// LLM client — Ollama (default), Anthropic, or any OpenAI-compatible endpoint
// Configure via env:
//   LLM_PROVIDER=ollama|anthropic|openai   (default: ollama)
//   LLM_BASE_URL=http://localhost:11434    (default for ollama)
//   LLM_MODEL=llama3                       (default)
//   LLM_API_KEY=...                        (required for anthropic/openai)

const PROVIDER = process.env.LLM_PROVIDER  || 'ollama'
const MODEL    = process.env.LLM_MODEL     || 'llama3'
const API_KEY  = process.env.LLM_API_KEY
const BASE_URL = process.env.LLM_BASE_URL  || 'http://localhost:11434'

export async function chat(messages) {
  if (PROVIDER === 'anthropic') return anthropic(messages)
  if (PROVIDER === 'openai')    return openaiCompat(messages, BASE_URL || 'https://api.openai.com/v1')
  return ollama(messages)
}

async function ollama(messages) {
  const r = await fetch(`${BASE_URL}/api/chat`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ model: MODEL, messages, stream: false }),
  })
  if (!r.ok) throw new Error(`Ollama ${r.status}: ${await r.text()}`)
  const data = await r.json()
  return data.message.content
}

async function anthropic(messages) {
  // Separate system message — Anthropic requires it at top level
  const system = messages.find(m => m.role === 'system')?.content
  const rest   = messages.filter(m => m.role !== 'system')

  const r = await fetch('https://api.anthropic.com/v1/messages', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'x-api-key': API_KEY,
      'anthropic-version': '2023-06-01',
    },
    body: JSON.stringify({
      model: MODEL || 'claude-sonnet-4-6',
      max_tokens: 2048,
      ...(system && { system }),
      messages: rest,
    }),
  })
  if (!r.ok) throw new Error(`Anthropic ${r.status}: ${await r.text()}`)
  const data = await r.json()
  return data.content[0].text
}

async function openaiCompat(messages, base) {
  const r = await fetch(`${base}/chat/completions`, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      ...(API_KEY && { Authorization: `Bearer ${API_KEY}` }),
    },
    body: JSON.stringify({ model: MODEL, messages, stream: false }),
  })
  if (!r.ok) throw new Error(`LLM ${r.status}: ${await r.text()}`)
  const data = await r.json()
  return data.choices[0].message.content
}