#!/usr/bin/env bash
# Shared helpers for ops/backup.sh, ops/backup-forgejo.sh, and
# tradein-mvp/deploy/backup-tradein-db.sh (#2203, missed-run detection).
#
# SOURCED, not executed directly — no shebang execution of its own. Inherits
# the caller's `set -euo pipefail`. Keep this dependency-free: bash builtins +
# coreutils (date, stat, mkdir, grep, awk, mktemp) + curl (only used by
# notify() when Telegram vars are actually set — curl is already a hard
# requirement of ops/uptime-healthcheck.sh on the same box, so this adds no
# new dependency).
#
# Load with (script computes its own dir so this works regardless of cron's
# CWD or which repo subdir the caller lives in):
#   SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
#   source "$SCRIPT_DIR/lib-backup.sh"           # caller is in ops/
#   source "$SCRIPT_DIR/../../ops/lib-backup.sh" # caller is in tradein-mvp/deploy/

log() { echo "[$(date -u +'%Y-%m-%dT%H:%M:%SZ')] $*"; }

# --- notify ------------------------------------------------------------
# Reuses the SAME Telegram channel/bot as ops/uptime-healthcheck.sh (#75) —
# this is NOT a second alerting system, just the same TELEGRAM_BOT_TOKEN /
# TELEGRAM_CHAT_ID variable names read from a DIFFERENT env file
# (/etc/default/gendesign-backup, not /etc/default/gendesign-uptime) so
# backup alerting doesn't depend on the uptime watchdog's config being
# present, and vice versa. Point both files at the same bot/chat if you want
# one Telegram destination for everything — that's an ops choice, not this
# script's concern.
#
# No-op (logs only) when unset — this is the extension point: to wire a
# different channel later, edit ONLY this function; every caller in this repo
# goes through notify(), never curl/telegram directly.
notify() {
    local text="$1"
    local backup_env="${BACKUP_ENV_FILE:-/etc/default/gendesign-backup}"

    if [[ -z "${TELEGRAM_BOT_TOKEN:-}" || -z "${TELEGRAM_CHAT_ID:-}" ]]; then
        # shellcheck source=/dev/null
        [[ -f "$backup_env" ]] && source "$backup_env"
    fi

    if [[ -z "${TELEGRAM_BOT_TOKEN:-}" || -z "${TELEGRAM_CHAT_ID:-}" ]]; then
        log "NOTIFY (telegram disabled — set TELEGRAM_BOT_TOKEN/TELEGRAM_CHAT_ID in ${backup_env}): $text"
        return 0
    fi

    curl -fsS --max-time 15 \
        -X POST "https://api.telegram.org/bot${TELEGRAM_BOT_TOKEN}/sendMessage" \
        -d "chat_id=${TELEGRAM_CHAT_ID}" \
        -d "disable_web_page_preview=true" \
        --data-urlencode "text=${text}" \
        >/dev/null 2>&1 \
        || log "WARN: telegram sendMessage failed"
}

# --- sentinel (missed-run detection) ------------------------------------
# write_sentinel <path> — call ONLY after every guard in the caller has
# already passed (mirrors the existing "never mark success before a dump is
# verified good" discipline in backup.sh/backup-tradein-db.sh). Content is
# just an ISO-8601 UTC timestamp for human debugging; the actual staleness
# check below is based on the file's mtime, not on parsing that content.
write_sentinel() {
    local sentinel_file="$1"
    mkdir -p "$(dirname "$sentinel_file")"
    date -u +'%Y-%m-%dT%H:%M:%SZ' > "$sentinel_file"
}

# sentinel_age_hours <path> — echoes the sentinel's age in whole hours on
# stdout. Returns 1 (nothing echoed) if the file doesn't exist or its mtime
# can't be read — caller treats that as "stale" (a backup that never
# succeeded is exactly the case this exists to catch).
sentinel_age_hours() {
    local sentinel_file="$1" now_epoch sentinel_epoch
    [[ -f "$sentinel_file" ]] || return 1
    now_epoch=$(date -u +%s)
    # GNU stat (prod VM, Debian) first; BSD stat fallback (local/macOS dev).
    sentinel_epoch=$(stat -c %Y "$sentinel_file" 2>/dev/null || stat -f %m "$sentinel_file" 2>/dev/null) || return 1
    echo $(( (now_epoch - sentinel_epoch) / 3600 ))
}

# --- transition-tracked alert state --------------------------------------
# Same idiom as ops/uptime-healthcheck.sh's prev_status()/set_status(): a
# flat "<label> <status>" file, one line per label, so repeated runs alert
# only on a STATE TRANSITION (fresh->stale, stale->fresh) instead of every
# single run — avoids Telegram spam from an hourly staleness-check cron.
# Intentionally a separate, independent implementation (not shared code with
# uptime-healthcheck.sh) — that script is out of scope for this change.
backup_prev_status() {
    local state_file="$1" label="$2" v
    [[ -f "$state_file" ]] || { echo "unknown"; return; }
    v="$(grep -E "^${label} " "$state_file" 2>/dev/null | tail -1 | awk '{print $2}')"
    echo "${v:-unknown}"
}

backup_set_status() {
    local state_file="$1" label="$2" status="$3" tmp
    mkdir -p "$(dirname "$state_file")"
    tmp="$(mktemp)"
    if [[ -f "$state_file" ]]; then
        grep -vE "^${label} " "$state_file" > "$tmp" 2>/dev/null || true
    fi
    echo "${label} ${status}" >> "$tmp"
    mv "$tmp" "$state_file"
}

# --- dump integrity (opt-in for NEW scripts only) ------------------------
# Identical logic to the verify_dump_integrity() already duplicated in
# ops/backup.sh and tradein-mvp/deploy/backup-tradein-db.sh — deliberately
# NOT deduped there (those two are proven/hardened; don't touch working
# code for a refactor nobody asked for). This copy exists so NEW scripts
# (ops/backup-forgejo.sh) get the same guard without a third copy-paste.
verify_dump_integrity() {
    local file="$1" trailer="$2" label="$3"
    if ! gzip -t "$file" 2>/dev/null; then
        log "ERROR: ${label} failed gzip integrity check -> $file" >&2
        return 1
    fi
    if ! gunzip -c "$file" 2>/dev/null | tail -5 | grep -qF -- "$trailer"; then
        log "ERROR: ${label} missing trailer '${trailer}' -> $file (truncated dump?)" >&2
        return 1
    fi
    return 0
}