/*
Copyright 2015 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 service

import (
	"bytes"
	"fmt"
	"hash/crc64"
	"sort"
	"strconv"

	mesos "github.com/mesos/mesos-go/mesosproto"
)

// compute a hashcode for ExecutorInfo that may be used as a reasonable litmus test
// with respect to compatibility across HA schedulers. the intent is that an HA scheduler
// should fail-fast if it doesn't pass this test, rather than generating (potentially many)
// errors at run-time because a Mesos master decides that the ExecutorInfo generated by a
// secondary scheduler doesn't match that of the primary scheduler.
//
// see https://github.com/apache/mesos/blob/0.22.0/src/common/type_utils.cpp#L110
func hashExecutorInfo(info *mesos.ExecutorInfo) uint64 {
	// !!! we specifically do NOT include:
	// - Framework ID because it's a value that's initialized too late for us to use
	// - Executor ID because it's a value that includes a copy of this hash
	buf := &bytes.Buffer{}
	buf.WriteString(info.GetName())
	buf.WriteString(info.GetSource())
	buf.Write(info.Data)

	if info.Command != nil {
		buf.WriteString(info.Command.GetValue())
		buf.WriteString(info.Command.GetUser())
		buf.WriteString(strconv.FormatBool(info.Command.GetShell()))
		if sz := len(info.Command.Arguments); sz > 0 {
			x := make([]string, sz)
			copy(x, info.Command.Arguments)
			sort.Strings(x)
			for _, item := range x {
				buf.WriteString(item)
			}
		}
		if vars := info.Command.Environment.GetVariables(); vars != nil && len(vars) > 0 {
			names := []string{}
			e := make(map[string]string)

			for _, v := range vars {
				if name := v.GetName(); name != "" {
					names = append(names, name)
					e[name] = v.GetValue()
				}
			}
			sort.Strings(names)
			for _, n := range names {
				buf.WriteString(n)
				buf.WriteString("=")
				buf.WriteString(e[n])
			}
		}
		if uris := info.Command.GetUris(); len(uris) > 0 {
			su := []string{}
			for _, uri := range uris {
				su = append(su, fmt.Sprintf("%s%t%t", uri.GetValue(), uri.GetExecutable(), uri.GetExtract()))
			}
			sort.Strings(su)
			for _, uri := range su {
				buf.WriteString(uri)
			}
		}
		//TODO(jdef) add support for Resources and Container
	}
	table := crc64.MakeTable(crc64.ECMA)
	return crc64.Checksum(buf.Bytes(), table)
}