import { LIMITS, type Warning } from './types.js';

function boundedMessage(message: string, suffix: string): string {
  const bytes = Buffer.from(message);
  let end = Math.min(bytes.length, LIMITS.MAX_ERROR_MESSAGE_BYTES - Buffer.byteLength(suffix));
  while (end < bytes.length && (bytes[end] & 0xc0) === 0x80) end--;
  return bytes.subarray(0, end).toString('utf8') + suffix;
}

/** Keep repeated warnings and overflow visible without extending the wire shape. */
export class WarningCollector {
  private entries: Warning[] = [];
  private groups = new Map<string, { warning: Warning; message: string; count: number }>();
  private overflow = 0;
  add(warning: Warning): void {
    const key = JSON.stringify([warning.code, warning.message, warning.tool_call_id, warning.name]);
    const existing = this.groups.get(key);
    if (existing) {
      existing.count++;
      existing.warning.message = boundedMessage(existing.message, ` (Repeated ${existing.count} times.)`);
      return;
    }
    if (!this.overflow && this.entries.length < LIMITS.MAX_WARNINGS) {
      const copy = { ...warning };
      this.entries.push(copy);
      this.groups.set(key, { warning: copy, message: copy.message, count: 1 });
      return;
    }
    if (!this.overflow) {
      const replaced = this.entries.pop()!;
      const removed = [...this.groups.entries()].find(([, group]) => group.warning === replaced)!;
      this.overflow = removed[1].count;
      this.groups.delete(removed[0]);
      this.entries.push({ code: 'warnings_aggregated', message: '' });
    }
    this.overflow++;
    this.entries.at(-1)!.message = `${this.overflow} additional warnings were aggregated after the warning limit.`;
  }
  snapshot(): Warning[] { return this.entries.map(w => ({ ...w })); }
}