#!/bin/bash
# -----------------------------------------------------------------------------------------------
# --------------------------------- ZFS Memory Snapshot ----------------------------------------
# -----------------------------------------------------------------------------------------------
# Captures a point-in-time snapshot of ZFS ARC statistics and system memory usage.
# Read-only diagnostic tool — no changes are made to the system regardless of flags.
# Dry run mode still collects and displays data since no modifications occur.
# -----------------------------------------------------------------------------------------------

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

source "$SCRIPT_DIR/../Master.conf"
source "$SCRIPT_DIR/../common.sh"

parse_args "$@"

# -----------------------------------------------------------------------------------------------
# ━━━ $ICON_GEAR Setup ━━━
# -----------------------------------------------------------------------------------------------
echo ""
echo "━━━ $ICON_GEAR Setup ━━━"

info "$ICON_ZFS ZFS ARC + Memory Snapshot"
info "$ICON_TIME $(date)"

# -----------------------------------------------------------------------------------------------
# ━━━ $ICON_SUMMARY Status ━━━
# -----------------------------------------------------------------------------------------------
if [[ "$SHOW_STATUS" == true ]]; then
    echo ""
    echo "━━━━━ $ICON_SUMMARY STATUS ━━━━━"
    echo "$ICON_ZFS  Mode:    Read-only diagnostics"
    echo "$ICON_MEM  Source:  ZFS ARC + system memory"
    echo "$ICON_GEAR Dry Run: $DRY_RUN"
    echo "━━━━━━━━━━━━━━━━━━━━━━━"
    exit 0
fi

# -----------------------------------------------------------------------------------------------
# FUNCTIONS
# -----------------------------------------------------------------------------------------------

# Reads ZFS ARC statistics from the kernel stats interface.
# Filters for the most useful ARC metrics — size, hits, misses and metadata.
# Skips gracefully if ZFS is not available on this system.
show_zfs_arc() {
    echo ""
    echo "━━━ $ICON_ZFS ZFS ARC Stats ━━━"

    if [[ ! -r /proc/spl/kstat/zfs/arcstats ]]; then
        warn "ZFS arcstats not available on this system — is ZFS loaded?"
        return
    fi

    grep -iE '^(c|size|hits|misses|arc_meta_used|demand_metadata_misses|mru_ghost_metadata|mfu_ghost_metadata)' \
        /proc/spl/kstat/zfs/arcstats 2>/dev/null || warn "Unable to read ARC stats"
}

# Reads current system memory and swap usage using free.
# Skips gracefully if free is not available.
show_memory_status() {
    echo ""
    echo "━━━ $ICON_MEM Memory Status ━━━"

    if ! command -v free >/dev/null 2>&1; then
        warn "free command not available on this system"
        return
    fi

    free -h | awk '
        NR==1      { print $0 }
        /Mem:/     { print $0 }
        /Swap:/    { print $0 }'
}

# -----------------------------------------------------------------------------------------------
# ━━━ $ICON_ZFS Snapshot ━━━
# -----------------------------------------------------------------------------------------------
echo ""
echo "━━━ $ICON_ZFS Snapshot ━━━"
echo "$ICON_ZFS  Source:  ZFS ARC + system memory"
echo "$ICON_GEAR Dry Run: $DRY_RUN"
echo ""

[[ "$DRY_RUN" == true ]] && warn "DRY RUN — this script is read-only, data will still be collected"

START=$(date +%s)

show_zfs_arc
show_memory_status

END=$(date +%s)

# -----------------------------------------------------------------------------------------------
# ━━━ $ICON_SUMMARY Summary ━━━
# -----------------------------------------------------------------------------------------------
echo ""
echo "━━━━━ $ICON_SUMMARY SNAPSHOT SUMMARY ━━━━━"
echo "$ICON_ZFS  Source:   ZFS ARC + system memory"
echo "$ICON_GEAR Mode:     READ-ONLY — no changes made"
echo "$ICON_TIME Duration: $(format_duration $((END - START)))"
echo "$ICON_DONE Status:   $ICON_SUCCESS DONE"
echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"