var app = new Vue({
  el: '#app',
  data: {
    books: [],
    authors: [],
    booksCount: 0,
    page: 1,
    perpage: 20
  },
  methods: {
    sendQuery: function(url, error, success) {
      var xmh = new XMLHttpRequest();
      var v;

      xmh.onreadystatechange = function() {
        v = xmh.responseText;
        if (xmh.readyState === 4 && xmh.status === 200) {
          var res;
          try  { 
            res = JSON.parse(v);
          } catch (err) {
            if (null !== error)
              error(err.name, err.message);
          }
          if (null !== success)
            success(res);
        } else if (xmh.readyState === 4) {
          if (null !== error)
            error(xmh.status, v);
        }
      };

      xmh.open('GET', url, true);
      xmh.send(null);
    },
    stdError: function(code, resp) {
      console.log('ERROR ' + code + ': ' + resp);
    },
    indexSuccess: function(resp) {
      this.booksCount = resp.count;
    },
    loadIndex: function() {
      this.sendQuery('cgi-bin/bouquins/index', this.stdError, this.indexSuccess);
    },
    authorsSuccess: function(resp) {
      this.authors = resp;
    },
    booksSuccess: function(resp) {
      this.books = resp;
    },
    prevPage: function() {
      if (this.page > 1) {
        this.page--;
        if (this.books.length > 0)
          this.loadBooks();
        if (this.authors.length > 0)
          this.loadAuthors();
      }
    },
    nextPage: function() {
      this.page++;
      if (this.books.length > 0)
        this.loadBooks();
      if (this.authors.length > 0)
        this.loadAuthors();
    },
    loadAuthors: function() {
      this.sendQuery('cgi-bin/bouquins/authors?page=' + this.page + '&perpage=' + this.perpage,
        this.stdError, this.authorsSuccess);
    },
    loadBooks: function() {
      this.sendQuery('cgi-bin/bouquins/books?page=' + this.page + '&perpage=' + this.perpage,
        this.stdError, this.booksSuccess);
    },
    showAuthors: function() {
      this.books = [];
      this.page = 1;
      this.perpage = 20;
      this.loadAuthors();
    },
    showBooks: function() {
      this.authors = [];
      this.page = 1;
      this.perpage = 20;
      this.loadBooks();
    }
  },
  mounted: function() {
    this.loadIndex();
  }
})