import { Hono } from "hono";
import { RequestHeaders } from "../../routes/types";
import { ApplicationError } from "../../errors";
import { HTTP_STATUS_CODE_BAD_REQUEST } from "../../constants";

/** RFC 9110 field-name token grammar. */
const HEADER_NAME_PATTERN = /^[!#$%&'*+\-.^_`|~0-9A-Za-z]+$/;

/** Hono variables populated by transport-boundary middleware. */
export type AppEnv = {
  Variables: {

      /** Decoded Extended JSON request body, when present. */
      parsedBody?: unknown;

      /** Raw JSON text preserved for signature verification. */
      rawJsonBody?: string;
  };
};

export abstract class BaseTransport {
    /** Attach wire endpoints and middleware to the shared Hono application. */
    abstract register(app: Hono<AppEnv>): void

    /** Close transport-owned long-lived connections during server shutdown. */
    abstract stop(): Promise<void>
    
    /**
     * Validate and normalize request headers at a transport boundary.
     *
     * Lowercase names give HTTP and WebSocket routes identical lookup semantics.
     * Case-insensitive duplicates are rejected instead of selecting an ambiguous
     * authentication value. Header values may not contain line breaks.
     */
    public static normalizeRequestHeaders(headers: Readonly<Record<string, string>>): RequestHeaders {
        const normalizedEntries: Array<[string, string]> = [];
        const names = new Set<string>();
    
        for (const [ name, value ] of Object.entries(headers)) {
            if (!HEADER_NAME_PATTERN.test(name)) {
                throw new ApplicationError(HTTP_STATUS_CODE_BAD_REQUEST, 'Invalid request header name');
            }
    
            if (value.includes('\r') || value.includes('\n')) {
                throw new ApplicationError(HTTP_STATUS_CODE_BAD_REQUEST, 'Invalid request header value');
            }
    
            const normalizedName = name.toLowerCase();
            if (names.has(normalizedName)) {
                throw new ApplicationError(HTTP_STATUS_CODE_BAD_REQUEST, 'Duplicate request header name');
            }
    
            names.add(normalizedName);
            normalizedEntries.push([ normalizedName, value ]);
        }
    
        return Object.freeze(Object.fromEntries(normalizedEntries));
    };
}