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predicate.go
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predicate.go
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package hconf
import (
"fmt"
"github.com/vulcand/predicate"
)
type hcpredicate func(*HC) bool
type toInt func(c *HC) int
type toFloat64 func(c *HC) float64
type toString func(c *HC) string
// parseExpression parses expression in the go language into predicates.
func parseExpression(in string) (hcpredicate, error) {
p, err := predicate.NewParser(predicate.Def{
Operators: predicate.Operators{
AND: and,
OR: or,
EQ: eq,
NEQ: neq,
LT: lt,
LE: le,
GT: gt,
GE: ge,
},
Functions: map[string]interface{}{
"local_Exec": localExec,
},
})
if err != nil {
return nil, err
}
out, err := p.Parse(in)
if err != nil {
return nil, err
}
pr, ok := out.(hcpredicate)
if !ok {
return nil, fmt.Errorf("expected predicate, got %T: %#v", out, out)
}
return pr, nil
}
// or returns predicate by joining the passed predicates with logical 'or'
func or(fns ...hcpredicate) hcpredicate {
return func(c *HC) bool {
for _, fn := range fns {
if fn(c) {
return true
}
}
return false
}
}
// and returns predicate by joining the passed predicates with logical 'and'
func and(fns ...hcpredicate) hcpredicate {
return func(c *HC) bool {
for _, fn := range fns {
if !fn(c) {
return false
}
}
return true
}
}
// not creates negation of the passed predicate
func not(p hcpredicate) hcpredicate {
return func(c *HC) bool {
return !p(c)
}
}
// eq returns predicate that tests for equality of the value of the mapper and the constant
func eq(m interface{}, value interface{}) (hcpredicate, error) {
switch mapper := m.(type) {
case toInt:
return intEQ(mapper, value)
case toFloat64:
return float64EQ(mapper, value)
case toString:
return stringEQ(mapper, value)
}
return nil, fmt.Errorf("eq: unsupported argument: %T", m)
}
// neq returns predicate that tests for inequality of the value of the mapper and the constant
func neq(m interface{}, value interface{}) (hcpredicate, error) {
p, err := eq(m, value)
if err != nil {
return nil, err
}
return not(p), nil
}
// lt returns predicate that tests that value of the mapper function is less than the constant
func lt(m interface{}, value interface{}) (hcpredicate, error) {
switch mapper := m.(type) {
case toInt:
return intLT(mapper, value)
case toFloat64:
return float64LT(mapper, value)
}
return nil, fmt.Errorf("lt: unsupported argument: %T", m)
}
// le returns predicate that tests that value of the mapper function is less or equal than the constant
func le(m interface{}, value interface{}) (hcpredicate, error) {
l, err := lt(m, value)
if err != nil {
return nil, err
}
e, err := eq(m, value)
if err != nil {
return nil, err
}
return func(c *HC) bool {
return l(c) || e(c)
}, nil
}
// gt returns predicate that tests that value of the mapper function is greater than the constant
func gt(m interface{}, value interface{}) (hcpredicate, error) {
switch mapper := m.(type) {
case toInt:
return intGT(mapper, value)
case toFloat64:
return float64GT(mapper, value)
}
return nil, fmt.Errorf("gt: unsupported argument: %T", m)
}
// ge returns predicate that tests that value of the mapper function is less or equal than the constant
func ge(m interface{}, value interface{}) (hcpredicate, error) {
g, err := gt(m, value)
if err != nil {
return nil, err
}
e, err := eq(m, value)
if err != nil {
return nil, err
}
return func(c *HC) bool {
return g(c) || e(c)
}, nil
}
func intEQ(m toInt, val interface{}) (hcpredicate, error) {
value, ok := val.(int)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *HC) bool {
return m(c) == value
}, nil
}
func float64EQ(m toFloat64, val interface{}) (hcpredicate, error) {
value, ok := val.(float64)
if !ok {
return nil, fmt.Errorf("expected float64, got %T", val)
}
return func(c *HC) bool {
return m(c) == value
}, nil
}
func stringEQ(m toString, val interface{}) (hcpredicate, error) {
value, ok := val.(string)
if !ok {
return nil, fmt.Errorf("expected string, got %T", val)
}
return func(c *HC) bool {
return m(c) == value
}, nil
}
func intLT(m toInt, val interface{}) (hcpredicate, error) {
value, ok := val.(int)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *HC) bool {
return m(c) < value
}, nil
}
func intGT(m toInt, val interface{}) (hcpredicate, error) {
value, ok := val.(int)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *HC) bool {
return m(c) > value
}, nil
}
func float64LT(m toFloat64, val interface{}) (hcpredicate, error) {
value, ok := val.(float64)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *HC) bool {
return m(c) < value
}, nil
}
func float64GT(m toFloat64, val interface{}) (hcpredicate, error) {
value, ok := val.(float64)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *HC) bool {
return m(c) > value
}, nil
}
func localExec(x string) toString {
return func(c *HC) string {
return x
}
}