1// Copyright 2017 Google Inc. All rights reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package parser
16
17import (
18	"strings"
19)
20
21type Scope interface {
22	Get(name string) string
23	Set(name, value string)
24	Call(name string, args []string) []string
25	SetFunc(name string, f func([]string) []string)
26}
27
28type scope struct {
29	variables map[string]string
30	functions map[string]func([]string) []string
31	parent    Scope
32}
33
34func (s *scope) Get(name string) string {
35	if val, ok := s.variables[name]; ok {
36		return val
37	} else if s.parent != nil {
38		return s.parent.Get(name)
39	} else if val, ok := builtinScope[name]; ok {
40		return val
41	} else {
42		return "<'" + name + "' unset>"
43	}
44}
45
46func (s *scope) Set(name, value string) {
47	s.variables[name] = value
48}
49
50func (s *scope) Call(name string, args []string) []string {
51	if f, ok := s.functions[name]; ok {
52		return f(args)
53	}
54
55	return []string{"<func:'" + name + "' unset>"}
56}
57
58func (s *scope) SetFunc(name string, f func([]string) []string) {
59	s.functions[name] = f
60}
61
62func NewScope(parent Scope) Scope {
63	return &scope{
64		variables: make(map[string]string),
65		functions: make(map[string]func([]string) []string),
66		parent:    parent,
67	}
68}
69
70var builtinScope map[string]string
71
72func init() {
73	builtinScope := make(map[string]string)
74	builtinScope[builtinDollar] = "$"
75}
76
77func (v Variable) EvalFunction(scope Scope) ([]string, bool) {
78	f := v.Name.SplitN(" \t", 2)
79	if len(f) > 1 && f[0].Const() {
80		fname := f[0].Value(nil)
81		if isFunctionName(fname) {
82			args := f[1].Split(",")
83			argVals := make([]string, len(args))
84			for i, a := range args {
85				argVals[i] = a.Value(scope)
86			}
87
88			if fname == "call" {
89				return scope.Call(argVals[0], argVals[1:]), true
90			} else {
91				return []string{"__builtin_func:" + fname + " " + strings.Join(argVals, " ")}, true
92			}
93		}
94	}
95
96	return []string{""}, false
97}
98
99func (v Variable) Value(scope Scope) string {
100	if ret, ok := v.EvalFunction(scope); ok {
101		if len(ret) > 1 {
102			panic("Expected a single value, but instead got a list")
103		}
104		return ret[0]
105	}
106	if scope == nil {
107		panic("Cannot take the value of a variable in a nil scope")
108	}
109	return scope.Get(v.Name.Value(scope))
110}
111
112func toVariable(ms *MakeString) (Variable, bool) {
113	if len(ms.Variables) == 1 && ms.Strings[0] == "" && ms.Strings[1] == "" {
114		return ms.Variables[0], true
115	}
116	return Variable{}, false
117}
118