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mdfmt.bash

#!/bin/bash

TAB=$(printf '\t')

in_code=0
previous_line=""

while IFS= read -r LINE
do
    previous_line=$line

    # Untabify
    line=$(echo "$LINE" | sed 's/$(printf '\t')/        /g')

    if echo $line | grep "^[[:space:]]*\`\`\`" > /dev/null; then
        in_code=$(( (in_code + 1) % 2 ))

        # Ensures there is an empty line before the code snippet.
        if [[ "$in_code" == "1" ]]; then
            if ! echo "$previous_line" | grep "^[[:space:]]*$" > /dev/null; then
                echo ""
            fi
        fi
        echo "$line"
    else
        # Ensures there is an empty line after a code snippet.
        if echo "$previous_line" | grep "^[[:space:]]*\`\`\`" > /dev/null; then
            if [[ "$in_code" == "0" && "$line" != "" ]]; then
                echo ""
            fi
        fi

        if [[ "$in_code" == "0" ]]; then
            echo "$line" | fold -s -w 80
        else
            echo "$line"
        fi
    fi
done