#!/usr/bin/env bash
set -e

# Fetch arguments
CMD=$1
if [ $# -gt 1 ]
then
    POOL_ID=$2
    shift 2
    PROC_CMD=$@    
fi

# Config: feel free to change at your own risks
TMPDIR=/tmp
POOL_FORMAT="pool_${POOL_ID}"
POOL="${TMPDIR}/${POOL_FORMAT}/"
POOL_STATUS="${POOL}/status"
REFRESH_EVERY=2

abort() {
    echo $@
    exit 1
}

write_status() {
    echo "maxproc=${maxproc}" > "$POOL_STATUS"
    echo "nproc=${nproc}" >> "$POOL_STATUS"
    echo "procs=\"${procs}\"" >> "$POOL_STATUS"
    echo "lastprocid=$lastprocid" >> "$POOL_STATUS"
}

create_properties() {
    file="${POOL}/proc_${procid}"
    echo cmd=\"${PROC_CMD}\" > "$file"
    echo "procpid=${procpid}" >> "$file"
    echo "procid=${procid}" >> "$file"
    echo "startat=${startat}" >> "$file"
}

setp() {
    file="${POOL}/proc_${procid}"
    echo $1=$2 >> "$file"
}

getp() {
    file="${POOL}/proc_${procid}"
    source "$file"
    echo "${!1}"
}


create() {
    [ -d "$POOL" ] && abort "Pool \"$POOL\" already exists"
    mkdir -p "$POOL"
    # Write pool status
    maxproc=$1
    nproc=0
    procs=""
    lastprocid=0
    write_status
}

remove() {
    refresh # Refresh process status and load status
    [ $nproc -gt 0 ] && abort "Processes are still running in the pool!"
    rm -rf "$POOL"
}

refresh() {
    source "$POOL_STATUS"
    procs_new=""
    for proc in $procs
    do
        if kill -0 $proc &>/dev/null
        then
            [ -z "$procs_new" ] && procs_new="$proc" || procs_new="$procs_new $proc"
        fi
    done
    procs=$procs_new
    nproc=$(echo "$procs"|wc -w)
    write_status
}

run() {
    refresh
    # Wait for room in the pool
    while [ $nproc -ge $maxproc ]
    do
        sleep $REFRESH_EVERY
        refresh
    done
    # Create new process
    nproc=$(( nproc + 1 ))
    procid=$(( lastprocid + 1 ))
    lastprocid=$procid
    startat=$(date +"%s")
    $PROC_CMD > "$POOL/out_$procid" &
    procpid=$!
    [ -z "$procs" ] && procs="$procpid" || procs="$procs $procpid"
    write_status # Update status
    create_properties # Create process properties
    echo $procid # Return process id
}

cat_output() {
    file="${POOL}/out_${procid}"
    cat "$file"
}

list_pool() {
    find "${TMPDIR}" -name "${POOL_FORMAT}*" -exec basename {} \; 2>/dev/null | sed "s/${POOL_FORMAT}//g"
}

wait_pool() {
    refresh
    while [ $nproc -gt 0 ]
    do
        sleep $REFRESH_EVERY
        refresh
    done
}

list_output() {
    refresh
    find "${POOL}" -name "out_*"
}

remove_force() {
    refresh
    for proc in $procs
    do
        kill -9 $proc
    done
    rm -rf "$POOL"    
}

# Ensure pool exists
[ ! "$CMD" == "create" ] && [ ! "$CMD" == "ls" ] && [ ! -d "$POOL" ] && abort "Pool $POOL_ID not found"

# Launch command
case "$CMD" in
    "create")
        create $1
        ;;
    "remove")
        remove
        ;;
    "run")
        run
        ;;
    "cat")
        procid=$1
        refresh
        [ $procid -gt $lastprocid ] && abort "Processus $procid not found"
        cat_output
        ;;
    "ls-output")
        list_output
        ;;
    "ls")
        list_pool
        ;;
    "wait")
        wait_pool
        ;;
    "remove-force")
        remove_force
        ;;
    "setp")
        procid=$1
        setp $2 $3
        ;;
    "getp")
        procid=$1
        getp $2
        ;;
    *)
        abort "Command $CMD unknown"
esac