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1/*
2  Copyright (C) 2015 Yusuke Suzuki <utatane.tea@gmail.com>
3
4  Redistribution and use in source and binary forms, with or without
5  modification, are permitted provided that the following conditions are met:
6
7    * Redistributions of source code must retain the above copyright
8      notice, this list of conditions and the following disclaimer.
9    * Redistributions in binary form must reproduce the above copyright
10      notice, this list of conditions and the following disclaimer in the
11      documentation and/or other materials provided with the distribution.
12
13  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
14  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
17  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
18  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
19  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
20  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23*/
24"use strict";
25
26/* eslint-disable no-undefined */
27
28const Syntax = require("estraverse").Syntax;
29const esrecurse = require("esrecurse");
30
31/**
32 * Get last array element
33 * @param {array} xs - array
34 * @returns {any} Last elment
35 */
36function getLast(xs) {
37    return xs[xs.length - 1] || null;
38}
39
40class PatternVisitor extends esrecurse.Visitor {
41    static isPattern(node) {
42        const nodeType = node.type;
43
44        return (
45            nodeType === Syntax.Identifier ||
46            nodeType === Syntax.ObjectPattern ||
47            nodeType === Syntax.ArrayPattern ||
48            nodeType === Syntax.SpreadElement ||
49            nodeType === Syntax.RestElement ||
50            nodeType === Syntax.AssignmentPattern
51        );
52    }
53
54    constructor(options, rootPattern, callback) {
55        super(null, options);
56        this.rootPattern = rootPattern;
57        this.callback = callback;
58        this.assignments = [];
59        this.rightHandNodes = [];
60        this.restElements = [];
61    }
62
63    Identifier(pattern) {
64        const lastRestElement = getLast(this.restElements);
65
66        this.callback(pattern, {
67            topLevel: pattern === this.rootPattern,
68            rest: lastRestElement !== null && lastRestElement !== undefined && lastRestElement.argument === pattern,
69            assignments: this.assignments
70        });
71    }
72
73    Property(property) {
74
75        // Computed property's key is a right hand node.
76        if (property.computed) {
77            this.rightHandNodes.push(property.key);
78        }
79
80        // If it's shorthand, its key is same as its value.
81        // If it's shorthand and has its default value, its key is same as its value.left (the value is AssignmentPattern).
82        // If it's not shorthand, the name of new variable is its value's.
83        this.visit(property.value);
84    }
85
86    ArrayPattern(pattern) {
87        for (let i = 0, iz = pattern.elements.length; i < iz; ++i) {
88            const element = pattern.elements[i];
89
90            this.visit(element);
91        }
92    }
93
94    AssignmentPattern(pattern) {
95        this.assignments.push(pattern);
96        this.visit(pattern.left);
97        this.rightHandNodes.push(pattern.right);
98        this.assignments.pop();
99    }
100
101    RestElement(pattern) {
102        this.restElements.push(pattern);
103        this.visit(pattern.argument);
104        this.restElements.pop();
105    }
106
107    MemberExpression(node) {
108
109        // Computed property's key is a right hand node.
110        if (node.computed) {
111            this.rightHandNodes.push(node.property);
112        }
113
114        // the object is only read, write to its property.
115        this.rightHandNodes.push(node.object);
116    }
117
118    //
119    // ForInStatement.left and AssignmentExpression.left are LeftHandSideExpression.
120    // By spec, LeftHandSideExpression is Pattern or MemberExpression.
121    //   (see also: https://github.com/estree/estree/pull/20#issuecomment-74584758)
122    // But espree 2.0 parses to ArrayExpression, ObjectExpression, etc...
123    //
124
125    SpreadElement(node) {
126        this.visit(node.argument);
127    }
128
129    ArrayExpression(node) {
130        node.elements.forEach(this.visit, this);
131    }
132
133    AssignmentExpression(node) {
134        this.assignments.push(node);
135        this.visit(node.left);
136        this.rightHandNodes.push(node.right);
137        this.assignments.pop();
138    }
139
140    CallExpression(node) {
141
142        // arguments are right hand nodes.
143        node.arguments.forEach(a => {
144            this.rightHandNodes.push(a);
145        });
146        this.visit(node.callee);
147    }
148}
149
150module.exports = PatternVisitor;
151
152/* vim: set sw=4 ts=4 et tw=80 : */
153