#!/usr/bin/env npx tsx
/**
 * REST API Template: Express.js Middleware
 * Monetize any Express API with per-route billing.
 *
 * This template uses settlegridMiddleware() — the REST equivalent of sg.wrap().
 * While MCP templates use sg.wrap() to bill function calls, REST templates use
 * settlegridMiddleware() to bill HTTP requests. Same billing pipeline, different
 * integration pattern.
 *
 * Works with all 10 SettleGrid protocols — protocol detection is automatic.
 *
 * Setup:
 *   1. npm install @settlegrid/mcp express
 *   2. Set SETTLEGRID_API_KEY in your env
 *   3. Register your tool at settlegrid.ai/dashboard/tools
 *   4. Run: npx tsx rest-express-api.ts
 *
 * Pricing: 3 cents for search, 10 cents for analysis
 *   - Search hits a lightweight index — low compute cost
 *   - Analysis runs Claude — ~$0.01 API cost per call
 *   - 10 cents gives you ~10x margin on analysis
 *
 * Revenue: You keep 95-100% (100% on Free tier, 95% on paid tiers)
 */

import express, { Request, Response, NextFunction } from 'express'
import { settlegridMiddleware } from '@settlegrid/mcp/rest'

const app = express()
app.use(express.json({ limit: '1mb' }))

// ── SettleGrid Billing Setup ────────────────────────────────────────────────
// Create a billing middleware instance for each pricing tier. Mount it on
// specific routes so different endpoints can charge different amounts.

const searchBilling = settlegridMiddleware({
  toolSlug: 'my-knowledge-api',       // Replace with your tool slug
  pricing: {
    defaultCostCents: 3,
    methods: {
      search: { costCents: 3, displayName: 'Knowledge Search' },
    },
  },
})

const analyzeBilling = settlegridMiddleware({
  toolSlug: 'my-knowledge-api',
  pricing: {
    defaultCostCents: 10,
    methods: {
      analyze: { costCents: 10, displayName: 'Deep Analysis' },
    },
  },
})

// ── Types ───────────────────────────────────────────────────────────────────

interface SearchResult {
  id: string
  title: string
  snippet: string
  score: number
}

interface AnalysisResult {
  summary: string
  keyTopics: string[]
  sentiment: 'positive' | 'neutral' | 'negative'
  confidence: number
}

// ── Implementation ──────────────────────────────────────────────────────────

async function searchKnowledgeBase(query: string, limit: number): Promise<SearchResult[]> {
  if (!query || query.trim().length === 0) {
    throw new Error('Query must be a non-empty string')
  }

  const safeLimit = Math.min(Math.max(limit, 1), 50)

  // Replace with your actual search backend (Elasticsearch, Typesense, pgvector, etc.)
  const response = await fetch(
    `${process.env.SEARCH_ENDPOINT!}/api/search`,
    {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${process.env.SEARCH_API_KEY!}`,
      },
      body: JSON.stringify({ query, limit: safeLimit }),
    }
  )

  if (!response.ok) {
    throw new Error(`Search backend returned ${response.status}`)
  }

  const data = await response.json()
  return (data.results ?? []).map((r: { id: string; title: string; snippet: string; score: number }) => ({
    id: r.id,
    title: r.title,
    snippet: r.snippet,
    score: r.score,
  }))
}

async function analyzeContent(text: string): Promise<AnalysisResult> {
  if (!text || text.trim().length === 0) {
    throw new Error('Text must be non-empty')
  }
  if (text.length > 50_000) {
    throw new Error('Text exceeds 50,000 character limit')
  }

  // Replace with your actual AI provider
  const response = await fetch('https://api.anthropic.com/v1/messages', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'x-api-key': process.env.ANTHROPIC_API_KEY!,
      'anthropic-version': '2023-06-01',
    },
    body: JSON.stringify({
      model: 'claude-sonnet-4-20250514',
      max_tokens: 2048,
      system: 'Analyze the provided text. Return a JSON object with: summary (string), keyTopics (string[]), sentiment ("positive"|"neutral"|"negative"), confidence (0-1 number). Return ONLY valid JSON.',
      messages: [{ role: 'user', content: text }],
    }),
  })

  if (!response.ok) {
    throw new Error(`Claude API returned ${response.status}`)
  }

  const data = await response.json()
  const raw = data.content?.[0]?.text ?? '{}'
  try {
    const cleaned = raw.replace(/```json\n?|\n?```/g, '').trim()
    return JSON.parse(cleaned) as AnalysisResult
  } catch {
    return { summary: raw, keyTopics: [], sentiment: 'neutral', confidence: 0 }
  }
}

// ── Routes ──────────────────────────────────────────────────────────────────

// POST /api/search — 3 cents per query
app.post('/api/search', async (req: Request, res: Response, next: NextFunction) => {
  try {
    await searchBilling(req, 'search')
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Billing error'
    res.status(402).json({ error: message })
    return
  }

  try {
    const { query, limit = 10 } = req.body as { query: string; limit?: number }
    const results = await searchKnowledgeBase(query, limit)
    res.json({ results, count: results.length })
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Internal error'
    res.status(500).json({ error: message })
  }
})

// POST /api/analyze — 10 cents per analysis
app.post('/api/analyze', async (req: Request, res: Response, next: NextFunction) => {
  try {
    await analyzeBilling(req, 'analyze')
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Billing error'
    res.status(402).json({ error: message })
    return
  }

  try {
    const { text } = req.body as { text: string }
    const analysis = await analyzeContent(text)
    res.json({ analysis })
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Internal error'
    res.status(500).json({ error: message })
  }
})

// ── Health check (no billing) ───────────────────────────────────────────────

app.get('/health', (_req: Request, res: Response) => {
  res.json({ status: 'ok', timestamp: new Date().toISOString() })
})

// ── Start Server ────────────────────────────────────────────────────────────

const PORT = parseInt(process.env.PORT ?? '3000', 10)
app.listen(PORT, () => {
  console.log(`Knowledge API running on :${PORT}`)
  console.log('  POST /api/search   — 3 cents/query')
  console.log('  POST /api/analyze  — 10 cents/call')
})