/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */

import { correctIndentation } from "./indentation";
import { getGrip, getFront } from "./evaluation-result";

const UNAVAILABLE_GRIP = { unavailable: true };

/*
 * wrap the expression input in a try/catch so that it can be safely
 * evaluated.
 *
 * NOTE: we add line after the expression to protect against comments.
 */
export function wrapExpression(input) {
  return correctIndentation(`
    try {
      ${input}
    } catch (e) {
      e
    }
  `);
}

function isUnavailable(value) {
  return (
    value &&
    !!value.isError &&
    (value.class === "ReferenceError" || value.class === "TypeError")
  );
}

/**
 *
 * @param {object} expression: Expression item as stored in state.expressions in reducers/expressions.js
 * @param {string} expression.input: evaluated expression string
 * @param {object} expression.value: evaluated expression result object as returned from ScriptCommand#execute
 * @param {object} expression.value.result: expression result, might be a primitive, a grip or a front
 * @param {object} expression.value.exception: expression result error, might be a primitive, a grip or a front
 * @returns {object} an object of the following shape:
 *                   - expressionResultGrip: A primitive or a grip
 *                   - expressionResultFront: An object front if it exists, or undefined
 */
export function getExpressionResultGripAndFront(expression) {
  const { value } = expression;

  if (!value) {
    return { expressionResultGrip: UNAVAILABLE_GRIP };
  }

  const expressionResultReturn = value.exception || value.result;
  const valueGrip = getGrip(expressionResultReturn);
  if (valueGrip == null || isUnavailable(valueGrip)) {
    return { expressionResultGrip: UNAVAILABLE_GRIP };
  }

  if (valueGrip.isError) {
    const { name, message } = valueGrip.preview;
    return { expressionResultGrip: `${name}: ${message}` };
  }

  return {
    expressionResultGrip: valueGrip,
    expressionResultFront: getFront(expressionResultReturn),
  };
}
