luke-j/switch

/**
 * @license
 *
 * Copyright 2016- Luke Jones (https://github.com/luke-j)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import CompilerInterface from './CompilerInterface';

export default class AbstractCompiler extends CompilerInterface {

    /**
     * The Compiler is responsible for turning syntax expressions into apache or nginx conf
     *
     * @implements CompilerInterface
     * @param {ApacheContext|NginxContext} Context - A Apache/Nginx Context instance
     */
    constructor(Context) {
        super();
        this._Context = Context;
    }

    /**
     * @inheritdoc
     */
    compile(expressions) {
        expressions.forEach(this._compileEach.bind(this));
    }

    /**
     * Compile an assignment expression, ie. an expression assigning a value to an identifier
     *
     * @param {Object} expression - A syntax expression
     * @protected
     */
    _assignmentExpression(expression) {
        if (!expression.hasOwnProperty('left') || !expression.hasOwnProperty('right')) {
            throw new Error('Assignment expression must have a left and right-side value');
        }

        this._expression(expression.left);
        this._expression(expression.right);
    }

    /**
     * Compile an identifier, ie. a known word to apache or nginx, like DocumentRoot or server_name
     *
     * @param {Object} expression - A syntax expression
     * @protected
     */
    _identifier(expression) {
        if (!expression.hasOwnProperty('value')) {
            throw new Error('Identifier must have a value');
        }

        this._line += expression.value + ' ';

        expression.right && this._expression(expression.right);
    }

    /**
     * Compile a literal, which can be any string
     *
     * @param {Object} expression - A syntax expression
     * @protected
     */
    _literal(expression) {
        if (!expression.hasOwnProperty('value')) {
            throw new Error('Literal must have a value');
        }

        this._line += expression.value + ' ';

        expression.right && this._expression(expression.right);
    }

    /**
     * Compile a variable, which is a pre-determined apache variable which holds a computed value
     *
     * @param {Object} expression - A syntax expression
     * @protected
     */
    _variable(expression) {
        if (!expression.hasOwnProperty('value')) {
            throw new Error('Variable must have a value');
        }

        this._line += expression.value + ' ';

        expression.right && this._expression(expression.right);
    }

    /**
     * Transforms expressions into apache/nginx conf
     *
     * @param {Object} expression - A syntax expression to be parsed
     * @private
     */
    _compileEach(expression) {
        this._line = '';
        this._expression(expression);
        if (this._line) {
            this._Context.lines.push(this._line.trim());
        }
    }
}