package parsekit

import (
	"fmt"
	"runtime"
	"strings"
)

// Error is used as the error type when parsing errors occur.
// The error includes some context information to allow for useful
// error messages to the user.
type Error struct {
	Message string
	Cursor  Cursor
}

func (err *Error) Error() string {
	if err == nil {
		callerPanic(1, "parsekit.Error.Error(): method called with nil error at {caller}")
	}
	return fmt.Sprintf("%s at %s", err.Message, err.Cursor)
}

func callerFunc(depth int) string {
	// No error handling, because we call this method ourselves with safe depth values.
	pc, _, _, _ := runtime.Caller(depth + 1)
	caller := runtime.FuncForPC(pc)
	parts := strings.Split(caller.Name(), ".")
	funcName := parts[len(parts)-1]
	return funcName
}

func callerFilepos(depth int) string {
	// No error handling, because we call this method ourselves with safe depth values.
	_, file, line, _ := runtime.Caller(depth + 1)
	return fmt.Sprintf("%s:%d", file, line)
}

func callerPanic(depth int, f string, args ...interface{}) {
	filepos := callerFilepos(depth + 1)
	m := fmt.Sprintf(f, args...)
	m = strings.Replace(m, "{caller}", filepos, 1)
	panic(m)
}