package sa9002

import (
	"fmt"
	"go/ast"
	"strconv"

	"honnef.co/go/tools/analysis/code"
	"honnef.co/go/tools/analysis/edit"
	"honnef.co/go/tools/analysis/lint"
	"honnef.co/go/tools/analysis/report"
	"honnef.co/go/tools/go/types/typeutil"

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

var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
	Analyzer: &analysis.Analyzer{
		Name:     "SA9002",
		Run:      run,
		Requires: []*analysis.Analyzer{inspect.Analyzer},
	},
	Doc: &lint.RawDocumentation{
		Title:    `Using a non-octal \'os.FileMode\' that looks like it was meant to be in octal.`,
		Since:    "2017.1",
		Severity: lint.SeverityWarning,
		MergeIf:  lint.MergeIfAny,
	},
})

var Analyzer = SCAnalyzer.Analyzer

func run(pass *analysis.Pass) (interface{}, error) {
	fn := func(node ast.Node) {
		call := node.(*ast.CallExpr)
		for _, arg := range call.Args {
			lit, ok := arg.(*ast.BasicLit)
			if !ok {
				continue
			}
			if !typeutil.IsTypeWithName(pass.TypesInfo.TypeOf(lit), "os.FileMode") &&
				!typeutil.IsTypeWithName(pass.TypesInfo.TypeOf(lit), "io/fs.FileMode") {
				continue
			}
			if len(lit.Value) == 3 &&
				lit.Value[0] != '0' &&
				lit.Value[0] >= '0' && lit.Value[0] <= '7' &&
				lit.Value[1] >= '0' && lit.Value[1] <= '7' &&
				lit.Value[2] >= '0' && lit.Value[2] <= '7' {

				v, err := strconv.ParseInt(lit.Value, 10, 64)
				if err != nil {
					continue
				}
				report.Report(pass, arg, fmt.Sprintf("file mode '%s' evaluates to %#o; did you mean '0%s'?", lit.Value, v, lit.Value),
					report.Fixes(edit.Fix("fix octal literal", edit.ReplaceWithString(arg, "0"+lit.Value))))
			}
		}
	}
	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
	return nil, nil
}