/**
 * Check for common misspelling $on('destroy', ...).
 *
 * It should be $on('$destroy', ...).
 * @version 0.1.0
 * @category misspelling
 * @sinceAngularVersion 1.x
 */
'use strict';

module.exports = {
    meta: {
        docs: {
            url: 'https://github.com/Gillespie59/eslint-plugin-angular/blob/master/docs/rules/on-destroy.md'
        },
        schema: []
    },
    create: function(context) {
        function report(node) {
            context.report(node, 'You probably misspelled $on("$destroy").');
        }

        /**
         * Return true if the given node is a call expression calling a function
         * named '$on'.
         */
        function isOn(node) {
            var calledFunction = node.callee;
            if (calledFunction.type !== 'MemberExpression') {
                return false;
            }

            // can only easily tell what name was used if a simple
            // identifiers were used to access it.
            var accessedFunction = calledFunction.property;
            if (accessedFunction.type !== 'Identifier') {
                return false;
            }

            var functionName = accessedFunction.name;

            return functionName === '$on';
        }

        /**
         * Return true if the given node is a call expression that has a first
         * argument of the string '$destroy'.
         */
        function isFirstArgDestroy(node) {
            var args = node.arguments;

            return (args.length >= 1 &&
                args[0].type === 'Literal' &&
                args[0].value === 'destroy');
        }

        return {
            CallExpression: function(node) {
                if (isOn(node) && isFirstArgDestroy(node)) {
                    report(node);
                }
            }
        };
    }
};