/*
Copyright 2014 The Kubernetes 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 runtime

import (
	"fmt"
	"runtime"

	"github.com/golang/glog"
)

// For testing, bypass HandleCrash.
var ReallyCrash bool

// PanicHandlers is a list of functions which will be invoked when a panic happens.
var PanicHandlers = []func(interface{}){logPanic}

//TODO search the public functions
// HandleCrash simply catches a crash and logs an error. Meant to be called via defer.
// Additional context-specific handlers can be provided, and will be called in case of panic
func HandleCrash(additionalHandlers ...func(interface{})) {
	if ReallyCrash {
		return
	}
	if r := recover(); r != nil {
		for _, fn := range PanicHandlers {
			fn(r)
		}
		for _, fn := range additionalHandlers {
			fn(r)
		}
	}
}

// logPanic logs the caller tree when a panic occurs.
func logPanic(r interface{}) {
	callers := getCallers(r)
	glog.Errorf("Recovered from panic: %#v (%v)\n%v", r, r, callers)
}

func getCallers(r interface{}) string {
	callers := ""
	for i := 0; true; i++ {
		_, file, line, ok := runtime.Caller(i)
		if !ok {
			break
		}
		callers = callers + fmt.Sprintf("%v:%v\n", file, line)
	}

	return callers
}

// ErrorHandlers is a list of functions which will be invoked when an unreturnable
// error occurs.
var ErrorHandlers = []func(error){logError}

// HandlerError is a method to invoke when a non-user facing piece of code cannot
// return an error and needs to indicate it has been ignored. Invoking this method
// is preferable to logging the error - the default behavior is to log but the
// errors may be sent to a remote server for analysis.
func HandleError(err error) {
	// this is sometimes called with a nil error.  We probably shouldn't fail and should do nothing instead
	if err == nil {
		return
	}

	for _, fn := range ErrorHandlers {
		fn(err)
	}
}

// logError prints an error with the call stack of the location it was reported
func logError(err error) {
	glog.ErrorDepth(2, err)
}

// GetCaller returns the caller of the function that calls it.
func GetCaller() string {
	var pc [1]uintptr
	runtime.Callers(3, pc[:])
	f := runtime.FuncForPC(pc[0])
	if f == nil {
		return fmt.Sprintf("Unable to find caller")
	}
	return f.Name()
}

// RecoverFromPanic replaces the specified error with an error containing the
// original error, and  the call tree when a panic occurs. This enables error
// handlers to handle errors and panics the same way.
func RecoverFromPanic(err *error) {
	if r := recover(); r != nil {
		callers := getCallers(r)

		*err = fmt.Errorf(
			"recovered from panic %q. (err=%v) Call stack:\n%v",
			r,
			*err,
			callers)
	}
}
