type Segment = {
  id: string;
  startDate?: string;
  endDate?: string;
  startTime?: string;
  endTime?: string;
}

type MaybeOptionalField = keyof Omit<Segment, "id">

const configurations: Record<MaybeOptionalField, {mandatory: boolean, text: string}> = {
  startDate: {
    mandatory: true,
    text: "test"
  },
  endDate: {
    mandatory: false,
    text: "test"
  },
  startTime: {
    mandatory: false,
    text: "test"
  },
  endTime: {
    mandatory: false,
    text: "test"
  }
};

const segments: Segment[] = [{
    id: 'foo',
    startDate: "now",
}, {
    id: 'bar',
}]

// figure out which fields are currently required
const mandatoryFields = Object.entries(configurations)
    .filter(([_, configuration]) => configuration.mandatory)
    // Object.entries treats 'key' to always be type any string, but we'd like to maintain the keys as being of type MaybeOptionalField
    // which keeps `segment[mandatoryField]` as being valid, one could instead push the type assertion into the for loop below
    .map(([key]) => key as MaybeOptionalField)

const validateSegment = (segment: Segment) => {
  for (const mandatoryField of mandatoryFields) {
    if (!segment[mandatoryField]) {
      return false
    }
  }
  return true
};

const validSegments = segments.filter(segment => validateSegment(segment))
const invalidSegments = segments.filter(segment => !validateSegment(segment))

console.log(validSegments, validSegments.length)
console.log(invalidSegments, invalidSegments.length)