trumpsignal-frontend/lib/postPage.ts

import type { TrumpPost } from '@/types'
import { getPosts, getPostsPage, type PostListResponse } from './api'

const LIVE_ARCHIVE_SOURCES = new Set([
  'truth',
  'btc_bottom_reversal',
  'funding_reversal',
  'kol_divergence',
])

function isAiScored(post: Pick<TrumpPost, 'ai_confidence' | 'ai_reasoning'>): boolean {
  return (post.ai_confidence ?? 0) > 0 || !!post.ai_reasoning
}

function buildSourceCounts(items: TrumpPost[]): PostListResponse['source_counts'] {
  const counts = new Map<string, { count: number; latest: string | null }>()
  for (const post of items) {
    const hit = counts.get(post.source)
    if (!hit) {
      counts.set(post.source, { count: 1, latest: post.published_at })
      continue
    }
    hit.count += 1
    if (!hit.latest || post.published_at > hit.latest) hit.latest = post.published_at
  }
  return Array.from(counts.entries())
    .map(([source, meta]) => ({ source, count: meta.count, latest: meta.latest }))
    .sort((a, b) => b.count - a.count || a.source.localeCompare(b.source))
}

export function buildPostListFallbackResponse(
  items: TrumpPost[],
  source: string,
  limit: number,
): PostListResponse {
  return {
    items,
    total: items.length,
    page: 1,
    limit,
    counts: {
      all: items.length,
      actionable: items.filter(p => p.signal === 'buy' || p.signal === 'short').length,
      buy: items.filter(p => p.signal === 'buy').length,
      short: items.filter(p => p.signal === 'short').length,
      off_topic: items.filter(p => !isAiScored(p)).length,
    },
    source_counts: [{ source, count: items.length, latest: items[0]?.published_at ?? null }],
  }
}

export function buildArchiveFallbackResponse(
  allPosts: TrumpPost[],
  page: number,
  limit: number,
  source = 'all',
): PostListResponse {
  const archivePosts = allPosts.filter(post => !LIVE_ARCHIVE_SOURCES.has(post.source))
  const sourceCounts = buildSourceCounts(archivePosts)
  const filtered = source === 'all'
    ? archivePosts
    : archivePosts.filter(post => post.source === source)
  const offset = (page - 1) * limit
  const items = filtered.slice(offset, offset + limit)

  return {
    items,
    total: filtered.length,
    page,
    limit,
    counts: {
      all: filtered.length,
      actionable: filtered.filter(p => p.signal === 'buy' || p.signal === 'short').length,
      buy: filtered.filter(p => p.signal === 'buy').length,
      short: filtered.filter(p => p.signal === 'short').length,
      off_topic: filtered.filter(p => !isAiScored(p)).length,
    },
    source_counts: sourceCounts,
  }
}

export async function getInitialPostPage(
  limit: number,
  page: number,
  options: {
    source?: string
    filters?: {
      sourceIn?: string[]
      sourceNotIn?: string[]
      archiveOnly?: boolean
      sentiment?: 'bullish' | 'bearish' | 'neutral'
      signal?: 'buy' | 'short' | 'actionable'
      aiScoredOnly?: boolean
    }
    legacyFallbackSource?: string
    legacyFallback?: () => Promise<PostListResponse | null>
  },
): Promise<PostListResponse | null> {
  return getPostsPage(limit, page, options.source, options.filters).catch(async (e) => {
    // Only fall back to legacy /posts on 404 (new endpoint not yet deployed).
    // Non-404 errors (500, network) should NOT silently mask as empty data —
    // a server-side fallback on 500 produces initial HTML that the client
    // cannot reproduce on re-fetch (it shows an error instead), causing a
    // hydration mismatch. Return null so the page renders empty and the
    // client fetches cleanly on mount.
    const detail = e instanceof Error ? e.message : ''
    if (!detail.includes('404')) return null

    if (options.legacyFallback) {
      return options.legacyFallback()
    }
    if (!options.legacyFallbackSource || options.filters?.archiveOnly || options.filters?.sourceIn || options.filters?.sourceNotIn) {
      return null
    }
    const fallbackItems = await getPosts(limit, page, options.legacyFallbackSource).catch(() => null)
    return fallbackItems ? buildPostListFallbackResponse(fallbackItems, options.legacyFallbackSource, limit) : null
  })
}