forked from PaesslerAG/gval
-
Notifications
You must be signed in to change notification settings - Fork 0
/
language.go
281 lines (250 loc) · 8.13 KB
/
language.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
package gval
import (
"context"
"fmt"
"text/scanner"
"unicode"
"github.com/shopspring/decimal"
)
// Language is an expression language
type Language struct {
prefixes map[interface{}]extension
operators map[string]operator
operatorSymbols map[rune]struct{}
init extension
def extension
selector func(Evaluables) Evaluable
}
// NewLanguage returns the union of given Languages as new Language.
func NewLanguage(bases ...Language) Language {
l := newLanguage()
for _, base := range bases {
for i, e := range base.prefixes {
l.prefixes[i] = e
}
for i, e := range base.operators {
l.operators[i] = e.merge(l.operators[i])
l.operators[i].initiate(i)
}
for i := range base.operatorSymbols {
l.operatorSymbols[i] = struct{}{}
}
if base.init != nil {
l.init = base.init
}
if base.def != nil {
l.def = base.def
}
if base.selector != nil {
l.selector = base.selector
}
}
return l
}
func newLanguage() Language {
return Language{
prefixes: map[interface{}]extension{},
operators: map[string]operator{},
operatorSymbols: map[rune]struct{}{},
}
}
// NewEvaluable returns an Evaluable for given expression in the specified language
func (l Language) NewEvaluable(expression string) (Evaluable, error) {
return l.NewEvaluableWithContext(context.Background(), expression)
}
// NewEvaluableWithContext returns an Evaluable for given expression in the specified language using context
func (l Language) NewEvaluableWithContext(c context.Context, expression string) (Evaluable, error) {
p := newParser(expression, l)
eval, err := p.parse(c)
if err == nil && p.isCamouflaged() && p.lastScan != scanner.EOF {
err = p.camouflage
}
if err != nil {
pos := p.scanner.Pos()
return nil, fmt.Errorf("parsing error: %s - %d:%d %s", p.scanner.Position, pos.Line, pos.Column, err)
}
return eval, nil
}
// Evaluate given parameter with given expression
func (l Language) Evaluate(expression string, parameter interface{}) (interface{}, error) {
return l.EvaluateWithContext(context.Background(), expression, parameter)
}
// Evaluate given parameter with given expression using context
func (l Language) EvaluateWithContext(c context.Context, expression string, parameter interface{}) (interface{}, error) {
eval, err := l.NewEvaluableWithContext(c, expression)
if err != nil {
return nil, err
}
v, err := eval(c, parameter)
if err != nil {
return nil, fmt.Errorf("can not evaluate %s: %v", expression, err)
}
return v, nil
}
// Function returns a Language with given function.
// Function has no conversion for input types.
//
// If the function returns an error it must be the last return parameter.
//
// If the function has (without the error) more then one return parameter,
// it returns them as []interface{}.
func Function(name string, function interface{}) Language {
l := newLanguage()
l.prefixes[name] = func(c context.Context, p *Parser) (eval Evaluable, err error) {
args := []Evaluable{}
scan := p.Scan()
switch scan {
case '(':
args, err = p.parseArguments(c)
if err != nil {
return nil, err
}
default:
p.Camouflage("function call", '(')
}
return p.callFunc(toFunc(function), args...), nil
}
return l
}
// Constant returns a Language with given constant
func Constant(name string, value interface{}) Language {
l := newLanguage()
l.prefixes[l.makePrefixKey(name)] = func(c context.Context, p *Parser) (eval Evaluable, err error) {
return p.Const(value), nil
}
return l
}
// PrefixExtension extends a Language
func PrefixExtension(r rune, ext func(context.Context, *Parser) (Evaluable, error)) Language {
l := newLanguage()
l.prefixes[r] = ext
return l
}
// Init is a language that does no parsing, but invokes the given function when
// parsing starts. It is incumbent upon the function to call ParseExpression to
// continue parsing.
//
// This function can be used to customize the parser settings, such as
// whitespace or ident behavior.
func Init(ext func(context.Context, *Parser) (Evaluable, error)) Language {
l := newLanguage()
l.init = ext
return l
}
// DefaultExtension is a language that runs the given function if no other
// prefix matches.
func DefaultExtension(ext func(context.Context, *Parser) (Evaluable, error)) Language {
l := newLanguage()
l.def = ext
return l
}
// PrefixMetaPrefix chooses a Prefix to be executed
func PrefixMetaPrefix(r rune, ext func(context.Context, *Parser) (call string, alternative func() (Evaluable, error), err error)) Language {
l := newLanguage()
l.prefixes[r] = func(c context.Context, p *Parser) (Evaluable, error) {
call, alternative, err := ext(c, p)
if err != nil {
return nil, err
}
if prefix, ok := p.prefixes[l.makePrefixKey(call)]; ok {
return prefix(c, p)
}
return alternative()
}
return l
}
//PrefixOperator returns a Language with given prefix
func PrefixOperator(name string, e Evaluable) Language {
l := newLanguage()
l.prefixes[l.makePrefixKey(name)] = func(c context.Context, p *Parser) (Evaluable, error) {
eval, err := p.ParseNextExpression(c)
if err != nil {
return nil, err
}
prefix := func(c context.Context, v interface{}) (interface{}, error) {
a, err := eval(c, v)
if err != nil {
return nil, err
}
return e(c, a)
}
if eval.IsConst() {
v, err := prefix(c, nil)
if err != nil {
return nil, err
}
prefix = p.Const(v)
}
return prefix, nil
}
return l
}
// PostfixOperator extends a Language.
func PostfixOperator(name string, ext func(context.Context, *Parser, Evaluable) (Evaluable, error)) Language {
l := newLanguage()
l.operators[l.makeInfixKey(name)] = postfix{
f: func(c context.Context, p *Parser, eval Evaluable, pre operatorPrecedence) (Evaluable, error) {
return ext(c, p, eval)
},
}
return l
}
// InfixOperator for two arbitrary values.
func InfixOperator(name string, f func(a, b interface{}) (interface{}, error)) Language {
return newLanguageOperator(name, &infix{arbitrary: f})
}
// InfixShortCircuit operator is called after the left operand is evaluated.
func InfixShortCircuit(name string, f func(a interface{}) (interface{}, bool)) Language {
return newLanguageOperator(name, &infix{shortCircuit: f})
}
// InfixTextOperator for two text values.
func InfixTextOperator(name string, f func(a, b string) (interface{}, error)) Language {
return newLanguageOperator(name, &infix{text: f})
}
// InfixNumberOperator for two number values.
func InfixNumberOperator(name string, f func(a, b float64) (interface{}, error)) Language {
return newLanguageOperator(name, &infix{number: f})
}
// InfixDecimalOperator for two decimal values.
func InfixDecimalOperator(name string, f func(a, b decimal.Decimal) (interface{}, error)) Language {
return newLanguageOperator(name, &infix{decimal: f})
}
// InfixBoolOperator for two bool values.
func InfixBoolOperator(name string, f func(a, b bool) (interface{}, error)) Language {
return newLanguageOperator(name, &infix{boolean: f})
}
// Precedence of operator. The Operator with higher operatorPrecedence is evaluated first.
func Precedence(name string, operatorPrecendence uint8) Language {
return newLanguageOperator(name, operatorPrecedence(operatorPrecendence))
}
// InfixEvalOperator operates on the raw operands.
// Therefore it cannot be combined with operators for other operand types.
func InfixEvalOperator(name string, f func(a, b Evaluable) (Evaluable, error)) Language {
return newLanguageOperator(name, directInfix{infixBuilder: f})
}
func newLanguageOperator(name string, op operator) Language {
op.initiate(name)
l := newLanguage()
l.operators[l.makeInfixKey(name)] = op
return l
}
func (l *Language) makePrefixKey(key string) interface{} {
runes := []rune(key)
if len(runes) == 1 && !unicode.IsLetter(runes[0]) {
return runes[0]
}
return key
}
func (l *Language) makeInfixKey(key string) string {
for _, r := range key {
l.operatorSymbols[r] = struct{}{}
}
return key
}
// VariableSelector returns a Language which uses given variable selector.
// It must be combined with a Language that uses the vatiable selector. E.g. gval.Base().
func VariableSelector(selector func(path Evaluables) Evaluable) Language {
l := newLanguage()
l.selector = selector
return l
}