require "cli/parser"
require "open-uri"
require "resource"
require "formula"

module Homebrew
  module_function

  def postgresql_upgrade_database_args
    Homebrew::CLI::Parser.new do
      usage_banner <<~EOS
        `postgresql-upgrade-database`

        Upgrades the database for the `postgresql` formula.
      EOS
    end
  end

  def postgresql_upgrade_database
    postgresql_upgrade_database_args.parse

    name = "postgresql"
    pg = Formula[name]
    bin = pg.bin
    var = pg.var
    version = pg.version
    pg_version_file = var/"postgres/PG_VERSION"

    pg_version_installed = version.to_s[/^\d+/]
    pg_version_data = pg_version_file.read.chomp
    if pg_version_installed == pg_version_data
      odie <<~EOS
        #{name} data already upgraded!
      EOS
    end

    datadir = var/"postgres"
    old_datadir = var/"postgres.old"
    if old_datadir.exist?
      odie <<~EOS
        #{old_datadir} already exists!
        Remove it if you want to upgrade data automatically.
      EOS
    end

    old_pg_name = "#{name}@#{pg_version_data}"
    old_pg_glob = "#{HOMEBREW_PREFIX}/Cellar/#{old_pg_name}/#{pg_version_data}.*/bin"
    old_bin = Pathname.glob(old_pg_glob).first
    old_bin ||= begin
      Formula[old_pg_name]
      ohai "brew install #{old_pg_name}"
      system "brew", "install", old_pg_name
      Pathname.glob(old_pg_glob).first
    rescue FormulaUnavailableError
      nil
    end

    odie "No #{name} #{pg_version_data}.* version installed!" unless old_bin

    server_stopped = false
    moved_data = false
    initdb_run = false
    upgraded = false

    begin
      # Following instructions from:
      # https://www.postgresql.org/docs/10/static/pgupgrade.html
      ohai "Upgrading #{name} data from #{pg_version_data} to #{pg_version_installed}..."

      if /#{name}\s+started/.match?(Utils.popen_read("brew", "services", "list"))
        system "brew", "services", "stop", name
        service_stopped = true
      elsif quiet_system "#{bin}/pg_ctl", "-D", datadir, "status"
        system "#{bin}/pg_ctl", "-D", datadir, "stop"
        server_stopped = true
      end

      # Shut down old server if it is up via brew services
      if /#{old_pg_name}\s+started/.match?(Utils.popen_read("brew", "services", "list"))
        system "brew", "services", "stop", old_pg_name
      end

      # get 'lc_collate' from old DB"
      unless quiet_system "#{old_bin}/pg_ctl", "-w", "-D", datadir, "status"
        system "#{old_bin}/pg_ctl", "-w", "-D", datadir, "start"
      end

      initdb_args = []
      locale_settings = %w[
        lc_collate
        lc_ctype
        lc_messages
        lc_monetary
        lc_numeric
        lc_time
        server_encoding
      ]
      locale_settings.each do |setting|
        sql = "SELECT setting FROM pg_settings WHERE name LIKE '#{setting}';"
        value = Utils.popen_read("#{old_bin}/psql", "postgres", "-qtAX", "-U", ENV["USER"], "-c", sql).strip

        next if value.empty?

        if setting == "server_encoding"
          initdb_args += ["-E #{value}"]
        else
          initdb_args += ["--#{setting.tr!("_", "-")}=#{value}"]
        end
      end

      if quiet_system "#{old_bin}/pg_ctl", "-w", "-D", datadir, "status"
        system "#{old_bin}/pg_ctl", "-w", "-D", datadir, "stop"
      end

      ohai "Moving #{name} data from #{datadir} to #{old_datadir}..."
      FileUtils.mv datadir, old_datadir
      moved_data = true

      (var/"postgres").mkpath
      ohai "Creating database..."
      safe_system "#{bin}/initdb", *initdb_args, "#{var}/postgres"
      initdb_run = true

      ohai "Migrating and upgrading data..."
      (var/"log").cd do
        safe_system "#{bin}/pg_upgrade",
          "-r",
          "-b", old_bin,
          "-B", bin,
          "-d", old_datadir,
          "-D", datadir,
          "-j", Hardware::CPU.cores.to_s
      end
      upgraded = true

      ohai "Upgraded #{name} data from #{pg_version_data} to #{pg_version_installed}!"
      ohai "Your #{name} #{pg_version_data} data remains at #{old_datadir}"
    ensure
      if upgraded
        if server_stopped
          safe_system "#{bin}/pg_ctl", "-D", datadir, "start"
        elsif service_stopped
          safe_system "brew", "services", "start", name
        end
      else
        onoe "Upgrading #{name} data from #{pg_version_data} to #{pg_version_installed} failed!"
        if initdb_run
          ohai "Removing empty #{name} initdb database..."
          FileUtils.rm_r datadir
        end
        if moved_data
          ohai "Moving #{name} data back from #{old_datadir} to #{datadir}..."
          FileUtils.mv old_datadir, datadir
        end
        if server_stopped
          system "#{bin}/pg_ctl", "-D", datadir, "start"
        elsif service_stopped
          system "brew", "services", "start", name
        end
      end
    end
  end
end