package noliteral

import (
	"go/ast"
	"go/token"
	"strings"
	"sync"

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

const LinterName = "noliteral"

var LogsAnalyzer = &analysis.Analyzer{
	Name: LinterName,
	Doc:  LinterName + " is a helper tool that ensures logging messages in Go code are structured and not written as simple text.",
	Run:  run,
}

var (
	aliasCache = sync.Map{}
)

type Configuration struct {
	TargetMethods    []string `mapstructure:"target-methods"`
	DisablePackages  []string `mapstructure:"disable-packages"`
	ConstantsPackage string   `mapstructure:"constants-package"`
}

var Config = Configuration{
	TargetMethods: []string{"Debug", "Info", "Warn", "Error"},
}

func run(pass *analysis.Pass) (interface{}, error) {
	for _, file := range pass.Files {
		ast.Inspect(file, func(n ast.Node) bool {
			expr, ok := n.(*ast.CallExpr)
			if !ok {
				return true
			}

			isLog, _ := isLogDot(expr.Fun)
			if !isLog || len(expr.Args) == 0 {
				return true
			}

			if !isStringValue(expr.Args[0]) {
				alias, _ := getAliasByPkgName(file, Config.ConstantsPackage)
				if Config.ConstantsPackage == "" || getPackageName(expr.Args[0]) == alias || getPackageName(expr.Args[0]) == "" {
					return true
				}

				for _, pkgName := range Config.DisablePackages {
					if pkgName == getPackageName(expr.Args[0]) {
						return true
					}
				}

				pass.Report(analysis.Diagnostic{
					Pos:            expr.Pos(),
					End:            expr.End(),
					Category:       LinterName,
					Message:        "Wrong package for constants",
					SuggestedFixes: nil,
				})
				return true
			}

			pass.Report(analysis.Diagnostic{
				Pos:            expr.Pos(),
				End:            expr.End(),
				Category:       LinterName,
				Message:        "Literals are not allowed in the body of the logger",
				SuggestedFixes: nil,
			})

			return false
		})
	}

	return nil, nil
}

func isLogDot(expr ast.Expr) (bool, string) {
	sel, ok := expr.(*ast.SelectorExpr)
	if !ok {
		return false, ""
	}

	for _, method := range Config.TargetMethods {
		if isIdent(sel.Sel, method) {
			return true, method
		}
	}
	return false, ""
}

func isIdent(expr ast.Expr, ident string) bool {
	id, ok := expr.(*ast.Ident)
	if ok && id.Name == ident {
		return true
	}

	return false
}

func isStringValue(expr ast.Expr) bool {
	basicLit, ok := expr.(*ast.BasicLit)
	return ok && basicLit.Kind == token.STRING
}

func getAliasByPkgName(file *ast.File, pkgName string) (string, error) {
	if alias, ok := aliasCache.Load(file); ok {
		return alias.(string), nil
	}

	var alias string
	specs := file.Imports

	for _, spec := range specs {
		alias = getAliasFromImportSpec(spec, pkgName)
		if alias != "" {
			break
		}
	}

	aliasCache.Store(file, alias)
	return alias, nil
}

func getAliasFromImportSpec(spec *ast.ImportSpec, pkgName string) string {
	if spec == nil {
		return ""
	}
	importName := strings.Replace(spec.Path.Value, "\"", "", -1)
	if importName != pkgName {
		return ""
	}

	split := strings.Split(importName, "/")

	if len(split) == 0 {
		return ""
	}
	alias := split[len(split)-1]
	if spec.Name != nil {
		alias = spec.Name.Name
	}

	return alias
}

func getPackageName(expr ast.Expr) string {
	if selectorExpr, ok := expr.(*ast.SelectorExpr); ok {
		if ident, ok := selectorExpr.X.(*ast.Ident); ok {
			return ident.Name
		}
	}
	return ""
}