#!/bin/bash
#
# cheatsheet_viewer.sh
#
# Copyright (C) 2025, Branko Majic <branko@majic.rs>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

# Treat unset variables as errors.
set -u

PROGRAM="cheatsheet_viewer.sh"
VERSION="0.0.1"

function usage() {
    cat <<EOF
$PROGRAM $VERSION, simple utility for viewing image cheatsheets

Usage:
  $PROGRAM [OPTIONS] list
  $PROGRAM [OPTIONS] info PROFILE
  $PROGRAM [OPTIONS] display [PROFILE]
  $PROGRAM [OPTIONS] toggle [PROFILE]
EOF
}

function short_help() {
    cat <<EOF
$(usage)

For more details see $PROGRAM -h.
EOF
}

function long_help() {
    cat <<EOF
$(usage)

$PROGRAM is a simple utility for viewing image cheatsheets with
support for multiple profiles.

Cheatsheets are shown using the pqiv image viewer.

All configuration is stored under user's own home directory at:

  - ~/.config/cheatsheet_viewer/

Individual profiles are stored as sub-directories, with each
sub-directory representing an individual profile that can be
activated. Base directory for profiles is:

  - ~/.config/cheatsheet_viewer/profiles/

Each profile definition consists out of a number of configuration
files:

  - ~/.config/cheatsheet_viewer/profiles/PROFILE/cheatsheets (list of
    cheatsheet files, one per line, blank lines are ignored, lines
    starting with '#' are ignored)
  - ~/.config/cheatsheet_viewer/profiles/PROFILE/overlay (list of
    window titles for which to automatically apply the overlay mode)

Multiple commands are provided for working with the profiles and
displaying the cheatsheets.

list

  Lists the available profiles.

info PROFILE

  Arguments:

    PROFILE (profile name)

  Shows detailed information about user-specified profile, such as
  list of defined cheatsheets etc.

display [PROFILE]

  Arguments:

    PROFILE (profile name)

  Displays cheatsheets from the specified profile (default profile
  name is 'default').

toggle [PROFILE]

  Arguments:

    PROFILE (profile name)

  Toggles display of cheatsheets from the specified profile (default
  profile name is 'default'). Unlike the display command, the toggle
  command is more intelligent and ensures that only one instance of
  cheatsheet-specific pqiv is present. Thex toggle command also keeps
  track of which cheatsheet was last selected, and will update the
  image viewer to point to it when opened.

$PROGRAM accepts the following options:

    -o
        Display cheatsheets in "overlay" mode, keeping the current
        window in focus, and making the cheatsheet window
        always-on-top. Useful when playing games and similar. The
        cheatsheet window can still be focused using keyboard and
        mouse-clicks.
    -q
        Quiet mode.
    -d
        Enable debug mode.
    -v
        Show script version and licensing information.
    -h
        Show full help.

Please report bugs and send feature requests to <branko@majic.rs>.
EOF
}

function version() {
    cat <<EOF
$PROGRAM, version $VERSION

+-----------------------------------------------------------------------+
| Copyright (C) 2025, Branko Majic <branko@majic.rs>                    |
|                                                                       |
| This program is free software: you can redistribute it and/or modify  |
| it under the terms of the GNU General Public License as published by  |
| the Free Software Foundation, either version 3 of the License, or     |
| (at your option) any later version.                                   |
|                                                                       |
| This program is distributed in the hope that it will be useful,       |
| but WITHOUT ANY WARRANTY; without even the implied warranty of        |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         |
| GNU General Public License for more details.                          |
|                                                                       |
| You should have received a copy of the GNU General Public License     |
| along with this program.  If not, see <http://www.gnu.org/licenses/>. |
+-----------------------------------------------------------------------+

EOF
}


# Commands
# ========

#
# Lists available profiles.
#
# Arguments:
#
#   $1 (config_dir)
#     Base directory under which all configuration files are stored.
#
# Returns:
#   0 on success, 1 otherwise.
#
function command_list() {
    local config_dir="$1"
    local profiles_dir="$config_dir/profiles"

    shopt -s nullglob
    local profiles=("$profiles_dir"/*)
    shopt -u nullglob

    if (( ${#profiles[@]} == 0 )); then
        echo "No profiles defined under $profiles_dir"
        return 0
    fi

    echo "Available profiles:"
    echo
    for profile in "${profiles[@]}"; do
        echo "  - $(basename "$profile")"
    done
}


#
# Displays profile information.
#
# Arguments:
#
#   $1 (config_dir)
#     Base directory under which all configuration files are stored.
#
#   $2 (profile)
#     Profile name.
#
# Returns:
#   0 on success, 1 otherwise.
#
function command_info() {
    local config_dir="$1"
    local profile="$2"

    local profile_dir="$config_dir/profiles/$profile"
    local cheatsheets_file="$profile_dir/cheatsheets"

    local cheatsheets=()

    if [[ ! -d $profile_dir ]]; then
        error "No such profile found under $profile_dir"
        return 1
    fi

    if [[ -e $cheatsheets_file ]]; then
        readarray -t cheatsheets < <(grep --invert-match --extended-regexp "(^[[:blank:]]*#|^[[:blank:]]*$)" "$cheatsheets_file")
    fi

    echo "Profile $profile"
    echo "========${profile//?/=}"
    echo
    echo "Base directory:   $profile_dir"
    echo "Cheatsheets list: $cheatsheets_file"
    echo

    if (( ${#cheatsheets[@]} == 0 )); then
        echo "No configured cheatsheets."
    else
        echo "Configured cheatsheets:"
        echo
        for cheatsheet in "${cheatsheets[@]}"; do
            echo "  - $cheatsheet"
        done
    fi
}


#
# Displays configured cheatsheets from a profile.
#
# Arguments:
#
#   $1 (config_dir)
#     Base directory under which all configuration files are stored.
#
#   $2 (profile)
#     Profile name.
#
#   $3 (overlay_mode)
#     Specify if cheatsheets should be shown in overlay mode.
#
# Returns:
#   0 on success, 1 otherwise.
#
function command_display() {
    local config_dir="$1"
    local profile="$2"
    local overlay_mode="$3"

    local profile_dir="$config_dir/profiles/$profile"
    local cheatsheets_file="$profile_dir/cheatsheets"
    local overlay_limits_file="$profile_dir/overlay"

    local caller_window_id caller_window_title window_title

    local cheatsheets=()
    local -A overlay_limits

    if [[ ! -d $profile_dir ]]; then
        error "No such profile found under $profile_dir"
        return 1
    fi

    if [[ -e $cheatsheets_file ]]; then
        readarray -t cheatsheets < <(grep --invert-match --extended-regexp "(^[[:blank:]]*#|^[[:blank:]]*$)" "$cheatsheets_file")
    fi

    if (( overlay_mode )); then
        overlay_limits[_ALL_]=1
    elif [[ -e $overlay_limits_file ]]; then
        while read -r window_title; do
            if [[ -n $window_title ]]; then
                overlay_limits[$window_title]=1
            fi
        done < <(grep --invert-match --extended-regexp "(^[[:blank:]]*#|^[[:blank:]]*$)" "$overlay_limits_file")
    else
        # Means that cheatsheets are not shown as overlays. Assignment
        # introduced to avoid unbound variable errors in checks.
        overlay_limits[_DISABLED_]=1
    fi

    if (( ${#cheatsheets[@]} == 0 )); then
        warning "No cheatsheets are defined under $cheatsheets_file"
        return 0
    fi

    if (( ! overlay_limits[_DISABLED_] )); then
        caller_window_id=$(xprop -root | grep '^_NET_ACTIVE_WINDOW(WINDOW)' | sed -e 's/.*window id # //')
        caller_window_title=$(xprop -id "$caller_window_id" _NET_WM_NAME | sed -Ee 's/^[^=]+ = "//;s/"$//')
    fi

    local pqiv_options=(
        "--scale-mode-screen-fraction=1.0"
        "--zoom-level=1.0"
        "--transparent-background"
        "--hide-info-box"
        "--window-title=cheatsheet-viewer-$profile"
    )

    pqiv "${pqiv_options[@]}" "${cheatsheets[@]}" &

    # The ${caller_window_title-_} is used to avoid invalid array subscript.
    if (( overlay_limits[_ALL_] || overlay_limits[${caller_window_title-_}] )); then
        local counter=0
        while (( counter < 10 )) && ! wmctrl -l | grep -q "cheatsheet-viewer-$profile"; do
            sleep 0.05
            (( counter+=1 ))
        done

        wmctrl -F -r "cheatsheet-viewer-$profile" -b add,above
        wmctrl -i -a "$caller_window_id"
    fi
}


#
# Toggles display of configured cheatsheets from a profile.
#
# Arguments:
#
#   $1 (config_dir)
#     Base directory under which all configuration files are stored.
#
#   $2 (profile)
#     Profile name.
#
#   $3 (overlay_mode)
#     Specify if cheatsheets should be shown in overlay mode.
#
# Returns:
#   0 on success, 1 otherwise.
#
function command_toggle() {
    local config_dir="$1"
    local profile="$2"
    local overlay_mode="$3"

    local profile_dir="$config_dir/profiles/$profile"
    local cheatsheets_file="$profile_dir/cheatsheets"
    local last_cheatsheet_file="$profile_dir/last"
    local overlay_limits_file="$profile_dir/overlay"

    local current_process_id current_profile last_cheatsheet caller_window_id caller_window_title window_title

    local cheatsheets=()
    local -A overlay_limits

    if [[ ! -d $profile_dir ]]; then
        error "No such profile found under $profile_dir"
        return 1
    fi

    if [[ -e $cheatsheets_file ]]; then
        readarray -t cheatsheets < <(grep --invert-match --extended-regexp "(^[[:blank:]]*#|^[[:blank:]]*$)" "$cheatsheets_file")
    fi

    if (( overlay_mode )); then
        overlay_limits[_ALL_]=1
    elif [[ -e $overlay_limits_file ]]; then
        while read -r window_title; do
            if [[ -n $window_title ]]; then
                overlay_limits[$window_title]=1
            fi
        done < <(grep --invert-match --extended-regexp "(^[[:blank:]]*#|^[[:blank:]]*$)" "$overlay_limits_file")
    else
        # Means that cheatsheets are not shown as overlays. Assignment
        # introduced to avoid unbound variable errors in checks.
        overlay_limits[_DISABLED_]=1
    fi

    if (( ${#cheatsheets[@]} == 0 )); then
        warning "No cheatsheets are defined under $cheatsheets_file"
        return 0
    fi

    if [[ -e $last_cheatsheet_file ]]; then
        last_cheatsheet=$(< "$last_cheatsheet_file")
    else
        last_cheatsheet=""
    fi

    # Get information about existing running cheatsheet viewer pqiv instance (if any).
    current_process_id=$(wmctrl -lp | grep 'cheatsheet-viewer-' | awk '{print $3}')
    current_profile=$(wmctrl -lp | grep 'cheatsheet-viewer-' | awk '{print $5}' | sed -e 's/cheatsheet-viewer-//')

    # Kill off the existing running process.
    if [[ -n $current_process_id ]]; then
        kill "$current_process_id"
    fi

    # If requested profile is not the same as current one, we want to
    # show cheatsheets from requested profile.
    if [[ $current_profile != "$profile" ]]; then
        if (( ! overlay_limits[_DISABLED_] )); then
            caller_window_id=$(xprop -root | grep '^_NET_ACTIVE_WINDOW(WINDOW)' | sed -e 's/.*window id # //')
            caller_window_title=$(xprop -id "$caller_window_id" _NET_WM_NAME | sed -Ee 's/^[^=]+ = "//;s/"$//')
        fi

        local pqiv_options=(
            "--scale-mode-screen-fraction=1.0"
            "--zoom-level=1.0"
            "--transparent-background"
            "--hide-info-box"
            "--window-title=cheatsheet-viewer-$profile"
        )

        if [[ -n $last_cheatsheet && -f $last_cheatsheet ]]; then
            pqiv_options+=("--action=goto_file_byname($last_cheatsheet); set_status_output(1)")
        else
            pqiv_options+=("--action=set_status_output(1)")
        fi

        (
            while read -r line; do
                eval "$line"
                echo "$CURRENT_FILE_NAME" > "$profile_dir/last"
            done < <(pqiv "${pqiv_options[@]}" "${cheatsheets[@]}" | grep --line-buffered '^CURRENT_FILE_NAME=')
        ) &

        # The ${caller_window_title-_} is used to avoid invalid array subscript.
        if (( overlay_limits[_ALL_] || overlay_limits[${caller_window_title-_}] )); then
            local counter=0
            while (( counter < 10 )) && ! wmctrl -l | grep -q "cheatsheet-viewer-$profile"; do
                sleep 0.05
                (( counter+=1 ))
            done

            wmctrl -F -r "cheatsheet-viewer-$profile" -b add,above
            wmctrl -i -a "$caller_window_id"
        fi
    fi
}


# Set-up colours for message printing if we're not piping and terminal is
# capable of outputting the colors.
_COLOR_TERMINAL=$(tput colors 2>&1)
if [[ -t 1 ]] && (( _COLOR_TERMINAL > 0 )); then
    _TEXT_BOLD=$(tput bold)
    _TEXT_WHITE=$(tput setaf 7)
    _TEXT_BLUE=$(tput setaf 6)
    _TEXT_GREEN=$(tput setaf 2)
    _TEXT_YELLOW=$(tput setaf 3)
    _TEXT_RED=$(tput setaf 1)
    _TEXT_RESET=$(tput sgr0)
else
    _TEXT_BOLD=""
    _TEXT_WHITE=""
    _TEXT_BLUE=""
    _TEXT_GREEN=""
    _TEXT_YELLOW=""
    _TEXT_RED=""
    _TEXT_RESET=""
fi

# Set-up functions for printing coloured messages.

function debug() {
    if [[ $DEBUG != 0 ]]; then
        echo "${_TEXT_BOLD}${_TEXT_BLUE}[DEBUG]${_TEXT_RESET}" "$@"
    fi
}

function info() {
    if [[ $QUIET == 0 ]]; then
        echo "${_TEXT_BOLD}${_TEXT_WHITE}[INFO] ${_TEXT_RESET}" "$@"
    fi
}

function success() {
    if [[ $QUIET == 0 ]]; then
        echo "${_TEXT_BOLD}${_TEXT_GREEN}[OK]   ${_TEXT_RESET}" "$@"
    fi
}

function warning() {
    echo "${_TEXT_BOLD}${_TEXT_YELLOW}[WARN] ${_TEXT_RESET}" "$@" >&2
}

function error() {
    echo "${_TEXT_BOLD}${_TEXT_RED}[ERROR]${_TEXT_RESET}" "$@" >&2
}

# Define error codes.
SUCCESS=0
ERROR_ARGUMENTS=1

# Disable debug and quiet modes by default.
DEBUG=0
QUIET=0

# Default paths, directories etc.
CONFIG_DIR="$HOME/.config/cheatsheet_viewer"

# Default option values.
OVERLAY_MODE=0

# If no arguments were given, just show usage help.
if [[ -z ${1-} ]]; then
    short_help
    exit "$SUCCESS"
fi

# Parse the arguments
while getopts "oqdvh" opt; do
    case "$opt" in
        o) OVERLAY_MODE=1;;
        q) QUIET=1;;
        d) DEBUG=1;;
        v) version
           exit "$SUCCESS";;
        h) long_help
           exit "$SUCCESS";;
        *) short_help
           exit "$ERROR_ARGUMENTS";;
    esac
done
i=$OPTIND
shift $(( i-1 ))

# Quiet and debug are mutually exclusive.
if [[ $QUIET != 0 && $DEBUG != 0 ]]; then
    error "Quiet and debug options are mutually exclusive."
    exit "$ERROR_ARGUMENTS"
fi

COMMAND="${1-}"
shift

if [[ $COMMAND == list ]]; then

    command_list "$CONFIG_DIR"

elif [[ $COMMAND == info ]]; then

    PROFILE="${1-}"
    shift

    if [[ -z $PROFILE ]]; then
        error "Profile name must be specified."
        exit "$ERROR_ARGUMENTS"
    fi

    command_info "$CONFIG_DIR" "$PROFILE"

elif [[ $COMMAND == display ]]; then

    PROFILE="${1-default}"
    shift

    command_display "$CONFIG_DIR" "$PROFILE" "$OVERLAY_MODE"

elif [[ $COMMAND == toggle ]]; then

    PROFILE="${1-default}"
    shift

    command_toggle "$CONFIG_DIR" "$PROFILE" "$OVERLAY_MODE"

else

    error "Unsupported command: $COMMAND"
    exit "$ERROR_ARGUMENTS"

fi