// A paid text-statistics API for AI agents, on Cloudflare Workers.
//   GET /stats?text=...   $0.002 in USDC on Base, paid with x402
//   GET /sample           free preview of the same output, so an agent can see what it gets
//   GET /                 what this is, in plain JSON
// A request that fails (no text, text too long) is never charged: payment settles
// only after the answer succeeds.
import { Hono } from "hono";
import { paymentMiddleware, x402ResourceServer } from "@x402/hono";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";
import { createFacilitatorConfig } from "@coinbase/x402";
import { bazaarResourceServerExtension, declareDiscoveryExtension } from "@x402/extensions/bazaar";

type Env = {
  PAY_TO: string;             // your wallet address on Base (0x...): where payments arrive
  CDP_API_KEY_ID: string;     // from portal.cdp.coinbase.com, stored as a secret
  CDP_API_KEY_SECRET: string; // same, stored as a secret
};

const PRICE = "$0.002";
const NETWORK = "eip155:8453"; // Base mainnet
const MAX_CHARS = 5000;
const SAMPLE_TEXT = "The quick brown fox jumps over the lazy dog.";

// ---------- the product: text statistics ----------
function countSyllables(word: string): number {
  const w = word.toLowerCase().replace(/[^a-z]/g, "");
  if (!w) return 0;
  if (w.length <= 3) return 1;
  const groups = w.replace(/(?:[^laeiouy]es|ed|[^laeiouy]e)$/, "").replace(/^y/, "").match(/[aeiouy]{1,2}/g);
  return Math.max(1, groups ? groups.length : 1);
}

function textStats(text: string) {
  const words = text.match(/[A-Za-z0-9'’-]+/g) ?? [];
  const wc = words.length;
  const sentences = wc ? Math.max(1, (text.match(/[.!?]+(\s|$)/g) ?? []).length) : 0;
  const syllables = words.reduce((n, w) => n + countSyllables(w), 0);
  // Flesch reading ease: higher is easier; 60-70 is plain English. Very short, simple text can exceed 100.
  const flesch = wc ? 206.835 - 1.015 * (wc / sentences) - 84.6 * (syllables / wc) : 0;
  const STOP = new Set("the a an and or but of to in on for with is are was were be been it this that as at by from".split(" "));
  const freq = new Map<string, number>();
  for (const w of words) {
    const k = w.toLowerCase();
    if (k.length > 2 && !STOP.has(k)) freq.set(k, (freq.get(k) ?? 0) + 1);
  }
  return {
    characters: text.length,
    words: wc,
    sentences,
    reading_time_seconds: Math.round((wc / 230) * 60),
    flesch_reading_ease: Math.round(flesch * 10) / 10,
    top_words: [...freq.entries()].sort((a, b) => b[1] - a[1]).slice(0, 5).map(([word, count]) => ({ word, count })),
  };
}

// ---------- the web app ----------
const app = new Hono<{ Bindings: Env }>();

app.get("/", (c) => c.json({
  name: "Text statistics",
  paid: { route: "/stats?text=...", price: PRICE + " USDC", network: "Base", protocol: "x402" },
  free_sample: "/sample",
  limits: { max_characters: MAX_CHARS },
}));

app.get("/sample", (c) => c.json({ sample: true, input: SAMPLE_TEXT, ...textStats(SAMPLE_TEXT) }));

// The payment step, built once per Worker instance from your settings.
let pay: ReturnType<typeof paymentMiddleware> | null = null;
app.use("/stats", async (c, next) => {
  if (!pay) {
    const facilitator = new HTTPFacilitatorClient(createFacilitatorConfig(c.env.CDP_API_KEY_ID, c.env.CDP_API_KEY_SECRET));
    const server = new x402ResourceServer(facilitator)
      .register(NETWORK, new ExactEvmScheme())
      .registerExtension(bazaarResourceServerExtension);
    pay = paymentMiddleware({
      "GET /stats": {
        accepts: [{ scheme: "exact", price: PRICE, network: NETWORK, payTo: c.env.PAY_TO }],
        description: "Text statistics: word, sentence and character counts, reading time, Flesch reading ease and top words. Pass the text as ?text= (up to 5,000 characters).",
        mimeType: "application/json",
        serviceName: "Text statistics",
        tags: ["text", "readability", "writing"],
        // Lets the Coinbase facilitator list this route in its Bazaar catalogue, where agents look for services.
        extensions: declareDiscoveryExtension({
          input: { text: SAMPLE_TEXT },
          inputSchema: { properties: { text: { type: "string", maxLength: MAX_CHARS } }, required: ["text"] },
          output: { example: textStats(SAMPLE_TEXT) },
        }),
      },
    }, server);
  }
  return pay(c, next);
});

app.get("/stats", (c) => {
  const text = c.req.query("text") ?? "";
  if (!text.trim()) return c.json({ error: "add ?text=... (the text to analyse)" }, 400);
  if (text.length > MAX_CHARS) return c.json({ error: `text is longer than ${MAX_CHARS} characters` }, 413);
  return c.json(textStats(text));
});

export default app;