// Learn more about F# at http://fsharp.org
//
//   - backup file list
//     /%appdata%/mbackup/mbackup-default.list
//     /%appdata%/mbackup/user-default.list
//     /%appdata%/mbackup/local.list (optional)
//   - exclude pattern
//     /%appdata%/mbackup/mbackup-default.exclude
//     /%appdata%/mbackup/local.exclude (optional)

module Mbackup.Program

open System
open System.IO
open System.Diagnostics
open System.Text.RegularExpressions
open System.Diagnostics.CodeAnalysis

open Argu

open Mbackup.Lib
open Mbackup.ConfigParser

let ExitBadParam = 1
let ExitTimeout = 2
let ExitIOError = 3

[<SuppressMessage("*", "UnionCasesNames")>]
type CLIArguments =
    | [<AltCommandLine("-n")>] Dry_Run
    | Target of backupTarget: string
    | Remote_User of remoteUser: string
    | [<AltCommandLine("-i")>] Itemize_Changes
    | Node_Name of nodeName: string
    | Ssh_Key of sshKeyFilename: string
with
    interface IArgParserTemplate with
        member s.Usage =
            match s with
            | Dry_Run _ -> "only show what will be done, do not transfer any file"
            | Target _ -> "rsync target, could be local dir in Windows or mingw format or remote ssh dir"
            | Remote_User _ -> "remote linux user to own the backup files"
            | Itemize_Changes _ -> "add -i option to rsync"
            | Node_Name _ -> "local node's name, used in remote logging"
            | Ssh_Key _ -> "ssh private key, used when backup to remote ssh node"

let appDataRoamingDir = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) |> toMingwPath |> ensureDir
let programDataDirWin = getEnv "PROGRAMDATA" |> ensureWinDir
let programDataDir = toMingwPath programDataDirWin
let appDataLocalDirWin =  Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData) |> ensureWinDir
let appDataLocalDir =  appDataLocalDirWin |> toMingwPath

let mbackupInstallDirWin = Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles) |> ensureDir |> fun s -> s + "mbackup"
let mbackupInstallDir = mbackupInstallDirWin |> toMingwPath

let userHomeWin =
  getEnvDefault "HOME" (Environment.GetFolderPath(Environment.SpecialFolder.UserProfile))
  |> ensureWinDir

let userHome = userHomeWin |> toMingwPath

let userConfigDirWin = programDataDirWin + "mbackup\\"
let userConfigDir = programDataDir + "mbackup/"
let runtimeDirWin = appDataLocalDirWin + "mbackup\\"
let runtimeDir = appDataLocalDir + "mbackup/"

let mbackupConfigFile = userConfigDirWin + "mbackup.txt"

// return true if target is a local dir. local dir can be unix style or windows style.
let isLocalTarget (target: string) =
  target.StartsWith "/" || Regex.IsMatch(target, "^[c-z]:", RegexOptions.IgnoreCase)

// expand user file to mingw64 rsync supported path.
// abc -> /cygdrive/c/Users/<user>/abc
// ^Documents -> expand to Documents path.
// ^Downloads -> expand to Downloads path.
// etc
let expandUserFile (fn: string) =
  let fn =
    let documentsDir = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) |> toMingwPath |> ensureDir
    let picturesDir = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures) |> toMingwPath |> ensureDir
    let desktopDir = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) |> toMingwPath |> ensureDir
    let fn = Regex.Replace(fn, "^My Documents/", documentsDir, RegexOptions.IgnoreCase)
    let fn = Regex.Replace(fn, "^Documents/", documentsDir, RegexOptions.IgnoreCase)
    let fn = Regex.Replace(fn, "^我的文档/", documentsDir)
    let fn = Regex.Replace(fn, "^文档/", documentsDir)
    let fn = Regex.Replace(fn, "^My Pictures/", picturesDir, RegexOptions.IgnoreCase)
    let fn = Regex.Replace(fn, "^Pictures/", picturesDir, RegexOptions.IgnoreCase)
    let fn = Regex.Replace(fn, "^图片/", picturesDir)
    let fn = Regex.Replace(fn, "^Desktop/", desktopDir, RegexOptions.IgnoreCase)
    let fn = Regex.Replace(fn, "^桌面/", desktopDir)
    fn
  if fn.StartsWith("/") then
    fn
  else
    userHome + fn

// generate mbackup.list file
let generateMbackupList (logger: Logger) =
    // TODO how to only regenerate if source file have changed? should I bundle GNU make with mbackup?
    // just compare mbackup.list mtime with its source files?
    let mbackupDefaultList = userConfigDirWin + "mbackup-default.list"
    let mbackupLocalList = userConfigDirWin + "local.list"
    let mbackupUserDefaultList = userConfigDirWin + "user-default.list"
    let mbackupList = runtimeDirWin + "mbackup.list"

    // local functions
    let dropEmptyLinesAndComments lines = Seq.filter (fun (line: string) -> not (line.TrimStart().StartsWith("#") || line.TrimEnd().Equals(""))) lines
    let readMbackupListFile fn = File.ReadAllLines(fn) |> dropEmptyLinesAndComments

    try
      let defaultListLines = readMbackupListFile mbackupDefaultList |> Seq.map toMingwPath
      let localListLinesMaybe =
        try
          let lines = readMbackupListFile mbackupLocalList |> Seq.map toMingwPath
          (true, lines)
        with
        | :? System.IO.FileNotFoundException ->
          (true, Seq.empty)
        | ex ->
          logger.Error "Read mbackupLocalList failed: %s" ex.Message
          (false, Seq.empty)
      match localListLinesMaybe with
      | (false, _) -> failwith "Read mbackup local.list file failed"
      | (true, localListLines) ->
        let userDefaultListLines = readMbackupListFile mbackupUserDefaultList |> Seq.map expandUserFile
        let allLines = Seq.append (Seq.append defaultListLines localListLines) userDefaultListLines
        // For mbackup-default.list and local.list, exclude empty lines and comment lines.
        // skip and give a warning on non-absolute path.
        // For user-default.list, auto prefix user's home dir, auto expand Documents, Downloads etc special folder.
        File.WriteAllLines(mbackupList, allLines)
        logger.Info "mbackup.list file written: %s" mbackupList
        true
    with
    | :? System.IO.IOException as ex ->
      logger.Error "Read/write file failed: %s %s" ex.Source ex.Message
      false
    | ex ->
      logger.Error "Read/write mbackup list file failed: %s" ex.Message
      false

[<EntryPoint>]
let main argv =
    let errorHandler = ProcessExiter(colorizer = function ErrorCode.HelpText -> None | _ -> Some ConsoleColor.Red)
    let parser = ArgumentParser.Create<CLIArguments>(programName = "mbackup.exe", errorHandler = errorHandler)
    let results = parser.Parse argv
    let dryRun = results.Contains Dry_Run
    let itemizeChanges = results.Contains Itemize_Changes

    let logger = Logger()

    logger.Info "user config dir: %s" userConfigDirWin
    logger.Info "runtime dir: %s" runtimeDirWin

    let rsyncCmd: string list = []
    let rsyncCmd = appendWhen dryRun rsyncCmd "--dry-run"
    let rsyncCmd = appendWhen itemizeChanges rsyncCmd "-i"
    let rsyncCmd = List.append rsyncCmd ("-h --stats -togr --delete --delete-excluded --ignore-missing-args".Split [|' '|] |> Array.toList)

    let mbackupFile = runtimeDir + "mbackup.list"
    if not (generateMbackupList logger) then
      failwith "Generate mbackup.list failed"
    let rsyncCmd = List.append rsyncCmd [sprintf "--files-from=%s" mbackupFile]

    let excludeFile = userConfigDir + "mbackup-default.exclude"
    let rsyncCmd = List.append rsyncCmd [sprintf "--exclude-from=%s" excludeFile]
    let localExcludeFile = userConfigDir + "local.exclude"
    let rsyncCmd = appendWhen (IO.File.Exists localExcludeFile) rsyncCmd (sprintf "--exclude-from=%s" localExcludeFile)

    let localLogFile = runtimeDir + "mbackup.log"
    let rsyncCmd = List.append rsyncCmd [sprintf "--log-file=%s" localLogFile]

    // TODO remove usage of test dir.
    let mbackupInstallDirWinTest = "D:\\downloads\\apps\\mbackupTest\\"
    let mbackupInstallDirTest = mbackupInstallDirWinTest |> toMingwPath |> ensureDir
    let sshExeFile = mbackupInstallDirTest + "rsync-w64/usr/bin/ssh.exe"
    let sshConfigFile = userHome + ".ssh/config"
    let sshPrivateKeyFile = results.GetResult(Ssh_Key, defaultValue = userHome + ".ssh/id_rsa") |> toMingwPath
    let rsyncCmd = List.append rsyncCmd [sprintf "-e \"%s -F %s -i %s -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null\"" sshExeFile sshConfigFile sshPrivateKeyFile]

    // precedence: command line argument > environment variable > config file
    let normalizeTarget target =
        if isLocalTarget target then
            toMingwPath target
        else
            target
    let backupTargetMaybe =
        match results.TryGetResult Target with
        | None ->
            let mbackupConfig = WellsConfig(mbackupConfigFile)
            let backupTargetMaybe = mbackupConfig.GetStr("target")
            Option.map normalizeTarget backupTargetMaybe
        | Some backupTarget ->
            Some (normalizeTarget backupTarget)
    match backupTargetMaybe with
    | None ->
        logger.Error "TARGET is not defined"
        ExitBadParam
    | Some backupTarget ->
        let rsyncCmd =
          if not (isLocalTarget backupTarget)
            then
              let nodeName = results.GetResult(Node_Name, defaultValue = Net.Dns.GetHostName())
              let remoteLogFile = sprintf "/var/log/mbackup/%s.log" nodeName
              let remoteUser = results.GetResult (Remote_User, defaultValue = Environment.UserName)
              let rsyncCmd = List.append rsyncCmd [sprintf "--remote-option=--log-file=%s" remoteLogFile]
              let rsyncCmd = List.append rsyncCmd [sprintf "--chown=%s:%s" remoteUser remoteUser]
              rsyncCmd
            else
              rsyncCmd
        let rsyncCmd = List.append rsyncCmd ["/"]
        let rsyncCmd = List.append rsyncCmd [backupTarget]
        let rsyncArgs = rsyncCmd |> String.concat " "
        let rsyncExe = mbackupInstallDirWinTest + "rsync-w64\\usr\\bin\\rsync.exe"
        let echoExe = "C:\\Program Files\\Git\\usr\\bin\\echo.exe"
        try
          IO.Directory.CreateDirectory(runtimeDir) |> ignore
          IO.Directory.CreateDirectory(userConfigDir) |> ignore
          let proc = Process.Start(rsyncExe, rsyncArgs)
          logger.Info "Note: if you run the following rsync command yourself, make sure the generated file list (%s) is up-to-date.\n%s" mbackupFile (rsyncExe + " " + rsyncArgs)
          if proc.WaitForExit Int32.MaxValue then
            logger.Info "mbackup exit"
            proc.ExitCode
          else
            logger.Error "mbackup timed out while waiting for rsync to complete"
            ExitTimeout
        with
        | :? System.IO.IOException as ex ->
          logger.Error "IO Error: %s %s" ex.Source ex.Message
          ExitIOError
        | ex ->
          logger.Error "Unexpected Error: %s" ex.Message
          ExitIOError