// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

package pointerToSlice

import (
	"go/ast"
	"strings"

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

var (
	Analyzer = &analysis.Analyzer{
		Name: "pointerToSlice",
		Doc:  "check for usage of pointer to slice in function definitions",
		Run:  run,
	}
	ignoreFilesPattern string
)

func init() {
	Analyzer.Flags.StringVar(&ignoreFilesPattern, "ignore", "", "Comma separated list of files to ignore")
}

func run(pass *analysis.Pass) (interface{}, error) {
	var ignoreFiles []string
	if ignoreFilesPattern != "" {
		ignoreFiles = strings.Split(ignoreFilesPattern, ",")
	}

	checkNode := func(expr ast.Expr) {
		sexpr, ok := expr.(*ast.StarExpr)
		if !ok {
			return
		}
		if _, ok := sexpr.X.(*ast.ArrayType); ok {
			pass.Reportf(sexpr.Pos(), "use of pointer to slice in function definition")
			return
		}
		if tv, ok := pass.TypesInfo.Types[sexpr.X]; ok {
			if strings.HasPrefix(tv.Type.String(), "[]") || strings.HasPrefix(tv.Type.Underlying().String(), "[]") {
				pass.Reportf(sexpr.Pos(), "use of pointer to slice in function definition")
				return
			}
		}
	}

	for _, file := range pass.Files {
		ast.Inspect(file, func(node ast.Node) bool {
			if node != nil {
				f := pass.Fset.File(node.Pos())
				if isIgnore(f.Name(), ignoreFiles) {
					return false
				}
			}

			f, ok := node.(*ast.FuncDecl)
			if !ok || f.Type == nil {
				return true
			}

			if params := f.Type.Params; params != nil {
				for _, p := range params.List {
					checkNode(p.Type)
				}
			}

			if results := f.Type.Results; results != nil {
				for _, r := range results.List {
					checkNode(r.Type)
				}
			}

			return true
		})
	}

	return nil, nil
}

func isIgnore(file string, ignoreFiles []string) bool {
	for _, f := range ignoreFiles {
		if strings.HasSuffix(file, f) {
			return true
		}
	}
	return false
}