#!/usr/bin/env bash

set -euo pipefail

# 物理清空指定 Kafka Topic 中当前已有的消息，但保留 Topic 本身、分区、副本和配置。
#
# 默认值对应当前客户现场，复制到 Kafka 主机后可直接执行：
#   bash 04-clear-topic-messages.sh
#
# 清理其他 Topic 时可覆盖 TARGET_TOPIC：
#   TARGET_TOPIC=other-topic bash 04-clear-topic-messages.sh
#
# 有认证的集群需额外设置：
#   COMMAND_CONFIG=/path/to/client.properties bash 04-clear-topic-messages.sh
#
# 注意：
# - 执行前必须停止目标 Topic 的生产者和消费者；
# - 消息删除后通常不可恢复；
# - 本脚本不会删除 Topic，也不会修改任何消费组 offset；
# - 若消费组 offset 低于删除后的日志起始 offset，消费者后续行为取决于 auto.offset.reset。

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}"
RAW_TOPIC="${RAW_TOPIC:-agent-01-syslog-topic}"
TARGET_TOPIC="${TARGET_TOPIC:-${RAW_TOPIC}}"

if [[ ! "${TARGET_TOPIC}" =~ ^[a-zA-Z0-9._-]+$ ]]; then
  echo "ERROR: TARGET_TOPIC 包含非法字符：${TARGET_TOPIC}" >&2
  exit 1
fi

# 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" \
    "/opt/kafka/bin"; do
    if [[ -x "${CANDIDATE_BIN}/kafka-topics.sh" ]] \
        && [[ -x "${CANDIDATE_BIN}/kafka-delete-records.sh" ]]; then
      KAFKA_BIN="${CANDIDATE_BIN}"
      break
    fi
  done
fi

if [[ -z "${KAFKA_BIN:-}" ]] \
    && command -v kafka-topics.sh >/dev/null 2>&1 \
    && command -v kafka-delete-records.sh >/dev/null 2>&1; then
  KAFKA_BIN=$(dirname -- "$(command -v kafka-topics.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

TOPICS_CMD="${KAFKA_BIN}/kafka-topics.sh"
DELETE_RECORDS_CMD="${KAFKA_BIN}/kafka-delete-records.sh"

if [[ ! -x "${TOPICS_CMD}" ]] || [[ ! -x "${DELETE_RECORDS_CMD}" ]]; then
  echo "ERROR: ${KAFKA_BIN} 下缺少 kafka-topics.sh 或 kafka-delete-records.sh" >&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

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

BEFORE_FILE="${AUDIT_DIR}/topic-before.txt"
DELETE_JSON="${AUDIT_DIR}/delete-records.json"
DELETE_RESULT="${AUDIT_DIR}/delete-result.txt"
AFTER_FILE="${AUDIT_DIR}/topic-after.txt"

echo "目标 Kafka：${BOOTSTRAP}"
echo "目标 Topic：${TARGET_TOPIC}"
echo "Kafka CLI：${KAFKA_BIN}"
echo "审计目录：${AUDIT_DIR}"

echo "[1/5] 测试 Kafka 连接并确认 Topic 存在"
"${TOPICS_CMD}" "${COMMON_ARGS[@]}" --list >/dev/null
TOPIC_INFO=$("${TOPICS_CMD}" "${COMMON_ARGS[@]}" --describe --topic "${TARGET_TOPIC}")
printf '%s\n' "${TOPIC_INFO}" | tee "${BEFORE_FILE}"

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 ${TARGET_TOPIC} 的分区数，拒绝继续" >&2
  exit 1
fi

echo "[2/5] 为 ${PARTITION_COUNT} 个分区生成删除清单"
printf '%s\n' "${TOPIC_INFO}" | awk -v topic="${TARGET_TOPIC}" '
  BEGIN {
    printf "{\"partitions\":["
    first=1
  }
  /Partition:/ {
    for (i=1; i<=NF; i++) {
      if ($i=="Partition:" && $(i+1)~/^[0-9]+$/) {
        if (!first) printf ","
        printf "{\"topic\":\"%s\",\"partition\":%s,\"offset\":-1}", topic, $(i+1)
        first=0
      }
    }
  }
  END {
    print "],\"version\":1}"
  }
' > "${DELETE_JSON}"

DELETE_ROWS=$(awk -F'"partition":' '{count+=NF-1} END {print count+0}' "${DELETE_JSON}")
if [[ "${DELETE_ROWS}" -ne "${PARTITION_COUNT}" ]]; then
  echo "ERROR: 删除清单只识别到 ${DELETE_ROWS}/${PARTITION_COUNT} 个分区，拒绝继续" >&2
  exit 1
fi

cat "${DELETE_JSON}"

EXPECTED_CONFIRM="CLEAR:${TARGET_TOPIC}:${PARTITION_COUNT}"
echo "[3/5] 等待人工确认"
echo "警告：将永久删除 ${TARGET_TOPIC} 当前已有的全部消息，但保留 Topic。"
echo "请确认生产者和消费者均已停止。"
echo "如确认执行，请完整输入：${EXPECTED_CONFIRM}"

if [[ -n "${CONFIRM_CLEAR:-}" ]]; then
  CONFIRM_INPUT="${CONFIRM_CLEAR}"
elif [[ -t 0 ]]; then
  read -r CONFIRM_INPUT
else
  echo "ERROR: 当前不是交互终端；必须通过 CONFIRM_CLEAR 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，未删除任何消息。" >&2
  exit 1
fi

echo "[4/5] 清空 Topic 当前已有消息"
"${DELETE_RECORDS_CMD}" "${COMMON_ARGS[@]}" \
  --offset-json-file "${DELETE_JSON}" | tee "${DELETE_RESULT}"

echo "[5/5] 再次检查 Topic"
"${TOPICS_CMD}" "${COMMON_ARGS[@]}" \
  --describe --topic "${TARGET_TOPIC}" | tee "${AFTER_FILE}"

echo "PASS: ${TARGET_TOPIC} 当前已有消息已提交物理删除。"
echo "Topic、分区、副本和配置均保留，消费组 offset 未修改。"
echo "执行记录：${AUDIT_DIR}"