// Copyright 2018 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package herrors contains common Hugo errors and error related utilities.
package herrors

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"runtime"
	"runtime/debug"
	"strconv"

	_errors "github.com/pkg/errors"
)

// As defined in https://godoc.org/github.com/pkg/errors
type causer interface {
	Cause() error
}

type stackTracer interface {
	StackTrace() _errors.StackTrace
}

// PrintStackTraceFromErr prints the error's stack trace to stdoud.
func PrintStackTraceFromErr(err error) {
	FprintStackTraceFromErr(os.Stdout, err)
}

// FprintStackTraceFromErr prints the error's stack trace to w.
func FprintStackTraceFromErr(w io.Writer, err error) {
	if err, ok := err.(stackTracer); ok {
		for _, f := range err.StackTrace() {
			fmt.Fprintf(w, "%+s:%d\n", f, f)
		}
	}
}

// PrintStackTrace prints the current stacktrace to w.
func PrintStackTrace(w io.Writer) {
	buf := make([]byte, 1<<16)
	runtime.Stack(buf, true)
	fmt.Fprintf(w, "%s", buf)
}

// ErrorSender is a, typically, non-blocking error handler.
type ErrorSender interface {
	SendError(err error)
}

// Recover is a helper function that can be used to capture panics.
// Put this at the top of a method/function that crashes in a template:
//     defer herrors.Recover()
func Recover(args ...interface{}) {
	if r := recover(); r != nil {
		fmt.Println("ERR:", r)
		args = append(args, "stacktrace from panic: \n"+string(debug.Stack()), "\n")
		fmt.Println(args...)
	}
}

// Get the current goroutine id. Used only for debugging.
func GetGID() uint64 {
	b := make([]byte, 64)
	b = b[:runtime.Stack(b, false)]
	b = bytes.TrimPrefix(b, []byte("goroutine "))
	b = b[:bytes.IndexByte(b, ' ')]
	n, _ := strconv.ParseUint(string(b), 10, 64)
	return n
}

// ErrFeatureNotAvailable denotes that a feature is unavailable.
//
// We will, at least to begin with, make some Hugo features (SCSS with libsass) optional,
// and this error is used to signal those situations.
var ErrFeatureNotAvailable = errors.New("this feature is not available in your current Hugo version, see https://goo.gl/YMrWcn for more information")