#!/bin/bash

# Check if two hardlinks point to same file
aresame()
{
    [ "$(ls -i $1 | awk '{print $1;}')" == "$(ls -i $2 | awk '{print $1;}')" ]
}

hardlink()
{
    ln $(readlink -f $1) $2;
}

# Move $1 to $2
pull()
{
    mkdir -p $(dirname $2);
    mv $1 $2;
}

# Pull $1 to $2 and link $2 into $1
pulllink()
{
    pull $1 $2
    hardlink $2 $1
}

# Ask a question and return the answer
y()
{
    local yn;
    read -p "$1" yn;
    case "$yn" in
        y|Y ) return 0;;
        n|N ) return 1;;
        * ) return $(y "$1");;
    esac
}

# Start of the script

if (( $# != 2 )); then
    echo "Usage: lincon <add|deploy> <path/to/file>"
    exit 0
fi

OPERATION=$1
ORIG=$2
BAK=$ORIG.orig
TARGET=$(dirname "$0")$ORIG

case $OPERATION in

    # Add a file to versioning
    add)
        # Error if original does not exist
        if [ ! -e $ORIG ]; then
            echo "Error: File $ORIG does not exist.";
            exit 1;
        fi

        # There is already a file in the repo
        if [ -e $TARGET ]; then
            # File is already linked
            if aresame $ORIG $TARGET; then
                echo "File $ORIG is already versioned.";
                exit;
            fi
            # Repo contains different copy
            echo "Versioned copy of $ORIG already exists.";
            if ! y "Overwrite it (y/n)?"; then
                exit;
            fi
        fi
        pulllink $ORIG $TARGET
        echo "File $ORIG versioned."
        ;;

    # Link a file from repo
    deploy)
        # Check if versioned copy exists
        if [ ! -e $TARGET ]; then
            echo "Error: No versioned copy of $ORIG found.";
            exit 1;
        fi

        # Backup any original files
        if [ -e $ORIG ]; then
            if aresame $ORIG $TARGET; then
                echo "File $ORIG is already versioned.";
                exit;
            else
                echo "Backup original file to $BAK.";
                mv $ORIG $BAK
            fi
        fi
        # Link it, baby!
        hardlink $TARGET $ORIG
        echo "File $ORIG deployed."
        ;;
    *)
        echo "Usage: repoconf <add|deploy> <path/to/file>";
        exit 0;
        ;;
esac