// 多版本自动补全(docs/design/subscriptions.md §2.2):非主版本目标在主版本已满足的单元上补下其他版本。
// 开关按 订阅 → 规则组(链上后者优先)→ 系统缺省(开)取值;补全预算按订阅、按自然日计,超出记延后。

export type AutoFillModeValue = "inherit" | "on" | "off";

export interface AutoFillResolution {
  enabled: boolean;
  mode: AutoFillModeValue;
  source: "subscription" | "rule_group" | "default";
  /** source = rule_group 时,决定取值的规则组 */
  ruleGroupId?: string;
}

/** groupFlags:订阅生效规则链上各组的 auto_fill(null = 未设),按链顺序 */
export function resolveAutoFill(
  mode: AutoFillModeValue | undefined,
  groupFlags: readonly { id: string; autoFill: boolean | null }[] = [],
  systemDefault = true,
): AutoFillResolution {
  if (mode === "on" || mode === "off") return { enabled: mode === "on", mode, source: "subscription" };
  for (let k = groupFlags.length - 1; k >= 0; k--) {
    const g = groupFlags[k]!;
    if (g.autoFill !== null) return { enabled: g.autoFill, mode: "inherit", source: "rule_group", ruleGroupId: g.id };
  }
  return { enabled: systemDefault, mode: "inherit", source: "default" };
}

export interface FillBudgetLimits {
  bytesPerDay?: number | undefined;
  unitsPerDay?: number | undefined;
}

export interface FillBudgetUsage {
  bytesToday: number;
  unitsToday: number;
}

export interface FillBudgetDecision {
  allow: boolean;
  violations: { kind: "bytes" | "units"; limit: number; current: number; requested: number }[];
}

/** 补全预算:未设的维度不限;请求体积未知时只看单元数(体积由全局预算的 unknown 规则兜底) */
export function checkFillBudget(
  limits: FillBudgetLimits | undefined,
  usage: FillBudgetUsage,
  request: { bytes?: number | null | undefined; units: number },
): FillBudgetDecision {
  const violations: FillBudgetDecision["violations"] = [];
  if (limits?.unitsPerDay !== undefined && usage.unitsToday + request.units > limits.unitsPerDay)
    violations.push({
      kind: "units",
      limit: limits.unitsPerDay,
      current: usage.unitsToday,
      requested: request.units,
    });
  if (
    limits?.bytesPerDay !== undefined &&
    request.bytes !== null &&
    request.bytes !== undefined &&
    usage.bytesToday + request.bytes > limits.bytesPerDay
  )
    violations.push({
      kind: "bytes",
      limit: limits.bytesPerDay,
      current: usage.bytesToday,
      requested: request.bytes,
    });
  return { allow: violations.length === 0, violations };
}