import { NextRequest, NextResponse } from 'next/server'
import { Prisma } from '@prisma/client'
import prisma from '@/lib/prisma'
import { auth } from '@/auth'
import { revalidatePath } from 'next/cache'
import { PatchNotebookSchema } from '@/lib/validators'

async function getDescendantIds(notebookId: string): Promise<string[]> {
  const ids: string[] = []
  const children = await prisma.notebook.findMany({
    where: { parentId: notebookId },
    select: { id: true },
  })
  for (const child of children) {
    ids.push(child.id)
    ids.push(...await getDescendantIds(child.id))
  }
  return ids
}

export async function PATCH(
  request: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const session = await auth()
  if (!session?.user?.id) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }

  try {
    const { id } = await params
    const body = await request.json()
    const parsed = PatchNotebookSchema.safeParse(body)
    if (!parsed.success) {
      return NextResponse.json(
        { success: false, error: 'Invalid request body', details: parsed.error.flatten() },
        { status: 400 }
      )
    }
    const { name, icon, color, order, trashedAt, parentId } = parsed.data

    const existing = await prisma.notebook.findUnique({
      where: { id },
      select: { userId: true }
    })

    if (!existing) {
      return NextResponse.json(
        { success: false, error: 'Notebook not found' },
        { status: 404 }
      )
    }

    if (existing.userId !== session.user.id) {
      return NextResponse.json(
        { success: false, error: 'Forbidden' },
        { status: 403 }
      )
    }

    if (parentId !== undefined) {
      if (parentId !== null) {
        if (parentId === id) {
          return NextResponse.json(
            { success: false, error: 'A notebook cannot be its own parent' },
            { status: 400 }
          )
        }
        const target = await prisma.notebook.findFirst({
          where: { id: parentId, userId: session.user.id }
        })
        if (!target) {
          return NextResponse.json(
            { success: false, error: 'Parent notebook not found' },
            { status: 404 }
          )
        }
        const descendants = await getDescendantIds(id)
        if (descendants.includes(parentId)) {
          return NextResponse.json(
            { success: false, error: 'Cannot move a notebook into its own descendant' },
            { status: 400 }
          )
        }
      }
    }

    const updateData: Prisma.NotebookUpdateInput = {}
    if (name !== undefined) updateData.name = name
    if (icon !== undefined) updateData.icon = icon
    if (color !== undefined) updateData.color = color
    if (order !== undefined) updateData.order = order
    if (trashedAt !== undefined) updateData.trashedAt = trashedAt ? new Date(trashedAt) : null
    if (parentId !== undefined) updateData.parentId = parentId

    if (trashedAt !== undefined) {
      const descendantIds = await getDescendantIds(id)
      const allIds = [id, ...descendantIds]
      await prisma.notebook.updateMany({
        where: { id: { in: allIds }, userId: session.user.id },
        data: { trashedAt },
      })
    } else {
      await prisma.notebook.update({
        where: { id },
        data: updateData,
      })
    }

    try { revalidatePath('/home') } catch {}

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

export async function DELETE(
  request: NextRequest,
  { params }: { params: Promise<{ id: string }> }
) {
  const session = await auth()
  if (!session?.user?.id) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }

  try {
    const { id } = await params

    const notebook = await prisma.notebook.findUnique({
      where: { id },
      select: { userId: true, name: true }
    })

    if (!notebook) {
      return NextResponse.json(
        { success: false, error: 'Notebook not found' },
        { status: 404 }
      )
    }

    if (notebook.userId !== session.user.id) {
      return NextResponse.json(
        { success: false, error: 'Forbidden' },
        { status: 403 }
      )
    }

    await prisma.notebook.delete({ where: { id } })

    try { revalidatePath('/home') } catch {}

    return NextResponse.json({
      success: true,
      message: `Notebook "${notebook.name}" permanently deleted`,
    })
  } catch (error) {
    console.error('Error deleting notebook:', error)
    return NextResponse.json(
      { success: false, error: 'Failed to delete notebook' },
      { status: 500 }
    )
  }
}