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| const allowedMethods = new Set(["getMe", "getChat", "getChatMember", "sendMessage", "editMessageText"]); | |
| const maxBytes = 65536; | |
| function reply(status, description) { | |
| return Response.json({ ok: false, description }, { | |
| status, | |
| headers: { "Cache-Control": "no-store" }, | |
| }); | |
| } | |
| async function authorized(actual, expected) { | |
| const encoder = new TextEncoder(); | |
| const [actualHash, expectedHash] = await Promise.all([ | |
| crypto.subtle.digest("SHA-256", encoder.encode(actual)), | |
| crypto.subtle.digest("SHA-256", encoder.encode(expected)), | |
| ]); | |
| const actualBytes = new Uint8Array(actualHash); | |
| const expectedBytes = new Uint8Array(expectedHash); | |
| let difference = 0; | |
| for (let index = 0; index < actualBytes.length; index += 1) { | |
| difference |= actualBytes[index] ^ expectedBytes[index]; | |
| } | |
| return difference === 0; | |
| } | |
| async function readBody(request) { | |
| if (!request.body) throw new Error("empty_body"); | |
| const reader = request.body.getReader(); | |
| const chunks = []; | |
| let size = 0; | |
| while (true) { | |
| const { value, done } = await reader.read(); | |
| if (done) break; | |
| size += value.byteLength; | |
| if (size > maxBytes) { | |
| await reader.cancel(); | |
| throw new Error("payload_too_large"); | |
| } | |
| chunks.push(value); | |
| } | |
| const body = new Uint8Array(size); | |
| let offset = 0; | |
| for (const chunk of chunks) { | |
| body.set(chunk, offset); | |
| offset += chunk.byteLength; | |
| } | |
| return JSON.parse(new TextDecoder("utf-8", { fatal: true }).decode(body)); | |
| } | |
| export default { | |
| async fetch(request, environment) { | |
| const url = new URL(request.url); | |
| if (url.pathname !== "/telegram" || url.search || request.method !== "POST") { | |
| return reply(404, "not_found"); | |
| } | |
| if (!/^\d+:[A-Za-z0-9_-]+$/.test(environment.TELEGRAM_BOT_TOKEN || "") | |
| || !/^[A-Za-z0-9_-]{32,}$/.test(environment.RELAY_SECRET || "") | |
| || !/^-?\d+$/.test(environment.TELEGRAM_CHAT_ID || "")) { | |
| return reply(503, "configuration_required"); | |
| } | |
| if (!await authorized(request.headers.get("Authorization") || "", "Bearer " + environment.RELAY_SECRET)) { | |
| return reply(401, "unauthorized"); | |
| } | |
| let input; | |
| try { | |
| input = await readBody(request); | |
| } catch (error) { | |
| return reply(error.message === "payload_too_large" ? 413 : 400, "invalid_payload"); | |
| } | |
| if (!input || typeof input !== "object" || !allowedMethods.has(input.method) | |
| || !input.payload || typeof input.payload !== "object" || Array.isArray(input.payload)) { | |
| return reply(400, "invalid_method_or_payload"); | |
| } | |
| if (input.method === "getMe") { | |
| input.payload = {}; | |
| } else if (String(input.payload.chat_id) !== environment.TELEGRAM_CHAT_ID) { | |
| return reply(403, "chat_not_allowed"); | |
| } | |
| try { | |
| const response = await fetch( | |
| "https://api.telegram.org/bot" + environment.TELEGRAM_BOT_TOKEN + "/" + input.method, | |
| { | |
| method: "POST", | |
| headers: { "Content-Type": "application/json" }, | |
| body: JSON.stringify(input.payload), | |
| redirect: "manual", | |
| signal: AbortSignal.timeout(8000), | |
| }, | |
| ); | |
| if (response.status >= 300 && response.status < 400) return reply(502, "telegram_unexpected_redirect"); | |
| const body = await response.text(); | |
| let data; | |
| try { | |
| data = JSON.parse(body); | |
| } catch { | |
| return reply(502, "telegram_upstream_non_json_http_" + response.status); | |
| } | |
| if (!data || typeof data.ok !== "boolean") return reply(502, "telegram_invalid_response"); | |
| return new Response(body, { | |
| status: response.status, | |
| headers: { "Content-Type": "application/json", "Cache-Control": "no-store" }, | |
| }); | |
| } catch (error) { | |
| if (typeof AbortSignal.timeout !== "function") return reply(502, "telegram_timeout_api_unavailable"); | |
| if (String(error.message).includes("Network connection lost")) return reply(502, "telegram_network_connection_lost"); | |
| if (String(error.message).includes("resolve")) return reply(502, "telegram_dns_error"); | |
| const category = ["TimeoutError", "AbortError", "TypeError"].includes(error.name) ? error.name : "unknown"; | |
| return reply(502, "telegram_upstream_" + category); | |
| } | |
| }, | |
| }; | |