import "../client/axiosTypes";
import { AxiosInstance } from "axios";
import { z } from "zod";
import { SapB1Config } from "../config";
import { SapB1Error, toSapB1Error } from "../errors/SapB1Error";
import { SapB1Logger, noopLogger, sanitizeLogMeta } from "../utils/logger";

const LoginResponseSchema = z.object({
  SessionId: z.string().optional(),
  Version: z.string().optional(),
  SessionTimeout: z.number().optional()
});

export interface SapB1Session {
  b1session: string;
  routeId?: string;
  expiresAt?: number;
}

export interface SapB1LoginInfo {
  version?: string;
  sessionTimeoutMinutes?: number;
}

export class SessionManager {
  private session?: SapB1Session;
  private loginPromise?: Promise<SapB1Session>;
  private lastLoginInfo?: SapB1LoginInfo;

  public constructor(
    private readonly http: AxiosInstance,
    private readonly config: SapB1Config,
    private readonly logger: SapB1Logger = noopLogger
  ) {}

  public get currentSession(): SapB1Session | undefined {
    return this.session;
  }

  // Survives logout on purpose: the login/logout roundtrip in the HTTP layer still
  // needs to report which Service Layer version answered.
  public get loginInfo(): SapB1LoginInfo | undefined {
    return this.lastLoginInfo;
  }

  public async getSession(forceRefresh = false): Promise<SapB1Session> {
    if (!forceRefresh && this.session && !this.isExpired(this.session)) {
      return this.session;
    }

    if (!this.loginPromise) {
      this.loginPromise = this.login().finally(() => {
        this.loginPromise = undefined;
      });
    }

    return this.loginPromise;
  }

  public async login(): Promise<SapB1Session> {
    this.logger.info("SAP B1 login request", sanitizeLogMeta({ baseUrl: this.config.baseUrl, companyDB: this.config.companyDB }));

    try {
      const response = await this.http.post(
        "/Login",
        {
          CompanyDB: this.config.companyDB,
          UserName: this.config.username,
          Password: this.config.password,
          // Service Layer expects Language as an integer language code (Edm.Int32).
          Language: this.normalizeLanguage(this.config.language)
        },
        { skipAuth: true }
      );

      const loginData = LoginResponseSchema.parse(response.data);
      const cookies = this.extractCookies(response.headers["set-cookie"]);
      const b1session = cookies.B1SESSION || loginData.SessionId;

      if (!b1session) {
        throw new SapB1Error({ message: "SAP B1 login did not return B1SESSION cookie or SessionId" });
      }

      const timeoutMinutes = typeof loginData.SessionTimeout === "number" ? loginData.SessionTimeout : 30;
      this.lastLoginInfo = {
        version: loginData.Version,
        sessionTimeoutMinutes: loginData.SessionTimeout
      };
      this.session = {
        b1session,
        routeId: cookies.ROUTEID,
        expiresAt: Date.now() + Math.max(timeoutMinutes - 1, 1) * 60_000
      };

      return this.session;
    } catch (error) {
      // Route login failures through the shared normalizer so the SAP status/code and
      // rejection message survive into the response. That is what lets the caller tell a
      // SAP-side rejection (wrong CompanyDB/user/password -> HTTP 401/400 with a SAP body)
      // apart from a transport problem (wrong BaseUrl/port, TLS, timeout -> no HTTP status).
      const sapError = toSapB1Error(error, "POST", "/Login", "SAP B1 login failed");
      this.logger.error(
        "SAP B1 login failed",
        sanitizeLogMeta({
          baseUrl: this.config.baseUrl,
          companyDB: this.config.companyDB,
          status: sapError.status,
          code: sapError.code,
          message: sapError.message
        })
      );
      throw sapError;
    }
  }

  public async logout(): Promise<void> {
    if (!this.session) {
      return;
    }

    const cookieHeader = this.buildCookieHeader(this.session);

    try {
      // Logout must carry the active session cookie, otherwise the Service Layer
      // cannot identify which session to terminate and leaves it open until timeout.
      await this.http.post("/Logout", undefined, {
        skipAuth: true,
        headers: { Cookie: cookieHeader }
      });
    } finally {
      this.session = undefined;
    }
  }

  public buildCookieHeader(session: SapB1Session): string {
    const parts = [`B1SESSION=${session.b1session}`];

    if (session.routeId) {
      parts.push(`ROUTEID=${session.routeId}`);
    }

    return parts.join("; ");
  }

  public clearSession(): void {
    this.session = undefined;
  }

  private normalizeLanguage(language: string | undefined): number | undefined {
    if (language === undefined || language === "") {
      return undefined;
    }

    const numeric = Number(language);
    return Number.isInteger(numeric) ? numeric : undefined;
  }

  private isExpired(session: SapB1Session): boolean {
    return session.expiresAt !== undefined && session.expiresAt <= Date.now();
  }

  private extractCookies(setCookieHeader: string[] | string | undefined): Record<string, string> {
    const headers = Array.isArray(setCookieHeader) ? setCookieHeader : setCookieHeader ? [setCookieHeader] : [];
    const cookies: Record<string, string> = {};

    for (const header of headers) {
      const [nameValue] = header.split(";");
      const separatorIndex = nameValue.indexOf("=");

      if (separatorIndex > 0) {
        cookies[nameValue.slice(0, separatorIndex)] = nameValue.slice(separatorIndex + 1);
      }
    }

    return cookies;
  }
}