#!/usr/bin/env bash

##############
### CONFIG ###
##############
### feel free to change those constants
# the dir where to store the cache (must be writable and readable by the current user)
# must be an absolute path
_KNIFE_AUTOCOMPLETE_CACHE_DIR="$HOME/.knife_autocomplete_cache"
# the maximum # of _seconds_ after which a cache will be considered stale
# (a cache is refreshed whenever it is used! this is only for caches that might not have been used for a long time)
# WARNING: keep that value > 100
_KNIFE_AUTOCOMPLETE_MAX_CACHE_AGE=86400

###############################################
### END OF CONFIG - DON'T CHANGE CODE BELOW ###
###############################################

### init
_KAC_CACHE_TMP_DIR="$_KNIFE_AUTOCOMPLETE_CACHE_DIR/tmp"
# make sure the cache dir exists
mkdir -p $_KAC_CACHE_TMP_DIR

##############################
### Cache helper functions ###
##############################

# GNU or BSD stat?
stat -c %Y /dev/null > /dev/null 2>&1 && _KAC_STAT_COMMAND="stat -c %Y" || _KAC_STAT_COMMAND="stat -f %m"

# returns 0 iff the file whose path is given as 1st argument
# exists and has last been modified in the last $2 seconds
# returns 1 otherwise
_KAC_is_file_newer_than()
{
    [ -f "$1" ] || return 1
    [ $(( $(date +%s) - $($_KAC_STAT_COMMAND "$1") )) -gt $2 ] && return 1 || return 0
}

# helper function for _KAC_get_and_regen_cache, see doc below
_KAC_regen_cache()
{
    local CACHE_NAME=$1
    local CACHE_PATH="$_KNIFE_AUTOCOMPLETE_CACHE_DIR/$CACHE_NAME"
    local TMP_FILE=$(mktemp "$_KAC_CACHE_TMP_DIR/$CACHE_NAME.XXXX")
    shift 1
    "$@" > $TMP_FILE 2> /dev/null
    # discard the temp file if it's empty AND the previous command didn't exit successfully, but still mark the cache as updated
    [[ $? != 0 ]] && [[ $(cat $TMP_FILE | wc -l) == 0 ]] && rm -f $TMP_FILE && touch $CACHE_PATH && return 1 \
    || mv -f $TMP_FILE $CACHE_PATH
}

# cached files can't have spaces in their names
_KAC_get_cache_name_from_command()
{
    echo "$@" | sed 's/ /_SPACE_/g'
}

# the reverse operation from the function above
_KAC_get_command_from_cache_name()
{
    echo "$@" | sed 's/_SPACE_/ /g'
}

# given a command as argument, it fetches the cache for that command if it can find it
# otherwise it waits for the cache to be generated
# in either case, it regenerates the cache, and sets the _KAC_CACHE_PATH env variable
# for obvious reason, do NOT call that in a sub-shell (in particular, no piping)
_KAC_get_and_regen_cache()
{
    # the cache name can't have space in it
    local CACHE_NAME=$(_KAC_get_cache_name_from_command "$@")
    local REGEN_CMD="_KAC_regen_cache $CACHE_NAME $@"
    _KAC_CACHE_PATH="$_KNIFE_AUTOCOMPLETE_CACHE_DIR/$CACHE_NAME"
    # no need to wait for the regen if the file already exists
    [ -f $_KAC_CACHE_PATH ] && ($REGEN_CMD &) || $REGEN_CMD
}

# performs two things: first, deletes all obsolete temp files
# then refreshes stale caches that haven't been called in a long time
_KAC_clean_cache()
{
    local FILE CMD
    # delete all obsolete temp files, could be lingering there for any kind of crash in the caching process
    for FILE in $(ls $_KAC_CACHE_TMP_DIR)
    do
        _KAC_is_file_newer_than $FILE $_KNIFE_AUTOCOMPLETE_MAX_CACHE_AGE || rm -f $FILE
    done
    # refresh really stale caches
    for FILE in $(find $_KNIFE_AUTOCOMPLETE_CACHE_DIR -maxdepth 1 -type f -not -name '.*')
    do
        _KAC_is_file_newer_than $FILE $_KNIFE_AUTOCOMPLETE_MAX_CACHE_AGE && continue
        # first let's get the original command
        CMD=$(_KAC_get_command_from_cache_name $(basename "$FILE"))
        # then regen the cache
        _KAC_get_and_regen_cache "$CMD" > /dev/null
    done
}

# perform a cache cleaning when loading this file
_KAC_clean_cache

#####################################
### End of cache helper functions ###
#####################################


# returns all the possible knife sub-commands
_KAC_knife_commands()
{
    knife --help | grep -E "^knife" | sed -E 's/ \(options\)//g'
}

# rebuilds the knife base command currently being completed, and assigns it to $_KAC_CURRENT_COMMAND
# additionnally, returns 1 iff the current base command is not complete, 0 otherwise
# also sets $_KAC_CURRENT_COMMAND_NB_WORDS if the base command is complete
_KAC_get_current_base_command()
{
    local PREVIOUS="knife"
    local I=1
    local CURRENT
    while [ $I -le $COMP_CWORD ]
    do
        # command words are all lower-case
        echo ${COMP_WORDS[$I]} | grep -E "^[a-z]+$" > /dev/null || break
        CURRENT="$PREVIOUS ${COMP_WORDS[$I]}"
        cat $_KAC_CACHE_PATH | grep -E "^$CURRENT" > /dev/null || break
        PREVIOUS=$CURRENT
        I=$(( $I + 1))
    done
    _KAC_CURRENT_COMMAND=$PREVIOUS
    [ $I -le $COMP_CWORD ] && _KAC_CURRENT_COMMAND_NB_WORDS=$I
}

# searches the position of the currently completed argument in the current base command
# (i.e. handles "plural" arguments such as knife cookbook upload cookbook1 cookbook2 and so on...)
# assumes the current base command is complete
_KAC_get_current_arg_position()
{
    local CURRENT_ARG_POS=$(( $_KAC_CURRENT_COMMAND_NB_WORDS + 1 ))
    local COMPLETE_COMMAND=$(cat $_KAC_CACHE_PATH | grep -E "^$_KAC_CURRENT_COMMAND")
    local CURRENT_ARG
    while [ $CURRENT_ARG_POS -le $COMP_CWORD ]
    do
        CURRENT_ARG=$(echo $COMPLETE_COMMAND | cut -d ' ' -f $CURRENT_ARG_POS)
        # we break if the current arg is a "plural" arg
        echo $CURRENT_ARG | grep -E "^\\[[^]]+(\\.\\.\\.\\]|$)" > /dev/null && break
        CURRENT_ARG_POS=$(( $CURRENT_ARG_POS + 1 ))
    done
    echo $CURRENT_ARG_POS
}

# the actual auto-complete function
_knife()
{
    _KAC_get_and_regen_cache _KAC_knife_commands
    local RAW_LIST ITEM REGEN_CMD ARG_POSITION
    COMREPLY=()
    # get correct command & arg pos
    _KAC_get_current_base_command && ARG_POSITION=$(_KAC_get_current_arg_position) || ARG_POSITION=$(( $COMP_CWORD + 1 ))
    RAW_LIST=$(cat $_KAC_CACHE_PATH | grep -E "^$_KAC_CURRENT_COMMAND" | cut -d ' ' -f $ARG_POSITION | uniq)

    # we need to process that raw list a bit, most notably for placeholders
    # NOTE: I chose to explicitely fetch & cache _certain_ informations for the server (cookbooks & node names, etc)
    # as opposed to a generic approach by trying to find a 'list' knife command corresponding to the
    # current base command - that might limit my script in some situation, but that way I'm sure it caches only
    # not-sensitive stuff (a generic approach could be pretty bad e.g. with the knife-rackspace plugin)
    LIST=""
    for ITEM in $RAW_LIST
    do
        # always relevant if only lower-case chars : continuation of the base command
        echo $ITEM | grep -E "^[a-z]+$" > /dev/null && LIST="$LIST $ITEM" && continue
        case $ITEM in
            *COOKBOOK*)
                # special case for cookbooks : from site or local
                [[ ${COMP_WORDS[2]} == 'site' ]] && REGEN_CMD="knife cookbook site list" || REGEN_CMD="knife cookbook list"
                _KAC_get_and_regen_cache $REGEN_CMD
                LIST="$LIST $(cat $_KAC_CACHE_PATH | cut -d ' ' -f 1)"
                continue
                ;;
            *ITEM*)
                # data bag item : another special case
                local DATA_BAG_NAME=${COMP_WORDS[$(( COMP_CWORD-1 ))]}
                REGEN_CMD="knife data bag show $DATA_BAG_NAME"
                ;;
            *INDEX*)
                # see doc @ http://docs.opscode.com/knife_search.html
                LIST="$LIST client environment node role"
                REGEN_CMD="knife data bag list"
                ;;
            *BAG*) REGEN_CMD="knife data bag list";;
            *CLIENT*) REGEN_CMD="knife client list";;
            *NODE*) REGEN_CMD="knife node list";;
            *ENVIRONMENT*) REGEN_CMD="knife environment list";;
            *ROLE*) REGEN_CMD="knife role list";;
            *USER*) REGEN_CMD="knife user list";;
            # not a generic argument we support...
            *) continue;;
        esac
        _KAC_get_and_regen_cache $REGEN_CMD
        LIST="$LIST $(cat $_KAC_CACHE_PATH)"
    done
    COMPREPLY=( $(compgen -W "${LIST}" -- ${COMP_WORDS[COMP_CWORD]}))
}

#complete -f -F _knife knife
complete -F _knife knife