#!/usr/bin/env bash

set -euo pipefail

# 将指定消费组在原始 Topic 上的 offset 重置到指定 Kafka 消息时间。
# 适用于“丢弃截止时间之前的历史积压，保留截止时间之后消息”的现场操作。
#
# 本脚本不会停止/启动应用，也不会删除 Topic 或消息：
# - 执行前必须由运维停止该消费组的全部 syslog-consumer-rule 实例；
# - 自动导出原 offset，Kafka 数据仍在 retention 内时可用于人工回退；
# - 先执行 dry-run，只有输入精确确认串才执行真正的 offset 重置。

SCRIPT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
BOOTSTRAP="${BOOTSTRAP:-10.141.121.35:9092,10.141.121.50:9092,10.141.121.59:9092}"
GROUP_ID="${GROUP_ID:-agent-01-syslog-group}"
RAW_TOPIC="${RAW_TOPIC:-agent-01-syslog-topic}"
CUTOFF_DATETIME="${CUTOFF_DATETIME:-2026-09-11T00:00:00.000}"
KAFKA_TIMEZONE="${KAFKA_TIMEZONE:-Asia/Shanghai}"

# 优先使用调用方显式指定的目录；否则自动识别脚本同目录、现场 Kafka 安装目录或 PATH。
if [[ -z "${KAFKA_BIN:-}" ]]; then
  for CANDIDATE_BIN in \
    "${SCRIPT_DIR}" \
    "/opt/kafka/kafka_2.13-3.6.1/bin"; do
    if [[ -x "${CANDIDATE_BIN}/kafka-consumer-groups.sh" ]] \
        && [[ -x "${CANDIDATE_BIN}/kafka-topics.sh" ]]; then
      KAFKA_BIN="${CANDIDATE_BIN}"
      break
    fi
  done
fi

if [[ -z "${KAFKA_BIN:-}" ]] && command -v kafka-consumer-groups.sh >/dev/null 2>&1; then
  KAFKA_BIN=$(dirname -- "$(command -v kafka-consumer-groups.sh)")
fi

if [[ -z "${KAFKA_BIN:-}" ]]; then
  echo "ERROR: 未找到 Kafka CLI；现场预期路径为 /opt/kafka/kafka_2.13-3.6.1/bin" >&2
  exit 1
fi

CONSUMER_GROUPS_CMD="${KAFKA_BIN}/kafka-consumer-groups.sh"
TOPICS_CMD="${KAFKA_BIN}/kafka-topics.sh"

if [[ ! -x "${CONSUMER_GROUPS_CMD}" ]] || [[ ! -x "${TOPICS_CMD}" ]]; then
  echo "ERROR: ${KAFKA_BIN} 下缺少可执行的 kafka-consumer-groups.sh 或 kafka-topics.sh" >&2
  exit 1
fi

if [[ ! "${CUTOFF_DATETIME}" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}$ ]]; then
  echo "ERROR: CUTOFF_DATETIME 格式必须是 YYYY-MM-DDTHH:mm:ss.SSS" >&2
  exit 1
fi

COMMON_ARGS=(--bootstrap-server "${BOOTSTRAP}")
if [[ -n "${COMMAND_CONFIG:-}" ]]; then
  if [[ ! -r "${COMMAND_CONFIG}" ]]; then
    echo "ERROR: 无法读取认证配置 ${COMMAND_CONFIG}" >&2
    exit 1
  fi
  COMMON_ARGS+=(--command-config "${COMMAND_CONFIG}")
fi

# Kafka 3.6 的 --to-datetime 不携带时区，显式固定 JVM 时区，避免宿主机差异造成 8 小时偏移。
export KAFKA_OPTS="${KAFKA_OPTS:-} -Duser.timezone=${KAFKA_TIMEZONE}"

RUN_ID=$(date '+%Y%m%d_%H%M%S')
AUDIT_DIR="${OFFSET_BACKUP_DIR:-./kafka-offset-reset-${RUN_ID}}"
mkdir -p "${AUDIT_DIR}"

BEFORE_FILE="${AUDIT_DIR}/before-describe.txt"
RESTORE_FILE="${AUDIT_DIR}/restore-current-offsets.csv"
DRY_RUN_FILE="${AUDIT_DIR}/reset-dry-run.txt"
EXECUTE_FILE="${AUDIT_DIR}/reset-execute.txt"
AFTER_FILE="${AUDIT_DIR}/after-describe.txt"

echo "目标 Kafka：${BOOTSTRAP}"
echo "目标消费组：${GROUP_ID}"
echo "目标 Topic：${RAW_TOPIC}"
echo "保留起点：${CUTOFF_DATETIME} (${KAFKA_TIMEZONE})"
echo "审计目录：${AUDIT_DIR}"

echo "[1/6] 检查 Topic"
TOPIC_INFO=$("${TOPICS_CMD}" "${COMMON_ARGS[@]}" --describe --topic "${RAW_TOPIC}")
printf '%s\n' "${TOPIC_INFO}"

PARTITION_COUNT=$(printf '%s\n' "${TOPIC_INFO}" | awk '
  /PartitionCount:/ {
    for (i=1; i<=NF; i++) if ($i=="PartitionCount:") { print $(i+1); exit }
  }
')
if [[ ! "${PARTITION_COUNT}" =~ ^[1-9][0-9]*$ ]]; then
  echo "ERROR: 无法确认 ${RAW_TOPIC} 的分区数" >&2
  exit 1
fi

echo "[2/6] 检查消费组是否已停止，并保存执行前快照"
"${CONSUMER_GROUPS_CMD}" "${COMMON_ARGS[@]}" \
  --describe --group "${GROUP_ID}" 2>&1 | tee "${BEFORE_FILE}"

MATCHED_ROWS=$(awk -v topic="${RAW_TOPIC}" '
  $2==topic && $3~/^[0-9]+$/ && $4~/^[0-9]+$/ && $5~/^[0-9]+$/ {count++}
  END {print count+0}
' "${BEFORE_FILE}")
if [[ "${MATCHED_ROWS}" -ne "${PARTITION_COUNT}" ]]; then
  echo "ERROR: 快照只识别到 ${MATCHED_ROWS}/${PARTITION_COUNT} 个目标分区，拒绝继续" >&2
  exit 1
fi

if awk -v topic="${RAW_TOPIC}" '
  $2==topic && $3~/^[0-9]+$/ && $7!="-" {active=1}
  END {exit(active ? 0 : 1)}
' "${BEFORE_FILE}"; then
  echo "ERROR: 消费组 ${GROUP_ID} 仍有在线成员。请先停止全部 syslog-consumer-rule 实例。" >&2
  exit 1
fi

CURRENT_LAG=$(awk -v topic="${RAW_TOPIC}" '
  $2==topic && $6~/^[0-9]+$/ {sum+=$6}
  END {printf "%.0f", sum+0}
' "${BEFORE_FILE}")
echo "当前积压：${CURRENT_LAG} 条"

echo "[3/6] 导出原 offset 回退文件"
"${CONSUMER_GROUPS_CMD}" "${COMMON_ARGS[@]}" \
  --group "${GROUP_ID}" \
  --topic "${RAW_TOPIC}" \
  --reset-offsets \
  --to-current \
  --dry-run \
  --export > "${RESTORE_FILE}"

RESTORE_ROWS=$(awk -F, -v topic="${RAW_TOPIC}" '
  $1==topic && $2~/^[0-9]+$/ && $3~/^[0-9]+$/ {count++}
  END {print count+0}
' "${RESTORE_FILE}")
if [[ "${RESTORE_ROWS}" -ne "${PARTITION_COUNT}" ]]; then
  echo "ERROR: 回退文件只包含 ${RESTORE_ROWS}/${PARTITION_COUNT} 个分区，拒绝继续" >&2
  exit 1
fi
echo "原 offset 已保存：${RESTORE_FILE}"

echo "[4/6] 预演按时间重置"
"${CONSUMER_GROUPS_CMD}" "${COMMON_ARGS[@]}" \
  --group "${GROUP_ID}" \
  --topic "${RAW_TOPIC}" \
  --reset-offsets \
  --to-datetime "${CUTOFF_DATETIME}" \
  --dry-run | tee "${DRY_RUN_FILE}"

PLAN_ROWS=$(awk -v topic="${RAW_TOPIC}" '
  $1==topic && $2~/^[0-9]+$/ && $3~/^[0-9]+$/ {count++; next}
  $2==topic && $3~/^[0-9]+$/ && $4~/^[0-9]+$/ {count++}
  END {print count+0}
' "${DRY_RUN_FILE}")
if [[ "${PLAN_ROWS}" -ne "${PARTITION_COUNT}" ]]; then
  echo "ERROR: dry-run 只生成 ${PLAN_ROWS}/${PARTITION_COUNT} 个分区，拒绝执行" >&2
  exit 1
fi

EXPECTED_CONFIRM="RESET:${GROUP_ID}:${RAW_TOPIC}:${CUTOFF_DATETIME}"
echo "[5/6] 等待人工确认"
echo "即将永久跳过 ${CUTOFF_DATETIME} (${KAFKA_TIMEZONE}) 之前尚未消费的消息。"
echo "原 offset 回退文件：${RESTORE_FILE}"
echo "如确认执行，请完整输入：${EXPECTED_CONFIRM}"

if [[ -n "${CONFIRM_RESET:-}" ]]; then
  CONFIRM_INPUT="${CONFIRM_RESET}"
elif [[ -t 0 ]]; then
  read -r CONFIRM_INPUT
else
  echo "ERROR: 当前不是交互终端；必须通过 CONFIRM_RESET 提供精确确认串" >&2
  exit 1
fi

if [[ "${CONFIRM_INPUT}" != "${EXPECTED_CONFIRM}" ]]; then
  echo "CANCELLED: 确认串不匹配，未修改任何 offset。" >&2
  exit 1
fi

echo "[6/6] 执行 offset 重置"
"${CONSUMER_GROUPS_CMD}" "${COMMON_ARGS[@]}" \
  --group "${GROUP_ID}" \
  --topic "${RAW_TOPIC}" \
  --reset-offsets \
  --to-datetime "${CUTOFF_DATETIME}" \
  --execute | tee "${EXECUTE_FILE}"

echo "保存执行后快照"
"${CONSUMER_GROUPS_CMD}" "${COMMON_ARGS[@]}" \
  --describe --group "${GROUP_ID}" 2>&1 | tee "${AFTER_FILE}"

echo "PASS: 已将 ${GROUP_ID}/${RAW_TOPIC} 重置到 ${CUTOFF_DATETIME} (${KAFKA_TIMEZONE})。"
echo "未删除 Topic；现在可以启动 syslog-consumer-rule 并检查 LAG。"
echo "回退文件：${RESTORE_FILE}（仅在 Kafka 原消息仍处于 retention 内时有效）。"