import { roundHalfUp } from "@/lib/math";

export type MarkupType = "percent" | "fixed";

export const MARKUP_PERCENT_MIN = 0;
export const MARKUP_PERCENT_MAX = 30;
export const MARKUP_PERCENT_DECIMALS = 2;
export const MARKUP_FIXED_MAX = 99_999.99;

export type ParsedMarkupInput = {
  markupType: MarkupType;
  markupPercent: number;
  markupFixedAmount: number | null;
};

export type MarkupValidationError =
  | { code: "INVALID_BODY"; message: string }
  | { code: "PERCENT_TOO_HIGH"; message: string }
  | { code: "INVALID_PERCENT"; message: string }
  | { code: "INVALID_FIXED"; message: string };

function parseMarkupType(value: unknown): MarkupType | null {
  if (value === undefined || value === null || value === "") {
    return "percent";
  }
  if (value === "percent" || value === "fixed") {
    return value;
  }
  return null;
}

function parsePercentValue(value: unknown): number | null {
  if (typeof value !== "number" || Number.isNaN(value)) {
    return null;
  }
  return roundHalfUp(value, MARKUP_PERCENT_DECIMALS);
}

function parseFixedAmount(value: unknown): number | null {
  if (typeof value !== "number" || Number.isNaN(value)) {
    return null;
  }
  if (value < 0 || value > MARKUP_FIXED_MAX) {
    return null;
  }
  return roundHalfUp(value, 2);
}

/** 解析并校验加价配置入参（宿主 API / 管理端共用） */
export function parseMarkupInput(body: {
  markup_type?: unknown;
  markup_percent?: unknown;
  markup_fixed_amount?: unknown;
}): ParsedMarkupInput | MarkupValidationError {
  const markupType = parseMarkupType(body.markup_type);
  if (!markupType) {
    return { code: "INVALID_BODY", message: "加价方式无效，请使用 percent 或 fixed" };
  }

  if (markupType === "fixed") {
    const fixed = parseFixedAmount(body.markup_fixed_amount);
    if (fixed === null) {
      if (
        typeof body.markup_fixed_amount === "number" &&
        body.markup_fixed_amount > MARKUP_FIXED_MAX
      ) {
        return {
          code: "INVALID_FIXED",
          message: `固定加价金额不能超过 $${MARKUP_FIXED_MAX.toFixed(2)}`,
        };
      }
      return {
        code: "INVALID_FIXED",
        message: "请提供有效的固定加价金额（≥ 0）",
      };
    }
    return {
      markupType: "fixed",
      markupPercent: 0,
      markupFixedAmount: fixed,
    };
  }

  const percent = parsePercentValue(body.markup_percent);
  if (percent === null) {
    return { code: "INVALID_PERCENT", message: "请提供有效的加价比例（0~30%，步长 0.01%）" };
  }
  if (percent > MARKUP_PERCENT_MAX) {
    return { code: "PERCENT_TOO_HIGH", message: "加价比例不能超过 30%" };
  }
  if (percent < MARKUP_PERCENT_MIN) {
    return { code: "INVALID_PERCENT", message: "请提供有效的加价比例（0~30%，步长 0.01%）" };
  }

  return {
    markupType: "percent",
    markupPercent: percent,
    markupFixedAmount: null,
  };
}