/**
 * CDP Session Management
 *
 * Wraps Playwright's CDP session access to provide a typed, injectable
 * interface for sending Chrome DevTools Protocol commands.
 *
 * Design: dependency injection over optional imports. The extractor receives
 * a session factory rather than importing Playwright directly.
 */

/**
 * Minimal CDP session interface. Any object that can send CDP commands
 * and return JSON-like responses satisfies this contract.
 */
export interface CDPSession {
  send<T = unknown>(method: string, params?: Record<string, unknown>): Promise<T>
  on(event: string, handler: (payload: unknown) => void): void
  off(event: string, handler: (payload: unknown) => void): void
  detach(): Promise<void>
}

/**
 * Factory that creates a CDP session for a given Playwright page.
 * This is injected so the package does not hard-depend on Playwright.
 */
export type CDPSessionFactory = (pageRef: unknown) => Promise<CDPSession>

/**
 * Playwright-backed session factory implementation.
 *
 * Usage:
 *   const session = await createPlaywrightCDPSession(page)
 *
 * Where `page` is a Playwright Page object.
 */
export async function createPlaywrightCDPSession(
  page: unknown
): Promise<CDPSession> {
  // Playwright pages expose context() and a CDP session method.
  // We access it dynamically to avoid a hard import dependency.
  const pwPage = page as {
    context: () => {
      newCDPSession: (p: unknown) => Promise<CDPSession>
    }
  }

  const context = pwPage.context()
  const session = await context.newCDPSession(page)
  return session
}

/**
 * Session manager that owns the lifecycle of a CDP session.
 *
 * Handles attach, detach, and basic error recovery.
 * Caches document root nodeId and enabled domains to minimize round-trips.
 */
export class CDPSessionManager {
  private session: CDPSession | null = null
  private attachPromise: Promise<CDPSession> | null = null
  private readonly factory: CDPSessionFactory
  private readonly pageRef: unknown
  private documentRootNodeId: number | null = null
  private enabledDomains = new Set<string>()

  constructor(factory: CDPSessionFactory, pageRef: unknown) {
    this.factory = factory
    this.pageRef = pageRef
  }

  /**
   * Ensure a session is attached. Idempotent and concurrency-safe.
   */
  async attach(): Promise<CDPSession> {
    if (this.session) return this.session
    if (this.attachPromise) return this.attachPromise
    this.attachPromise = this.factory(this.pageRef).then((s) => {
      this.session = s
      this.documentRootNodeId = null
      this.enabledDomains.clear()
      return s
    })
    return this.attachPromise
  }

  /**
   * Get cached document root nodeId, or fetch and cache it.
   */
  async getDocumentRootNodeId(): Promise<number> {
    if (this.documentRootNodeId !== null) {
      return this.documentRootNodeId
    }
    const s = await this.attach()
    const result = await s.send<{ root: { nodeId: number } }>('DOM.getDocument')
    this.documentRootNodeId = result.root.nodeId
    return this.documentRootNodeId
  }

  /**
   * Enable a CDP domain if not already enabled.
   */
  async enableDomain(domain: string): Promise<void> {
    if (this.enabledDomains.has(domain)) {
      return
    }
    const s = await this.attach()
    await s.send(`${domain}.enable`)
    this.enabledDomains.add(domain)
  }

  /**
   * Get the current session, throwing if not attached.
   */
  getSession(): CDPSession {
    if (!this.session) {
      throw new Error('CDP session not attached. Call attach() first.')
    }
    return this.session
  }

  /**
   * Send a CDP command, automatically attaching if needed.
   */
  async send<T = unknown>(
    method: string,
    params?: Record<string, unknown>
  ): Promise<T> {
    const s = await this.attach()
    return s.send<T>(method, params)
  }

  /**
   * Detach and clean up the session.
   */
  async detach(): Promise<void> {
    if (this.session) {
      await this.session.detach()
      this.session = null
    }
    this.attachPromise = null
  }
}

/**
 * Convenient builder for a manager using the Playwright factory.
 */
export function createSessionManager(page: unknown): CDPSessionManager {
  return new CDPSessionManager(createPlaywrightCDPSession, page)
}