import type { Message, OpenAIMessage, OpenAIStreamChunk } from '@/types';

export async function* streamChatCompletion(
  messages: Message[],
  apiUrl: string,
  apiKey: string,
  model: string,
  temperature: number,
  maxTokens: number,
  systemPrompt: string,
  abortSignal: AbortSignal
): AsyncGenerator<OpenAIStreamChunk, void, unknown> {
  const formattedMessages: OpenAIMessage[] = [
    { role: 'system', content: systemPrompt },
    ...messages.map((m) => ({ role: m.role, content: m.content }) as OpenAIMessage),
  ];

  const response = await fetch('/api/v1/chat/completions', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      apiUrl,
      apiKey,
      model,
      temperature,
      max_tokens: maxTokens,
      messages: formattedMessages,
      stream: true,
    }),
    signal: abortSignal,
  });

  if (!response.ok) {
    const errorData = await response.json().catch(() => ({}));
    throw new Error(errorData.error?.message || `HTTP error! status: ${response.status}`);
  }

  const reader = response.body?.getReader();
  if (!reader) {
    throw new Error('No response body');
  }

  const decoder = new TextDecoder();
  let buffer = '';

  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;

      buffer += decoder.decode(value, { stream: true });
      const lines = buffer.split('\n');
      buffer = lines.pop() || '';

      for (const line of lines) {
        const trimmed = line.trim();
        if (!trimmed || trimmed === 'data: [DONE]') continue;
        if (trimmed.startsWith('data: ')) {
          try {
            const data: OpenAIStreamChunk = JSON.parse(trimmed.slice(6));
            yield data;
          } catch {
            // Ignore parse errors for incomplete chunks
          }
        }
      }
    }
  } finally {
    reader.releaseLock();
  }
}

export async function fetchModels(
  apiUrl: string,
  apiKey: string
): Promise<string[]> {
  const response = await fetch('/api/v1/models', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({ apiUrl, apiKey }),
  });

  if (!response.ok) {
    const errorData = await response.json().catch(() => ({}));
    throw new Error(errorData.error?.message || `HTTP error! status: ${response.status}`);
  }

  const data = await response.json();
  return data.models || [];
}