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 (
	methodsToSearchOnce = &sync.Once{}
	methodsToSearch     = []string{"Debug", "Info", "Warn", "Error"}
	customLogs          = "reportFlushError, reportError"
)

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 && isStringValue(expr.Args[0]) {
				pass.Report(analysis.Diagnostic{
					Pos:            expr.Pos(),
					End:            0,
					Category:       LinterName,
					Message:        "Literals are not allowed in the body of the logger",
					SuggestedFixes: nil,
				})
				return false
			}
			return true
		})
	}

	return nil, nil
}

func isLogDot(expr ast.Expr) (bool, string) {
	sel, ok := expr.(*ast.SelectorExpr)
	if !ok {
		return false, ""
	}
	methodsToSearchOnce.Do(func() {
		for _, cl := range strings.Split(customLogs, ",") {
			cl = strings.Trim(cl, " ")
			if len(cl) > 0 {
				methodsToSearch = append(methodsToSearch, cl)
			}
		}
	})

	for _, method := range methodsToSearch {
		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 {
		return false
	}
	if id.Name == ident {
		return true
	}
	return false
}

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