import { Injectable, Inject, UnauthorizedException } from "@nestjs/common";
import { eq, and } from "drizzle-orm";
import { users, userIdentities, type Database } from "@courtmitra/db";
import { DB } from "../db/db.module.js";

export interface ClerkUser {
  id: string;
  emailAddresses: { emailAddress: string }[];
  firstName: string | null;
  lastName: string | null;
  imageUrl: string | null;
}

@Injectable()
export class AuthService {
  constructor(@Inject(DB) private readonly db: Database) {}

  /**
   * Find or create a user from Clerk OAuth data.
   * Maps Clerk userId -> our users table via userIdentities.
   */
  async findOrCreateUser(clerkUser: ClerkUser): Promise<{ id: string; email: string | null }> {
    const providerSubject = clerkUser.id;

    // Try to find existing identity by provider + providerSubject (CRITICAL: must match the specific Clerk user)
    const existingIdentity = await this.db
      .select({ userId: userIdentities.userId })
      .from(userIdentities)
      .where(
        and(
          eq(userIdentities.provider, "google"),
          eq(userIdentities.providerSubject, providerSubject),
        ),
      )
      .limit(1);

    if (existingIdentity[0]) {
      const user = await this.db
        .select()
        .from(users)
        .where(eq(users.id, existingIdentity[0].userId))
        .limit(1);
      if (user[0]) {
        return { id: user[0].id, email: user[0].email ?? null };
      }
    }

    // Create new user
    const email = clerkUser.emailAddresses[0]?.emailAddress ?? null;
    const fullName = [clerkUser.firstName, clerkUser.lastName].filter(Boolean).join(" ") || null;

    const [userRow] = await this.db
      .insert(users)
      .values({
        displayName: fullName ?? email ?? "User",
        email,
        avatarUrl: clerkUser.imageUrl,
        fullName,
      })
      .returning();

    if (!userRow) {
      throw new UnauthorizedException("Failed to create user");
    }

    // Create identity link
    await this.db.insert(userIdentities).values({
      userId: userRow.id,
      provider: "google",
      providerSubject,
      isVerified: true,
      metadata: { source: "clerk_oauth" },
    });

    return { id: userRow.id, email };
  }

  /** Look up a user by their internal DB id. */
  async findUserById(id: string) {
    const rows = await this.db.select().from(users).where(eq(users.id, id)).limit(1);
    return rows[0] ?? null;
  }
}