#!/usr/bin/env bash

set -euo pipefail

SOURCE_BRANCH="${SOURCE_BRANCH:-master}"
COMMIT_HASH="${COMMIT_HASH:-}"
GIT_REMOTE_URL="${GIT_REMOTE_URL:-}"
GIT_REMOTE_FALLBACK_URL="${GIT_REMOTE_FALLBACK_URL:-}"
SOURCE_COMMIT_FILE="${SOURCE_COMMIT_FILE:-.jenkins-source-commit}"

# Windows PowerShell 5.1 的 UTF-8 输出可能带 BOM；下游参数校验前先剥离不可见字节。
SOURCE_BRANCH="$(printf "%s" "${SOURCE_BRANCH}" | sed $'s/^\xef\xbb\xbf//' | tr -d '\r\n')"
COMMIT_HASH="$(printf "%s" "${COMMIT_HASH}" | sed $'s/^\xef\xbb\xbf//' | tr -d '\r\n')"
GIT_REMOTE_URL="$(printf "%s" "${GIT_REMOTE_URL}" | sed $'s/^\xef\xbb\xbf//' | tr -d '\r\n')"
GIT_REMOTE_FALLBACK_URL="$(printf "%s" "${GIT_REMOTE_FALLBACK_URL}" | sed $'s/^\xef\xbb\xbf//' | tr -d '\r\n')"

if [[ ! "${SOURCE_BRANCH}" =~ ^[0-9A-Za-z._/-]+$ ]]; then
  echo "[jenkins-checkout-source] SOURCE_BRANCH 只能包含数字、字母、点、下划线、短横线和斜杠: ${SOURCE_BRANCH}" >&2
  exit 1
fi

if [[ "${SOURCE_BRANCH}" == /* || "${SOURCE_BRANCH}" == */ || "${SOURCE_BRANCH}" == *..* ]]; then
  echo "[jenkins-checkout-source] SOURCE_BRANCH 不能以斜杠开头/结尾，也不能包含连续点号: ${SOURCE_BRANCH}" >&2
  exit 1
fi

if [[ -n "${COMMIT_HASH}" && ! "${COMMIT_HASH}" =~ ^[0-9a-fA-F]{7,40}$ ]]; then
  echo "[jenkins-checkout-source] COMMIT_HASH 只能填写 7 到 40 位十六进制 Git commit hash: ${COMMIT_HASH}" >&2
  exit 1
fi

GIT_REMOTE_CANDIDATES=()
add_git_remote_candidate() {
  local candidate="$1"
  local existing
  if [[ -z "${candidate}" ]]; then
    return
  fi
  for existing in "${GIT_REMOTE_CANDIDATES[@]}"; do
    if [[ "${existing}" == "${candidate}" ]]; then
      return
    fi
  done
  GIT_REMOTE_CANDIDATES+=("${candidate}")
}

fetch_source_branch() {
  local remote_url="$1"
  if [[ -n "${remote_url}" ]]; then
    git remote set-url origin "${remote_url}"
  fi

  echo "[jenkins-checkout-source] 尝试 Git 远端: ${remote_url:-origin}"
  git fetch --no-tags --prune --depth=1 origin "+refs/heads/${SOURCE_BRANCH}:refs/remotes/origin/${SOURCE_BRANCH}"
}

is_shallow_repository() {
  [[ "$(git rev-parse --is-shallow-repository 2>/dev/null || echo false)" == "true" ]]
}

resolve_requested_commit_if_on_branch() {
  local requested_commit="$1"
  local resolved_commit

  if ! git cat-file -e "${requested_commit}^{commit}" 2>/dev/null; then
    return 1
  fi

  resolved_commit="$(git rev-parse "${requested_commit}^{commit}")"
  if ! git merge-base --is-ancestor "${resolved_commit}" "refs/remotes/origin/${SOURCE_BRANCH}" 2>/dev/null; then
    return 1
  fi

  printf "%s\n" "${resolved_commit}"
}

resolve_requested_commit_with_deepen() {
  local requested_commit="$1"
  local deepen_steps_raw="${GENARRATIVE_JENKINS_CHECKOUT_DEEPEN_STEPS:-50 200 1000 5000}"
  local deepen_steps=()
  local deepen_depth
  local resolved_commit

  # 中文注释：上游构建 commit 通常就是分支 HEAD，先吃浅克隆；确实不是浅历史内提交时再逐步加深。
  if resolved_commit="$(resolve_requested_commit_if_on_branch "${requested_commit}")"; then
    printf "%s\n" "${resolved_commit}"
    return 0
  fi

  read -r -a deepen_steps <<<"${deepen_steps_raw}"
  for deepen_depth in "${deepen_steps[@]}"; do
    if [[ ! "${deepen_depth}" =~ ^[0-9]+$ || "${deepen_depth}" -le 1 ]]; then
      echo "[jenkins-checkout-source] 忽略无效加深深度: ${deepen_depth}" >&2
      continue
    fi

    echo "[jenkins-checkout-source] 浅历史未命中 commit=${requested_commit}，加深到 depth=${deepen_depth}" >&2
    if is_shallow_repository; then
      git fetch --no-tags --prune --depth="${deepen_depth}" origin "+refs/heads/${SOURCE_BRANCH}:refs/remotes/origin/${SOURCE_BRANCH}"
    else
      git fetch --no-tags --prune origin "+refs/heads/${SOURCE_BRANCH}:refs/remotes/origin/${SOURCE_BRANCH}"
    fi

    if resolved_commit="$(resolve_requested_commit_if_on_branch "${requested_commit}")"; then
      printf "%s\n" "${resolved_commit}"
      return 0
    fi
  done

  if is_shallow_repository; then
    echo "[jenkins-checkout-source] 逐步加深仍未命中 commit=${requested_commit}，最后尝试展开完整历史" >&2
    git fetch --unshallow --no-tags origin "+refs/heads/${SOURCE_BRANCH}:refs/remotes/origin/${SOURCE_BRANCH}" || \
      git fetch --no-tags --prune origin "+refs/heads/${SOURCE_BRANCH}:refs/remotes/origin/${SOURCE_BRANCH}"
  else
    git fetch --no-tags --prune origin "+refs/heads/${SOURCE_BRANCH}:refs/remotes/origin/${SOURCE_BRANCH}"
  fi

  resolve_requested_commit_if_on_branch "${requested_commit}"
}

add_git_remote_candidate "${GIT_REMOTE_URL}"
add_git_remote_candidate "${GIT_REMOTE_FALLBACK_URL}"

git reset --hard HEAD
if [[ "${#GIT_REMOTE_CANDIDATES[@]}" -eq 0 ]]; then
  fetch_source_branch ""
else
  fetch_ok=0
  for git_remote_candidate in "${GIT_REMOTE_CANDIDATES[@]}"; do
    if fetch_source_branch "${git_remote_candidate}"; then
      GIT_REMOTE_URL="${git_remote_candidate}"
      fetch_ok=1
      break
    fi
    echo "[jenkins-checkout-source] Git 远端拉取失败: ${git_remote_candidate}" >&2
  done
  if [[ "${fetch_ok}" -ne 1 ]]; then
    echo "[jenkins-checkout-source] 所有 Git 远端均拉取失败。" >&2
    exit 1
  fi
fi

git cat-file -e "refs/remotes/origin/${SOURCE_BRANCH}^{commit}"

if [[ -n "${COMMIT_HASH}" ]]; then
  if ! RESOLVED_COMMIT="$(resolve_requested_commit_with_deepen "${COMMIT_HASH}")"; then
    echo "[jenkins-checkout-source] 指定 commit 不属于 origin/${SOURCE_BRANCH}: ${COMMIT_HASH}" >&2
    exit 1
  fi
else
  RESOLVED_COMMIT="$(git rev-parse "refs/remotes/origin/${SOURCE_BRANCH}^{commit}")"
fi

git checkout --detach "${RESOLVED_COMMIT}"
git reset --hard HEAD
git clean -fd

printf "%s\n" "${RESOLVED_COMMIT}" >"${SOURCE_COMMIT_FILE}"
echo "[jenkins-checkout-source] 使用源码: branch=${SOURCE_BRANCH} commit=${RESOLVED_COMMIT} remote=${GIT_REMOTE_URL:-origin}"