import type { DcpMessage } from '../messages.js';

export function deduplicate(messages: DcpMessage[]): { messages: DcpMessage[]; stats: { removedCount: number; freedTokens: number } } {
  const result: DcpMessage[] = [];
  let removedCount = 0;
  let freedTokens = 0;
  let i = 0;

  while (i < messages.length) {
    const current: DcpMessage = messages[i]!;
    const next = messages[i + 1];

    if (
      current.role === 'assistant' &&
      current.tool_calls &&
      next &&
      next.role === 'tool' &&
      next.tool_call_id === current.tool_calls[0]?.id
    ) {
      const nextNext = messages[i + 2];
      const nextNextNext = messages[i + 3];

      if (
        nextNext &&
        nextNext.role === 'assistant' &&
        nextNext.tool_calls &&
        nextNextNext &&
        nextNextNext.role === 'tool' &&
        nextNextNext.tool_call_id === nextNext.tool_calls[0]?.id &&
        nextNext.tool_calls[0]?.name === current.tool_calls[0]?.name &&
        nextNext.tool_calls[0]?.arguments === current.tool_calls[0]?.arguments &&
        nextNextNext.content === next.content
      ) {
        result.push(current, next);
        i += 4;
        removedCount += 2;
        freedTokens += Math.ceil(nextNext.content.length / 4);
        freedTokens += Math.ceil(current.content.length / 4);
      } else {
        result.push(current);
        i++;
      }
    } else {
      result.push(current);
      i++;
    }
  }

  return { messages: result, stats: { removedCount, freedTokens } };
}