#!/usr/bin/env bash

_md2_help() {
    cat <<- EOF
Convert Markdown to different formats.

Usage:  md2 [-v|-h] <command> [args]..
        md2 html <input> [<output>]
        md2 man <input> [<output>]
        md2 pdf <input> [<output>]

Options:
    -h, --help      print this message and exit.
    -v, --version   print version and exit.

Commands:
    html        convert to HTML.
    man|roff    convert to ROFF. Pass only <input> for preview.
    pdf         convert to PDF.

Also you can use se symlbolic links to md2 to run commands.
E.g.: symlink md2pdf -> md2 runs \`md2 pdf\`

md2 is just Pandoc wrapper. Edit md2 source code for customize.
EOF
    exit 0
}

_md2_usage() {
    echo "Usage: ${func:1} <input> [<output>]"
    [ "$func" == "_md2man" ] && \
    echo "Pass only <input> for preview."
    exit 0
}

_md2_version() {
    cat <<- EOF
	md2 0.1.0
	EOF
    exit 0
}

_md2() {
    # Wrapper function
    local inp out args preview

    [[ ! "$@" ]] && _md2_usage

    while (( "$#" )); do
    case "$1" in
        -h|--help)     _md2_usage   ;;
        -v|--version)  _md2_version ;;
        -*) echo "${func:1}: $1: bad option." >&2
            _md2_usage              ;;
        *)  args+=("$1"); shift     ;;
    esac
    done

    if   [ ${#args[@]} -eq 2 ]; then
        inp="${args[0]}"; out="${args[1]}"
    elif [ ${#args[@]} -eq 1 ]; then
        inp="${args[0]}"; out="${args[0]%%.*}.${ext}"
        [ "$func" == "_md2man" ] && preview=1
    else
        _md2_usage
    fi

    echo -e "\e[1mInput:\e[0m \e[37m${inp}\e[0m"

    if [ "$preview" ]; then
        _md2man_preview "$inp"
    else
        echo -e "\e[1mOutput:\e[0m \e[37m${out}\e[0m"
        eval "$func" "$inp" "$out"
    fi
}

_md2_run() {
    # Another wrapper function.
    case "$1" in
        -h|--help)      _md2_help   ;;
        -v|--version)   _md2_version;;
        html)       func=_md2html; ext='html'; shift;;
        man|roff)   func=_md2man;  ext='1';    shift;;
        pdf)        func=_md2pdf;  ext='pdf';  shift;;
        *)  _md2_help               ;;
    esac

    _md2 "$@"
    exit $?
}

# BEGIN Pandoc wrapper functions ##########################################

_md2html() {
    # HTML
    pandoc  \
        --from=markdown \
        --to=html       \
        --standalone    \
        "$1"            \
        --output="$2"   \
        --variable document-css=true \
        --variable linkcolor='[HTML]{0000ff}' \
        --metadata title="${1%.*}"
}

_md2man() {
    # ROFF
    pandoc  \
        --from=markdown \
        --to=man        \
        --standalone    \
        "$1"            \
        --output="$2"
}

_md2man_preview() {
    # ROFF
    # View ROFF in pager without saving.
    pandoc --standalone --to man ${1:-"-"} | # Read into Pandoc
    groff -T utf8 -man         | # format for pager.
    sed 1,4d | head -n -4      | # Chop off 4 leading/trailing
                                 # (empty) lines.
    less
}

_md2pdf() {
    # PDF
    pandoc \
        --from=markdown-implicit_figures \
        --to=pdf        \
        "$1"            \
        --output="$2"   \
        --pdf-engine=xelatex    \
        --variable mainfont='FreeSans' \
        --variable fontsize='12pt' \
        --variable urlcolor='[HTML]{0000ff}' \
        --variable pagestyle=empty \
        --variable margin-left='20mm'   \
        --variable margin-right='20mm'  \
        --variable margin-top='20mm'    \
        --variable margin-bottom='20mm' \
        --highlight-style haddock
}

# END Pandoc wrapper functions ############################################

case "$0" in
    *md2)     _md2_run "$@"; shift "$#" ;;
    *md2html) func=_md2html; ext='html' ;;
    *md2man)  func=_md2man;  ext='1'    ;;
    *md2pdf)  func=_md2pdf;  ext='pdf'  ;;
    *) echo "$0: bad command"; _md2_help;;
esac

_md2 "$@"