136 lines
3.9 KiB
Go
136 lines
3.9 KiB
Go
package exprhelpers
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import (
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"fmt"
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"strconv"
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"strings"
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"github.com/antonmedv/expr/parser"
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"github.com/sirupsen/logrus"
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log "github.com/sirupsen/logrus"
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"github.com/antonmedv/expr"
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"github.com/antonmedv/expr/ast"
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"github.com/antonmedv/expr/vm"
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)
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/*
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Visitor is used to reconstruct variables with its property called in an expr filter
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Thus, we can debug expr filter by displaying all variables contents present in the filter
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*/
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type visitor struct {
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newVar bool
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currentID string
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properties []string
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vars []string
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}
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/*
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Enter should be present for the interface but is never used
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*/
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func (v *visitor) Enter(node *ast.Node) {}
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/*
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Exit is called when running ast.Walk(node, visitor), each time a node exit.
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So we have the node information and we can get the identifier (first level of the struct)
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and its properties to reconstruct the complete variable.
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*/
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func (v *visitor) Exit(node *ast.Node) {
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if n, ok := (*node).(*ast.IdentifierNode); ok {
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if !v.newVar {
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v.newVar = true
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v.currentID = n.Value
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} else {
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fullVar := fmt.Sprintf("%s.%s", v.currentID, strings.Join(v.properties, "."))
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v.vars = append(v.vars, fullVar)
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v.properties = []string{}
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v.currentID = n.Value
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}
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} else if n, ok := (*node).(*ast.PropertyNode); ok {
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v.properties = append(v.properties, n.Property)
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}
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}
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/*
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Build reconstruct all the variables used in a filter (to display their content later).
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*/
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func (v *visitor) Build(filter string, exprEnv expr.Option) (*ExprDebugger, error) {
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var expressions []*expression
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ret := &ExprDebugger{
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filter: filter,
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}
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if filter == "" {
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log.Debugf("unable to create expr debugger with empty filter")
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return &ExprDebugger{}, nil
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}
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v.newVar = false
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tree, err := parser.Parse(filter)
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if err != nil {
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return nil, err
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}
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ast.Walk(&tree.Node, v)
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if v.currentID != "" && len(v.properties) > 0 { // if its a variable with property (eg. evt.Line.Labels)
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fullVar := fmt.Sprintf("%s.%s", v.currentID, strings.Join(v.properties, "."))
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v.vars = append(v.vars, fullVar)
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} else if v.currentID != "" && len(v.properties) == 0 { // if it's a variable without property
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fullVar := v.currentID
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v.vars = append(v.vars, fullVar)
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} else {
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log.Debugf("no variable in filter : '%s'", filter)
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}
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v.properties = []string{}
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v.currentID = ""
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for _, variable := range v.vars {
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debugFilter, err := expr.Compile(variable, exprEnv)
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if err != nil {
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return ret, fmt.Errorf("compilation of variable '%s' failed: %v", variable, err)
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}
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tmpExpression := &expression{
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variable,
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debugFilter,
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}
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expressions = append(expressions, tmpExpression)
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}
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ret.expression = expressions
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return ret, nil
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}
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// ExprDebugger contains the list of expression to be run when debugging an expression filter
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type ExprDebugger struct {
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filter string
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expression []*expression
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}
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// expression is the structure that represents the variable in string and compiled format
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type expression struct {
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Str string
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Compiled *vm.Program
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}
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/*
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Run display the content of each variable of a filter by evaluating them with expr,
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again the expr environment given in parameter
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*/
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func (e *ExprDebugger) Run(logger *logrus.Entry, filterResult bool, exprEnv map[string]interface{}) {
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if len(e.expression) == 0 {
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logger.Tracef("no variable to eval for filter '%s'", e.filter)
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return
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}
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logger.Debugf("eval(%s) = %s", e.filter, strings.ToUpper(strconv.FormatBool(filterResult)))
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logger.Debugf("eval variables:")
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for _, expression := range e.expression {
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debug, err := expr.Run(expression.Compiled, exprEnv)
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if err != nil {
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logger.Errorf("unable to print debug expression for '%s': %s", expression.Str, err)
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}
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logger.Debugf(" %s = '%v'", expression.Str, debug)
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}
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}
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// NewDebugger is the exported function that build the debuggers expressions
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func NewDebugger(filter string, exprEnv expr.Option) (*ExprDebugger, error) {
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visitor := &visitor{}
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exprDebugger, err := visitor.Build(filter, exprEnv)
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return exprDebugger, err
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}
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