import 'server-only'

import prisma from '@/lib/prisma'
import type { DashboardPath } from '@/lib/dashboard/path-types'

export type { DashboardPath, DashboardPathType } from '@/lib/dashboard/path-types'

interface BuildPathsInput {
  userId: string
  aiActive: boolean
  recentNotes: Array<{
    id: string
    title: string | null
    notebookId: string | null
    updatedAt: Date
    content: string
  }>
  inboxCount: number
  dueFlashcards: number
  insights: Array<{
    id: string
    insight: string
    score: number
    viewed: boolean
    note1: { id: string; title: string | null }
    note2: { id: string; title: string | null }
    note1Excerpt?: string
    note2Excerpt?: string
  }>
  bridgeSuggestions: Array<{
    clusterAId: number
    clusterBId: number
    clusterAName: string
    clusterBName: string
    suggestedTitle: string
    suggestedContent: string
    justification: string
  }>
  agentSuggestions: Array<{
    id: string
    topic: string
    reason: string
    clusterId: number | null
  }>
}

function excerpt(text: string, max = 120): string {
  const plain = text.replace(/<[^>]+>/g, ' ').replace(/\s+/g, ' ').trim()
  if (plain.length <= max) return plain
  return `${plain.slice(0, max)}…`
}

function jaccardSimilarity(a: string, b: string): number {
  const tokenize = (s: string) =>
    new Set(s.toLowerCase().replace(/[^\w\s]/g, '').split(/\s+/).filter(w => w.length > 3))
  const A = tokenize(a)
  const B = tokenize(b)
  if (A.size === 0 || B.size === 0) return 0
  let intersection = 0
  A.forEach(w => { if (B.has(w)) intersection++ })
  return intersection / (A.size + B.size - intersection)
}

async function findLinkSuggestions(
  userId: string,
  sourceNote: { id: string; title: string | null; content: string },
  limit = 2,
): Promise<Array<{ noteId: string; noteTitle: string; snippet: string; score: number }>> {
  const sourcePlain = excerpt(sourceNote.content, 400)
  const sourceText = `${sourceNote.title || ''} ${sourcePlain}`.toLowerCase()

  const candidates = await prisma.note.findMany({
    where: { userId, id: { not: sourceNote.id }, isArchived: false, trashedAt: null },
    select: { id: true, title: true, content: true },
    take: 12,
    orderBy: { updatedAt: 'desc' },
  })

  const scored: Array<{ noteId: string; noteTitle: string; snippet: string; score: number }> = []
  for (const note of candidates) {
    const notePlain = excerpt(note.content, 300)
    const sim = jaccardSimilarity(sourceText, `${note.title || ''} ${notePlain}`)
    if (sim < 0.06) continue
    scored.push({
      noteId: note.id,
      noteTitle: note.title || '',
      snippet: notePlain.slice(0, 100),
      score: Math.round(sim * 100),
    })
  }

  return scored.sort((a, b) => b.score - a.score).slice(0, limit)
}

function pathsFromInsights(
  focus: BuildPathsInput['recentNotes'][0],
  insights: BuildPathsInput['insights'],
  paths: DashboardPath[],
): void {
  for (const ins of insights
    .filter(i => i.note1.id === focus.id || i.note2.id === focus.id)
    .slice(0, 2)) {
    const other = ins.note1.id === focus.id ? ins.note2 : ins.note1
    if (paths.some(p => p.note2Id === other.id && p.type === 'connect')) continue
    paths.push({
      id: `connect-${focus.id}-${other.id}`,
      type: 'connect',
      priority: 90 - paths.length,
      title: other.title || 'Untitled',
      description: ins.insight || ins.note2Excerpt || ins.note1Excerpt || '',
      actionKey: 'compare',
      noteId: focus.id,
      note2Id: other.id,
      notebookId: focus.notebookId ?? undefined,
      score: Math.round(ins.score * 100),
    })
  }
}

async function findOpenLoops(userId: string, limit = 3): Promise<Array<{ id: string; title: string | null; notebookId: string | null; daysStale: number }>> {
  const threeDaysAgo = new Date()
  threeDaysAgo.setDate(threeDaysAgo.getDate() - 3)
  const thirtyDaysAgo = new Date()
  thirtyDaysAgo.setDate(thirtyDaysAgo.getDate() - 30)

  const stale = await prisma.note.findMany({
    where: {
      userId,
      trashedAt: null,
      isArchived: false,
      updatedAt: { lt: threeDaysAgo, gte: thirtyDaysAgo },
      OR: [
        { notebookId: null },
        { isPinned: true },
        { reminder: { not: null }, isReminderDone: false },
      ],
    },
    select: { id: true, title: true, notebookId: true, updatedAt: true },
    orderBy: { updatedAt: 'desc' },
    take: limit,
  })

  const now = Date.now()
  return stale.map(n => ({
    id: n.id,
    title: n.title,
    notebookId: n.notebookId,
    daysStale: Math.floor((now - n.updatedAt.getTime()) / (1000 * 60 * 60 * 24)),
  }))
}

export async function buildDashboardPaths(input: BuildPathsInput): Promise<DashboardPath[]> {
  const paths: DashboardPath[] = []
  const focus = input.recentNotes[0]

  let focusClusterId: number | null = null
  if (focus) {
    const member = await prisma.clusterMember.findFirst({
      where: { userId: input.userId, noteId: focus.id },
      select: { clusterId: true },
    })
    focusClusterId = member?.clusterId ?? null

    paths.push({
      id: `continue-${focus.id}`,
      type: 'continue',
      priority: 100,
      title: focus.title || 'Untitled',
      description: excerpt(focus.content, 140),
      actionKey: 'continue',
      noteId: focus.id,
      notebookId: focus.notebookId ?? undefined,
    })

    pathsFromInsights(focus, input.insights, paths)

    const linkSuggestions = await findLinkSuggestions(input.userId, focus, 2)
    for (const link of linkSuggestions) {
      paths.push({
        id: `add-link-${focus.id}-${link.noteId}`,
        type: 'add-link',
        priority: 75,
        title: link.noteTitle || 'Untitled',
        description: link.snippet,
        actionKey: 'addLink',
        noteId: focus.id,
        note2Id: link.noteId,
        notebookId: focus.notebookId ?? undefined,
        score: link.score,
      })
    }
  }

  const freshInsight = input.insights.find(i => !i.viewed)
  if (freshInsight) {
    paths.push({
      id: `resurface-${freshInsight.id}`,
      type: 'resurface',
      priority: 85,
      title: `${freshInsight.note1.title || '…'} ↔ ${freshInsight.note2.title || '…'}`,
      description: freshInsight.insight,
      actionKey: 'openInsight',
      insightId: freshInsight.id,
      noteId: freshInsight.note1.id,
      note2Id: freshInsight.note2.id,
      score: Math.round(freshInsight.score * 100),
    })
  }

  for (const bridge of input.bridgeSuggestions.slice(0, 2)) {
    const relevant = focusClusterId === null
      || bridge.clusterAId === focusClusterId
      || bridge.clusterBId === focusClusterId
    paths.push({
      id: `bridge-${bridge.clusterAId}-${bridge.clusterBId}`,
      type: 'bridge',
      priority: relevant ? 80 : 55,
      title: bridge.suggestedTitle,
      description: bridge.justification || bridge.suggestedContent.slice(0, 140),
      actionKey: 'createBridge',
      clusterAId: bridge.clusterAId,
      clusterBId: bridge.clusterBId,
      notebookId: focus?.notebookId ?? undefined,
    })
  }

  for (const agent of input.agentSuggestions.slice(0, 2)) {
    const relevant = focusClusterId !== null && agent.clusterId === focusClusterId
    paths.push({
      id: `research-${agent.id}`,
      type: 'research',
      priority: relevant ? 78 : 50,
      title: agent.topic,
      description: agent.reason,
      actionKey: 'createAgent',
      agentSuggestionId: agent.id,
      notebookId: focus?.notebookId ?? undefined,
    })
  }

  if (focusClusterId !== null) {
    const cluster = await prisma.noteCluster.findFirst({
      where: { userId: input.userId, clusterId: focusClusterId },
      select: { name: true, noteCount: true },
    })
    if (cluster) {
      paths.push({
        id: `explore-cluster-${focusClusterId}`,
        type: 'explore',
        priority: 60,
        title: cluster.name || `Cluster ${focusClusterId}`,
        description: `${cluster.noteCount} notes in this theme`,
        actionKey: 'exploreTheme',
        clusterAId: focusClusterId,
      })
    }
  }

  if (input.inboxCount > 0) {
    paths.push({
      id: 'organize-inbox',
      type: 'organize',
      priority: 70,
      title: `${input.inboxCount} notes`,
      description: 'inbox',
      actionKey: 'organizeInbox',
    })
  }

  if (input.dueFlashcards > 0) {
    paths.push({
      id: 'review-flashcards',
      type: 'review',
      priority: 65,
      title: `${input.dueFlashcards}`,
      description: 'flashcards',
      actionKey: 'reviewCards',
    })
  }

  paths.push({
    id: 'daily-journal',
    type: 'daily',
    priority: 40,
    title: new Date().toISOString().slice(0, 10),
    description: 'daily',
    actionKey: 'openDaily',
  })

  return paths
    .sort((a, b) => b.priority - a.priority)
    .slice(0, 8)
}

export async function buildOpenLoops(userId: string) {
  return findOpenLoops(userId, 5)
}