import type { RelativeTime, TimeStamp } from '@datadog/browser-core'
import { assign, getRelativeTime, isNumber } from '@datadog/browser-core'
import {
  RumPerformanceEntryType,
  supportPerformanceTimingEvent,
  type RumPerformanceNavigationTiming,
} from './performanceObservable'

export function getNavigationEntry(): RumPerformanceNavigationTiming {
  if (supportPerformanceTimingEvent(RumPerformanceEntryType.NAVIGATION)) {
    const navigationEntry = performance.getEntriesByType(
      RumPerformanceEntryType.NAVIGATION
    )[0] as unknown as RumPerformanceNavigationTiming
    if (navigationEntry) {
      return navigationEntry
    }
  }

  const timings = computeTimingsFromDeprecatedPerformanceTiming()
  const entry = assign(
    {
      entryType: RumPerformanceEntryType.NAVIGATION as const,
      initiatorType: 'navigation' as const,
      name: window.location.href,
      startTime: 0 as RelativeTime,
      duration: timings.responseEnd,
      decodedBodySize: 0,
      encodedBodySize: 0,
      transferSize: 0,
      workerStart: 0 as RelativeTime,
      toJSON: () => assign({}, entry, { toJSON: undefined }),
    },
    timings
  )
  return entry
}

export type TimingsFromDeprecatedPerformanceTiming = {
  -readonly [key in keyof Omit<PerformanceTiming, 'toJSON'>]: RelativeTime
}

export function computeTimingsFromDeprecatedPerformanceTiming() {
  const result: Partial<TimingsFromDeprecatedPerformanceTiming> = {}
  const timing = performance.timing

  for (const key in timing) {
    if (isNumber(timing[key as keyof PerformanceTiming])) {
      const numberKey = key as keyof TimingsFromDeprecatedPerformanceTiming
      const timingElement = timing[numberKey] as TimeStamp
      result[numberKey] = timingElement === 0 ? (0 as RelativeTime) : getRelativeTime(timingElement)
    }
  }
  return result as TimingsFromDeprecatedPerformanceTiming
}