package main

import (
    "os"
    "os/exec"
    "encoding/json"
    "io/ioutil"
    "log"
    "bytes"
    "time"
    "fmt"
    "path/filepath"
    "strings"
)

var (
    configFile = "config.json"
)

// Config -- General config
type Config struct {
    TimeHour int
    TimeMinute int
    WorkingDir string
    BackupPeriods []BackupPeriod
    Hosts []Host
}

// Host -- Struct for each host in the config
type Host struct {
    Name string
    IPAddr string
    Port int
    Username string
    PrivKey string
    RemoteDir string
}

// BackupPeriod -- Struct for individual backup period
type BackupPeriod struct {
    Interval int
    Count int
}

func loadConfig(configFile string) Config {
    var config Config

    fileBytes, err := ioutil.ReadFile(configFile)
    if err != nil {
        log.Println(err)
    }

    err = json.Unmarshal(fileBytes, &config)
    if err != nil {
        log.Println(err)
    }

    return config
}

func runCommand(cmdline string) {
    var errBuff bytes.Buffer
    var outBuff bytes.Buffer
    cmd := exec.Command("/bin/bash", "-c", cmdline)
    cmd.Stderr = &errBuff
    cmd.Stdout = &outBuff
    log.Printf("Executing: " + cmdline)
    err := cmd.Run()
    log.Printf("Command finished with error: %v", err)
    log.Printf("Std Out: %s", outBuff.String())
    log.Printf("Std Err: %s", errBuff.String())
}

func getNDay(hour int, min int, offset int) time.Time {
    today := time.Now()
    nextDate := time.Date(today.Year(), today.Month(), today.Day() + offset, hour, min, 0, 0, today.Location())
    return nextDate
}

func getDir(path string, filter string) ([]string, []time.Time) {
    var names []string
    var dates []time.Time

    files, err := ioutil.ReadDir(path)
    if err != nil {
        log.Fatal(err)
    }

    for _, file := range files {
        if strings.Contains(file.Name(), filter) {
            name := file.Name()
            timeNow := time.Now()
            workingDateStr := name[len(filter)+1:len(name)]
            workingDate, err := time.Parse("2006-01-02", workingDateStr)
            workingDate = time.Date(workingDate.Year(), workingDate.Month(), workingDate.Day(), 0, 0, 0, 0, timeNow.Location())
            if err!= nil {
                log.Println(err)
            } else {
                name = path + "/" + file.Name()
                names = append(names, name)
                dates = append(dates, workingDate)
                log.Printf("%v found\n", workingDate)
            }
        }
    }

    log.Printf("%s: %v\n", path, dates)
    return names, dates
}

func backupToday(timeToday time.Time, config Config, host Host) {
    dirDateStr := fmt.Sprintf("%04d-%02d-%02d", timeToday.Year(), timeToday.Month(), timeToday.Day())
    dirCommand := fmt.Sprintf("mkdir \"%s/%s-%s\"", config.WorkingDir, host.Name, dirDateStr)
    runCommand(dirCommand)

    log.Printf("Current Host: %s", host.Name)
    dateStr := fmt.Sprintf("%04d-%02d-%02d", timeToday.Year(), timeToday.Month(), timeToday.Day())
    command := fmt.Sprintf("rsync -azvhe \"ssh -i %s -p %d\" %s@%s:\"%s\" \"%s/%s-%s/\"",
        host.PrivKey, host.Port, host.Username, host.IPAddr, host.RemoteDir, config.WorkingDir, host.Name, dateStr)
    runCommand(command)
}

func findBackupDate(dates []time.Time, findDate time.Time) int {
    for i, date := range(dates) {
        if date == findDate {
            log.Printf("%v found", date)
            return i
        }
    }
    log.Printf("%v not found", findDate)
    return 0
}

func enumerateDates(dates []time.Time, currDate time.Time, searchDayNum int) bool {
    for i:=1; i<=searchDayNum; i++ {
        for _, date := range(dates) {
            if currDate.Add(-time.Hour * time.Duration(24 * i)) == date {
                log.Printf("Existing backup exists at %v\n", date)
                return true
            }
        }
    }
    return false
}

func main() {
    ex, err := os.Executable()
    if err != nil {
        panic(err)
    }
    exPath := filepath.Dir(ex)

    config := loadConfig(exPath + "/" + configFile)
    logFile, err := os.OpenFile(config.WorkingDir + "backup.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
    if err != nil {
        log.Println(err)
    }
    defer logFile.Close()
    log.SetOutput(logFile)
    for true {
        timeNow := time.Now()
        timeToday := time.Date(timeNow.Year(), timeNow.Month(), timeNow.Day(), 0, 0, 0, 0, timeNow.Location())
        log.Printf("New Date: %v", timeToday)
        var workingTime time.Time
        for _, host := range config.Hosts {
            log.Printf("New Host: %s", host.Name)
            // creating backup for today
            backupToday(timeToday, config, host)

            // go through each interval for deletion
            workingTime = timeToday
            filePaths, fileDates := getDir(config.WorkingDir, host.Name)
            for i, backupPeriod := range(config.BackupPeriods) {
                // get to the time
                if err != nil {
                    fmt.Println(err)
                }
                workingTime = workingTime.Add(-time.Duration(backupPeriod.Interval * backupPeriod.Count) * 24 * time.Hour)
                log.Printf("Working time: %v\n", workingTime)

                // check if file exists
                workingFileCount := findBackupDate(fileDates, workingTime)

                // file exist...
                if workingFileCount != 0 {
                    // if there's a copy out there within interval...
                    if i+1 == len(config.BackupPeriods) || enumerateDates(fileDates, workingTime, config.BackupPeriods[i+1].Interval) {
                        // delete it
                        removeCommand := fmt.Sprintf("rm -rf \"%s\"", filePaths[workingFileCount])
                        runCommand(removeCommand)
                    }
                }
            }

            log.Printf("Final working time: %v", workingTime)
            // delete the rest
            for i, date := range(fileDates) {
                if date.Before(workingTime) {
                    removeCommand := fmt.Sprintf("rm -rf \"%s\"", filePaths[i])
                    runCommand(removeCommand)
                }
            }

            // deleteDate := getNDay(0, 0, -1 * config.MaxRecords)
            // deleteDateStr := fmt.Sprintf("%04d-%02d-%02d", deleteDate.Year(), deleteDate.Month(), deleteDate.Day())
            // removeCommand := fmt.Sprintf("rm -rf \"%s/%s-%s\"", config.WorkingDir, host.Name, deleteDateStr)
            // runCommand(removeCommand)
        }
        nextDay := getNDay(config.TimeHour, config.TimeMinute, 1)
        log.Printf("Sleeping until: %v", nextDay)
        time.Sleep(time.Until(nextDay))
    }
}