#!/usr/bin/env bash
# git-sync.sh — 对指定 git 仓库做同步：pull → commit → push（分叉/冲突时中断并交回决策）
#
# 用法:
#   git-sync.sh <repo> status                      # fetch + 状态 + 变更摘要（拟提交说明用）
#   git-sync.sh <repo> sync -m "<提交说明>"         # 全流程同步
#   git-sync.sh <repo> pull-ff                     # 仅 fast-forward pull
#   git-sync.sh <repo> resolve merge|remote|local  # 分叉后处理；remote/local 需 GIT_SYNC_CONFIRM=yes
#
# 退出码: 0=成功  2=参数错  3=分叉/push被拒需决策  4=冲突  5=无变更
#         6=非git仓库或无upstream  7=缺提交说明  8=破坏性操作缺确认

set -uo pipefail

die() { echo "ERROR: $*" >&2; exit "${2:-2}"; }

[ $# -lt 2 ] && { echo "usage: git-sync.sh <repo> <status|sync|pull-ff|resolve> [...args]" >&2; exit 2; }
REPO="$1"; CMD="$2"; shift 2

[ -d "$REPO" ] || die "目录不存在: $REPO" 2
REPO="$(cd "$REPO" && pwd)"
cd "$REPO"
git rev-parse --is-inside-work-tree >/dev/null 2>&1 || die "不是 git 仓库: $REPO" 6
BRANCH="$(git symbolic-ref --short HEAD 2>/dev/null || true)"
UPSTREAM="$(git rev-parse --abbrev-ref --symbolic-full-name '@{u}' 2>/dev/null || true)"
[ -n "$UPSTREAM" ] || die "分支 $BRANCH 无 upstream（先 git push -u origin $BRANCH）" 6

ahead_behind() {
  local L R
  read -r L R < <(git rev-list --left-right --count HEAD..."$UPSTREAM" 2>/dev/null)
  echo "${L:-0} ${R:-0}"
}

status_cmd() {
  git fetch origin >/dev/null 2>&1 || true
  local AHEAD BEHIND
  read -r AHEAD BEHIND < <(ahead_behind)
  echo "repo: $REPO"
  echo "branch: $BRANCH  (upstream: $UPSTREAM)"
  echo "ahead: $AHEAD   behind: $BEHIND"
  [ "$AHEAD" -gt 0 ] && [ "$BEHIND" -gt 0 ] && echo "STATE: DIVERGED — 需用户选择 merge / 以远程为主 / 以本地为主"

  local PORCELAIN UNMERGED
  PORCELAIN="$(git status --porcelain)"
  UNMERGED="$(git ls-files -u | head -1)"
  if [ -z "$PORCELAIN" ]; then
    echo "changes: 无（工作区干净）"
  else
    echo "changes: $(printf '%s\n' "$PORCELAIN" | wc -l | tr -d ' ') 项未提交"
    [ -n "$UNMERGED" ] && echo "STATE: UNMERGED_PATHS — 存在未解决冲突，sync 会拒绝提交"
    echo "--- git status --short ---"
    printf '%s\n' "$PORCELAIN"
    echo "--- diff --stat（已跟踪改动） ---"
    git diff --stat HEAD 2>/dev/null | tail -n +1
    echo "--- 未跟踪文件 ---"
    git ls-files --others --exclude-standard
  fi
  exit 0
}

rebase_hint() {
  [ "$(git config pull.rebase 2>/dev/null || true)" = "true" ] \
    && echo "  hint: 本仓库 pull.rebase=true — 若本地改动与远端无文件重叠（git diff --name-only HEAD origin/main 为空交集），可用: git -c pull.rebase=false pull --ff-only" >&2
}

pull_ff() {
  local AHEAD BEHIND
  read -r AHEAD BEHIND < <(ahead_behind)
  [ "$AHEAD" -eq 0 ] && [ "$BEHIND" -eq 0 ] && { echo "already up to date"; exit 0; }
  if [ "$AHEAD" -gt 0 ] && [ "$BEHIND" -gt 0 ]; then
    echo "DIVERGED: ahead=$AHEAD behind=$BEHIND — 需用户决策后再处理（resolve）" >&2
    exit 3
  fi
  echo "==> git pull --ff-only origin $BRANCH"
  if ! git pull --ff-only origin "$BRANCH" 2>&1; then
    echo "CONFLICT: pull 失败 — 本地未提交改动与远端更新冲突，或需要 merge" >&2
    rebase_hint
    exit 4
  fi
  git log -1 --format='pulled: %h %s'
  exit 0
}

sync_cmd() {
  local MSG
  [ "${1:-}" = "-m" ] && shift
  MSG="${1:-}"
  [ -n "$MSG" ] || die "sync 需要 -m 提供提交说明: git-sync.sh <repo> sync -m \"...\"" 7

  # 未解决冲突禁止提交
  git ls-files -u | grep -q . \
    && { echo "CONFLICT: 存在未解决冲突（unmerged paths），先解决再 sync" >&2; exit 4; }

  git fetch origin >/dev/null 2>&1 || true
  local AHEAD BEHIND PORCELAIN PUSH_OUT PUSH_OK
  read -r AHEAD BEHIND < <(ahead_behind)

  if [ "$AHEAD" -gt 0 ] && [ "$BEHIND" -gt 0 ]; then
    echo "DIVERGED: ahead=$AHEAD behind=$BEHIND — 需用户选择 merge / 以远程为主 / 以本地为主" >&2
    exit 3
  fi
  if [ "$BEHIND" -gt 0 ]; then
    echo "==> pull --ff-only origin $BRANCH"
    if ! git pull --ff-only origin "$BRANCH" 2>&1; then
      echo "CONFLICT: pull 失败 — 本地未提交改动与远端更新冲突" >&2
      rebase_hint
      exit 4
    fi
  fi

  PORCELAIN="$(git status --porcelain)"
  if [ -z "$PORCELAIN" ]; then
    echo "NO_CHANGES: 工作区干净，无需提交"
    exit 5
  fi

  echo "==> git add -A"
  git add -A
  echo "==> git commit -m \"$MSG\""
  git commit -m "$MSG" >/dev/null || die "commit 失败" 2

  echo "==> git push origin $BRANCH"
  PUSH_OUT="$(git push origin "$BRANCH" 2>&1)"
  PUSH_OK=$?
  if [ $PUSH_OK -ne 0 ]; then
    echo "PUSH_FAILED: 远端可能有新提交，重新 status 后走决策流程" >&2
    printf '%s\n' "$PUSH_OUT" >&2
    exit 3
  fi

  echo "---"
  echo "SYNC_OK"
  echo "repo: $REPO"
  echo "branch: $BRANCH"
  git log -1 --format='commit: %h (%H)'
  git log -1 --format='title: %s'
  git log -1 --format='author: %an <%ae>  date: %ci'
  git show --stat --oneline HEAD | tail -1 | sed 's/^/stats: /'
  printf 'push: %s\n' "$(printf '%s\n' "$PUSH_OUT" | grep -v '^$' | tail -1)"
  exit 0
}

resolve_cmd() {
  local SIDE="${1:-}" CONFIRM="${GIT_SYNC_CONFIRM:-}"
  case "$SIDE" in
    merge)
      echo "==> git pull --no-rebase origin $BRANCH (合并远端，两边内容都保留)"
      if ! git pull --no-rebase origin "$BRANCH" 2>&1; then
        echo "CONFLICT: 合并产生冲突 — 查看 git status 的 unmerged paths，解决后 git add + git commit，再重跑 sync" >&2
        exit 4
      fi
      git log -1 --format='merged: %h %s'
      ;;
    remote)
      [ "$CONFIRM" = "yes" ] || { echo "DESTRUCTIVE: 以远程为主将丢弃本地提交（git reset --hard @{u}），需 GIT_SYNC_CONFIRM=yes" >&2; exit 8; }
      git reset --hard "$UPSTREAM"
      echo "reset to $UPSTREAM: $(git log -1 --format='%h %s')"
      ;;
    local)
      [ "$CONFIRM" = "yes" ] || { echo "DESTRUCTIVE: 以本地为主将强制推送覆盖远端（push --force-with-lease），需 GIT_SYNC_CONFIRM=yes" >&2; exit 8; }
      local PUSH_OUT PUSH_OK
      PUSH_OUT="$(git push --force-with-lease origin "$BRANCH" 2>&1)"
      PUSH_OK=$?
      if [ $PUSH_OK -ne 0 ]; then
        printf '%s\n' "$PUSH_OUT" >&2
        die "force push 失败" 3
      fi
      printf '%s\n' "$PUSH_OUT" | grep -v '^$' | tail -1
      ;;
    *) die "resolve 选项: merge|remote|local" 2 ;;
  esac
  exit 0
}

case "$CMD" in
  status)  status_cmd ;;
  sync)    sync_cmd "$@" ;;
  pull-ff) pull_ff ;;
  resolve) resolve_cmd "${1:-}" ;;
  *) die "未知命令: $CMD（可用 status|sync|pull-ff|resolve）" 2 ;;
esac