#!/bin/bash

# Script: docker-cleanup.sh
# Description: Cleans up unused Docker images, volumes, networks, and builder cache.
#              Preserves stopped containers.
#              Calculates reclaimed space and logs it to syslog.
# Dependencies: docker, bc, grep (with PCRE support)

USAGE_TAG="docker-cleanup"

# Logging functions
log_info() {
    logger -t "$USAGE_TAG" -p user.info "$1"
}

log_error() {
    logger -t "$USAGE_TAG" -p user.error "$1"
}

# Check for 'bc' dependency
if ! command -v bc &> /dev/null; then
    log_error "Error: 'bc' is not installed. Please install it (apt install bc) to calculate reclaimed space."
    # Fail safe: don't run blindly if we can't calculate/log properly, or just run without logging space?
    # User requested logging to syslog, assuming they want the space report.
    exit 1
fi

log_info "Starting Docker cleanup (Images, Volumes, Networks, Builder)..."

# Initialize output variable
OUTPUT=""

# 1. Prune Images (all unused images, not just dangling) with input 'y' just in case, though -f usually covers it
# Note: 'image prune -a' removes images not used by ANY container (including stopped ones).
CMD_OUTPUT=$(docker image prune -a -f 2>&1)
OUTPUT="${OUTPUT}${CMD_OUTPUT}"$'\n'

# 2. Prune Volumes
CMD_OUTPUT=$(docker volume prune -f 2>&1)
OUTPUT="${OUTPUT}${CMD_OUTPUT}"$'\n'

# 3. Prune Networks
CMD_OUTPUT=$(docker network prune -f 2>&1)
OUTPUT="${OUTPUT}${CMD_OUTPUT}"$'\n'

# 4. Prune Builder Cache
CMD_OUTPUT=$(docker builder prune -f 2>&1)
OUTPUT="${OUTPUT}${CMD_OUTPUT}"$'\n'

# Check for critical failures (though docker commands might succeed partially)
# We proceed to calculate space regardless.

# Extract reclaimed space amounts using grep with Perl-compatible regex.
RECLAIMED_SPACES=$(echo "$OUTPUT" | grep -Po '(?<=Total reclaimed space: )[0-9.]+[A-Z]+' | grep -v '^0B$')

# Initialize total reclaimed space counter
TOTAL_RECLAIMED=0

# Loop through each reclaimed space value
for SPACE in $RECLAIMED_SPACES; do
  # Extract the unit (KB, MB, GB)
  UNIT=${SPACE: -2}
  # Extract the numeric value
  VALUE=${SPACE%${UNIT}}
  
  # Normalize to GB
  case $UNIT in
    kB|KB) VAL_IN_GB=$(echo "$VALUE / 1024 / 1024" | bc -l) ;;
    mB|MB) VAL_IN_GB=$(echo "$VALUE / 1024" | bc -l) ;;
    gB|GB) VAL_IN_GB=$VALUE ;;
    *) VAL_IN_GB=0 ;; 
  esac

  # Add to total
  TOTAL_RECLAIMED=$(echo "$TOTAL_RECLAIMED + $VAL_IN_GB" | bc -l)
done

# Check if we reclaimed anything significant (greater than 0)
IS_POSITIVE=$(echo "$TOTAL_RECLAIMED > 0" | bc -l)

if [ "$IS_POSITIVE" -eq 1 ]; then
  # Format to 3 decimal places
  FORMATTED_TOTAL=$(printf "%.3f" "$TOTAL_RECLAIMED")
  log_info "Cleanup finished. Total reclaimed space: ${FORMATTED_TOTAL} GB"
else
  log_info "Cleanup finished. No significant space was reclaimed."
fi

exit 0