defmodule Mix.Tasks.Version.Bin.Db do
  use Mix.Task

  @shortdoc "Create 'rel/commands' helper scripts for managing database backup / restore"
  def run([]), do: run([nil, nil])
  def run([backup_root]), do: run([backup_root, nil])
  def run([backup_root, dbname]) do

    [
      "./rel/commands",
    ]
    |> Enum.each(fn dirname ->
         :ok = dirname |> Path.expand |> File.mkdir_p!
       end)

    appname = Mix.Project.config[:app]
    default_root = "/src/#{appname}backup"
    backup_root = backup_root || default_root
    dbname = dbname || appname

    """
    #!/bin/bash

    NOW=${NOW:=$(date +"%Y%m%d%H%M%S")}
    VERSION=${VERSION:=$(mix version.current)}
    DBNAME=#{dbname}
    BACKUP_ROOT=#{backup_root}
    FNAME=${DBNAME}_${VERSION}_${NOW}

    (cd ${BACKUP_ROOT} && \\
     pg_dump --clean ${DBNAME} > ${FNAME}.sql && \\
     tar zcf ${FNAME}.tar.gz ${FNAME}.sql && \\
     ln -sf ${FNAME}.tar.gz ${DBNAME}_${VERSION}.tar.gz && \\
     ln -sf ${FNAME}.tar.gz ${DBNAME}.tar.gz && \\
     git add . && \\
     git commit -m "Backup ${DBNAME} v${VERSION} (${NOW})" && \\
     git push)
    """
    |> write!("./rel/commands/backup")

    """
    #!/bin/bash

    DBNAME=#{dbname}
    BACKUP_ROOT=#{backup_root}

    (cd ${BACKUP_ROOT} && \\
     psql -d ${DBNAME} -f $(tar zxfv ${DBNAME}.tar.gz))
    """
    |> write!("./rel/commands/restore")


    [
      "./rel/commands/backup",
      "./rel/commands/restore",
    ]
    |> Enum.each(fn filename ->
         :ok = filename
               |> Path.expand
               |> File.chmod(0o755)
       end)

    IO.puts "Installed the following scripts into ./rel/commands"
    IO.puts "   + backup     \# Backup your database (named #{appname})"
    IO.puts "   + restore    \# Restore your database (named #{appname})"
    IO.puts ""

    IO.puts "To enable those to be part of the release,"
    IO.puts "then ensure you update your ./rel/config.exs with:"
    IO.puts ""

    example = """
    release :#{appname} do
      ...
      set commands: [
        "backup": "rel/commands/backup"
        "restore": "rel/commands/restore"
      ]
    end
    """

    IO.puts example
    IO.puts ""

  end

  defp write!(content, relative_name) do
    File.write!(relative_name |> Path.expand, content)
  end

end