import {
  MONTHLY_WEIGHTS,
  type RateStructure,
  type ScalarVariable,
  type ScenarioVariable,
  requiredVariables,
} from './rate.js'

/**
 * The published scenario. #10 put it in the RFP so price is bindable up front,
 * and #29 made its variable set closed (see rate.ts).
 *
 * Note what a scenario variable IS: an assumption declared for comparison, not
 * a contract term. Chesapeake's delivery frequency is changeable mid-term on
 * two weeks' notice, so the awarded price will not match the derived cost and
 * nobody should be surprised by that. Naming it an assumption here is cheaper
 * than explaining it during a protest.
 */
export interface Scenario {
  /** Per price line. Fractional quantities are fine; the evaluator scales to integers. */
  readonly quantities: Readonly<Record<string, number>>
  readonly scalars: Readonly<Partial<Record<ScalarVariable, number>>>
  /**
   * Relative volume per month, index 0 = January. Non-negative integers in any
   * consistent unit — instructional days is the natural one for a school food
   * contract. Only the ratios are read, so nothing here needs normalising and
   * therefore nothing here gets rounded.
   */
  readonly monthlyWeights?: readonly number[]
}

/**
 * Submission-time validation: a structure that reads a variable this RFP did
 * not publish is rejected NOW, while the vendor can still fix it — not
 * resolved to a null in the evaluator months later when nobody can act on it.
 */
export function missingVariables(rate: RateStructure, scenario: Scenario): ScenarioVariable[] {
  return requiredVariables(rate).filter((v) =>
    v === MONTHLY_WEIGHTS
      ? scenario.monthlyWeights === undefined
      : scenario.scalars[v] === undefined,
  )
}

/**
 * A malformed published scenario is a bug, not a bid outcome — so this throws
 * rather than abstaining. Abstention is reserved for facts about the response.
 */
export function assertWellFormed(scenario: Scenario): void {
  const w = scenario.monthlyWeights
  if (w === undefined) return
  if (w.length !== 12) throw new Error(`monthlyWeights has ${w.length} entries, expected 12`)
  if (w.some((n) => !Number.isInteger(n) || n < 0)) {
    throw new Error('monthlyWeights must be non-negative integers')
  }
  if (w.reduce((a, b) => a + b, 0) <= 0) throw new Error('monthlyWeights sum to zero')
}