import {
  evaluateCandidateSeparation,
  type CandidateScoreRow,
  type CandidateSeparation,
} from "./candidate-separation.ts";
import type { CandidateDiscriminatorProbe } from "./candidate-contrast-packet.ts";

export type RectificationNextActionType =
  | "ask_fact_collection"
  | "ask_candidate_discriminator"
  | "ask_holdout_validation"
  | "offer_provisional_range"
  | "ready_to_adopt";

export type HoldoutValidationStatus = "not_started" | "passed" | "failed" | "unavailable";

export type DecideNextActionInput = Readonly<{
  methodCoverageAll: boolean;
  proposeAllowed: boolean;
  confirmationAllowed?: boolean;
  userStopped?: boolean;
  selectionAllowed?: boolean;
  snapshotCurrent?: boolean;
  candidateScores: readonly CandidateScoreRow[];
  discriminatorProbe?: CandidateDiscriminatorProbe | null;
  holdoutValidation?: HoldoutValidationStatus;
}>;

export type RectificationNextAction = Readonly<{
  type: RectificationNextActionType;
  separation: CandidateSeparation;
  probe: CandidateDiscriminatorProbe | null;
}>;

/**
 * Coverage complete only unlocks discrimination. It never grants adoption.
 */
export function decideNextAction(input: DecideNextActionInput): RectificationNextAction {
  const separation = evaluateCandidateSeparation(input.candidateScores);
  const probe = input.discriminatorProbe ?? null;
  const holdout = input.holdoutValidation ?? "unavailable";
  const userStopped = input.userStopped === true;

  if (input.confirmationAllowed === true) {
    return { type: "ready_to_adopt", separation, probe: null };
  }
  if (userStopped && input.selectionAllowed === true) {
    if (!separation.sufficient) {
      return { type: "offer_provisional_range", separation, probe: null };
    }
    return { type: "ready_to_adopt", separation, probe: null };
  }
  if (!input.methodCoverageAll || input.snapshotCurrent === false) {
    return { type: "ask_fact_collection", separation, probe: null };
  }
  if (!separation.sufficient) {
    if (probe) {
      return { type: "ask_candidate_discriminator", separation, probe };
    }
    return { type: "offer_provisional_range", separation, probe: null };
  }
  if (holdout === "not_started") {
    return { type: "ask_holdout_validation", separation, probe: null };
  }
  if (holdout === "failed") {
    if (probe) {
      return { type: "ask_candidate_discriminator", separation, probe };
    }
    return { type: "offer_provisional_range", separation, probe: null };
  }
  if (input.proposeAllowed !== true) {
    return { type: "ask_fact_collection", separation, probe: null };
  }
  return { type: "ready_to_adopt", separation, probe: null };
}

export function sessionKindFromNextAction(
  type: RectificationNextActionType,
): "collect_evidence" | "discriminate_candidates" | "validate_holdout" | "provisional_range" | "adopt_representative" {
  if (type === "ask_fact_collection") return "collect_evidence";
  if (type === "ask_candidate_discriminator") return "discriminate_candidates";
  if (type === "ask_holdout_validation") return "validate_holdout";
  if (type === "offer_provisional_range") return "provisional_range";
  return "adopt_representative";
}

export function offerSessionKinds(): readonly string[] {
  return ["adopt_representative", "awaiting_confirmation", "provisional_range"];
}