/**
 * @fileoverview The schema to validate language options
 * @author Nicholas C. Zakas
 */

"use strict";

//-----------------------------------------------------------------------------
// Data
//-----------------------------------------------------------------------------

const globalVariablesValues = new Set([
    true, "true", "writable", "writeable",
    false, "false", "readonly", "readable", null,
    "off"
]);

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

/**
 * Check if a value is a non-null object.
 * @param {any} value The value to check.
 * @returns {boolean} `true` if the value is a non-null object.
 */
function isNonNullObject(value) {
    return typeof value === "object" && value !== null;
}

/**
 * Check if a value is a non-null non-array object.
 * @param {any} value The value to check.
 * @returns {boolean} `true` if the value is a non-null non-array object.
 */
function isNonArrayObject(value) {
    return isNonNullObject(value) && !Array.isArray(value);
}

/**
 * Check if a value is undefined.
 * @param {any} value The value to check.
 * @returns {boolean} `true` if the value is undefined.
 */
function isUndefined(value) {
    return typeof value === "undefined";
}

//-----------------------------------------------------------------------------
// Schemas
//-----------------------------------------------------------------------------

/**
 * Validates the ecmaVersion property.
 * @param {string|number} ecmaVersion The value to check.
 * @returns {void}
 * @throws {TypeError} If the value is invalid.
 */
function validateEcmaVersion(ecmaVersion) {

    if (isUndefined(ecmaVersion)) {
        throw new TypeError("Key \"ecmaVersion\": Expected an \"ecmaVersion\" property.");
    }

    if (typeof ecmaVersion !== "number" && ecmaVersion !== "latest") {
        throw new TypeError("Key \"ecmaVersion\": Expected a number or \"latest\".");
    }

}

/**
 * Validates the sourceType property.
 * @param {string} sourceType The value to check.
 * @returns {void}
 * @throws {TypeError} If the value is invalid.
 */
function validateSourceType(sourceType) {

    if (typeof sourceType !== "string" || !/^(?:script|module|commonjs)$/u.test(sourceType)) {
        throw new TypeError("Key \"sourceType\": Expected \"script\", \"module\", or \"commonjs\".");
    }

}

/**
 * Validates the globals property.
 * @param {Object} globals The value to check.
 * @returns {void}
 * @throws {TypeError} If the value is invalid.
 */
function validateGlobals(globals) {

    if (!isNonArrayObject(globals)) {
        throw new TypeError("Key \"globals\": Expected an object.");
    }

    for (const key of Object.keys(globals)) {

        // avoid hairy edge case
        if (key === "__proto__") {
            continue;
        }

        if (key !== key.trim()) {
            throw new TypeError(`Key "globals": Global "${key}" has leading or trailing whitespace.`);
        }

        if (!globalVariablesValues.has(globals[key])) {
            throw new TypeError(`Key "globals": Key "${key}": Expected "readonly", "writable", or "off".`);
        }
    }
}

/**
 * Validates the parser property.
 * @param {Object} parser The value to check.
 * @returns {void}
 * @throws {TypeError} If the value is invalid.
 */
function validateParser(parser) {

    if (!parser || typeof parser !== "object" ||
        (typeof parser.parse !== "function" && typeof parser.parseForESLint !== "function")
    ) {
        throw new TypeError("Key \"parser\": Expected object with parse() or parseForESLint() method.");
    }

}

/**
 * Validates the language options.
 * @param {Object} languageOptions The language options to validate.
 * @returns {void}
 * @throws {TypeError} If the language options are invalid.
 */
function validateLanguageOptions(languageOptions) {

    if (!isNonArrayObject(languageOptions)) {
        throw new TypeError("Expected an object.");
    }

    const {
        ecmaVersion,
        sourceType,
        globals,
        parser,
        parserOptions,
        ...otherOptions
    } = languageOptions;

    if ("ecmaVersion" in languageOptions) {
        validateEcmaVersion(ecmaVersion);
    }

    if ("sourceType" in languageOptions) {
        validateSourceType(sourceType);
    }

    if ("globals" in languageOptions) {
        validateGlobals(globals);
    }

    if ("parser" in languageOptions) {
        validateParser(parser);
    }

    if ("parserOptions" in languageOptions) {
        if (!isNonArrayObject(parserOptions)) {
            throw new TypeError("Key \"parserOptions\": Expected an object.");
        }
    }

    const otherOptionKeys = Object.keys(otherOptions);

    if (otherOptionKeys.length > 0) {
        throw new TypeError(`Unexpected key "${otherOptionKeys[0]}" found.`);
    }

}

module.exports = { validateLanguageOptions };