import type { Bug, BugLog, BugStatus } from './bug';
import { canBugTransition } from './bug';

export interface BugTransitionOptions {
  now?: Date;
  resolution?: string;
}

export interface BugWorkflowResult {
  ok: boolean;
  patch?: Partial<Bug>;
  message?: string;
}

function makeBugLog(
  action: BugLog['action'],
  operator: string,
  nowIso: string,
  from?: string,
  to?: string,
  remark?: string,
): BugLog {
  return {
    id: `log-${Date.now()}-${Math.random().toString(36).slice(2, 6)}`,
    action,
    fromValue: from,
    toValue: to,
    operator,
    remark,
    createdAt: nowIso,
  };
}

export function applyBugTransition(
  bug: Bug,
  to: BugStatus,
  operator: string,
  options: BugTransitionOptions = {},
): BugWorkflowResult {
  if (!canBugTransition(bug.status, to)) {
    return { ok: false, message: `不允许从「${bug.status}」流转到「${to}」` };
  }

  const nowIso = (options.now ?? new Date()).toISOString();
  const patch: Partial<Bug> = { status: to };

  if (to === 'fixed') patch.resolvedAt = nowIso;
  if (to === 'closed') patch.closedAt = nowIso;
  if (options.resolution?.trim()) patch.resolution = options.resolution.trim();

  const log = makeBugLog(
    to === 'fixed' ? 'resolve' : 'status_change',
    operator,
    nowIso,
    bug.status,
    to,
    options.resolution,
  );
  patch.logs = [...(bug.logs || []), log];

  return { ok: true, patch };
}