import {
  ConflictException,
  Injectable,
  Logger,
  NotFoundException,
  UnauthorizedException,
} from "@nestjs/common";
import { PrismaService } from "../database/prisma.service";
import { v4 as uuidv4 } from "uuid";
import { JwtService } from "@nestjs/jwt";
import * as crypto from "crypto";
import { EmailService } from "../email/email.service";

export interface FacilityLinkTokenPayload {
  facilityId: string;
  facilityName: string;
  /** jti — unique token ID so each QR can only be used once */
  jti: string;
  /** standard JWT exp — set to 48h */
  exp?: number;
}

@Injectable()
export class FacilitiesService {
  private readonly logger = new Logger(FacilitiesService.name);

  constructor(
    private prisma: PrismaService,
    private readonly jwtService: JwtService,
    private readonly emailService: EmailService,
  ) {}

  // ─── FACILITY CRUD ───────────────────────────────────────────────────────

  async create(data: {
    organizationId?: string;
    name: string;
    address?: string;
    phone?: string;
    adminFirstName: string;
    adminLastName: string;
    adminEmail: string;
    adminPhone?: string;
    adminType?: string;
  }) {
    if (data.organizationId) {
      const organization = await this.prisma.organization.findUnique({
        where: { id: data.organizationId },
      });

      if (!organization) {
        throw new NotFoundException("Organization not found");
      }
    }

    // Check if admin email already exists
    const existingUser = await this.prisma.userAuth.findUnique({
      where: { email: data.adminEmail.toLowerCase() },
    });
    if (existingUser) {
      throw new ConflictException("Admin email already exists");
    }

    const facilityCode = uuidv4().split("-")[0].toUpperCase();

    // Generate password setup token
    const setupToken = crypto.randomBytes(32).toString("hex");
    const expires = new Date();
    expires.setHours(expires.getHours() + 24);

    // Use transaction to ensure all operations succeed or fail together
    const facility = await this.prisma.$transaction(async (tx) => {
      // 1. Create facility
      const facility = await tx.facility.create({
        data: {
          name: data.name,
          address: data.address,
          phone: data.phone,
          facilityCode,
          organizationId: data.organizationId ?? null,
        },
        include: {
          organization: true,
        },
      });

      // 2. Create user auth (no password yet)
      const userAuth = await tx.userAuth.create({
        data: {
          email: data.adminEmail.toLowerCase(),
          phone: data.adminPhone,
          role: "FACILITY_ADMIN",
          passwordSetupToken: setupToken,
          passwordSetupExpiresAt: expires,
          status: "PENDING",
        },
      });

      // 3. Create healthcare worker
      await tx.healthcareWorker.create({
        data: {
          userId: userAuth.id,
          facilityId: facility.id,
          type: (data.adminType || "COMMUNITY_HEALTH_WORKER") as any,
          firstName: data.adminFirstName,
          lastName: data.adminLastName,
        },
      });

      return facility;
    });

    // 4. Send welcome email asynchronously
    this.emailService
      .sendFacilityAdminWelcome(
        data.adminEmail,
        `${data.adminFirstName} ${data.adminLastName}`,
        facility.name,
        setupToken,
      )
      .catch((err) =>
        this.logger.error(
          `Failed to send welcome email to ${data.adminEmail}`,
          err,
        ),
      );

    return facility;
  }

  async findAll() {
    return this.prisma.facility.findMany({
      include: {
        organization: true,
      },
      orderBy: {
        createdAt: "desc",
      },
    });
  }

  async findOne(id: string) {
    const facility = await this.prisma.facility.findUnique({
      where: { id },
      include: {
        organization: true,
      },
    });

    if (!facility) {
      throw new NotFoundException("Facility not found");
    }

    return facility;
  }

  async update(
    id: string,
    data: {
      organizationId?: string | null;
      name?: string;
      address?: string;
      phone?: string;
      isActive?: boolean;
    },
  ) {
    if (data.organizationId) {
      const organization = await this.prisma.organization.findUnique({
        where: {
          id: data.organizationId,
        },
      });

      if (!organization) {
        throw new NotFoundException("Organization not found");
      }
    }

    return this.prisma.facility.update({
      where: { id },
      data: {
        ...data,
      },
      include: {
        organization: true,
      },
    });
  }

  async deactivate(id: string) {
    return this.prisma.facility.update({
      where: { id },
      data: { isActive: false },
    });
  }

  // ─── QR FACILITY LINKING ─────────────────────────────────────────────────

  /**
   * Called by a health worker on the dashboard.
   * Returns a short-lived signed JWT that gets encoded into a QR code.
   *
   * Uses FACILITY_LINK_SECRET — separate from the auth JWT secret so a
   * leaked link token cannot be replayed as an auth token.
   *
   * Expiry: 48 hours.
   */
  async generateLinkToken(healthWorkerId: string): Promise<{
    token: string;
    facilityId: string;
    facilityName: string;
    expiresAt: Date;
  }> {
    const worker = await this.prisma.healthcareWorker.findUnique({
      where: { id: healthWorkerId },
      include: { facility: true },
    });

    if (!worker || worker.isSuspended) {
      throw new UnauthorizedException("Health worker not found or suspended");
    }

    const jti = uuidv4();
    const expiresAt = new Date(Date.now() + 48 * 60 * 60 * 1000);

    const payload: FacilityLinkTokenPayload = {
      facilityId: worker.facilityId,
      facilityName: worker.facility.name,
      jti,
    };

    const token = this.jwtService.sign(payload, {
      secret: process.env.FACILITY_LINK_SECRET,
      expiresIn: "48h",
    });

    this.logger.log(
      `Link token generated for facility ${worker.facilityId} by worker ${healthWorkerId}`,
    );

    return {
      token,
      facilityId: worker.facilityId,
      facilityName: worker.facility.name,
      expiresAt,
    };
  }

  /**
   * Called by the patient app after scanning the QR code.
   *
   * Flow:
   * 1. Verify JWT signature and expiry
   * 2. Confirm facility is still active
   * 3. Check if Patient record already exists for this user:
   *    - Same facility  → idempotent success (alreadyLinked: true)
   *    - Diff facility  → ConflictException, must unlink first
   *    - No record      → create Patient record
   */
  async linkPatientViaQR(
    userId: string,
    token: string,
  ): Promise<{
    facilityId: string;
    facilityName: string;
    patientCode: string;
    alreadyLinked: boolean;
  }> {
    // 1. Verify token signature + expiry
    let payload: FacilityLinkTokenPayload;
    try {
      payload = this.jwtService.verify<FacilityLinkTokenPayload>(token, {
        secret: process.env.FACILITY_LINK_SECRET,
      });
    } catch {
      throw new UnauthorizedException(
        "This QR code has expired or is invalid. Ask your health worker to generate a new one.",
      );
    }

    const { facilityId, facilityName } = payload;

    // 2. Confirm facility is active
    const facility = await this.prisma.facility.findUnique({
      where: { id: facilityId },
    });
    if (!facility || !facility.isActive) {
      throw new NotFoundException("Facility not found or no longer active");
    }

    // 3. Get patient's auth record + any existing Patient row
    const userAuth = await this.prisma.userAuth.findUnique({
      where: { id: userId },
      include: { patient: true },
    });
    if (!userAuth) throw new NotFoundException("User not found");

    // 4. Handle existing Patient record
    if (userAuth.patient) {
      if (userAuth.patient.facilityId === facilityId) {
        return {
          facilityId,
          facilityName,
          patientCode: userAuth.patient.patientId,
          alreadyLinked: true,
        };
      }
      throw new ConflictException(
        "You are already linked to another facility. Please contact your current facility to unlink first.",
      );
    }

    // 5. Create Patient record — pull gestational age from UserProfile if available
    const profile = await this.prisma.userProfile.findUnique({
      where: { userId },
    });

    const patientCode = uuidv4().split("-")[0].toUpperCase();

    const patient = await this.prisma.patient.create({
      data: {
        userId,
        facilityId,
        patientId: patientCode,
        // Self-registered users have no name — health worker can update from dashboard
        firstName: userAuth.email?.split("@")[0] ?? "Unknown",
        lastName: "",
        phone: userAuth.phone ?? "",
        age: 0,
        gestationalAge: profile?.pregnancyWeeks ?? 0,
        qrCode: patientCode,
      },
    });

    this.logger.log(
      `Patient ${userId} linked to facility ${facilityId} via QR`,
    );

    return {
      facilityId,
      facilityName,
      patientCode: patient.patientId,
      alreadyLinked: false,
    };
  }

  /**
   * Get a patient's current facility link status.
   * Returns { linked: false } if not linked.
   */
  async getLinkStatus(userId: string) {
    const patient = await this.prisma.patient.findUnique({
      where: { userId },
      include: {
        facility: { select: { name: true, address: true, phone: true } },
      },
    });

    if (!patient || !patient.facility) {
      return {
        linked: false,
      };
    }
    return {
      linked: !!patient.facility,
      facilityId: patient.facilityId,
      facilityName: patient.facility?.name ?? null,
      facilityAddress: patient.facility?.address ?? null,
      facilityPhone: patient.facility?.phone ?? null,
      patientCode: patient.patientId,
      linkedAt: patient.createdAt,
    };
  }

  /**
   * Unlink a patient from their facility.
   * Deletes the Patient record only — UserAuth + UserProfile are preserved.
   */
  async unlinkPatient(userId: string): Promise<void> {
    const patient = await this.prisma.patient.findUnique({
      where: { userId },
    });

    if (!patient) {
      throw new NotFoundException("No facility link found for this user");
    }

    await this.prisma.patient.delete({ where: { userId } });

    this.logger.log(
      `Patient ${userId} unlinked from facility ${patient.facilityId}`,
    );
  }
}