#!/usr/bin/env bash
# infra/bin/fly-retention — fly-retention.service, run hourly by
# fly-retention.timer (also called directly by fly-watchdog's disk guard
# at 85%/95%, see bin/fly-watchdog check_disk). docs/design/infra.md
# section 3: "prune segments > 7 d, highlights > 90 d, checkpoints per
# policy" and "Retention runs hourly rather than daily on purpose: a
# runaway recorder must not get 24 hours of rope."
#
# Usage: fly-retention [--aggressive]
#   --aggressive: called from the watchdog's 95% disk guard. Shrinks the
#   segment retention window to 1 day for this pass only (nothing else
#   changes) so a runaway recorder gets pruned immediately rather than
#   waiting for the next scheduled hourly pass.
set -euo pipefail

: "${FLY_STATE_DIR:=/srv/fly/state}"
: "${FLY_MEDIA_DIR:=/srv/fly/media}"
: "${SEGMENT_RETENTION_DAYS:=7}"
: "${HIGHLIGHT_RETENTION_DAYS:=90}"
: "${TEXTFILE_DIR:=/var/lib/node_exporter/textfile}"

AGGRESSIVE=0
[ "${1:-}" = "--aggressive" ] && AGGRESSIVE=1

log() { echo "fly-retention: $*" >&2; }

retention_days="$SEGMENT_RETENTION_DAYS"
[ "$AGGRESSIVE" -eq 1 ] && retention_days=1

rec_dir="${FLY_MEDIA_DIR}/rec"
highlight_dir="${FLY_MEDIA_DIR}/highlights"
state_checkpoint_dir="$FLY_STATE_DIR"

pruned_segments=0
pruned_highlights=0
pruned_checkpoints=0

# --- segments ----------------------------------------------------------------
if [ -d "$rec_dir" ]; then
    while IFS= read -r -d '' f; do
        rm -f "$f"
        pruned_segments=$((pruned_segments + 1))
    done < <(find "$rec_dir" -maxdepth 1 -type f -name '*.ts' -mtime "+${retention_days}" -print0)
fi

# Keep segments.csv in sync: drop rows whose file no longer exists. The
# index growing unbounded is its own slow disk leak otherwise.
segments_csv="${FLY_STATE_DIR}/segments.csv"
if [ -f "$segments_csv" ]; then
    tmp="${segments_csv}.tmp.$$"
    awk -F, '{ if (system("test -f \"" $1 "\"") == 0) print }' "$segments_csv" > "$tmp" 2>/dev/null || cp "$segments_csv" "$tmp"
    mv -f "$tmp" "$segments_csv"
fi

# --- highlights ----------------------------------------------------------
if [ -d "$highlight_dir" ]; then
    while IFS= read -r -d '' f; do
        rm -f "$f"
        pruned_highlights=$((pruned_highlights + 1))
    done < <(find "$highlight_dir" -maxdepth 1 -type f -name '*.mp4' -mtime "+${HIGHLIGHT_RETENTION_DAYS}" -print0)
fi

# --- checkpoints ---------------------------------------------------------
# Policy: never delete anything manifest.json references (latest, previous,
# or any rank in archives — docs/design/flysim.md section 8: "Later
# rotations never unlink archived generations"). This script only removes
# generation files that are NOT referenced by manifest.json at all — the
# unreferenced leftovers a crash-before-rename can produce
# (docs/design/flysim.md section 8: "a crash before the manifest rename
# leaves an unreferenced file that is never loaded"). flysim itself is
# expected to clean its own obsolete generations after a successful
# commit; this is strictly a safety-net pass, and it is conservative: any
# file it cannot positively prove is unreferenced is left alone.
manifest="${state_checkpoint_dir}/manifest.json"
if [ -f "$manifest" ] && command -v jq >/dev/null 2>&1; then
    referenced="$(jq -r '
        [.latest, .previous, (.archives // {} | to_entries[] | .value)]
        | map(select(. != null))
        | map(tostring)
        | .[]
    ' "$manifest" 2>/dev/null || true)"

    if [ -n "$referenced" ]; then
        while IFS= read -r -d '' f; do
            base="$(basename "$f")"
            gen="$(echo "$base" | sed -n 's/^\([0-9]\+\)\.checkpoint$/\1/p')"
            [ -z "$gen" ] && continue
            if ! echo "$referenced" | grep -qx "$gen"; then
                # mtime guard: never touch a checkpoint written in the last
                # hour, in case it is mid-commit (write happens before the
                # manifest rename, so a brand-new file can briefly look
                # unreferenced).
                if [ -z "$(find "$f" -mmin -60 2>/dev/null)" ]; then
                    rm -f "$f"
                    pruned_checkpoints=$((pruned_checkpoints + 1))
                fi
            fi
        done < <(find "$state_checkpoint_dir" -maxdepth 1 -type f -name '*.checkpoint' -not -name 'milestone-*' -print0)
    fi
fi

log "pruned: ${pruned_segments} segments, ${pruned_highlights} highlights, ${pruned_checkpoints} orphan checkpoints (aggressive=${AGGRESSIVE}, window=${retention_days}d)"

if [ -d "$TEXTFILE_DIR" ]; then
    tmp="${TEXTFILE_DIR}/fly_retention.prom.$$"
    {
        echo "# HELP fly_retention_pruned_total Files removed by the most recent fly-retention pass, by kind."
        echo "# TYPE fly_retention_pruned_total gauge"
        echo "fly_retention_pruned_total{kind=\"segment\"} ${pruned_segments}"
        echo "fly_retention_pruned_total{kind=\"highlight\"} ${pruned_highlights}"
        echo "fly_retention_pruned_total{kind=\"checkpoint\"} ${pruned_checkpoints}"
        echo "# HELP fly_retention_last_run_seconds Unix time of the last completed retention pass."
        echo "# TYPE fly_retention_last_run_seconds gauge"
        echo "fly_retention_last_run_seconds $(date +%s)"
    } > "$tmp"
    mv -f "$tmp" "${TEXTFILE_DIR}/fly_retention.prom"
fi