/**
 * Single authoritative rectification decision.
 *
 * phase, nextAction, canOfferRange, canAdopt, and canConfirmExactMinute are
 * computed here. precision_stage, selection_allowed, and active_focus policy
 * are derived from this object and must not be judged independently.
 */

import type { CandidateDiscriminatorProbe } from "./candidate-contrast-packet.ts";
import {
  evaluateCandidateSeparation,
  type CandidateScoreRow,
  type CandidateSeparation,
} from "./candidate-separation.ts";
import { rangeFromTimes } from "./credible-range.ts";
import type { DroppedProbe } from "../v9/probe-question-contract.ts";
import type { RectificationPhase, ResultStatus } from "./types.ts";

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

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

export type DecisionSessionOutcome =
  | "collect_evidence"
  | "discriminate_candidates"
  | "validate_holdout"
  | "provisional_range"
  | "provisional_range_user_stopped"
  | "completed_with_range"
  | "validated_range"
  | "exact_minute_confirmed"
  | "adopt_representative"
  | "awaiting_confirmation";

export type CompletionStatus =
  | "provisional_range_user_stopped"
  | "validated_range"
  | "exact_minute_confirmed";

export type DerivedPrecisionStage = "collect_events" | "theme_refine" | "ready_to_adopt";

export type RectificationDecision = Readonly<{
  phase: RectificationPhase;
  nextAction: RectificationNextActionType;
  sessionOutcome: DecisionSessionOutcome;
  resultStatus: ResultStatus;
  canOfferRange: boolean;
  canAdopt: boolean;
  canConfirmExactMinute: boolean;
  selectionAllowed: boolean;
  proposeAllowed: boolean;
  precisionStage: DerivedPrecisionStage;
  activeFocusPolicy: "keep" | "close";
  completionStatus: CompletionStatus | null;
  validated: boolean;
  credibleRange: readonly [string, string] | null;
  representativeTime: string | null;
  separation: CandidateSeparation;
  probe: CandidateDiscriminatorProbe | null;
  holdoutValidation: HoldoutValidationStatus;
  droppedProbes: readonly DroppedProbe[];
}>;

export type DecideRectificationInput = Readonly<{
  methodCoverageAll: boolean;
  confirmationAllowed?: boolean;
  userStopped?: boolean;
  snapshotCurrent?: boolean;
  trainingGateOpen?: boolean;
  candidateScores: readonly CandidateScoreRow[];
  discriminatorProbe?: CandidateDiscriminatorProbe | null;
  holdoutValidation?: HoldoutValidationStatus;
  accepted?: boolean;
  inferenceCredibleRange?: readonly [string, string] | null;
  engineAcceptAllowed?: boolean;
  engineProposeAllowed?: boolean;
  datedMethodCollectOpen?: boolean;
}>;

export function decideRectification(input: DecideRectificationInput): RectificationDecision {
  const separation = evaluateCandidateSeparation(input.candidateScores);
  const probe = input.discriminatorProbe ?? null;
  const holdout = input.holdoutValidation ?? "unavailable";
  const userStopped = input.userStopped === true;
  const confirmationAllowed = input.confirmationAllowed === true;
  const range = input.inferenceCredibleRange
    ?? rangeFromTimes(separation.credibleRange)
    ?? (separation.representativeTime
      ? [separation.representativeTime, separation.representativeTime] as const
      : null);

  if (input.accepted) {
    return finish(confirmationAllowed ? "awaiting_confirmation" : "adopt_representative", {
      input,
      separation,
      holdout,
      range,
      probe: null,
      canConfirmExactMinute: confirmationAllowed,
    });
  }
  if (confirmationAllowed) {
    return finish("awaiting_confirmation", {
      input,
      separation,
      holdout,
      range,
      probe: null,
      canConfirmExactMinute: true,
    });
  }
  const canDiscriminateDespiteCoverage = Boolean(probe)
    && !separation.sufficient
    && input.trainingGateOpen !== false;
  const coverageBlocks = (!input.methodCoverageAll && !canDiscriminateDespiteCoverage)
    || input.trainingGateOpen === false;
  if (coverageBlocks && !(userStopped && input.candidateScores.length > 0)) {
    const trainingOpen = input.trainingGateOpen !== false;
    const engineOffers = input.engineAcceptAllowed === true || input.engineProposeAllowed === true;
    if (
      trainingOpen
      && input.candidateScores.length > 0
      && !probe
      && engineOffers
      && input.datedMethodCollectOpen !== true
    ) {
      return offerRangeWithoutAdopt(separation, holdout, range);
    }
    return collect(separation, holdout, range, probe);
  }
  if (input.snapshotCurrent === false) {
    if (probe && !userStopped && input.trainingGateOpen !== false) {
      return discriminate(separation, holdout, range, probe);
    }
    if (!(userStopped && input.candidateScores.length > 0)) {
      return collect(separation, holdout, range, probe);
    }
  }
  if (!separation.sufficient) {
    if (probe && !userStopped) {
      return discriminate(separation, holdout, range, probe);
    }
    return completeWithRange(separation, holdout, range, userStopped ? "user_stopped" : "offer");
  }
  if (holdout === "not_started" && !userStopped) {
    return holdoutValidation(separation, range);
  }
  if (holdout === "failed") {
    if (probe && !userStopped) {
      return discriminate(separation, holdout, range, probe);
    }
    return completeWithRange(separation, holdout, range, "exhausted");
  }
  if (holdout === "unavailable") {
    if (userStopped) {
      return completeWithRange(separation, holdout, range, "user_stopped");
    }
    return finish("adopt_representative", {
      input,
      separation,
      holdout,
      range,
      probe: null,
      canConfirmExactMinute: false,
    });
  }
  if (userStopped && holdout !== "passed") {
    return completeWithRange(separation, holdout, range, "user_stopped");
  }
  return finish("adopt_representative", {
    input,
    separation,
    holdout,
    range,
    probe: null,
    canConfirmExactMinute: false,
  });
}

function collect(
  separation: CandidateSeparation,
  holdout: HoldoutValidationStatus,
  range: readonly [string, string] | null,
  probe: CandidateDiscriminatorProbe | null,
): RectificationDecision {
  return {
    phase: "event_collection",
    nextAction: "ask_fact_collection",
    sessionOutcome: "collect_evidence",
    resultStatus: "insufficient_evidence",
    canOfferRange: false,
    canAdopt: false,
    canConfirmExactMinute: false,
    selectionAllowed: false,
    proposeAllowed: false,
    precisionStage: "collect_events",
    activeFocusPolicy: "keep",
    completionStatus: null,
    validated: false,
    credibleRange: range,
    representativeTime: separation.representativeTime,
    separation,
    probe,
    holdoutValidation: holdout,
    droppedProbes: [],
  };
}

function offerRangeWithoutAdopt(
  separation: CandidateSeparation,
  holdout: HoldoutValidationStatus,
  range: readonly [string, string] | null,
): RectificationDecision {
  return {
    phase: "discrimination",
    nextAction: "offer_provisional_range",
    sessionOutcome: "provisional_range",
    resultStatus: "insufficient_evidence",
    canOfferRange: true,
    canAdopt: false,
    canConfirmExactMinute: false,
    selectionAllowed: false,
    proposeAllowed: false,
    precisionStage: "theme_refine",
    activeFocusPolicy: "close",
    completionStatus: null,
    validated: false,
    credibleRange: range,
    representativeTime: separation.representativeTime,
    separation,
    probe: null,
    holdoutValidation: holdout,
    droppedProbes: [],
  };
}

export function isNonConvergingRangeOffer(decision: Pick<
  RectificationDecision,
  "canOfferRange" | "canAdopt" | "canConfirmExactMinute" | "nextAction"
>): boolean {
  return decision.canOfferRange
    && !decision.canAdopt
    && !decision.canConfirmExactMinute
    && decision.nextAction === "offer_provisional_range";
}

export const REPRESENTATIVE_MINUTE_DISCLAIMER = "代表分钟只是代表性候选，不是已确认的唯一出生分钟。";

export function nonConvergingRangeNarration(input: {
  credibleRange?: readonly [string, string] | null;
  representativeTime?: string | null;
} = {}): string {
  const range = input.credibleRange;
  const representative = input.representativeTime?.trim() || null;
  const rangeText = range?.[0] && range[1]
    ? range[0] === range[1] ? range[0] : `${range[0]}–${range[1]}`
    : null;
  if (rangeText && representative) {
    return `当前可信区间是 ${rangeText}，代表分钟 ${representative}。${REPRESENTATIVE_MINUTE_DISCLAIMER}`;
  }
  if (rangeText) {
    return `当前可信区间是 ${rangeText}。${REPRESENTATIVE_MINUTE_DISCLAIMER}`;
  }
  if (representative) {
    return `当前代表分钟 ${representative}。${REPRESENTATIVE_MINUTE_DISCLAIMER}`;
  }
  return `当前几个候选还分不开。${REPRESENTATIVE_MINUTE_DISCLAIMER}`;
}

function discriminate(
  separation: CandidateSeparation,
  holdout: HoldoutValidationStatus,
  range: readonly [string, string] | null,
  probe: CandidateDiscriminatorProbe,
): RectificationDecision {
  return {
    phase: "discrimination",
    nextAction: "ask_candidate_discriminator",
    sessionOutcome: "discriminate_candidates",
    resultStatus: "discriminating",
    canOfferRange: false,
    canAdopt: false,
    canConfirmExactMinute: false,
    selectionAllowed: false,
    proposeAllowed: false,
    precisionStage: "theme_refine",
    activeFocusPolicy: "keep",
    completionStatus: null,
    validated: false,
    credibleRange: range,
    representativeTime: separation.representativeTime,
    separation,
    probe,
    holdoutValidation: holdout,
    droppedProbes: [],
  };
}

function holdoutValidation(
  separation: CandidateSeparation,
  range: readonly [string, string] | null,
): RectificationDecision {
  return {
    phase: "holdout_validation",
    nextAction: "ask_holdout_validation",
    sessionOutcome: "validate_holdout",
    resultStatus: "discriminating",
    canOfferRange: false,
    canAdopt: false,
    canConfirmExactMinute: false,
    selectionAllowed: false,
    proposeAllowed: false,
    precisionStage: "theme_refine",
    activeFocusPolicy: "keep",
    completionStatus: null,
    validated: false,
    credibleRange: range,
    representativeTime: separation.representativeTime,
    separation,
    probe: null,
    holdoutValidation: "not_started",
    droppedProbes: [],
  };
}

function completeWithRange(
  separation: CandidateSeparation,
  holdout: HoldoutValidationStatus,
  range: readonly [string, string] | null,
  kind: "user_stopped" | "offer" | "exhausted",
): RectificationDecision {
  const userStopped = kind === "user_stopped";
  const terminal = kind !== "offer";
  const nextAction = terminal ? "complete_with_range" : "offer_provisional_range";
  const sessionOutcome = userStopped
    ? "provisional_range_user_stopped"
    : terminal
      ? "completed_with_range"
      : "provisional_range";
  return {
    phase: terminal ? "completed" : "discrimination",
    nextAction,
    sessionOutcome,
    resultStatus: "completed_with_range",
    canOfferRange: true,
    canAdopt: true,
    canConfirmExactMinute: false,
    selectionAllowed: true,
    proposeAllowed: true,
    precisionStage: "ready_to_adopt",
    activeFocusPolicy: "close",
    completionStatus: userStopped ? "provisional_range_user_stopped" : null,
    validated: false,
    credibleRange: range,
    representativeTime: separation.representativeTime,
    separation,
    probe: null,
    holdoutValidation: holdout,
    droppedProbes: [],
  };
}

function finish(
  fallbackOutcome: "adopt_representative" | "awaiting_confirmation" | "validated_range" | "exact_minute_confirmed",
  input: {
    input: DecideRectificationInput;
    separation: CandidateSeparation;
    holdout: HoldoutValidationStatus;
    range: readonly [string, string] | null;
    probe: CandidateDiscriminatorProbe | null;
    canConfirmExactMinute: boolean;
  },
): RectificationDecision {
  const completionStatus: CompletionStatus | null = input.canConfirmExactMinute && input.input.accepted
    ? "exact_minute_confirmed"
    : input.holdout === "passed"
      ? "validated_range"
      : input.input.userStopped === true
        ? "provisional_range_user_stopped"
        : null;
  const kind = input.canConfirmExactMinute
    ? (input.input.accepted ? "exact_minute_confirmed" : "awaiting_confirmation")
    : input.holdout === "passed"
      ? "validated_range"
      : fallbackOutcome;
  return {
    phase: "completed",
    nextAction: "ready_to_adopt",
    sessionOutcome: kind,
    resultStatus: kind === "awaiting_confirmation" || kind === "exact_minute_confirmed"
      ? "converged"
      : "completed_with_range",
    canOfferRange: true,
    canAdopt: true,
    canConfirmExactMinute: input.canConfirmExactMinute,
    selectionAllowed: true,
    proposeAllowed: true,
    precisionStage: "ready_to_adopt",
    activeFocusPolicy: "close",
    completionStatus,
    validated: completionStatus === "validated_range" || completionStatus === "exact_minute_confirmed",
    credibleRange: input.range,
    representativeTime: input.separation.representativeTime,
    separation: input.separation,
    probe: input.probe,
    holdoutValidation: input.holdout,
    droppedProbes: [],
  };
}

export function sessionKindFromNextAction(
  type: RectificationNextActionType,
): DecisionSessionOutcome {
  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";
  if (type === "complete_with_range") return "completed_with_range";
  return "adopt_representative";
}

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

export function publicNextAction(decision: RectificationDecision): Readonly<{
  type: RectificationNextActionType;
  session_outcome: DecisionSessionOutcome;
  completion_status: CompletionStatus | null;
  validated: boolean;
  can_offer_range: boolean;
  can_adopt: boolean;
  can_confirm_exact_minute: boolean;
  selection_allowed: boolean;
  propose_allowed: boolean;
  precision_stage: DerivedPrecisionStage;
  representative_time: string | null;
  credible_range: readonly [string, string] | null;
}> {
  return {
    type: decision.nextAction,
    session_outcome: decision.sessionOutcome,
    completion_status: decision.completionStatus,
    validated: decision.validated,
    can_offer_range: decision.canOfferRange,
    can_adopt: decision.canAdopt,
    can_confirm_exact_minute: decision.canConfirmExactMinute,
    selection_allowed: decision.selectionAllowed,
    propose_allowed: decision.proposeAllowed,
    precision_stage: decision.precisionStage,
    representative_time: decision.representativeTime,
    credible_range: decision.credibleRange,
  };
}

export function publicDecisionFields(
  decision: RectificationDecision,
): ReturnType<typeof publicNextAction> {
  return publicNextAction(decision);
}