import { NextRequest } from 'next/server'
import { prisma } from '@/lib/prisma'
import { noteSchema, NoteInput } from '@/lib/validators'
import { createErrorResponse, createSuccessResponse, ValidationError } from '@/lib/errors'
import { syncBacklinks } from '@/lib/backlinks'
import { createBackupSnapshot } from '@/lib/backup'
import { notesToMarkdownZip, noteToMarkdown } from '@/lib/export-markdown'
import { notesToHtmlZip, noteToHtml } from '@/lib/export-html'

export async function GET(req: NextRequest) {
  try {
    const { searchParams } = new URL(req.url)
    const format = searchParams.get('format')

    if (format === 'backup') {
      const backup = await createBackupSnapshot('manual')
      return createSuccessResponse(backup)
    }

    const notes = await prisma.note.findMany({
      include: { tags: { include: { tag: true } } },
    })

    const exportData = notes.map(note => ({
      ...note,
      tags: note.tags.map(nt => nt.tag.name),
      createdAt: note.createdAt.toISOString(),
      updatedAt: note.updatedAt.toISOString(),
    }))

    if (format === 'markdown') {
      const notesForExport = notes.map(note => ({
        ...note,
        tags: note.tags,
        createdAt: note.createdAt.toISOString(),
        updatedAt: note.updatedAt.toISOString(),
      }))
      if (notes.length === 1) {
        return createSuccessResponse({
          filename: notesToMarkdownZip(notesForExport).files[0].name,
          content: noteToMarkdown(notesForExport[0]),
        })
      }
      return createSuccessResponse(notesToMarkdownZip(notesForExport))
    }

    if (format === 'html') {
      const notesForExport = notes.map(note => ({
        ...note,
        tags: note.tags,
        createdAt: note.createdAt.toISOString(),
        updatedAt: note.updatedAt.toISOString(),
      }))
      if (notes.length === 1) {
        return createSuccessResponse({
          filename: notesToHtmlZip(notesForExport).files[0].name,
          content: noteToHtml(notesForExport[0]),
        })
      }
      return createSuccessResponse(notesToHtmlZip(notesForExport))
    }

    return createSuccessResponse(exportData)
  } catch (error) {
    return createErrorResponse(error)
  }
}

export async function POST(req: NextRequest) {
  try {
    const body = await req.json()

    if (!Array.isArray(body)) {
      throw new ValidationError([{ path: 'body', message: 'Invalid format: expected array' }])
    }

    const importedNotes: NoteInput[] = []
    const errors: string[] = []

    for (let i = 0; i < body.length; i++) {
      const result = noteSchema.safeParse(body[i])
      if (!result.success) {
        errors.push(`Item ${i}: ${result.error.issues.map(e => e.message).join(', ')}`)
        continue
      }
      importedNotes.push(result.data)
    }

    if (errors.length > 0) {
      throw new ValidationError(errors)
    }

    const parseDate = (dateStr: string | undefined): Date => {
      if (!dateStr) return new Date()
      const parsed = new Date(dateStr)
      return isNaN(parsed.getTime()) ? new Date() : parsed
    }

    let processed = 0

    await prisma.$transaction(async (tx) => {
      for (const item of importedNotes) {
        const tags = item.tags || []
        const { tags: _, ...noteData } = item

        const createdAt = parseDate((item as { createdAt?: string }).createdAt)
        const updatedAt = parseDate((item as { updatedAt?: string }).updatedAt)
        const itemWithId = item as { id?: string }

        if (itemWithId.id) {
          const existing = await tx.note.findUnique({ where: { id: itemWithId.id } })
          if (existing) {
            await tx.note.update({
              where: { id: itemWithId.id },
              data: { ...noteData, createdAt, updatedAt },
            })
            await tx.noteTag.deleteMany({ where: { noteId: itemWithId.id } })
            processed++
          } else {
            await tx.note.create({
              data: {
                ...noteData,
                id: itemWithId.id,
                createdAt,
                updatedAt,
                creationSource: 'import',
              },
            })
            processed++
          }
        } else {
          const existingByTitle = await tx.note.findFirst({
            where: { title: item.title },
          })
          if (existingByTitle) {
            await tx.note.update({
              where: { id: existingByTitle.id },
              data: { ...noteData, updatedAt },
            })
            await tx.noteTag.deleteMany({ where: { noteId: existingByTitle.id } })
          } else {
            await tx.note.create({
              data: {
                ...noteData,
                createdAt,
                updatedAt,
                creationSource: 'import',
              },
            })
          }
          processed++
        }

        const noteId = itemWithId.id
          ? (await tx.note.findUnique({ where: { id: itemWithId.id } }))?.id
          : (await tx.note.findFirst({ where: { title: item.title } }))?.id

        if (noteId && tags.length > 0) {
          for (const tagName of tags) {
            const tag = await tx.tag.upsert({
              where: { name: tagName },
              create: { name: tagName },
              update: {},
            })
            await tx.noteTag.create({
              data: { noteId, tagId: tag.id },
            })
          }
        }

        if (noteId) {
          const note = await tx.note.findUnique({ where: { id: noteId } })
          if (note) {
            await syncBacklinks(note.id, note.content)
          }
        }
      }
    })

    return createSuccessResponse({ success: true, count: processed }, 201)
  } catch (error) {
    return createErrorResponse(error)
  }
}