import { diagnosticsAllowedForCurrentProcess } from './privacy'

type PackageIncompatibility = {
  kind: 'package_incompatibility'
  packageName: string
  packageVersion: string
  unsupportedApi?: string
}

type ErrorShape = {
  kind: 'error_shape'
  errorClass: string
}

export type CliDiagnostic = PackageIncompatibility | ErrorShape

type Config = { apiKey: string; host: string }

function loadConfig(): Config | null {
  if (!diagnosticsAllowedForCurrentProcess()) return null
  const apiKey =
    process.env.CONTRAST_POSTHOG_API_KEY || process.env.VITE_POSTHOG_API_KEY || ''
  if (!apiKey) return null
  const host =
    process.env.CONTRAST_POSTHOG_HOST ||
    process.env.VITE_POSTHOG_HOST ||
    'https://us.i.posthog.com'
  return { apiKey, host: host.replace(/\/+$/, '') }
}

function bounded(value: string, max: number): string {
  return value.trim().slice(0, max)
}

export function buildCliDiagnosticEvent(diagnostic: CliDiagnostic) {
  const properties =
    diagnostic.kind === 'package_incompatibility'
      ? {
          package_name: bounded(diagnostic.packageName, 160),
          package_version: bounded(diagnostic.packageVersion, 80),
          ...(diagnostic.unsupportedApi
            ? { unsupported_api: bounded(diagnostic.unsupportedApi, 160) }
            : {}),
        }
      : { error_class: bounded(diagnostic.errorClass, 160) }

  return {
    event: diagnostic.kind,
    distinct_id: 'rnx-cli-diagnostic',
    properties,
  }
}

const queue: CliDiagnostic[] = []

export function trackCliDiagnostic(diagnostic: CliDiagnostic): void {
  if (!diagnosticsAllowedForCurrentProcess()) return
  queue.push(diagnostic)
}

export function trackCliError(error: unknown): void {
  const errorClass = error instanceof Error ? error.constructor.name : typeof error
  trackCliDiagnostic({ kind: 'error_shape', errorClass })
}

export async function flushCliTelemetry(): Promise<void> {
  if (queue.length === 0) return
  const config = loadConfig()
  if (!config) {
    queue.length = 0
    return
  }
  const batch = queue.splice(0, queue.length).map(buildCliDiagnosticEvent)
  try {
    await fetch(`${config.host}/batch/`, {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify({ api_key: config.apiKey, batch }),
      signal: AbortSignal.timeout(2_000),
    })
  } catch {
    // diagnostics never change a command's result.
  }
}