/*
 * Copyright (c) 2022, MegaEase
 * 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 global

import (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"time"

	log "github.com/sirupsen/logrus"
	"golang.org/x/exp/constraints"
)

const (
	// Org is the organization
	Org = "MegaEase"
	// Prog is the program name
	Prog = "EaseProbe"
	// Ver is the program version
	Ver = "v1.1.2"

	//OrgProg combine organization and program
	OrgProg = Org + " " + Prog
	//OrgProgVer combine organization and program and version
	OrgProgVer = Org + " " + Prog + "/" + Ver

	// Icon is the default icon which used in Slack or Discord
	Icon = "https://megaease.cn/favicon.png"
)

const (
	// DefaultRetryTimes is 3 times
	DefaultRetryTimes = 3
	// DefaultRetryInterval is 5 seconds
	DefaultRetryInterval = time.Second * 5
	// DefaultTimeFormat is "2006-01-02 15:04:05 UTC"
	DefaultTimeFormat = "2006-01-02 15:04:05 UTC"
	// DefaultProbeInterval is 1 minutes
	DefaultProbeInterval = time.Second * 60
	// DefaultTimeOut is 30 seconds
	DefaultTimeOut = time.Second * 30
)

const (
	// DefaultHTTPServerIP is the default ip of the HTTP server
	DefaultHTTPServerIP = "0.0.0.0"
	// DefaultHTTPServerPort is the default port of the HTTP server
	DefaultHTTPServerPort = "8181"
	// DefaultAccessLogFile is the default access log file name
	DefaultAccessLogFile = "access.log"
	// DefaultDataFile is the default data file name
	DefaultDataFile = "data.yaml"
	// DefaultPIDFile is the default pid file name
	DefaultPIDFile = "easeprobe.pid"
)

const (
	// DefaultMaxLogSize is the default max log size
	DefaultMaxLogSize = 10 // 10M
	// DefaultMaxLogAge is the default max log age
	DefaultMaxLogAge = 7 // 7 days
	// DefaultMaxBackups is the default backup file number
	DefaultMaxBackups = 5 // file
	// DefaultLogCompress is the default compress log
	DefaultLogCompress = true
)

// Retry is the settings of retry
type Retry struct {
	Times    int           `yaml:"times"`
	Interval time.Duration `yaml:"interval"`
}

// TLS is the configuration for TLS files
type TLS struct {
	CA   string `yaml:"ca"`
	Cert string `yaml:"cert"`
	Key  string `yaml:"key"`
}

// The normalize() function logic as below:
// - if both global and local are not set, then return the _default.
// - if set the global, but not the local, then return the global
// - if set the local, but not the global, then return the local
// - if both global and local are set, then return the local
func normalize[T constraints.Ordered](global, local, valid, _default T) T {
	// if the val is invalid, then assign the default value
	if local <= valid {
		local = _default
		//if the global configuration is validated, assign the global
		if global > valid {
			local = global
		}
	}
	return local
}

// Config return a tls.Config object
func (t *TLS) Config() (*tls.Config, error) {
	if len(t.CA) <= 0 || len(t.Cert) <= 0 || len(t.Key) <= 0 {
		return nil, nil
	}

	cert, err := ioutil.ReadFile(t.CA)
	if err != nil {
		return nil, err
	}
	caCertPool := x509.NewCertPool()
	caCertPool.AppendCertsFromPEM(cert)

	certificate, err := tls.LoadX509KeyPair(t.Cert, t.Key)
	if err != nil {
		return nil, err
	}
	return &tls.Config{
		RootCAs:      caCertPool,
		Certificates: []tls.Certificate{certificate},
	}, nil
}

// DoRetry is a help function to retry the function if it returns error
func DoRetry(kind, name, tag string, r Retry, fn func() error) error {
	var err error
	for i := 0; i < r.Times; i++ {
		err = fn()
		if err == nil {
			return nil
		}
		log.Warnf("[%s / %s / %s] Retried to send %d/%d - %v", kind, name, tag, i+1, r.Times, err)

		// last time no need to sleep
		if i < r.Times-1 {
			time.Sleep(r.Interval)
		}
	}
	return fmt.Errorf("[%s / %s / %s] failed after %d retries - %v", kind, name, tag, r.Times, err)
}

// GetWorkDir return the current working directory
func GetWorkDir() string {
	dir, err := os.Getwd()
	if err != nil {
		log.Warnf("Cannot get the current directory: %v, using $HOME directory!", err)
		dir, err = os.UserHomeDir()
		if err != nil {
			log.Warnf("Cannot get the user home directory: %v, using /tmp directory!", err)
			dir = os.TempDir()
		}
	}
	return dir
}

// MakeDirectory return the writeable filename
func MakeDirectory(filename string) string {
	dir, file := filepath.Split(filename)
	if len(dir) <= 0 {
		dir = GetWorkDir()
	}
	if len(file) <= 0 {
		return dir
	}
	if strings.HasPrefix(dir, "~/") {
		home, err := os.UserHomeDir()
		if err != nil {
			log.Warnf("Cannot get the user home directory: %v, using /tmp directory as home", err)
			home = os.TempDir()
		}
		dir = filepath.Join(home, dir[2:])
	}
	dir, err := filepath.Abs(dir)
	if err != nil {
		log.Warnf("Cannot get the absolute path: %v", err)
		dir = GetWorkDir()
	}

	if _, err := os.Stat(dir); os.IsNotExist(err) {
		err = os.MkdirAll(dir, os.ModePerm)
		if err != nil {
			log.Warnf("Cannot create the directory: %v", err)
			dir = GetWorkDir()
		}
	}

	return filepath.Join(dir, file)
}