import type {
  ChronicDisease,
  ExerciseFrequency,
  PainLevel,
  RiskLevel,
  SelfAssessmentRequest,
  WantedImprovement,
} from "@/api/types";

export interface GuestSelfAssessmentDraft {
  assessment: SelfAssessmentRequest;
  provisionalRiskLevel: RiskLevel;
  /** 同一份草稿重送正式自評時沿用同一個 key。 */
  idempotencyKey?: string;
}

export const GUEST_SELF_ASSESSMENT_DRAFT_KEY = "guest-self-assessment-draft";

const EXERCISE_FREQUENCY_VALUES: ExerciseFrequency[] = [
  "none",
  "oneToTwo",
  "threeOrMore",
];
const PAIN_LEVEL_VALUES: PainLevel[] = ["none", "mild", "moderate", "severe"];
const RISK_LEVEL_VALUES: RiskLevel[] = ["low", "followUp", "consultation"];
const WANTED_IMPROVEMENT_VALUES: WantedImprovement[] = [
  "strength",
  "balance",
  "cardio",
  "flexibility",
  "agility",
  "bodyComposition",
];
const CHRONIC_DISEASE_VALUES: ChronicDisease[] = [
  "hypertension",
  "diabetes",
  "hyperlipidemia",
  "heartDisease",
  "osteoarthritis",
  "osteoporosis",
];

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null;
}

function isOneOf<T extends string>(
  values: readonly T[],
  value: unknown,
): value is T {
  return typeof value === "string" && values.includes(value as T);
}

function isStringArray<T extends string>(
  values: readonly T[],
  value: unknown,
): value is T[] {
  return (
    Array.isArray(value) &&
    value.every((item) => isOneOf(values, item)) &&
    new Set(value).size === value.length
  );
}

function isValidAssessment(value: unknown): value is SelfAssessmentRequest {
  if (!isRecord(value)) {
    return false;
  }

  return (
    isOneOf(EXERCISE_FREQUENCY_VALUES, value.exerciseFrequency) &&
    isStringArray(WANTED_IMPROVEMENT_VALUES, value.wantedImprovements) &&
    typeof value.hasFalls === "boolean" &&
    isOneOf(PAIN_LEVEL_VALUES, value.painLevel) &&
    isStringArray(CHRONIC_DISEASE_VALUES, value.chronicDiseases)
  );
}

function isValidDraft(value: unknown): value is GuestSelfAssessmentDraft {
  if (!isRecord(value)) {
    return false;
  }

  return (
    isValidAssessment(value.assessment) &&
    isOneOf(RISK_LEVEL_VALUES, value.provisionalRiskLevel) &&
    (value.idempotencyKey === undefined ||
      typeof value.idempotencyKey === "string")
  );
}

/** 依後端規則計算訪客階段的暫存結果；正式結果仍以後端回應為準。 */
export function calculateProvisionalRiskLevel(
  assessment: SelfAssessmentRequest,
): RiskLevel {
  if (
    assessment.painLevel === "moderate" ||
    assessment.painLevel === "severe" ||
    assessment.chronicDiseases.length >= 2
  ) {
    return "consultation";
  }

  if (assessment.exerciseFrequency === "none" || assessment.hasFalls === true) {
    return "followUp";
  }

  return "low";
}

/** 僅在自評完成並確認送出後保存不含身分資料的訪客草稿。 */
export function saveGuestSelfAssessmentDraft(
  draft: GuestSelfAssessmentDraft,
): void {
  if (typeof window === "undefined") {
    return;
  }

  try {
    window.sessionStorage.setItem(
      GUEST_SELF_ASSESSMENT_DRAFT_KEY,
      JSON.stringify(draft),
    );
  } catch {
    // 儲存空間不可用時不讓表單提交流程因瀏覽器安全設定而崩潰。
  }
}

/** 讀取並驗證訪客草稿；格式不正確的資料視為不存在。 */
export function readGuestSelfAssessmentDraft(): GuestSelfAssessmentDraft | null {
  if (typeof window === "undefined") {
    return null;
  }

  try {
    const rawDraft = window.sessionStorage.getItem(
      GUEST_SELF_ASSESSMENT_DRAFT_KEY,
    );
    if (!rawDraft) {
      return null;
    }

    const parsedDraft: unknown = JSON.parse(rawDraft);
    if (!isValidDraft(parsedDraft)) {
      return null;
    }

    const sanitizedDraft: GuestSelfAssessmentDraft = {
      assessment: {
        ...parsedDraft.assessment,
        wantedImprovements: [...parsedDraft.assessment.wantedImprovements],
        chronicDiseases: [...parsedDraft.assessment.chronicDiseases],
      },
      provisionalRiskLevel: parsedDraft.provisionalRiskLevel,
      ...(parsedDraft.idempotencyKey
        ? { idempotencyKey: parsedDraft.idempotencyKey }
        : {}),
    };
    saveGuestSelfAssessmentDraft(sanitizedDraft);
    return sanitizedDraft;
  } catch {
    return null;
  }
}

/** 正式保存成功後清除訪客草稿；登入取消或 API 失敗時不應呼叫。 */
export function clearGuestSelfAssessmentDraft(): void {
  if (typeof window === "undefined") {
    return;
  }

  try {
    window.sessionStorage.removeItem(GUEST_SELF_ASSESSMENT_DRAFT_KEY);
  } catch {
    // sessionStorage 不可用時沒有可清除的資料，保持流程可繼續。
  }
}