import {
  Injectable,
  OnModuleDestroy,
  BadRequestException,
  NotFoundException,
} from "@nestjs/common";
import type { Browser, BrowserContext, Page } from "playwright";
import { TraceLogger } from "../common/trace-logger";
import { SessionService } from "./session.service";

export interface SessionHandle {
  browser: Browser;
  context: BrowserContext;
  page: Page;
}

/**
 * Keeps live Playwright browser contexts in memory, keyed by sessionName.
 * A session must be explicitly registered (after login) to be usable.
 * Sessions marked as closed in the DB cannot be used via getHandle().
 */
@Injectable()
export class SessionContextService implements OnModuleDestroy {
  private readonly logger = new TraceLogger(SessionContextService.name);
  private readonly handles = new Map<string, SessionHandle>();

  constructor(private readonly sessionService: SessionService) {}

  /**
   * Store a live browser context after a successful login.
   * If a handle already exists for this session it is closed first.
   */
  register(
    sessionName: string,
    browser: Browser,
    context: BrowserContext,
    page: Page,
  ): void {
    const existing = this.handles.get(sessionName);
    if (existing) {
      existing.browser.close().catch((err: unknown) => {
        this.logger.warn(
          `Error closing stale browser for "${sessionName}": ${(err as Error).message}`,
        );
      });
    }
    this.handles.set(sessionName, { browser, context, page });
    this.logger.log(`Session "${sessionName}" registered in context pool`);
  }

  /**
   * Return the live handle for a named session and bump lastUsedAt.
   * Throws 404 if session does not exist in DB.
   * Throws 400 if session is closed or context is not in memory.
   */
  async getHandle(sessionName: string): Promise<SessionHandle> {
    const handle = this.handles.get(sessionName);
    if (handle) {
      await this.sessionService.touchLastUsed(sessionName);
      return handle;
    }

    const session = await this.sessionService.findBySessionName(sessionName);
    if (!session) {
      throw new NotFoundException(`Session not found: ${sessionName}`);
    }
    if (session.status === "closed") {
      throw new BadRequestException(
        `Session "${sessionName}" is closed — please login again`,
      );
    }
    // Session is open in DB but context is not in memory (e.g. after unexpected restart).
    throw new BadRequestException(
      `Session "${sessionName}" context is not available — please login again`,
    );
  }

  /**
   * Close the Playwright browser for a session and mark it as closed in DB.
   * Safe to call even if the session is not currently in memory.
   */
  async close(sessionName: string): Promise<void> {
    const handle = this.handles.get(sessionName);
    if (handle) {
      try {
        await handle.browser.close();
      } catch (err) {
        this.logger.warn(
          `Error closing browser for session "${sessionName}": ${(err as Error).message}`,
        );
      }
      this.handles.delete(sessionName);
    }
    await this.sessionService.markClosed(sessionName);
    this.logger.log(`Session "${sessionName}" closed`);
  }

  /**
   * Close all in-memory handles and mark every open session as closed in DB.
   */
  async closeAll(): Promise<void> {
    const names = Array.from(this.handles.keys());
    await Promise.allSettled(names.map((name) => this.close(name)));
    if (names.length > 0) {
      this.logger.log(`Closed ${names.length} session context(s)`);
    }
  }

  /**
   * Close the context (if open) and delete the session record from DB.
   * Throws 404 if the session ID does not exist.
   */
  async delete(id: number): Promise<void> {
    const session = await this.sessionService.findById(id);
    if (!session) {
      throw new NotFoundException(`Session ${id} not found`);
    }
    if (this.handles.has(session.sessionName)) {
      await this.close(session.sessionName);
    }
    await this.sessionService.remove(id);
  }

  /** Returns true if a live Playwright context exists for this session. */
  isOpen(sessionName: string): boolean {
    return this.handles.has(sessionName);
  }

  async onModuleDestroy(): Promise<void> {
    await this.closeAll();
  }
}