#!/bin/sh

## SPDX-FileCopyrightText: 2023 Benjamin Grande M. S. <ben.grande.b@gmail.com>
##
## SPDX-License-Identifier: AGPL-3.0-or-later

set -eu

command -v tmux >/dev/null || exit 1
: "${TMUX:=}"
ta_session="${1:-}"

## Attach to session if it exists or not and from inside tmux or not.
## If name is supplied and doesn't exist, create session with given name.
## If no name is supplied and there is last session, switch client to it,
## else ask for the user to choose the wanted session.
## usage: ta SESSION ARGS
## example: ta dotfiles -d
ta_new(){
  ## Session name was not specified.
  ta_list="$(tmux list-sessions 2>/dev/null)"

  printf "Choose session or create one by providing a new name:\n"
  if test -n "$ta_list"; then
    printf %s"\n${ta_list}\n"
  fi

  printf "\nEnter session name: "
  read -r ta_name

  if test -z "$ta_name"; then
    printf "Name cannot be empty.\n"
    return 1
  fi
}

main(){
  if test -n "$TMUX"; then
    ## Inside tmux.
    if test -n "$ta_session" && tmux has-session -t "$ta_session" >/dev/null 2>&1; then
      ## Session name was specified and it exists.
      tmux switch-client -t "$ta_session"
      tmux display-message "Switched to session $ta_session"

    elif test -n "$ta_session"; then
      ## Session name was specified but it doesn't exist.
      tmux new-session -d -s "$ta_session"
      tmux switch-client -t "$ta_session"
      tmux display-message "Created and switched to session $ta_session"

    else

      ## Session name was not specified.
      ta_last="$(tmux display-message -p "#{client_last_session}")"
      if test -n "$ta_last" && tmux has-session -t "$ta_last"; then
        ## If tmux has a last session, use it.
        tmux switch-client -t "$ta_last"
        tmux display-message "Switched to session $ta_last"

      else

        ## No last session, choose one or create one.
        printf "Last session not found.\n"
        ta_new || return 1

        if tmux has-session -t "$ta_name" 2>/dev/null; then
          ## Chosen session exists.
          tmux switch-client -t "$ta_name"
          tmux display-message "Switched to session $ta_name"

        else
          ## Chosen session doesn't exist.
          tmux new-session -d -s "$ta_name"
          tmux switch-client -t "$ta_name"
          tmux display-message "Created and switched to session $ta_name"
        fi
      fi
    fi
  else

    ## Outside of tmux.
    if test -n "$ta_session" && ! tmux list-sessions >/dev/null 2>&1; then
      ## Session name was specified but server is not running.
      tmux new-session -s "$ta_session"
      tmux display-message "Created session $ta_session"
      return 0

    elif ! tmux list-sessions >/dev/null 2>&1; then
      ## Server is not running.
      ta_new || return 1
      tmux new-session -s "$ta_name"
      tmux display-message "Created session $ta_name"
      return 0
    fi

    if test -n "$ta_session" && tmux has-session -t "$ta_session" >/dev/null 2>&1; then
      ## Session name was specified and it exists.
      tmux attach-session -t "$ta_session"
      tmux display-message "Attached to session $ta_session"

    elif test -n "$ta_session"; then
      ## Session name was specified but it doesn't exist.
      tmux new-session -s "$ta_session"
      tmux display-message "Created new session $ta_session"

    else
      ## Session name was not specified.
      ta_last="$(tmux display-message -p "#{session_name}")"

      if test -n "$ta_last" && tmux has-session -t "$ta_last"; then
        ## If tmux has a session name, use it.
        tmux attach-session -t "$ta_last"
        tmux display-message "Attached to session $ta_last"

      else
        ta_new || return 1

        if tmux has-session -t "$ta_name" 2>/dev/null; then
          ## Chosen session exists.
          tmux attach-session -t "$ta_name"
          tmux display-message "Attached to session $ta_name"

        else
          ## Chosen session doesn't exist.
          tmux new-session -s "$ta_name"
          tmux display-message "Created session $ta_name"
        fi
      fi
    fi
  fi
}

main "$@"