// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Only build when go-fuzz is in use
// +build gofuzz

package promql

import "github.com/prometheus/prometheus/pkg/textparse"

// PromQL parser fuzzing instrumentation for use with
// https://github.com/dvyukov/go-fuzz.
//
// Fuzz each parser by building appropriately instrumented parser, ex.
// FuzzParseMetric and execute it with it's
//
//     go-fuzz-build -func FuzzParseMetric -o FuzzParseMetric.zip github.com/prometheus/prometheus/promql
//
// And then run the tests with the appropriate inputs
//
//     go-fuzz -bin FuzzParseMetric.zip -workdir fuzz-data/ParseMetric
//
// Further input samples should go in the folders fuzz-data/ParseMetric/corpus.
//
// Repeat for ParseMetricSelection, ParseExpr and ParseStmt.

// Tuning which value is returned from Fuzz*-functions has a strong influence
// on how quick the fuzzer converges on "interesting" cases. At least try
// switching between fuzzMeh (= included in corpus, but not a priority) and
// fuzzDiscard (=don't use this input for re-building later inputs) when
// experimenting.
const (
	fuzzInteresting = 1
	fuzzMeh         = 0
	fuzzDiscard     = -1
)

// Fuzz the metric parser.
//
// Note that his is not the parser for the text-based exposition-format; that
// lives in github.com/prometheus/client_golang/text.
func FuzzParseMetric(in []byte) int {
	p := textparse.New(in)
	for p.Next() {
	}

	if p.Err() == nil {
		return fuzzInteresting
	}

	return fuzzMeh
}

// Fuzz the metric selector parser.
func FuzzParseMetricSelector(in []byte) int {
	_, err := ParseMetricSelector(string(in))
	if err == nil {
		return fuzzInteresting
	}

	return fuzzMeh
}

// Fuzz the expression parser.
func FuzzParseExpr(in []byte) int {
	_, err := ParseExpr(string(in))
	if err == nil {
		return fuzzInteresting
	}

	return fuzzMeh
}

// Fuzz the parser.
func FuzzParseStmts(in []byte) int {
	_, err := ParseStmts(string(in))
	if err == nil {
		return fuzzInteresting
	}

	return fuzzMeh
}