import { Injectable, Inject } from "@nestjs/common";
import { ConfigService } from "@nestjs/config";
import { Redis } from "ioredis";
import { Logger } from "nestjs-pino";

@Injectable()
export class TokenBlacklistService {
  constructor(
    @Inject("REDIS_CLIENT") private readonly redis: Redis,
    private readonly configService: ConfigService,
    @Inject(Logger) private readonly logger: Logger
  ) {}

  async blacklistToken(token: string, _expiresIn?: number): Promise<void> {
    // Extract JWT payload to get expiry time
    try {
      const payload = JSON.parse(Buffer.from(token.split(".")[1] ?? "", "base64").toString()) as {
        exp?: number;
      };
      const expiryTime = (payload.exp ?? 0) * 1000; // Convert to milliseconds
      const currentTime = Date.now();
      const ttl = Math.max(0, Math.floor((expiryTime - currentTime) / 1000)); // Convert to seconds

      if (ttl > 0) {
        await this.redis.setex(`blacklist:${token}`, ttl, "1");
      }
    } catch {
      // If we can't parse the token, blacklist it for the default JWT expiry time
      try {
        const defaultTtl = this.parseJwtExpiry(this.configService.get("JWT_EXPIRES_IN", "7d"));
        await this.redis.setex(`blacklist:${token}`, defaultTtl, "1");
      } catch (err) {
        this.logger.warn(
          "Failed to write token to Redis blacklist; proceeding without persistence",
          {
            error: err instanceof Error ? err.message : String(err),
          }
        );
      }
    }
  }

  async isTokenBlacklisted(token: string): Promise<boolean> {
    try {
      const result = await this.redis.get(`blacklist:${token}`);
      return result !== null;
    } catch (err) {
      // If Redis is unavailable, treat as not blacklisted to avoid blocking auth
      this.logger.warn("Redis unavailable during blacklist check; allowing request", {
        error: err instanceof Error ? err.message : String(err),
      });
      return false;
    }
  }

  private parseJwtExpiry(expiresIn: string): number {
    // Convert JWT expiry string to seconds
    const unit = expiresIn.slice(-1);
    const value = parseInt(expiresIn.slice(0, -1), 10);

    switch (unit) {
      case "s":
        return value;
      case "m":
        return value * 60;
      case "h":
        return value * 60 * 60;
      case "d":
        return value * 24 * 60 * 60;
      default:
        return 7 * 24 * 60 * 60; // Default 7 days in seconds
    }
  }
}