sha256 as hasher } from 'multiformats/hashes/sha2';

import * as dagCBOR from '@ipld/dag-cbor';
import * as dagJSON from '@ipld/dag-json';

/**
 * Utils
 */
export class Util {
  /**
   * Sorts JSON object.
   */
  static sortJSON (obj: any) {
    if (obj instanceof Array) {
      for (let i = 0; i < obj.length; i++) {
        obj[i] = Util.sortJSON(obj[i]);
      }
      return obj;
    }
    if (typeof obj !== 'object' || obj === null) return obj;

    let keys = Object.keys(obj);
    keys = keys.sort();
    const newObject: {[key: string]: any} = {};

    for (let i = 0; i < keys.length; i++) {
      newObject[keys[i]] = Util.sortJSON(obj[keys[i]]);
    }
    return newObject;
  }

  /**
   * Marshal object into gql 'attributes' variable.
   */
  static toGQLAttributes (obj: any) {
    const vars: any[] = [];
    Object.keys(obj).forEach(key => {
      const value = this.toGQLValue(obj[key]);

      if (value !== undefined) {
        vars.push({ key, value });
      }
    });
    return vars;
  }

  static toGQLValue (obj: any) {
    if (obj === null) {
      return null;
    }
    let type: string = typeof obj;
    switch (type) {
      case 'number':
        type = (obj % 1 === 0) ? 'int' : 'float';
        return { [type]: obj };
      case 'string':
        return { string: obj };
      case 'boolean':
        return { boolean: obj };
      case 'object':
        if (obj['/'] !== undefined) {
          return { link: obj['/'] };
        }
        if (obj instanceof Array) {
          return { array: obj };
        }
        return { map: obj };
      case 'undefined':
        return undefined;
      default:
        throw new Error(`Unknown object type '${type}': ${obj}`);
    }
  }

  /**
   * Unmarshal attributes array to object.
   */
  static fromGQLAttributes (attributes: any[] = []) {
    const res: {[key: string]: any} = {};

    attributes.forEach(attr => {
      res[attr.key] = (attr.value === null) ? null : this.fromGQLValue(attr.value);
    });

    return res;
  }

  static fromGQLValue (obj: any) {
    // Get first non-null key
    const present = Object.keys(obj).find(k => obj[k] !== null);
    if (present === undefined) {
      throw new Error('Object has no non-null values');
    }

    // Create an array if array type attribute
    if (present === 'array') {
      return obj[present].map((e: any) => {
        return this.fromGQLValue(e);
      });
    }

    return obj[present];
  }

  /**
   * Get record content ID.
   */
  static async getContentId (record: any) {
    const serialized = dagJSON.encode(record);
    const recordData = dagJSON.decode(serialized);

    const block = await Block.encode({
      value: recordData,
      codec: dagCBOR,
      hasher
    });

    return block.cid.toString();
  }
}