import { NextRequest, NextResponse } from 'next/server'
import { prisma } from '@/lib/prisma'
import { auth } from '@/lib/auth'
import { compareSortKey, keyAfterLast, keyForPosition } from '@/lib/sort-key'
import { v4 as uuidv4 } from 'uuid'

// GET /api/levels - Get all levels
export async function GET(request: NextRequest) {
  try {
    const session = await auth.api.getSession({
      headers: request.headers,
    })

    if (!session) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }

    // 注意：不能交给 MySQL 排序。默认 collation 大小写不敏感，
    // 会把 fractional-indexing 的 Z 系列 key 错排到 z 系列之后。
    // 拉全表到应用层按字节序排。
    const rows = await prisma.level.findMany()
    rows.sort((a, b) => {
      const c = compareSortKey(a.sortKey, b.sortKey)
      if (c !== 0) return c
      if (a.sortOrder !== b.sortOrder) return a.sortOrder - b.sortOrder
      return a.createdAt.getTime() - b.createdAt.getTime()
    })

    // 响应层回填连续整数 sortOrder，保持前端 / 小程序对这个字段的既有依赖
    const levels = rows.map((r, i) => ({ ...r, sortOrder: i }))

    return NextResponse.json(levels)
  } catch (error) {
    console.error('Error fetching levels:', error)
    return NextResponse.json(
      { error: 'Failed to fetch levels' },
      { status: 500 }
    )
  }
}

/**
 * 解析 position：
 * - undefined / null → 返回 undefined，交给调用方走"默认行为"
 * - 数字字符串 → 解析成整数
 * - 其它 → 抛错
 *
 * 合法范围的校验由调用方根据当前上下文（创建 / 编辑）判断。
 */
function parsePosition(raw: unknown): number | undefined {
  if (raw === undefined || raw === null || raw === '') return undefined
  const n = typeof raw === 'number' ? raw : Number(raw)
  if (!Number.isInteger(n) || n < 1) {
    throw new Error('position 必须是 >= 1 的整数')
  }
  return n
}

// POST /api/levels - Create a new level
// body.position 可选：1..N+1；不传则追加末尾
export async function POST(request: NextRequest) {
  try {
    const session = await auth.api.getSession({
      headers: request.headers,
    })

    if (!session) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }

    const body = await request.json()
    const {
      image1Url,
      image1Description,
      image2Url,
      image2Description,
      answer,
      punchline,
      hint1,
      hint2,
      hint3,
    } = body

    if (!image1Url || !image2Url || !answer) {
      return NextResponse.json(
        { error: 'image1Url, image2Url and answer are required' },
        { status: 400 }
      )
    }

    let position: number | undefined
    try {
      position = parsePosition(body.position)
    } catch (e) {
      return NextResponse.json(
        { error: e instanceof Error ? e.message : 'invalid position' },
        { status: 400 }
      )
    }

    let sortKey: string
    if (position === undefined) {
      sortKey = await keyAfterLast()
    } else {
      const total = await prisma.level.count()
      if (position > total + 1) {
        return NextResponse.json(
          { error: `position 超出范围，合法区间 [1, ${total + 1}]` },
          { status: 400 }
        )
      }
      sortKey = await keyForPosition(position)
    }

    const level = await prisma.level.create({
      data: {
        id: uuidv4(),
        image1Url,
        image1Description: image1Description || null,
        image2Url,
        image2Description: image2Description || null,
        answer,
        punchline: punchline || null,
        hint1: hint1 || null,
        hint2: hint2 || null,
        hint3: hint3 || null,
        sortKey,
      },
    })

    return NextResponse.json(level, { status: 201 })
  } catch (error) {
    console.error('Error creating level:', error)
    return NextResponse.json(
      { error: 'Failed to create level' },
      { status: 500 }
    )
  }
}

// PUT /api/levels - Update a level
// body.position 可选：1..N（N 含当前行）。不传表示不移动位置。
export async function PUT(request: NextRequest) {
  try {
    const session = await auth.api.getSession({
      headers: request.headers,
    })

    if (!session) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }

    const body = await request.json()
    const {
      id,
      image1Url,
      image1Description,
      image2Url,
      image2Description,
      answer,
      punchline,
      hint1,
      hint2,
      hint3,
    } = body

    if (!id) {
      return NextResponse.json({ error: 'id is required' }, { status: 400 })
    }

    let position: number | undefined
    try {
      position = parsePosition(body.position)
    } catch (e) {
      return NextResponse.json(
        { error: e instanceof Error ? e.message : 'invalid position' },
        { status: 400 }
      )
    }

    // 只有在 position 确实变化时才重算 sortKey，避免无谓写入
    let newSortKey: string | undefined
    if (position !== undefined) {
      const total = await prisma.level.count()
      if (position > total) {
        return NextResponse.json(
          { error: `position 超出范围，合法区间 [1, ${total}]` },
          { status: 400 }
        )
      }
      newSortKey = await keyForPosition(position, id)
    }

    const level = await prisma.level.update({
      where: { id },
      data: {
        image1Url,
        image1Description: image1Description || null,
        image2Url,
        image2Description: image2Description || null,
        answer,
        punchline: punchline || null,
        hint1: hint1 || null,
        hint2: hint2 || null,
        hint3: hint3 || null,
        ...(newSortKey ? { sortKey: newSortKey } : {}),
      },
    })

    return NextResponse.json(level)
  } catch (error) {
    console.error('Error updating level:', error)
    return NextResponse.json(
      { error: 'Failed to update level' },
      { status: 500 }
    )
  }
}

// DELETE /api/levels - Delete a level
export async function DELETE(request: NextRequest) {
  try {
    const session = await auth.api.getSession({
      headers: request.headers,
    })

    if (!session) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }

    const { searchParams } = new URL(request.url)
    const id = searchParams.get('id')

    if (!id) {
      return NextResponse.json({ error: 'id is required' }, { status: 400 })
    }

    await prisma.level.delete({
      where: { id },
    })

    return NextResponse.json({ success: true })
  } catch (error) {
    console.error('Error deleting level:', error)
    return NextResponse.json(
      { error: 'Failed to delete level' },
      { status: 500 }
    )
  }
}