#!/bin/bash

#
# Bottles of Beer song in Bash
#
# A way-overcomplicated implementation of the bottles of beer song in bash.
# Optional argument:
#
#  *  `--careless` - Generate the "happen to fall" version
#
# NOTE:  This is an altered version of a "99 bottles of beer" song
# Bash script by Bill Brown.  The intent of the altered version is
# to show the style, so the above text is preserved from [the
# original][99b].
#
#   [99b]: http://99-bottles-of-beer.net/language-bash-1831.html
#

#
# Default transition mode
#
# 'standard' to use the standard form; 'careless' to have the
# song consider effects of gravity on the bottles.
#
# Default is 'standard'.
#
NN_BOTTLES__MODE=${NN_BOTTLES__MODE:-standard}

#
# Starting bottle amount
#
# Initial amount of bottles specified as numeral.  Numerals up
# to 99 are supported.
#
# Default is 'ninety-nine'.
#
NN_STARTING_AMOUNT=${NN_STARTING_AMOUNT:-ninety-nine}

pred() {
    #
    # Get predecessor to a number $1
    #
    local numeral=$1    # number in word form
    case $numeral in
        *nine)      echo "${numeral%nine}eight" ;;
        *eight)     echo "${numeral%eight}seven" ;;
        *seven)     echo "${numeral%seven}six" ;;
        *six)       echo "${numeral%six}five" ;;
        *five)      echo "${numeral%five}four" ;;
        *four)      echo "${numeral%four}three" ;;
        *three)     echo "${numeral%three}two" ;;
        *two)       echo "${numeral%two}one" ;;
        one)        echo "zero" ;;
        *-one)      echo "${numeral%-one}" ;;
        *one)       echo "${numeral%one}" ;;
        ten)        echo "nine" ;;
        eleven)     echo "ten" ;;
        twelve)     echo "eleven" ;;
        *teen)      teenpred "$numeral" ;;
        *ty)        tenspred "$numeral" ;;
        zero)       echo "";  #to terminate
    esac
}

teenpred() {
    #
    # Get predecessor of a teen $1
    #
    local numeral=$1    # number in word form
    case $numeral in
        thirteen)   echo twelve;;
        *)          echo "$(crunchprefix "$(pred "$(uncrunchprefix "${numeral%teen}")")")teen" ;;
    esac
}

tenspred() {
    #
    # Get predecessor of a multiple of ten $1
    #
    local numeral=$1    # number in word form
    case $numeral in
        twenty)     echo nineteen;;
        *) echo "$(crunchprefix --tens "$(pred "$(uncrunchprefix "${numeral%ty}")")")ty-nine";;
    esac
}

crunchprefix() {
    #
    # Crunch number prefix $1 to its conventional form
    #
    # ...such as `three` --> `thir`
    #
    # option `--tens` - multiples of ten are a bit different
    #
    local numeral       # number in word form
    local tensop        # 'true' if --tens option is active
    [ "$1" = --tens ] && { tensop=true; shift; }
    numeral=$1
    case $numeral in
        two)    [ -n "$tensop" ] && echo twen || echo "$numeral";;
        three)  echo thir;;
        four)   [ -n "$tensop" ] && echo 'for' || echo "$numeral";;
        five)   echo fif;;
        eight)  [ -n "$tensop" ] && echo eigh || echo "$numeral";;
        *)      echo "$numeral" ;;
    esac
}

uncrunchprefix() {
    #
    # Reverse crunchprefix $1
    #
    local prefix=$1     # numeral crunch-prefix
    case $prefix in
        twen)   echo two;;
        thir)   echo three;;
        'for')  echo four;;
        fif)    echo five;;
        eigh)   echo eight;;
        *)      echo "$prefix";;
    esac
}

grammar() {
    #
    # Apply peculiarities of English grammar to text on stdin
    #
    local oneBottle=false   # 'true' if this line affects the following line
    local line              # every line
    while read -r line; do
        line="${line/one more bottles/one more bottle}"
        case "$line" in
            *"one of those bottles"*)   line="$(
                                            [ $oneBottle = true ] \
                                             && echo "${line/one of those bottles/that lone bottle}" \
                                             || echo "$line"
                                        )"
                                        ;;
            *"one down"*)               line="$(
                                            [ $oneBottle = true ] \
                                             && echo "${line/one down/it down}" \
                                             || echo "$line"
                                        )"
                                        ;;
            *bottles*)                  oneBottle=false;;
            *bottle*)                   oneBottle=true;;
        esac
        #Some say the twenties should have no hyphen
        line="${line/twenty-/twenty }"
        echo "$line"
    done
}

capitalize() {
    #
    # Fix capitalization of each line on stdin
    #
    local line      # every line
    while read -r line; do
        echo -n "${line:0:1}" | tr '[:lower:]' '[:upper:]'
        echo "${line#?}"
    done
}

punctuate() {
    #
    # Add punctuation to each line on stdin
    #
    local line      # every line
    while read -r line; do
        case "${line}" in
            [Ii]f*)     echo "${line},";;
            '')         echo;;
            *)          echo "${line}.";;
        esac
    done
}

verse() {
    #
    # Write one verse with number $1
    #
    local nb=$1     # numeral
    echo "$nb bottles of beer on the wall"
    echo "$nb bottles of beer"
    if [ "$nb" = zero ]; then
        echo "Go to the store and buy some more"
        nb=ninety-nine
    else
        echo "$TransitionLine"
        nb=$(pred "$nb")
    fi
    echo "$nb bottles of beer on the wall"
}

poeticize() {
    #
    # Make text on stdin nice
    #
    local first     # first word of a line
    local rest      # remainder of a line
    local syl       # number of syllables in the first word
    while read -r first rest; do
        case "$rest" in
            *beer*)
                first=${first/zero/no}
                syl=$(syllables "${first% *}")
                case $syl in  #improve meter
                    1|2)    echo "$first more $rest";;
                    *)      echo "$first $rest" ;;
                esac
                ;;
            *)  echo "$first $rest"
        esac
    done
}

syllables() {
    #
    # Estimate number of syllables in word $1
    #
    local word=$1   # word (numeral) to do the estimation on
    local n=1
    case $word in
        eleven)     n=2;; #sounds better if not considered 3
        *teen)      n=2;;
        *ty)        n=2;;
        *-*)        n=3;; #don't care about more than 3
    esac
    case $word in
        *seven*)    ((n = n+1)) ;;
    esac
    echo "$n"
}

main() {
    local TransitionLine    # transition line between verses
    local togo=$NN_STARTING_AMOUNT  # bottles to go
    local mode=$NN_BOTTLES__MODE    # transition mode
    while true; do case $1 in
        --careless)     mode=careless; shift ;;
        *)              break ;;
    esac done
    TransitionLine=$(
        case $mode in
            standard)   echo "Take one down and pass it around" ;;
            careless)   echo "If one of those bottles should happen to fall" ;;
        esac
    )
    togo=ninety-nine
    while [ -n "$togo" ]; do
        verse "$togo"
        echo
        togo=$(pred "$togo")
    done  \
      | poeticize \
      | grammar \
      | punctuate \
      | capitalize
}

main "$@"