/*
Copyright (c) 2020 Thomas Weber

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

window.O = (function() {
  const options = Object.create(null);

  const onchange = (e) => {
    const target = e.target;
    const name = target.name;
    const value = getValue(target);
    options[name] = value;
    setLocalValue(name, value);

    if (options.onchange) {
      options.onchange();
    }
  };

  const getValue = (el) => {
    const tag = el.tagName.toLowerCase();

    if (tag === 'select') {
      return el.value;
    }

    if (tag === 'input') {
      switch (el.type) {
      case 'text':
      case 'number':
      case 'radio':
        return el.value;
      case 'checkbox':
        return el.checked;
      case 'file':
        if (el.multiple) {
          return el.files;
        }
        return el.files[0] || null;
      }
    }
  };

  const setValue = (el, value) => {
    const tag = el.tagName.toLowerCase();

    if (tag === 'select') {
      el.value = value;
    }

    if (tag === 'input') {
      switch (el.type) {
      case 'text':
      case 'number':
        el.value = value;
        break;
      case 'radio':
        el.checked = el.value === value;
        break;
      case 'checkbox':
        el.checked = value;
        break;
      }
    }
  };

  /**
   * Returns all possible values for an HTML element
   * @returns {string[]|null} list of possible values, or null if all values are possible
   */
  const getPossibleValues = (el) => {
    const tag = el.tagName.toLowerCase();

    if (tag === 'select') {
      return Array.from(el.options).map(i => i.value)
    }

    if (tag === 'input' && el.type === 'radio') {
      const allChoices = Array.from(document.getElementsByName(el.name));
      return allChoices.map(i => i.value);
    }

    return null;
  };

  const setLocalValue = (name, value) => {
    try {
      localStorage.setItem(name, JSON.stringify(value));
    } catch (e) {
      // ignore
    }
  };

  const getLocalValue = (name) => {
    try {
      const v = localStorage.getItem(name);
      if (v !== null) {
        return JSON.parse(v);
      }
    } catch (e) {
      // ignore
    }
    return null;
  };

  const inputs = document.querySelectorAll('input, select, textarea');
  for (const input of inputs) {
    const name = input.name;
    if (!name) continue;

    input.addEventListener('change', onchange);

    const defaultValue = getValue(input);
    const localValue = getLocalValue(name);
    const possibleValues = getPossibleValues(input);

    let value = defaultValue;
    if (localValue !== null) {
      if (possibleValues === null || possibleValues.includes(localValue)) {
        value = localValue;
        setValue(input, value);
      }
    }

    options[name] = value;
  };

  return options;
}());