#!/bin/bash
# Emergency rollback for AI QC.
#
# Usage:
#   rollback.sh last              Roll back to the checkpoint saved by deploy.sh
#   rollback.sh <commit-hash>     Roll back to an explicit commit

set -euo pipefail

APP_DIR=/opt/ai_qc
SERVICE=ai-qc.service
HEALTH_URL=http://127.0.0.1:7183/health
ROLLBACK_FILE="$APP_DIR/.last_deploy_rollback"

TARGET=${1:-}

if [[ -z "$TARGET" || "$TARGET" == "last" ]]; then
    if [[ ! -f "$ROLLBACK_FILE" ]]; then
        echo "No .last_deploy_rollback file. Specify a commit hash explicitly."
        echo "Usage: $(basename "$0") last | <commit-hash>"
        exit 1
    fi
    TARGET=$(cat "$ROLLBACK_FILE")
fi

cd "$APP_DIR"

if ! git rev-parse --verify --quiet "$TARGET^{commit}" > /dev/null; then
    echo "ERROR: Commit '$TARGET' not found"
    exit 1
fi

CURRENT_REV=$(git rev-parse HEAD)
CURRENT_SHORT=$(git rev-parse --short HEAD)
TARGET_REV=$(git rev-parse "$TARGET")
TARGET_SHORT=$(git rev-parse --short "$TARGET")

if [[ "$CURRENT_REV" == "$TARGET_REV" ]]; then
    echo "Already at $TARGET_SHORT — nothing to do."
    exit 0
fi

echo "============================================"
echo "  AI QC rollback"
echo "============================================"
echo "Current: $CURRENT_SHORT  $(git log -1 --format='%s' HEAD)"
echo "Target:  $TARGET_SHORT  $(git log -1 --format='%s' "$TARGET")"
echo ""

read -r -p "Proceed? (y/N): " confirm
if [[ ! $confirm =~ ^[Yy]$ ]]; then
    echo "Cancelled."
    exit 0
fi

git reset --hard "$TARGET_REV"
sudo systemctl restart "$SERVICE"
sleep 3

if curl -sf -o /dev/null "$HEALTH_URL"; then
    echo "Rollback OK. Now at $TARGET_SHORT."
    exit 0
fi

echo "Service unhealthy after rollback."
echo "sudo journalctl -u $SERVICE -n 100"
exit 1