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expr.go
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expr.go
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package stateful
import (
"fmt"
"time"
"github.com/influxdata/kapacitor/tick/ast"
)
// Expression is interface that describe expression with state and
// it's evaluation.
type Expression interface {
Reset()
Type(scope ReadOnlyScope) (ast.ValueType, error)
EvalFloat(scope *Scope) (float64, error)
EvalInt(scope *Scope) (int64, error)
EvalString(scope *Scope) (string, error)
EvalBool(scope *Scope) (bool, error)
EvalDuration(scope *Scope) (time.Duration, error)
Eval(scope *Scope) (interface{}, error)
// Return a copy of the expression but with a Reset state.
CopyReset() Expression
}
type expression struct {
nodeEvaluator NodeEvaluator
executionState ExecutionState
}
// NewExpression accept a node and try to "compile"/ "specialise" it
// in order to achieve better runtime performance.
//
// For example:
// Given a BinaryNode{ReferNode("value"), NumberNode{Float64:10}} during runtime
// we can find the type of "value" and find the most matching comparison function - (float64,float64) or (int64,float64)
func NewExpression(node ast.Node) (Expression, error) {
nodeEvaluator, err := createNodeEvaluator(node)
if err != nil {
return nil, err
}
return &expression{
nodeEvaluator: nodeEvaluator,
executionState: CreateExecutionState(),
}, nil
}
func (se *expression) CopyReset() Expression {
return &expression{
nodeEvaluator: se.nodeEvaluator,
executionState: CreateExecutionState(),
}
}
func (se *expression) Reset() {
se.executionState.ResetAll()
}
func (se *expression) Type(scope ReadOnlyScope) (ast.ValueType, error) {
return se.nodeEvaluator.Type(scope)
}
func (se *expression) EvalBool(scope *Scope) (bool, error) {
return se.nodeEvaluator.EvalBool(scope, se.executionState)
}
func (se *expression) EvalInt(scope *Scope) (int64, error) {
return se.nodeEvaluator.EvalInt(scope, se.executionState)
}
func (se *expression) EvalFloat(scope *Scope) (float64, error) {
return se.nodeEvaluator.EvalFloat(scope, se.executionState)
}
func (se *expression) EvalString(scope *Scope) (string, error) {
return se.nodeEvaluator.EvalString(scope, se.executionState)
}
func (se *expression) EvalDuration(scope *Scope) (time.Duration, error) {
return se.nodeEvaluator.EvalDuration(scope, se.executionState)
}
func (se *expression) EvalMissing(scope *Scope) (*ast.Missing, error) {
return se.nodeEvaluator.EvalMissing(scope, se.executionState)
}
func (se *expression) Eval(scope *Scope) (interface{}, error) {
typ, err := se.nodeEvaluator.Type(scope)
if err != nil {
return nil, err
}
switch typ {
case ast.TInt:
result, err := se.EvalInt(scope)
if err != nil {
return nil, err
}
return result, err
case ast.TFloat:
result, err := se.EvalFloat(scope)
if err != nil {
return nil, err
}
return result, err
case ast.TString:
result, err := se.EvalString(scope)
if err != nil {
return nil, err
}
return result, err
case ast.TBool:
result, err := se.EvalBool(scope)
if err != nil {
return nil, err
}
return result, err
case ast.TDuration:
result, err := se.EvalDuration(scope)
if err != nil {
return nil, err
}
return result, err
case ast.TMissing:
result, err := se.EvalMissing(scope)
if err != nil {
return nil, err
}
return result, err
default:
return nil, fmt.Errorf("expression returned unexpected type %s", typ)
}
}