#!/bin/sh

get_entries() {
    echo $(echo "$(ls -1 $1)" | grep -E "^[0-9]+$" | sort - -g)
}

next_entry() {
    lv=$(echo "$1" | sed 's/ /\n/g' | tail -n 1)
    nv=$(( $lv + 1 ))
    echo $nv
}

# Shifts pages if one is missing.
# i.e (1, 3, 4) -> (1, 2, 3)
check_notebook() {
    entries=$(get_entries $1)
    journal=$(basename $1)

    i=1
    n=0
    for old_name in $entries
    do
        if [ "$old_name" != "$i" ]; then
            mv "$journal/$old_name" "$journal/$i" 
            n=$(( $n + 1 ))
        fi

        i=$(( $i + 1 ))
    done

    next=$(next_entry "$entries")

    if [ "$n" -ne "0" ]; then
        echo "Shifted $n pages."
    fi
}

# $1 = notebook path
new_page() {
    entries=$(get_entries $1)

    next=$(next_entry "$entries")
    path="$1/$next"

    timestamp=$(date +"%a %b %d %I:%M:%S %p")

    echo "$timestamp" > "$path"
    $EDITOR "$path"

    # check that changes were made, we don't 
    # want to store empty pages

    newcontents=$(cat $path)
    if [ "$newcontents" = "$timestamp" ]; then
        rm "$path"
    fi
}

simple_du() {
    echo $(du -h "$1" | sed -e 's/\s.*$//')
}

notebook_info() {
    size=$(simple_du $1)
    pages=$(get_entries "$1" | wc -w)
    created=$(stat "$1" | grep "Birth" | sed 's/Birth: //g' | cut -b 2-11)
    largest=$(ls -1S "$1" | head -n 1)
    echo "Size: $size"
    echo "Pages: $pages"
    echo "Created: $created"
    echo "Largest page: p$largest ($(simple_du "$1/$largest"))"
}

backup_notebook() {
    timestamp=$(date +"%Y-%m-%d-%H:%M:%S")
    path="$1-$timestamp.tar"

    # use --force-local because tar interprets the `:` from the timestamp
    # as a file on another machine.
    tar --force-local -zcf "$path" "$1"
    gzip "$path"
    ls "$path.gz"
}

edit_page() {
    $EDITOR "$1/$2"
}

main() {
    if [ "$1" != "" ]; then
        if [ ! -e $1 ]; then
            echo "Couldn't access notebook."
            exit 1
        fi

    else
        echo "Please provide a notebook directory."
        exit 1
    fi

    if [ "$2" = "" ]; then
        echo "Please provide one of the following commands:"
        echo "  \"new\": create a new page using \$EDITOR ($EDITOR)."
        echo "  \"edit [page]\": edit a page using \$EDITOR ($EDITOR)."
        echo "  \"view [page]\": view a page using \$PAGER ($PAGER)."
        echo "  \"remove [page]\": remove a page."
        echo "  \"info\": print notebook information."
        echo "  \"backup\": create notebook backup."
        exit 1
    fi

    notebook=$(basename "$1")
    check_notebook "$notebook"

    if [ "$2" = "new" ]; then
        new_page "$notebook"
    fi

    if [ "$2" = "edit" ]; then
        if [ "$3" = "" ]; then
            echo "Please provide a page."
            exit 1
        fi

       edit_page "$notebook" "$3"
    fi

    if [ "$2" = "view" ]; then
        if [ "$3" = "" ]; then
            echo "Please provide a page."
            exit 1
        fi

        $PAGER "$notebook/$3"
    fi
    
    if [ "$2" = "remove" ]; then
        if [ "$3" = "" ]; then
            echo "Please provide a page."
            exit 1
        fi

        rm -rf "$notebook/$3"

        # fix the pages
        check_notebook "$notebook" 
    fi

    if [ "$2" = "info" ]; then
        notebook_info "$notebook"
    fi

    if [ "$2" = "backup" ]; then
        backup_notebook "$notebook"
    fi
}

main $@