#!/bin/sh
#
# pfetch - Simple POSIX sh fetch script.

log() {
    # The 'log()' function handles the printing of information.
    # In 'pfetch' (and 'neofetch'!) the printing of the ascii art and info
    # happen independently of each other.
    #
    # The size of the ascii art is stored and the ascii is printed first.
    # Once the ascii is printed, the cursor is located right below the art
    # (See marker $[1]).
    #
    # Using the stored ascii size, the cursor is then moved to marker $[2].
    # This is simply a cursor up escape sequence using the "height" of the
    # ascii art.
    #
    # 'log()' then moves the cursor to the right the "width" of the ascii art
    # with an additional amount of padding to add a gap between the art and
    # the information (See marker $[3]).
    #
    # When 'log()' has executed the cursor is then located at marker $[4].
    # When 'log()' is run a second time, the next line of information is
    # printed, moving the cursor to marker $[5].
    #
    # Markers $[4] and $[5] repeat all the way down through the ascii art
    # until there is no more information left to print.
    #
    # Every time 'log()' is called the script keeps track of how many lines
    # were printed. When printing is complete the cursor is then manually
    # placed below the information and the art according to the "heights"
    # of both.
    #
    # The math is simple: move cursor down $((ascii_height - info_height)).
    # If the aim is to move the cursor from marker $[5] to marker $[6],
    # plus the ascii height is 8 while the info height is 2 it'd be a move
    # of 6 lines downwards.
    #
    # Once the cursor is at marker $[6], the script exits. This is the gist
    # of how this "dynamic" printing and layout works.
    #
    # This method allows ascii art to be stored without markers for info
    # and it allows for easy swapping of info order and amount.
    #
    # $[2] ___      $[3] goldie@KISS
    # $[4](.· |     $[5] os KISS Linux
    #     (<> |
    #    / __  \
    #   ( /  \ /|
    #  _/\ __)/_)
    #  \/-____\/
    # $[1]
    #
    # $[6] /home/goldie $
    #
    # '$PF_COL1':  Control color of info name.
    # '$PF_SEP':   Control the separator between info name and info data.
    # '$PF_COL2':  Control color of info data.
    # '$PF_ALIGN': Control the alignment amount.
    #
    # '\033[14C':  Move cursor 14 characters to the right.
    #              TODO: Base this on ASCII art width.
    #
    # '\033[3%s':  Color formatting.
    # '\033[m':    Reset formatting.
    #
    # '\033[%sD':  Move cursor '${#1}' characters to the left.
    #              This allows for aligned info names and data.
    #
    # '\033[6C':   Move cursor 6 characters to the right.
    #              This aligns the info.
    #
    # This is ugly, I know!
    printf '\033[%sC\033[3%s;1m%s\033[m%s\033[3%sm\033[%sD\033[%sC%s\033[m\n' \
           "${ascii_width:--1}" \
           "${PF_COL1:-5}" \
           "$1" \
           "$PF_SEP" \
           "${PF_COL2:-7}" \
           "${#1}" \
           "${PF_ALIGN:-$((info_length + 1))}" \
           "$2"

    # Keep track of the number of times 'log()' has been run.
    info_height=$((info_height + 1))
}

get_title() {
    case $os in
        Linux*|GNU*)
            read -r hostname < /proc/sys/kernel/hostname
        ;;
    esac

    # Username is retrieved by first checking '$USER' with a fallback
    # to the 'whoami' command.
    #
    # Hostname is retrieved by first checking '$HOSTNAME' with a fallback
    # to the OS specific detection above and finally an additional fallback
    # to the 'hostname' command.
    #
    # Disable the warning about '$HOSTNAME' being undefined in POSIX sh as
    # it is intended for allowing the user to overwrite the value on invocation.
    # shellcheck disable=SC2039
    log "$c4${USER:-$(whoami)}$c7@$c4${HOSTNAME:-${hostname:-$(hostname)}}"
}

get_distro() {
    case $os in
        Linux*|GNU*)
            # Disable warning about shellcheck not being able
            # to read '/etc/os-release'. This is fine.
            # shellcheck source=/dev/null
            . /etc/os-release && distro=$PRETTY_NAME
        ;;
    esac

    log os "$distro"
}

get_kernel() {
    log kernel "$kernel"
}

get_host() {
    case $os in
        Linux*|GNU*)
            # Despite what these files are called, version doesn't
            # always contain the version nor does name always contain
            # the name.
            read -r name    < /sys/devices/virtual/dmi/id/product_name
            read -r version < /sys/devices/virtual/dmi/id/product_version
            read -r model   < /sys/firmware/devicetree/base/model

            host="$name $version $model"
        ;;
    esac

    log host "$host"
}

get_uptime() {
    # Uptime works by retrieving the data in total seconds and then
    # converting that data into days, hours and minutes using simple
    # math.
    case $os in
        Linux*|GNU*)
            IFS=. read -r s _ < /proc/uptime
        ;;
    esac

    # Convert the uptime from seconds into days, hours and minutes.
    d=$((s / 60 / 60 / 24))
    h=$((s / 60 / 60 % 24))
    m=$((s / 60 % 60))

    # Only append days, hours and minutes if they're non-zero.
    [ "$d" = 0 ] || uptime="${uptime}${d}d "
    [ "$h" = 0 ] || uptime="${uptime}${h}h "
    [ "$m" = 0 ] || uptime="${uptime}${m}m "

    log uptime "${uptime:-0m}"
}

get_pkgs() {
    # Simple function to avoid '>/dev/null' spam.
    # This checks to see if a command is in '$PATH'.
    has() { command -v "$1" >/dev/null; }

    # This works by first checking for which package managers are
    # isntalled and finally by printing each package manager's
    # package list with each package one per line.
    #
    # The output from this is then piped to 'wc -l' to count each
    # line, giving us the total package count of whatever package
    # managers are installed.
    packages=$(
        case $os in
            Linux*|GNU*)
                # Commands which print packages one per line.
                has kiss       && kiss l
                has bonsai     && bonsai list
                has pacman-key && pacman -Qq
                has dpkg       && dpkg-query -f '.\n' -W
                has rpm        && rpm -qa
                has xbps-query && xbps-query -l
                has apk        && apk info

                # Directories containing packages.
                has brew       && printf '%s\n' "$(brew --cellar)/"*
                has emerge     && printf '%s\n' /var/db/pkg/*/*/
            ;;
        esac | wc -l
    )

    log pkgs "$packages"
}

get_memory() {
    case $os in
        # Used memory is calculated using the following "formula" (Linux):
        # MemUsed = MemTotal + Shmem - MemFree - Buffers - Cached - SReclaimable
        # Source: https://github.com/KittyKatt/screenFetch/issues/386
        Linux*|GNU*)
            # Parse the '/proc/meminfo' file splitting on ':' and 'k'.
            # The format of the file is 'key:   000kB' and an additional
            # split is used on 'k' to filter out 'kB'.
            while IFS=:k read -r key val _; do
                case $key in
                    MemTotal)
                        mem_used=$((mem_used + val))
                        mem_total=$val
                    ;;

                    Shmem)
                        mem_used=$((mem_used + val))
                    ;;

                    MemFree|Buffers|Cached|SReclaimable)
                        mem_used=$((mem_used - val))
                    ;;
                esac
            done < /proc/meminfo

            mem_used=$((mem_used / 1024))
            mem_total=$((mem_total / 1024))
        ;;
    esac

    log memory "${mem_used}MiB / ${mem_total}MiB"
}

get_ascii() {
    case $os in
        Linux*|GNU*)
            ascii="\
${c4}    ___
   (${c7}.· ${c4}|
   (${c5}<> ${c4}|
  / ${c7}__  ${c4}\\
 ( ${c7}/  \\ ${c4}/|
${c5}_${c4}/\\ ${c7}__)${c4}/${c5}_${c4})
${c5}\/${c4}-____${c5}\/
"
        ;;

        *)
            printf 'error: %s is not currently supported.\n' "$os"
            printf 'error: Open an issue on GitHub for support to be added.\n'
            exit 1
        ;;
    esac

    # Store the "width" (longest line) and "height" (number of lines)
    # of the ascii art for positioning. This script prints to the screen
    # *almost* like a TUI does. It uses escape sequences to allow dynamic
    # printing of the information through user configuration.
    #
    # Iterate over each line of the ascii art to retrieve the above
    # information. The 'sed' is used to strip '\033[3Xm' color codes from
    # the ascii art so they don't affect the width variable.
    #
    # The "   " acts as the padding between the ascii art and the text as
    # it appends 3 spaces to the end of each line.
    while read -r line || [ -n "$line" ]; do
        ascii_height=$((ascii_height + 1))
        ascii_width=$((${#line} > ascii_width ? ${#line} : ascii_width))
    done <<-EOF
		$(printf %s "$ascii" | sed 's/\[3.m//g')
	EOF

    # Add a gap between the ascii art and the information.
    ascii_width=$((ascii_width + 4))

    # Print the ascii art and position the cursor back where we
    # started prior to printing it.
    # '\033[?7l':  Disable line-wrapping.
    # '\033[?25l': Hide the cursor.
    # '\033[1m':   Print the ascii in bold.
    # '\033[m':    Clear bold.
    # '\033[%sA:   Move the cursor up '$ascii_height' amount of lines.
    printf '\033[?7l\033[?25l\033[1m%s\033[m\033[%sA' "$ascii" "$ascii_height"
}

main() {
    # Hide 'stderr' unless the first argument is '-v'. This saves
    # polluting the script with '2>/dev/null'.
    [ "$1" = -v ] || exec 2>/dev/null

    # Generic color list.
    # Disable warning about unused variables.
    # shellcheck disable=2034
    {
        c1=''; c2=''
        c3=''; c4=''
        c5=''; c6=''
        c7=''; c8=''
    }

    # Store the output of 'uname' to avoid calling it multiple times
    # throughout the script. 'read <<EOF' is the simplest way of reading
    # a command into a list of variables.
    read -r os kernel <<-EOF
		$(uname -sr)
	EOF

    # Allow the user to specify the order and inclusion of information
    # functions through the 'PF_INFO' environment variable.
    # shellcheck disable=2086
    {
        # Disable globbing and set the positional parameters to the
        # contents of 'PF_INFO'.
        set -f
        set +f ${PF_INFO-ascii title distro host kernel uptime pkgs memory}

        # Iterate over the info functions to determine the lengths of the
        # "info names" for output alignment. The option names and subtitles
        # match 1:1 so this is thankfully simple.
        for info; do
            command -v "get_$info" >/dev/null &&
                info_length=$((${#info} > info_length ? ${#info} : info_length))
        done

        # Iterate over the above list and run any existing "get_" functions.
        for info; do
            "get_$info"
        done
    }

    # Position the cursor below both the ascii art and information lines
    # according to the height of both. If the information exceeds the ascii
    # art in height, don't touch the cursor, else move it down N lines.
    #
    # 'log' contains the amount of 'get_' info lines that were printed.
    #
    # '\033[?7h':  Enable line-wrapping.
    # '\033[%sB':  Move the cursor down N lines.
    # '\033[?25h': Un-hide the cursor.
    printf '\033[?7h\033[%sB\n\033[?25h' \
           "$((info_height > ascii_height ? 0 : ascii_height - info_height))"
}

main "$@"