import uuid from 'uuid/v4';

import {compose, merge, Property} from '@avocado/core';

const decorate = compose(
  Property('instanceUuid'),
  Property('uri'),
  Property('uuid'),
)

export class Resource extends decorate(class {}) {

  constructor() {
    super();
    this.instanceUuid = Resource.uuid();
  }

  fromJSON({uri, uuid}) {
    if (uri) {
      this.uri = uri;
    }
    if (uuid) {
      this.uuid = uuid;
    }
    return this;
  }

  static load(uri) {
    return this.read(uri).then((json) => {
      return new this({
        uri,
        ...json,
      });
    });
  }

  static loadOrInstance(json) {
    if (json.uri) {
      return this.read(json.uri).then((readJson) => {
        return new this(readJson, json);
      });
    }
    else {
      return Promise.resolve(new this(json));
    }
  }

  static read(uri) {
    if (!this.readCache) {
      this.readCache = {};
    }
    if (this.readCache[uri]) {
      return this.readCache[uri].then((json) => {
        return JSON.parse(JSON.stringify(json));
      });
    }
    if ('undefined' !== typeof window) {
      this.readCache[uri] = fetch(uri).then((response) => {
        return response.json();
      });
    }
    else {
      this.readCache[uri] = new Promise((resolve, reject) => {
        const fs = require('fs');
        const path = require('path');
        const resourcePath = path.resolve(process.cwd(), 'resource');
        fs.readFile(`${resourcePath}${uri}`, (error, buffer) => {
          if (error) {
            return reject(error);
          }
          resolve(JSON.parse(buffer.toString('utf8')));
        });
      });
    }
    // Allow "base" JSON.
    return this.readCache[uri].then((json) => {
      if ('undefined' !== typeof json.base) {
        return this.read(json.base).then((baseJSON) => {
          return merge({}, baseJSON, json);
        });
      }
      return json;
    }).catch((error) => {
      console.error(`Failed loading '${uri}'.`);
    });
  }

  regenerateUuid() {
    this.uuid = Resource.uuid();
  }

  toJSON() {
    return {
      uuid: this.uuid,
      uri: this.uri,
    };
  }

  static uuid() {
    return uuid();
  }

}