package sa1018

import (
	"fmt"
	"go/constant"

	"honnef.co/go/tools/analysis/callcheck"
	"honnef.co/go/tools/analysis/lint"
	"honnef.co/go/tools/go/ir"
	"honnef.co/go/tools/internal/passes/buildir"

	"golang.org/x/tools/go/analysis"
)

var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
	Analyzer: &analysis.Analyzer{
		Name:     "SA1018",
		Requires: []*analysis.Analyzer{buildir.Analyzer},
		Run:      callcheck.Analyzer(rules),
	},
	Doc: &lint.RawDocumentation{
		Title: `\'strings.Replace\' called with \'n == 0\', which does nothing`,
		Text: `With \'n == 0\', zero instances will be replaced. To replace all
instances, use a negative number, or use \'strings.ReplaceAll\'.`,
		Since:    "2017.1",
		Severity: lint.SeverityWarning,
		MergeIf:  lint.MergeIfAny, // MergeIfAny if we only flag literals, not named constants
	},
})

var Analyzer = SCAnalyzer.Analyzer

var rules = map[string]callcheck.Check{
	"strings.Replace": check("strings.Replace", 3),
	"bytes.Replace":   check("bytes.Replace", 3),
}

func check(name string, arg int) callcheck.Check {
	return func(call *callcheck.Call) {
		arg := call.Args[arg]
		if k, ok := arg.Value.Value.(*ir.Const); ok && k.Value.Kind() == constant.Int {
			if v, ok := constant.Int64Val(k.Value); ok && v == 0 {
				arg.Invalid(fmt.Sprintf("calling %s with n == 0 will return no results, did you mean -1?", name))
			}
		}
	}
}