package rule

import (
	"go/ast"

	"github.com/mgechev/revive/lint"
)

// NestedStructs lints nested structs.
type NestedStructs struct{}

// Apply applies the rule to given file.
func (*NestedStructs) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
	var failures []lint.Failure

	walker := &lintNestedStructs{
		onFailure: func(failure lint.Failure) {
			failures = append(failures, failure)
		},
	}

	ast.Walk(walker, file.AST)

	return failures
}

// Name returns the rule name.
func (*NestedStructs) Name() string {
	return "nested-structs"
}

type lintNestedStructs struct {
	onFailure func(lint.Failure)
}

func (l *lintNestedStructs) Visit(n ast.Node) ast.Visitor {
	if v, ok := n.(*ast.StructType); ok {
		ls := &lintStruct{l.onFailure}
		ast.Walk(ls, v.Fields)
	}

	return l
}

type lintStruct struct {
	onFailure func(lint.Failure)
}

func (l *lintStruct) Visit(n ast.Node) ast.Visitor {
	switch s := n.(type) {
	case *ast.StructType:
		l.fail(s)
		return nil
	case *ast.ArrayType:
		if _, ok := s.Elt.(*ast.StructType); ok {
			l.fail(s)
		}
		return nil
	case *ast.ChanType:
		return nil
	case *ast.MapType:
		return nil
	default:
		return l
	}
}

func (l *lintStruct) fail(n ast.Node) {
	l.onFailure(lint.Failure{
		Failure:    "no nested structs are allowed",
		Category:   "style",
		Node:       n,
		Confidence: 1,
	})
}