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lambda.go
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lambda.go
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// Copyright 2021-2022 Zenauth Ltd.
// SPDX-License-Identifier: Apache-2.0
package engine
import (
"fmt"
"github.com/google/cel-go/common/operators"
exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
)
type lambdaAST struct {
iterRange *exprpb.Expr
lambdaExpr *exprpb.Expr
operator string
iterVar string
}
func buildLambdaAST(e *exprpb.Expr_Comprehension) (*lambdaAST, error) {
obj := &lambdaAST{
iterVar: e.IterVar,
iterRange: e.IterRange,
}
var step *exprpb.Expr_CallExpr
var ok bool
if step, ok = e.LoopStep.ExprKind.(*exprpb.Expr_CallExpr); !ok {
return nil, fmt.Errorf("expected loop-step expression type CallExpr, got: %T", e.LoopStep.ExprKind)
}
switch step.CallExpr.Function {
case operators.LogicalAnd:
obj.operator = All
obj.lambdaExpr = step.CallExpr.Args[1]
case operators.LogicalOr:
obj.operator = Exists
obj.lambdaExpr = step.CallExpr.Args[1]
case operators.Add:
obj.operator = Map
if elements := step.CallExpr.Args[1].GetListExpr().GetElements(); len(elements) > 0 {
obj.lambdaExpr = elements[0]
}
case operators.Conditional:
switch e.AccuInit.ExprKind.(type) {
case *exprpb.Expr_ListExpr:
obj.operator = Filter
case *exprpb.Expr_ConstExpr:
obj.operator = ExistsOne
default:
return nil, fmt.Errorf("expected loop-accu-init expression type ConstExpr or ListExpr, got: %T", e.AccuInit.ExprKind)
}
obj.lambdaExpr = step.CallExpr.Args[0]
default:
return nil, fmt.Errorf("unexpected loop-step function: %q", step.CallExpr.Function)
}
return obj, nil
}