#!/bin/bash
# ==============================================================================================
# ================================= Backup Verify ==============================================
# ==============================================================================================
# Verifies the rsync mirror is healthy by comparing random file samples between
# local and remote servers using MD5 checksums.
#
# ── WHAT IT DOES ──────────────────────────────────────────────────────────────────────────────
# Randomly samples BACKUP_VERIFY_SAMPLE files per share above BACKUP_VERIFY_MIN_SIZE,
# computes MD5 checksums locally, then computes the same checksums on the remote via SSH
# and compares results. Catches silent corruption or incomplete syncs that rsync itself
# would not detect.
#
# ── RESULTS PER FILE ──────────────────────────────────────────────────────────────────────────
#   MATCH   — checksums identical, file is correctly mirrored ✅
#   MISMATCH — file exists on both but checksums differ — sync may have partially failed
#   MISSING  — file exists locally but not on remote — not yet synced or deleted on remote
#
# ── SHARE SELECTION ───────────────────────────────────────────────────────────────────────────
# Uses HOST*_BACKUP_VERIFY_SHARES if defined, falls back to HOST*_DAILY_SYNC_SHARES.
# Both aliased by detect_hosts() — no manual HOST1/HOST2 selection needed.
#
# ── SAFEGUARDS ────────────────────────────────────────────────────────────────────────────────
#   acquire_lock         — prevents concurrent runs producing duplicate/conflicting results
#   check_connectivity() — verifies remote reachable before attempting SSH calls
#   check_remote_array() — verifies remote array mounted before checksums
#                          remote array down = all files "missing" = false alarm ✅
#   version parity       — verifies both servers on compatible unRAID before trusting results
#   SSH_TIMEOUT          — all SSH calls protected against hangs
#   validate_unraid_cmd  — notify script validated before use
#   Silent by default    — only issues produce output, all-match runs are silent
#
# ── CONFIGURATION (master_host*.conf) ─────────────────────────────────────────────────────────
#   HOST*_BACKUP_VERIFY_SHARES — override share list (empty = use DAILY_SYNC_SHARES)
#   HOST*_DAILY_SYNC_SHARES    — fallback share list
#   All aliased by detect_hosts()
#
# ── CONFIGURATION (master.conf) ───────────────────────────────────────────────────────────────
#   BACKUP_VERIFY_SAMPLE   — random files to check per share (default 10)
#   BACKUP_VERIFY_MIN_SIZE — minimum file size to include in sample (default 1M)
#
# ── USAGE ─────────────────────────────────────────────────────────────────────────────────────
#   backup_verify.sh              — normal run
#   backup_verify.sh --dry-run    — show sample selection only, no checksums
#   backup_verify.sh --log        — verbose output
#   backup_verify.sh --status     — show config and exit
# ==============================================================================================

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

source "$SCRIPT_DIR/../load_config.sh"

parse_args "$@"

SSH_TIMEOUT=15

# ==============================================================================================
# ━━━ Setup ━━━
# ==============================================================================================
echo ""
echo "━━━ $ICON_GEAR Setup ━━━"

if [[ "$EUID" -ne 0 ]]; then
    error "Must be run as root"
    exit 1
fi

validate_unraid_cmd \
    "/usr/local/emhttp/plugins/dynamix/scripts/notify" \
    "" "" \
    "unRAID notify script" || warn "unRAID notify script not found — native notifications disabled"

acquire_lock

# detect_hosts() sets MY_ID and aliases BACKUP_VERIFY_SHARES + DAILY_SYNC_SHARES
detect_hosts

# Share selection — configured list or fallback to daily sync shares
if [[ ${#BACKUP_VERIFY_SHARES[@]} -gt 0 ]]; then
    VERIFY_SHARES=("${BACKUP_VERIFY_SHARES[@]}")
    log "Using BACKUP_VERIFY_SHARES (${#VERIFY_SHARES[@]} shares)"
else
    VERIFY_SHARES=("${DAILY_SYNC_SHARES[@]}")
    log "BACKUP_VERIFY_SHARES not set — using DAILY_SYNC_SHARES (${#VERIFY_SHARES[@]} shares)"
fi

if [[ ${#VERIFY_SHARES[@]} -eq 0 ]]; then
    warn "No shares configured for $MY_ID — nothing to verify"
    warn "Check HOST*_BACKUP_VERIFY_SHARES or HOST*_DAILY_SYNC_SHARES in master_host*.conf"
    exit 0
fi

[[ "$DRY_RUN" == true ]] && warn "DRY RUN — showing sample selection only, no checksums computed"

# ==============================================================================================
# ━━━ Status ━━━
# ==============================================================================================
if [[ "$SHOW_STATUS" == true ]]; then
    echo ""
    echo "━━━━━ $ICON_SUMMARY STATUS ━━━━━"
    echo "$ICON_HOST    My ID:      $MY_ID ($LOCAL_SERVER_NAME)"
    echo "$ICON_HOST    Remote:     $REMOTE_ID ($REMOTE_SERVER_NAME — $REMOTE_SERVER)"
    echo "$ICON_VERIFY  Shares:     ${#VERIFY_SHARES[@]}"
    echo "$ICON_VERIFY  Sample:     $BACKUP_VERIFY_SAMPLE files per share"
    echo "$ICON_VERIFY  Min size:   $BACKUP_VERIFY_MIN_SIZE"
    echo "$ICON_GEAR    Dry Run:    $DRY_RUN"
    echo ""
    echo "  Shares to verify:"
    for share in "${VERIFY_SHARES[@]}"; do
        echo "    $share"
    done
    echo "━━━━━━━━━━━━━━━━━━━━━━━"
    exit 0
fi

# ==============================================================================================
# ━━━ Pre-flight ━━━
# ==============================================================================================
echo ""
echo "━━━ $ICON_SHIELD Pre-flight ━━━"

resolve_remote_ip

# Connectivity — no point making 100+ SSH calls if remote is unreachable
check_connectivity

# Version parity — mismatched unRAID could cause md5sum path differences
check_unraid_version_parity || {
    warn "Version parity check failed — proceeding with caution"
    warn "Checksum results may be unreliable if md5sum path changed between versions"
}

# Remote array — if array is down all files appear "missing" = false alarm
if ! check_remote_array; then
    error "Remote array not mounted on $REMOTE_SERVER_NAME"
    error "All files would appear as MISSING — aborting to prevent false alarm"
    notify "Backup verify aborted on $(hostname) — remote array not mounted on $REMOTE_SERVER_NAME" \
        "Backup Verify" "warning"
    exit 1
fi

log "Pre-flight passed ✅"

# ==============================================================================================
# ━━━ Backup Verification ━━━
# ==============================================================================================
echo ""
echo "━━━ $ICON_VERIFY Backup Verification — $(date '+%Y-%m-%d %H:%M:%S') ━━━"
echo "$ICON_HOST    $MY_ID ($LOCAL_SERVER_NAME) → $REMOTE_ID ($REMOTE_SERVER_NAME)"
echo "$ICON_VERIFY  Sample: $BACKUP_VERIFY_SAMPLE files per share (min: $BACKUP_VERIFY_MIN_SIZE)"
echo ""

START=$(date +%s)
TOTAL_CHECKED=0
TOTAL_MATCH=0
TOTAL_MISMATCH=0
TOTAL_MISSING=0
SHARES_WITH_ISSUES=()

for share in "${VERIFY_SHARES[@]}"; do
    SHARE_NAME=$(basename "$share")
    echo "━━━ $ICON_VERIFY $SHARE_NAME ━━━"

    if [[ ! -d "$share" ]]; then
        warn "$SHARE_NAME not found locally — skipping"
        echo ""
        continue
    fi

    # Sample random files above minimum size
    mapfile -t SAMPLE_FILES < <(
        find "$share" -type f -size +"$BACKUP_VERIFY_MIN_SIZE" 2>/dev/null | \
        shuf | head -n "$BACKUP_VERIFY_SAMPLE"
    )

    if [[ ${#SAMPLE_FILES[@]} -eq 0 ]]; then
        log "$SHARE_NAME — no files found above $BACKUP_VERIFY_MIN_SIZE"
        echo ""
        continue
    fi

    log "$SHARE_NAME — sampled ${#SAMPLE_FILES[@]} files"

    if [[ "$DRY_RUN" == true ]]; then
        for f in "${SAMPLE_FILES[@]}"; do
            warn "DRY RUN — would check: $(basename "$f")"
        done
        echo ""
        continue
    fi

    SHARE_MATCH=0
    SHARE_MISMATCH=0
    SHARE_MISSING=0

    for local_file in "${SAMPLE_FILES[@]}"; do
        [[ -z "$local_file" ]] && continue

        # Local checksum
        local_md5=$(md5sum "$local_file" 2>/dev/null | awk '{print $1}')
        if [[ -z "$local_md5" ]]; then
            warn "Could not checksum locally: $(basename "$local_file") — skipping"
            continue
        fi

        # Remote checksum via SSH — timeout protected
        remote_md5=$(timeout "$SSH_TIMEOUT" ssh -i "$SSH_KEY" \
            -o ConnectTimeout="$SSH_TIMEOUT" \
            -o StrictHostKeyChecking=no \
            root@"$REMOTE_SERVER" \
            "md5sum '$local_file' 2>/dev/null | awk '{print \$1}'" 2>/dev/null)

        (( TOTAL_CHECKED++ ))

        if [[ -z "$remote_md5" ]]; then
            warn "$ICON_ERROR MISSING: $(basename "$local_file")"
            (( SHARE_MISSING++ ))
            (( TOTAL_MISSING++ ))
        elif [[ "$local_md5" == "$remote_md5" ]]; then
            log "MATCH: $(basename "$local_file")"
            (( SHARE_MATCH++ ))
            (( TOTAL_MATCH++ ))
        else
            error "MISMATCH: $(basename "$local_file")"
            error "  local:  $local_md5"
            error "  remote: $remote_md5"
            (( SHARE_MISMATCH++ ))
            (( TOTAL_MISMATCH++ ))
        fi
    done

    # Per-share result — only visible if issues found
    if [[ "$SHARE_MISMATCH" -gt 0 || "$SHARE_MISSING" -gt 0 ]]; then
        warn "$SHARE_NAME — match: $SHARE_MATCH  missing: $SHARE_MISSING  mismatch: $SHARE_MISMATCH"
        SHARES_WITH_ISSUES+=("$SHARE_NAME")
    else
        log "$SHARE_NAME — all $SHARE_MATCH files match ✅"
    fi

    echo ""
done

END=$(date +%s)

# ==============================================================================================
# ━━━ Summary ━━━
# ==============================================================================================
echo "━━━━━ $ICON_SUMMARY BACKUP VERIFY SUMMARY ━━━━━"
echo "$ICON_HOST    My ID:     $MY_ID ($LOCAL_SERVER_NAME)"
echo "$ICON_HOST    Remote:    $REMOTE_ID ($REMOTE_SERVER_NAME)"
echo "$ICON_VERIFY  Checked:   $TOTAL_CHECKED files"
echo "$ICON_TIME    Duration:  $(format_duration $(( END - START )))"
echo ""

if [[ "$TOTAL_MISMATCH" -gt 0 || "$TOTAL_MISSING" -gt 0 ]]; then
    echo "$ICON_SUCCESS Match:     $TOTAL_MATCH"
    warn "Missing:   $TOTAL_MISSING"
    [[ "$TOTAL_MISMATCH" -gt 0 ]] && echo "$ICON_ERROR   Mismatch:  $TOTAL_MISMATCH"
fi

if [[ "$DRY_RUN" == true ]]; then
    warn "DRY RUN — no checksums computed"
elif [[ "$TOTAL_MISMATCH" -gt 0 || "$TOTAL_MISSING" -gt 0 ]]; then
    echo "$ICON_ERROR Status: ISSUES FOUND — ${#SHARES_WITH_ISSUES[@]} share(s) need attention: ${SHARES_WITH_ISSUES[*]}"
    notify "Backup verify FAILED on $(hostname) → $REMOTE_SERVER_NAME — mismatches: $TOTAL_MISMATCH missing: $TOTAL_MISSING — shares: ${SHARES_WITH_ISSUES[*]}" \
        "Backup Verify" "warning"
else
    log "$ICON_DONE Status: all $TOTAL_CHECKED files match across ${#VERIFY_SHARES[@]} shares ✅"
fi
echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"

[[ "$TOTAL_MISMATCH" -gt 0 ]] && exit 1
exit 0