import type { Logger } from '../utils/logger.js';

export type AccountAuthStatus =
  | 'login-required'
  | 'checking'
  | 'authenticated';

export interface AuthenticatedAccount {
  accountId: string;
  redditUsername: string;
  matrixUserId: string;
}

export interface AccountAuthSnapshot {
  status: AccountAuthStatus;
  accountId: string | null;
  redditUsername: string | null;
  matrixUserId: string | null;
  reason: string | null;
}

export interface AccountAuthGate {
  isFullyAuthenticated(): boolean;
  invalidate(reason: string): void;
}

export type AccountAuthenticator = () => Promise<AuthenticatedAccount | null>;
export type AccountAuthenticatedListener = (account: AuthenticatedAccount) => void | Promise<void>;

export interface AccountAuthContextOptions {
  leaseMs?: number;
  retryDelayMs?: number;
  now?: () => number;
}

export interface CurrentAccountAuthentication {
  getRedditUsername(): Promise<string | null>;
  refreshMatrixCredentials(): Promise<{ userId: string } | null>;
}

export async function authenticateCurrentAccount(
  authentication: CurrentAccountAuthentication,
): Promise<AuthenticatedAccount | null> {
  const redditUsername = await authentication.getRedditUsername();
  if (!redditUsername) return null;

  const credentials = await authentication.refreshMatrixCredentials();
  if (!credentials?.userId) return null;
  return {
    accountId: credentials.userId,
    redditUsername,
    matrixUserId: credentials.userId,
  };
}

export const denyAccountAuth: AccountAuthGate = {
  isFullyAuthenticated: () => false,
  invalidate: () => undefined,
};

export class AccountAuthContext implements AccountAuthGate {
  private snapshot: AccountAuthSnapshot = {
    status: 'login-required',
    accountId: null,
    redditUsername: null,
    matrixUserId: null,
    reason: 'Full Reddit and Matrix authentication has not been verified',
  };
  private authenticator: AccountAuthenticator | null = null;
  private authenticationInFlight: Promise<boolean> | null = null;
  private readonly listeners = new Set<AccountAuthenticatedListener>();
  private authenticatedUntil = 0;
  private nextAuthenticationAttemptAt = 0;
  private readonly leaseMs: number;
  private readonly retryDelayMs: number;
  private readonly now: () => number;

  constructor(
    private readonly logger: Logger,
    options: AccountAuthContextOptions = {},
  ) {
    this.leaseMs = options.leaseMs ?? 30 * 60 * 1000;
    this.retryDelayMs = options.retryDelayMs ?? 60 * 1000;
    this.now = options.now ?? Date.now;
  }

  setAuthenticator(authenticator: AccountAuthenticator): void {
    this.authenticator = authenticator;
  }

  isFullyAuthenticated(): boolean {
    if (this.snapshot.status !== 'authenticated') return false;
    if (this.now() < this.authenticatedUntil) return true;
    this.invalidate('Full account authentication lease expired');
    return false;
  }

  getSnapshot(): AccountAuthSnapshot {
    this.isFullyAuthenticated();
    return { ...this.snapshot };
  }

  markAuthenticated(account: AuthenticatedAccount): void {
    if (!account.accountId || !account.redditUsername || !account.matrixUserId) {
      throw new Error('A fully authenticated account requires Reddit and Matrix identities');
    }
    if (account.accountId !== account.matrixUserId) {
      throw new Error('Authenticated account ID must match the Matrix user ID');
    }

    const changedAccount = this.snapshot.accountId !== account.accountId;
    const wasAuthenticated = this.isFullyAuthenticated();
    this.snapshot = {
      status: 'authenticated',
      accountId: account.accountId,
      redditUsername: account.redditUsername,
      matrixUserId: account.matrixUserId,
      reason: null,
    };
    this.authenticatedUntil = this.now() + this.leaseMs;
    this.nextAuthenticationAttemptAt = 0;
    if (!wasAuthenticated || changedAccount) {
      for (const listener of this.listeners) {
        void Promise.resolve(listener(account)).catch((error) => {
          this.logger.error('Authenticated account listener failed:', error);
        });
      }
    }
  }

  invalidate(reason: string): void {
    this.authenticatedUntil = 0;
    this.snapshot = {
      status: 'login-required',
      accountId: null,
      redditUsername: null,
      matrixUserId: null,
      reason,
    };
  }

  onAuthenticated(listener: AccountAuthenticatedListener): () => void {
    this.listeners.add(listener);
    return () => this.listeners.delete(listener);
  }

  ensureFullyAuthenticated(): Promise<boolean> {
    if (this.isFullyAuthenticated()) return Promise.resolve(true);
    if (this.authenticationInFlight) return this.authenticationInFlight;
    if (!this.authenticator) return Promise.resolve(false);
    if (this.now() < this.nextAuthenticationAttemptAt) return Promise.resolve(false);

    this.snapshot = { ...this.snapshot, status: 'checking', reason: null };
    this.authenticationInFlight = this.authenticate().finally(() => {
      this.authenticationInFlight = null;
    });
    return this.authenticationInFlight;
  }

  private async authenticate(): Promise<boolean> {
    try {
      const account = await this.authenticator!();
      if (!account) {
        this.invalidate('Full Reddit and Matrix authentication is required');
        this.nextAuthenticationAttemptAt = this.now() + this.retryDelayMs;
        return false;
      }
      this.markAuthenticated(account);
      return true;
    } catch (error) {
      this.invalidate(error instanceof Error ? error.message : String(error));
      this.nextAuthenticationAttemptAt = this.now() + this.retryDelayMs;
      this.logger.warn('Full account authentication failed:', error);
      return false;
    }
  }
}