// 任务模块: 跨项目拷贝 (T-CP-*)
// 拷贝而非移动: 新建记录 + 深拷贝子任务, 源任务零改动.
import { prisma } from '../db.js'

/**
 * 拷贝一条任务(含子任务)到目标项目。
 *
 * 规则:
 *  - 全字段复制: 标题/描述/状态/列/扩展卡片/标签 (T-CP-02)
 *  - 子任务一并复制, 且归属目标项目 (T-CP-03, T-CP-08)
 *  - creatorId = 操作者 (T-CP-04)
 *  - 负责人 / 任务成员只保留"属于目标项目成员"的部分, 其余丢弃并回报 (T-CP-07, T-EX-08)
 *  - 状态与列沿用源值, 不强行纠正 (T-EX-14)
 *
 * @returns {{ task, dropped: { assignee: null|{id,name}, members: {id,name}[] } }}
 */
export async function copyTask({ source, targetProject, targetColumns, operatorId, targetMemberIds }) {
  const memberSet = new Set(targetMemberIds)

  // 列映射: 目标项目里找同名列, 找不到就用第一列 (保证 columnId 合法)
  const pickColumn = (sourceColumnId) => {
    const srcCol = source.__columns?.find((c) => c.id === sourceColumnId)
    if (srcCol) {
      const same = targetColumns.find((c) => c.name === srcCol.name)
      if (same) return same.id
    }
    return targetColumns[0]?.id
  }

  // 人员过滤
  const keepAssignee = source.assigneeId && memberSet.has(source.assigneeId) ? source.assigneeId : null
  const droppedMembers = []
  const keptMemberIds = []
  for (const m of source.members || []) {
    if (memberSet.has(m.userId)) keptMemberIds.push(m.userId)
    else droppedMembers.push(m.user)
  }
  const droppedAssignee = source.assigneeId && !memberSet.has(source.assigneeId) ? source.assignee : null

  const baseData = (extra) => ({
    projectId: targetProject.id,
    title: source.title,
    description: source.description || '',
    status: source.status,
    columnId: extra.columnId,
    parentId: extra.parentId ?? null,
    assigneeId: extra.parentId ? (source.assigneeId && memberSet.has(source.assigneeId) ? source.assigneeId : null) : keepAssignee,
    creatorId: operatorId,
    extras: source.extras ?? [],
    doneAt: source.status === 'done' ? (source.doneAt || new Date()) : null,
    sortOrder: source.sortOrder ?? 0,
    tags: {
      create: (source.tags || []).map((t) => ({ name: t.name })),
    },
  })

  const newTask = await prisma.task.create({
    data: {
      ...baseData({ columnId: pickColumn(source.columnId) }),
      members: {
        create: keptMemberIds.map((uid) => ({ userId: uid })),
      },
    },
  })

  // 子任务: 同法复制, parentId 指向新父任务
  for (const child of source.children || []) {
    const childMembers = (child.members || [])
      .filter((m) => memberSet.has(m.userId))
      .map((m) => m.userId)
    await prisma.task.create({
      data: {
        ...baseData({
          columnId: pickColumn(child.columnId),
          parentId: newTask.id,
        }),
        members: { create: childMembers.map((uid) => ({ userId: uid })) },
      },
    })
  }

  return {
    task: newTask,
    dropped: {
      assignee: droppedAssignee ? { id: droppedAssignee.id, name: droppedAssignee.name } : null,
      members: droppedMembers.map((u) => ({ id: u.id, name: u.name })),
    },
  }
}