chad-music/front/src/App.js

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

function CategoryFlatList(props) {
  const { error, isLoaded, items } = props.state;
  var content;
  if (error) {
    content = <div>Error: {error.message}</div>
  } else if (!isLoaded) {
    content = <div>Loading</div>
  } else {
    content = (
        <select size="10" defaultValue="" onChange={props.onChange}>
        <option value="">[ANY]</option>
        {items.map(item => (
            <option key={item.item} value={item.item}>{item.item} - {item.count}</option>
        ))}
      </select>
    );
  }
  return (
      <div className="category-list">
      <h2>{props.title}</h2>
      {content}
    </div>
  );
}

class App extends Component {
  constructor(props) {
    super(props);
    this.categories = [{type: 'artist', title: 'Artists'},
                       {type: 'year', title: 'Years'},
                       {type: 'publisher', title: 'Labels'},
                       {type: 'country', title: 'Countries'},
                       {type: 'type', title: 'Album types'},
                       {type: 'status', title: 'Album statuses'}];
    this.state = {};
    for (var {type} of this.categories) {
      this.state[type] = {
        error: null,
        isLoaded: false,
        items: []
      };
    }
  }
  fetchCategory(cat) {
    const {restrictions} = this.state;

    function getQueryString(params) {
      var esc = encodeURIComponent;
      return Object.keys(params)
        .map(k => esc(k) + '=' + esc(params[k]))
        .join('&');
    }
    const params = Object.assign({}, restrictions, {offset:0, limit:100});
    const qs = getQueryString(params);

    fetch('/cat/' + cat + (qs ? ('?' + qs) : ''))
      .then(res => (res.ok ? res.json() : Promise.reject({message:res.statusText})))
      .then(result => {
        this.setState({[cat]: {
          isLoaded: true,
          items: result
        }});
      })
      .catch(error => {
        this.setState({[cat]: {
          isLoaded: true,
          error: error
        }});
      })
  }
  fetchAll() {
    const {restrictions} = this.state;
    console.log(restrictions);
    this.categories.map(({type}) => !restrictions[type] && this.fetchCategory(type))
  }
  componentDidMount() {
    this.setState({restrictions: {}});
  }
  componentDidUpdate(prevProps, prevState) {
    if (this.state.restrictions !== prevState.restrictions) {
      // Reload category filters on restriction changes
      this.fetchAll();
    }
  }
  handleCategoryChange(type, value) {
    console.log(type, value);
    var restrictions = Object.assign({}, this.state.restrictions);
    if (value) {
      restrictions[type] = value;
    } else {
      delete restrictions[type];
    }
    this.setState({restrictions: restrictions});
  }
  render() {
    return (
      <div className="App">
        <header className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <h1 className="App-title">Chad Music</h1>
        </header>
        {this.categories.map(({type, title}) => (
            <CategoryFlatList key={type} title={title} state={this.state[type]} onChange={e => this.handleCategoryChange(type, e.target.value)}/>
        ))}
      </div>
    );
  }
}

export default App;