/**
 * Helper method to determine the name of the innermost (i.e. current)
 * mode. Think of this as an abstraction over CodeMirror's innerMode
 * with added type guards.
 */
function getInnerModeName(
  mode: CodeMirror.Mode<{}>,
  state: any
): string | null {
  const inner = innerMode(mode, state)
  return inner && inner.mode ? getModeName(inner.mode) : null
}

function detectMode(request: IHighlightRequest): CodeMirror.Mode<{}> | null {
  const mimeType =
    extensionMIMEMap.get(request.extension) || guessMimeType(request.contents)

  if (!mimeType) {
    return null
  }

  return getMode({}, mimeType) || null
}

async function detectMode(
  request: IHighlightRequest
): Promise<CodeMirror.Mode<{}> | null> {
  const mimeType =
    extensionMIMEMap.get(request.extension.toLowerCase()) ||
    guessMimeType(request.contents)

  if (!mimeType) {
    return null
  }

  const modeDefinition = mimeModeMap.get(mimeType)

  if (modeDefinition === undefined) {
    return null
  }

  await modeDefinition.install()

  return getMode({}, mimeType) || null
}