import { NextResponse } from 'next/server'
import prisma from '@/lib/prisma'
import { auth } from '@/auth'

const WIKILINK_RE = /\[\[([^\]|#]+?)(?:[|#][^\]]+)?\]\]/g

function extractWikilinks(content: string): { title: string; snippet: string }[] {
  const plain = content.replace(/<[^>]+>/g, ' ')
  const results: { title: string; snippet: string }[] = []
  const seen = new Set<string>()
  let match: RegExpExecArray | null

  WIKILINK_RE.lastIndex = 0
  while ((match = WIKILINK_RE.exec(plain)) !== null) {
    const title = match[1].trim()
    if (!title || seen.has(title.toLowerCase())) continue
    seen.add(title.toLowerCase())
    const start = Math.max(0, match.index - 50)
    const end = Math.min(plain.length, match.index + match[0].length + 50)
    const snippet = plain.slice(start, end).replace(/\s+/g, ' ').trim()
    results.push({ title, snippet })
  }

  return results
}

/**
 * POST /api/graph/sync-all
 * Batch-sync [[wikilinks]] for ALL notes of the authenticated user.
 * Call once to populate the NoteLink table from existing notes.
 */
export async function POST() {
  const session = await auth()
  if (!session?.user?.id) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }
  const userId = session.user.id

  // Get all non-trashed notes with content
  const notes = await prisma.note.findMany({
    where: { userId, trashedAt: null, content: { not: '' } },
    select: { id: true, content: true, notebookId: true },
  })

  let totalLinks = 0

  for (const note of notes) {
    if (!note.content.includes('[[')) continue

    const wikilinks = extractWikilinks(note.content)
    if (wikilinks.length === 0) continue

    for (const { title, snippet } of wikilinks) {
      let targetNote = await prisma.note.findFirst({
        where: {
          userId,
          title: { equals: title, mode: 'insensitive' },
          trashedAt: null,
        },
        select: { id: true },
      })

      if (!targetNote) {
        // Skip stubs in batch sync — we only link existing notes
        continue
      }

      if (targetNote.id === note.id) continue

      try {
        await (prisma as any).noteLink.upsert({
          where: { sourceNoteId_targetNoteId: { sourceNoteId: note.id, targetNoteId: targetNote.id } },
          update: { contextSnippet: snippet },
          create: { sourceNoteId: note.id, targetNoteId: targetNote.id, contextSnippet: snippet },
        })
        totalLinks++
      } catch {
        // ignore duplicate constraint errors
      }
    }
  }

  return NextResponse.json({ synced: notes.length, links: totalLinks })
}