declare global {
  interface Window {
    timings: {
      cache: Record<string, number[]>
      addLog: (
        key: string,
        startTime: DOMHighResTimeStamp,
        endTime: DOMHighResTimeStamp
      ) => void
      log: (key: string, logAll: boolean) => number | void
      logAll: (keyStartsWith?: string) => void
      dumpKeys: () => string[]
    }
  }
}

const ENABLE_TIMINGS = process.env.REACT_APP_ENABLE_TIMINGS === 'true'

export const timingsWrapper = (fn: (...args: any[]) => any, name: string) => {
  if (ENABLE_TIMINGS) {
    return (...args: any[]) => {
      // Reference: https://developer.mozilla.org/en-US/docs/Web/API/Performance/now
      const startTime = performance.now()
      const result = fn(...args)
      const endTime = performance.now()

      window.timings.addLog(name, startTime, endTime)

      return result
    }
  }

  return fn
}

export const initTimings = () => {
  if (ENABLE_TIMINGS) {
    window.timings = {
      cache: {} as Record<string, number[]>,
      addLog: (
        key: string,
        startTime: DOMHighResTimeStamp,
        endTime: DOMHighResTimeStamp
      ) => {
        if (!window.timings.cache[key]) {
          window.timings.cache[key] = []
        }

        window.timings.cache[key].push(endTime - startTime)
      },
      log: (key: string, logAll: boolean = false): number | void => {
        const timings = window.timings.cache[key]
        if (timings) {
          const totalSamples = timings.length
          const totalMs = timings.reduce((acc, timing) => acc + timing, 0)
          const headline = `Timings for ${key} (${totalSamples} samples, ${totalMs}ms)`

          if (logAll === true) {
            console.groupCollapsed(headline)
          } else {
            console.group(headline)
          }

          console.log('Timings:')
          console.table(timings)
          console.log('Timing samples:', timings.length)
          console.log('Total (ms):', totalMs)

          console.groupEnd()

          if (logAll === true) {
            return totalMs
          }
        }

        if (logAll === true) {
          return 0
        }
      },
      logAll: (keyStartsWith?: string) => {
        let totalMs = 0

        for (const key in window.timings.cache) {
          if (
            typeof keyStartsWith === 'string' &&
            keyStartsWith.length !== 0 &&
            !key.startsWith(keyStartsWith)
          ) {
            continue
          }

          const totalMsForKey = window.timings.log(key, true)

          if (typeof totalMsForKey === 'number') {
            totalMs += totalMsForKey
          }
        }

        console.log('Total (ms) for all timings:', totalMs)
      },
      dumpKeys: () => {
        return Object.keys(window.timings.cache)
      },
    }

    console.log('Timings initialised')
    console.log('To dump an individual timing, run `window.timings.log("key")`')
    console.log('To dump all timings, run `window.timings.logAll()`')
    console.log('To dump all keys, run `window.timings.dumpKeys()`')
  }

  // no-op
}