#!/usr/bin/env bash
# gstack-update-check — daily version check for all skills.
#
# Output (one line, or nothing):
#   JUST_UPGRADED <old> <new>       — marker found from recent upgrade
#   UPGRADE_AVAILABLE <old> <new>   — remote VERSION differs from local
#   (nothing)                       — up to date or check skipped
#
# Env overrides (for testing):
#   GSTACK_DIR          — override auto-detected gstack root
#   GSTACK_REMOTE_URL   — override remote VERSION URL
#   GSTACK_STATE_DIR    — override ~/.gstack state directory
set -euo pipefail

GSTACK_DIR="${GSTACK_DIR:-$(cd "$(dirname "$0")/.." && pwd)}"
STATE_DIR="${GSTACK_STATE_DIR:-$HOME/.gstack}"
CACHE_FILE="$STATE_DIR/last-update-check"
MARKER_FILE="$STATE_DIR/just-upgraded-from"
VERSION_FILE="$GSTACK_DIR/VERSION"
REMOTE_URL="${GSTACK_REMOTE_URL:-https://raw.githubusercontent.com/garrytan/gstack/main/VERSION}"

# ─── Step 1: Read local version ──────────────────────────────
LOCAL=""
if [ -f "$VERSION_FILE" ]; then
  LOCAL="$(cat "$VERSION_FILE" 2>/dev/null | tr -d '[:space:]')"
fi
if [ -z "$LOCAL" ]; then
  exit 0  # No VERSION file → skip check
fi

# ─── Step 2: Check "just upgraded" marker ─────────────────────
if [ -f "$MARKER_FILE" ]; then
  OLD="$(cat "$MARKER_FILE" 2>/dev/null | tr -d '[:space:]')"
  rm -f "$MARKER_FILE"
  mkdir -p "$STATE_DIR"
  echo "UP_TO_DATE $LOCAL" > "$CACHE_FILE"
  if [ -n "$OLD" ]; then
    echo "JUST_UPGRADED $OLD $LOCAL"
  fi
  exit 0
fi

# ─── Step 3: Check cache freshness (24h = 1440 min) ──────────
if [ -f "$CACHE_FILE" ]; then
  # Cache is fresh if modified within 1440 minutes
  STALE=$(find "$CACHE_FILE" -mmin +1440 2>/dev/null || true)
  if [ -z "$STALE" ]; then
    # Cache is fresh — read it
    CACHED="$(cat "$CACHE_FILE" 2>/dev/null || true)"
    case "$CACHED" in
      UP_TO_DATE*)
        exit 0
        ;;
      UPGRADE_AVAILABLE*)
        # Verify local version still matches cached old version
        CACHED_OLD="$(echo "$CACHED" | awk '{print $2}')"
        if [ "$CACHED_OLD" = "$LOCAL" ]; then
          echo "$CACHED"
          exit 0
        fi
        # Local version changed (manual upgrade?) — fall through to re-check
        ;;
    esac
  fi
fi

# ─── Step 4: Slow path — fetch remote version ────────────────
mkdir -p "$STATE_DIR"

REMOTE=""
REMOTE="$(curl -sf --max-time 5 "$REMOTE_URL" 2>/dev/null || true)"
REMOTE="$(echo "$REMOTE" | tr -d '[:space:]')"

# Validate: must look like a version number (reject HTML error pages)
if ! echo "$REMOTE" | grep -qE '^[0-9]+\.[0-9.]+$'; then
  # Invalid or empty response — assume up to date
  echo "UP_TO_DATE $LOCAL" > "$CACHE_FILE"
  exit 0
fi

if [ "$LOCAL" = "$REMOTE" ]; then
  echo "UP_TO_DATE $LOCAL" > "$CACHE_FILE"
  exit 0
fi

# Versions differ — upgrade available
echo "UPGRADE_AVAILABLE $LOCAL $REMOTE" > "$CACHE_FILE"
echo "UPGRADE_AVAILABLE $LOCAL $REMOTE"