/*
 * webhook.ts — the Worker entry (D-11, D-14, D-16, D-17).
 * --------------------------------------------------------
 * Routes:
 *   POST /telegram/webhook  → grammY's webhook adapter (cloudflare-mod) with
 *     the configured secret token — Telegram's updates must carry
 *     X-Telegram-Bot-Api-Secret-Token = env.WEBHOOK_SECRET or they are 401'd
 *     by a constant-time compare BEFORE any bot processing or KV touch
 *     (T-02-03). FAIL-CLOSED (WR-02): if the WEBHOOK_SECRET binding is
 *     missing/empty at request time, the route rejects outright — grammY's
 *     compareSecretToken silently accepts EVERY request when its secret is
 *     undefined, so an unarmed binding must never reach it. The bot is
 *     instantiated per request because the token only arrives with `env`
 *     (research-verified Workers pattern).
 *   POST /api/session       → the phase's security gate (T-02-01): the caller
 *     posts a verbatim Telegram.WebApp.initData string — capped at 4 KB
 *     (WR-01: over-cap bodies are rejected 413 before any parsing; real
 *     initData is ≪ 1 KB, so this touches no legitimate client); only an
 *     HMAC-validated, fresh identity obtains a one-time opaque session
 *     token (D-06). Rotation of any prior token for the chat is mintSession's
 *     own invariant (D-07 — best-effort under KV eventual consistency, see
 *     sessions.ts) — this endpoint adds no extra branch and no extra write
 *     path (T-02-06).
 *   GET  /api/location      → GEO-02 relay (T-03-01): the Mini App polls
 *     here with its memory-held Bearer token; the token resolves through
 *     getClaimByToken and the KV key loc:<chat_id> derives from the
 *     CLAIM — never from a client-supplied id — so one user's token can
 *     never read another user's pin. No pin or expired token → honest
 *     nulls / 401, nothing fabricated.
 *   POST /api/location-fallback → GEO-02 keyboard trigger (T-03-26): the
 *     app's denied card asks the BOT to send the request_location reply
 *     keyboard into the user's own chat. The target chat_id AND the
 *     locale come from the resolved claim (T-03-27) — the request body
 *     is never read, and no chat id or language is accepted from the
 *     client. A rejected Telegram send is a category-only 502 (T-03-28).
 *   POST|GET|DELETE /api/guidance → the Phase 6 envelope endpoints (06-03,
 *     GUID-05/06, D-14): POST mints a guidance session (7200 s TTL) with
 *     the chat_id taken from the CLAIM — a client-supplied chat_id is
 *     structurally ignored (T-06-02); GET/DELETE resolve the record and
 *     compare envelope.chat_id === claim.chat_id, so foreign and absent
 *     are indistinguishable 404s (T-06-02b). DELETE is D-14's server half.
 *   POST /api/route        → engine A's arm (06-04, D-01): Bearer-claim
 *     gated EXACTLY like /api/location (T-06-01); the handler lives in
 *     ./routing/worker-router.ts — the R2-hosted road graph, snap, A*, and
 *     the honest-null degradation (D-03) all live there. Every miss class
 *     answers 200 null; rejections are category-only (T-06-04).
 * Anything else → 404.
 *
 * scheduled() — the repo's FIRST Cron Trigger (06-07, GUID-05, D-11): every
 * minute it lists the KV prefix guidance:, reads each envelope through
 * getGuidanceSession (a corrupt record reads null and is skipped honestly),
 * projects progress along the frozen snapshot via the PURE projectTurnCards,
 * and pushes due cards to envelope.chat_id ONLY (T-06-02 — no request path
 * exists in a cron tick). Street reconstruction (D-12 default) awaits the
 * worker-router's loadGraph memo once per tick; a null graph degrades the
 * card to the bare-verb street-less composition — the send still fires.
 * STATELESS: the cron performs ZERO KV writes (the free-plan budget law).
 *
 * The handler object is built by createExportedHandler(opts) — production
 * passes nothing (the default export); offline tests inject a recording
 * baseFetch through the same factory (the createBot({baseFetch}) seam).
 *
 * D-14: the ONLY log statements are category-only — malformed/tampered/stale
 * on the initData gate, misconfigured on the fail-closed webhook gate —
 * never the raw payload, never user ids, never timestamps. Rejection
 * responses carry the category only.
 * D-17: no secret is ever logged or echoed; the bot token / webhook secret
 * exist only inside `env` at runtime.
 */
import { webhookCallback } from "grammy";
import type { Env } from "./config.ts";
import { createBot } from "./bot/bot.ts";
import { requestLocationFallback } from "./bot/handlers/location-fallback.ts";
import { mintSession, getClaimByToken } from "./kv/sessions.ts";
import { getPin } from "./kv/location-pin.ts";
import {
  mintGuidanceSession,
  getGuidanceSession,
  deleteGuidanceSession,
  GUIDANCE_KEY_PREFIX,
  type GuidanceRouteSnapshot,
  type GuidanceSessionEnvelope,
} from "./kv/guidance-sessions.ts";
import { handleRoute, loadGraph } from "./routing/worker-router.ts";
import { decodePolyline6 } from "@araharah/routing/src/polyline.ts";
import { projectTurnCards, makeStreetAt } from "./guidance/cron.ts";
import { validateInitData } from "./security/initdata.ts";
import { pickLocale, strings } from "./i18n/strings.ts";

export function createExportedHandler(opts: { baseFetch?: typeof fetch } = {}): ExportedHandler<Env> {
  return {
    async fetch(req: Request, env: Env, _ctx: ExecutionContext): Promise<Response> {
      const url = new URL(req.url);
      if (url.pathname === "/telegram/webhook") {
        // WR-02 fail-closed: grammY's compareSecretToken accepts EVERY request
        // when its secret is undefined (research-confirmed runtime behavior,
        // convenience/webhook.js). A WEBHOOK_SECRET binding left unarmed after
        // deploy would therefore silently disable webhook authentication and
        // admit unsigned POSTs that inject fabricated updates. This guard runs
        // BEFORE createBot/webhookCallback; the rejection is a constant 500
        // and the log carries the category only.
        if (!env.WEBHOOK_SECRET) {
          console.log("[webhook] rejected: misconfigured");
          return new Response("Server misconfigured", { status: 500 });
        }
        const bot = createBot(env); // env-bound token → per-request instantiation
        const cb = webhookCallback(bot, "cloudflare-mod", undefined, undefined, env.WEBHOOK_SECRET);
        return cb(req);
      }
      if (url.pathname === "/api/session") {
        return handleSession(req, env);
      }
      if (url.pathname === "/api/location") {
        return handleLocation(req, env);
      }
      if (url.pathname === "/api/location-fallback") {
        return handleLocationFallback(req, env);
      }
      if (url.pathname === "/api/guidance") {
        return handleGuidance(req, env);
      }
      if (url.pathname === "/api/route") {
        return handleRoute(req, env);
      }
      return new Response("Not found", { status: 404 });
    },

    async scheduled(controller: ScheduledController, env: Env, ctx: ExecutionContext): Promise<void> {
      // waitUntil wraps the whole tick: the runtime keeps the isolate alive
      // past the handler's return, so a slow Telegram send still lands.
      ctx.waitUntil(runGuidanceCronTick(controller, env, opts));
    },
  } satisfies ExportedHandler<Env>;
}

export default createExportedHandler();

/** The envelope key scheme's prefix, sliced into a session id. */
function envelopeIdOf(keyName: string): string {
  return keyName.slice(GUIDANCE_KEY_PREFIX.length);
}

/**
 * scheduled()'s body: scan → validate → project → push.
 *
 * - FAIL-CLOSED posture (the webhook guard's shape): a missing BOT_TOKEN,
 *   namespace, or Mini App origin logs `skipped: unconfigured` and returns —
 *   an unarmed cron must never half-run.
 * - The graph memo is awaited ONCE per tick (worker-router's loadGraph —
 *   the ONLY R2 loader; a second one is forbidden). A null graph is the
 *   street-less bare-verb degradation, not a tick failure.
 * - Per key: getGuidanceSession (defensive — garbage reads null and the key
 *   is skipped honestly), projectTurnCards, then sendPhoto inside try/catch.
 *   One bad key cannot kill the tick (delivery variance is best-effort, D-13).
 * - EVERY log line is a category — never a chat id, coordinate, or payload.
 */
async function runGuidanceCronTick(
  controller: ScheduledController,
  env: Env,
  opts: { baseFetch?: typeof fetch },
): Promise<void> {
  if (!env.BOT_TOKEN || !env.chat_sessions || !env.MINI_APP_URL) {
    console.log("[guidance-cron] skipped: unconfigured");
    return;
  }
  const nowSec = Math.floor(controller.scheduledTime / 1000);
  const graph = await loadGraph(env);
  let cursor: string | undefined;
  do {
    const page = await env.chat_sessions.list({ prefix: GUIDANCE_KEY_PREFIX, cursor });
    for (const key of page.keys) {
      let envelope: GuidanceSessionEnvelope | null = null;
      try {
        envelope = await getGuidanceSession(env.chat_sessions, envelopeIdOf(key.name));
      } catch {
        envelope = null; // a throwing read is the same honest skip class (one bad key ≠ a dead tick)
      }
      if (envelope === null) {
        console.log("[guidance-cron] skipped: malformed");
        continue;
      }
      const streetAt =
        graph === null
          ? undefined // street-less bare-verb degradation (D-03) — the send still fires
          : makeStreetAt(graph, decodePolyline6(envelope.route_snapshot.geometry));
      const card = projectTurnCards(envelope, nowSec, streetAt);
      if (!card.due || card.glyph === null || card.caption === null) continue;
      try {
        await createBot(env, opts).api.sendPhoto(envelope.chat_id, `${env.MINI_APP_URL}/glyphs/${card.glyph}.png`, {
          caption: card.caption,
          parse_mode: "HTML",
          reply_markup: {
            inline_keyboard: [
              [{ text: strings.en.cardOpenButton, web_app: { url: `${env.MINI_APP_URL}/?g=${envelope.id}` } }],
            ],
          },
        });
      } catch {
        // Telegram rejected the push (blocked bot, rate limit, delivery
        // variance). Category only — never the chat id or error text (D-13).
        console.log("[guidance-cron] send failed");
      }
    }
    cursor = page.list_complete ? undefined : page.cursor;
  } while (cursor !== undefined);
}

/** initData is Telegram's verbatim WebApp string — a few hundred bytes on
 *  the wire (research: known-good fixtures ≪ 1 KB). 4 KB is generous
 *  headroom; anything beyond is abuse aimed at the isolate's memory/CPU
 *  budget (WR-01) — unbounded, `raw.split("&")` would allocate millions of
 *  entries per multi-MB request. */
const MAX_INITDATA_CHARS = 4096;

/** Category-only 413 for over-cap bodies (WR-01) — the error carries the
 *  D-14 category, nothing of the request payload. */
function oversizeBody(): Response {
  return new Response(JSON.stringify({ error: "malformed" }), {
    status: 413,
    headers: { "content-type": "application/json" },
  });
}

/** Phase-2 security gate: initData in, one-time opaque session token out —
 *  nothing else; unvalidated identities get a category-only 401 (T-02-01). */
async function handleSession(req: Request, env: Env): Promise<Response> {
  if (req.method !== "POST") return new Response("Method not allowed", { status: 405 });
  // WR-01: reject over-cap bodies before any parse work. A declared
  // Content-Length lets us say no without buffering the stream; lying or
  // absent headers are covered by the post-read length check. The character
  // bound is what governs the `split("&")` allocation below — the DoS
  // surface this cap exists to close.
  if (Number(req.headers.get("content-length") ?? "0") > MAX_INITDATA_CHARS) {
    console.log("[initdata] rejected: malformed"); // category ONLY — no payload, no ids, no timestamps
    return oversizeBody();
  }
  const raw = await req.text(); // the verbatim Telegram.WebApp.initData string
  if (raw.length > MAX_INITDATA_CHARS) {
    console.log("[initdata] rejected: malformed"); // category ONLY — no payload, no ids, no timestamps
    return oversizeBody();
  }
  const result = await validateInitData(raw, env.BOT_TOKEN);
  if (!result.ok) {
    console.log(`[initdata] rejected: ${result.reason}`); // D-14: category ONLY — no payload, no ids, no timestamps
    return new Response(JSON.stringify({ error: result.reason }), {
      status: 401,
      headers: { "content-type": "application/json" },
    });
  }
  const token = await mintSession(env.chat_sessions, {
    user_id: result.user.id,
    chat_id: result.chat?.id ?? result.user.id, // private chat: Telegram conflates; claim surface unchanged (D-08)
    issued_at: Math.floor(Date.now() / 1000),
    language_code: result.languageCode,
  });
  return new Response(JSON.stringify({ token }), { status: 200, headers: { "content-type": "application/json" } });
}

/** GEO-02 relay (T-03-01): the Mini App polls here with its memory-held
 *  Bearer token to pick up a pin the user shared in chat. V4 Access
 *  Control (RESEARCH §Security Domain): the bearer token is resolved via
 *  getClaimByToken; a missing/expired token is a 401. The KV key is
 *  derived from the CLAIM's chat_id — NEVER from a client-supplied chat
 *  id, so one user's token can never read another user's pin. */
async function handleLocation(req: Request, env: Env): Promise<Response> {
  if (req.method !== "GET") return new Response("Method not allowed", { status: 405 });
  const header = req.headers.get("authorization") ?? "";
  const match = header.match(/^Bearer ([A-Za-z0-9-]+)$/);
  const token = match !== null && match[1] ? match[1] : null;
  const claim = token === null ? null : await getClaimByToken(env.chat_sessions, token);
  if (claim === null) {
    console.log("[location] rejected: unauthorized"); // category ONLY (D-14)
    return new Response(JSON.stringify({ error: "unauthorized" }), {
      status: 401,
      headers: { "content-type": "application/json" },
    });
  }
  const pin = await getPin(env.chat_sessions, claim.chat_id);
  return new Response(JSON.stringify({ pin }), {
    status: 200,
    headers: { "content-type": "application/json" },
  });
}

/** GEO-02 trigger (T-03-26): the Mini App's denied card taps ASK VIA CHAT
 *  and POSTs here; the Worker asks the BOT to send the request_location
 *  reply keyboard in the user's own chat. Same V4 access control as
 *  handleLocation — the target chat_id comes from the resolved CLAIM,
 *  never from the request body, so one user's token can never push a
 *  keyboard into another user's chat.
 *
 *  The locale comes from `claim.language_code`, which mintSession already
 *  recorded from the validated initData — the Worker does NOT re-derive it
 *  from client input, and no language is accepted from the request body
 *  (T-03-27). */
async function handleLocationFallback(req: Request, env: Env): Promise<Response> {
  if (req.method !== "POST") return new Response("Method not allowed", { status: 405 });
  const header = req.headers.get("authorization") ?? "";
  const match = header.match(/^Bearer ([A-Za-z0-9-]+)$/);
  const token = match !== null && match[1] ? match[1] : null;
  const claim = token === null ? null : await getClaimByToken(env.chat_sessions, token);
  if (claim === null) {
    console.log("[location-fallback] rejected: unauthorized"); // category ONLY (D-14)
    return new Response(JSON.stringify({ error: "unauthorized" }), {
      status: 401,
      headers: { "content-type": "application/json" },
    });
  }
  try {
    await requestLocationFallback(createBot(env), claim.chat_id, pickLocale(claim.language_code));
    return new Response(JSON.stringify({ ok: true }), {
      status: 200,
      headers: { "content-type": "application/json" },
    });
  } catch {
    // Telegram rejected the send (user blocked the bot, chat not found, rate
    // limit). Category only — never the chat id, never the error text (D-14, T-03-28).
    console.log("[location-fallback] failed: telegram-send");
    return new Response(JSON.stringify({ error: "unavailable" }), {
      status: 502,
      headers: { "content-type": "application/json" },
    });
  }
}

/** The guidance envelope's POST body cap (WR-01, the initData precedent):
 *  an honest envelope is ≪ 2 KB (six snapshot fields); 8 KB is generous
 *  headroom, anything beyond is abuse aimed at the isolate's memory/CPU
 *  budget. The pre/post-read double check closes the lying-Content-Length
 *  blind spot (WK2b's lesson). */
const MAX_GUIDANCE_BODY_CHARS = 8192;

/** Destination ids are gazetteer slugs — the search workspace's own law
 *  (search/src/source.ts ENTRY_ID_PATTERN); a body carrying anything else
 *  never reaches storage. */
const DESTINATION_ID_PATTERN = /^[a-z0-9-]{1,64}$/;

/** Display names come from the gazetteer (short); 200 chars bounds the
 *  envelope line any cron card would ever render. */
const MAX_DESTINATION_NAME_CHARS = 200;

/** Hand-rolled snapshot validation (no zod — RESEARCH V5): every field is
 *  type-checked, range-checked, and the geometry must decode as polyline6
 *  to ≥ 2 points. Returns a NEW object built field-by-field — anything the
 *  body carries beyond the six snapshot fields (chat_id included) is
 *  structurally dropped (T-06-02: identity and shape are server-owned). */
function validateSnapshot(body: unknown): GuidanceRouteSnapshot | null {
  if (body === null || typeof body !== "object" || Array.isArray(body)) return null;
  const b = body as Record<string, unknown>;
  if (typeof b.destinationId !== "string" || !DESTINATION_ID_PATTERN.test(b.destinationId)) return null;
  if (
    typeof b.destinationName !== "string" ||
    b.destinationName.length === 0 ||
    b.destinationName.length > MAX_DESTINATION_NAME_CHARS
  ) {
    return null;
  }
  if (typeof b.distanceM !== "number" || !Number.isFinite(b.distanceM) || b.distanceM < 0) return null;
  if (typeof b.durationS !== "number" || !Number.isFinite(b.durationS) || b.durationS < 0) return null;
  if (typeof b.startedAtSec !== "number" || !Number.isSafeInteger(b.startedAtSec) || b.startedAtSec <= 0) {
    return null;
  }
  if (typeof b.geometry !== "string") return null;
  try {
    if (decodePolyline6(b.geometry).length < 2) return null;
  } catch {
    return null; // truncated/malformed polyline6 never reaches storage
  }
  return {
    destinationId: b.destinationId,
    destinationName: b.destinationName,
    distanceM: b.distanceM,
    durationS: b.durationS,
    geometry: b.geometry,
    startedAtSec: b.startedAtSec,
  };
}

function guidanceUnauthorized(): Response {
  console.log("[guidance] rejected: unauthorized"); // category ONLY (D-14) — never the token, never the body
  return new Response(JSON.stringify({ error: "unauthorized" }), {
    status: 401,
    headers: { "content-type": "application/json" },
  });
}

function guidanceMalformed(): Response {
  console.log("[guidance] rejected: malformed"); // category ONLY (D-14) — never the payload, never ids
  return new Response(JSON.stringify({ error: "malformed" }), {
    status: 400,
    headers: { "content-type": "application/json" },
  });
}

/** Foreign and absent are INDISTINGUISHABLE (T-06-02b) — no existence
 *  oracle for cross-chat probing. */
function guidanceNotFound(): Response {
  return new Response(JSON.stringify({ error: "not_found" }), {
    status: 404,
    headers: { "content-type": "application/json" },
  });
}

/** Guidance sessions over HTTP (GUID-05/06 server surface, D-14's delete).
 *  V4 access control, the handleLocation posture verbatim: the Bearer
 *  token resolves through getClaimByToken, and EVERYTHING chat-scoped
 *  derives from that CLAIM — the envelope's chat_id is minted server-side
 *  (a body chat_id is structurally ignored, T-06-02), and GET/DELETE
 *  resolve the record then compare envelope.chat_id === claim.chat_id, so
 *  one user's token can never read or delete another user's session. The
 *  envelope shape and its TTL (7200 s) are the service's own laws (GE1/GE2). */
async function handleGuidance(req: Request, env: Env): Promise<Response> {
  if (req.method !== "POST" && req.method !== "GET" && req.method !== "DELETE") {
    return new Response("Method not allowed", { status: 405 });
  }
  const header = req.headers.get("authorization") ?? "";
  const match = header.match(/^Bearer ([A-Za-z0-9-]+)$/);
  const token = match !== null && match[1] ? match[1] : null;
  const claim = token === null ? null : await getClaimByToken(env.chat_sessions, token);
  if (claim === null) return guidanceUnauthorized();

  if (req.method === "POST") {
    // WR-01: reject over-cap bodies before any parse work; the post-read
    // check backstops a lying or absent Content-Length.
    if (Number(req.headers.get("content-length") ?? "0") > MAX_GUIDANCE_BODY_CHARS) {
      console.log("[guidance] rejected: malformed");
      return oversizeBody();
    }
    const raw = await req.text();
    if (raw.length > MAX_GUIDANCE_BODY_CHARS) {
      console.log("[guidance] rejected: malformed");
      return oversizeBody();
    }
    let parsed: unknown;
    try {
      parsed = JSON.parse(raw);
    } catch {
      return guidanceMalformed();
    }
    const snapshot = validateSnapshot(parsed);
    if (snapshot === null) return guidanceMalformed();
    const envelope = await mintGuidanceSession(env.chat_sessions, claim.chat_id, snapshot);
    return new Response(JSON.stringify({ id: envelope.id }), {
      status: 201,
      headers: { "content-type": "application/json" },
    });
  }

  // GET/DELETE: resolve, then OWN. The id is the only client input, and the
  // service UUID-guards it before any KV touch (V5).
  const id = new URL(req.url).searchParams.get("id") ?? "";
  const envelope = await getGuidanceSession(env.chat_sessions, id);
  if (envelope === null || envelope.chat_id !== claim.chat_id) {
    return guidanceNotFound();
  }
  if (req.method === "DELETE") {
    await deleteGuidanceSession(env.chat_sessions, id);
    return new Response(JSON.stringify({ deleted: true }), {
      status: 200,
      headers: { "content-type": "application/json" },
    });
  }
  return new Response(JSON.stringify(envelope), {
    status: 200,
    headers: { "content-type": "application/json" },
  });
}