import axios from 'axios';
import { getLLMConfig, getOpenCodeHttpsAgent } from './config.js';
import { recordUsage } from './usage.js';
import { line, error } from './log.js';

function opencodeModelConfig(model) {
  const [providerID, modelID] = model.includes('/') ? model.split('/', 2) : [process.env.OPENCODE_PROVIDER || 'google', model];
  return { providerID, modelID };
}

function opencodeAxiosOptions(headers) {
  return {
    headers,
    httpsAgent: getOpenCodeHttpsAgent(),
  };
}

function extractOpenCodeContent(data) {
  const parts = data.parts || data.data?.parts || data.info?.content || data.data?.info?.content || [];
  return parts
    .map(part => part.text || part.content || '')
    .filter(Boolean)
    .join('');
}

async function chatOpenCode(baseURL, model, systemPrompt, userContent, headers) {
  const base = baseURL.replace(/\/$/, '');
  const { providerID, modelID } = opencodeModelConfig(model);
  const session = await axios.post(
    `${base}/session`,
    { title: 'AI Code Review', model: { providerID, id: modelID } },
    opencodeAxiosOptions(headers)
  );
  const sessionID = session.data.id || session.data.data?.id;
  if (!sessionID) throw new Error('OpenCode session 建立失敗：回應中沒有 session id');

  const resp = await axios.post(
    `${base}/session/${sessionID}/message`,
    {
      model: { providerID, modelID },
      system: systemPrompt,
      parts: [{ type: 'text', text: userContent }],
    },
    opencodeAxiosOptions(headers)
  );
  return { content: extractOpenCodeContent(resp.data), data: resp.data };
}

export async function chat(systemPrompt, userContent) {
  const { provider, baseURL, model } = getLLMConfig();
  if (!provider) throw new Error('未設定 OpenCode server，請設定 OPENCODE_BASE_URL');

  line(`[LLM] provider=${provider} model=${model}`);

  const headers = { 'Content-Type': 'application/json' };

  try {
    const { content, data } = await chatOpenCode(baseURL, model, systemPrompt, userContent, headers);
    recordUsage(data);
    return content;
  } catch (e) {
    line(`[LLM] OpenCode 呼叫失敗: ${e.message}`);
  }
  error('[LLM] OpenCode 呼叫失敗，終止流程');
  process.exit(1);
}

export async function chatJSON(systemPrompt, userContent) {
  const text = await chat(systemPrompt, userContent);
  try {
    return JSON.parse(extractJSONText(text));
  } catch (e) {
    line(`[LLM] JSON 解析失敗: ${e.message}`);
    return [];
  }
}

function stripOuterFence(text) {
  return String(text)
    .trim()
    .replace(/^```[a-zA-Z0-9_-]*\n?/, '')
    .replace(/```$/, '')
    .trim();
}

function extractBalancedJSON(text, startIndex) {
  const source = String(text);
  const open = source[startIndex];
  const close = open === '{' ? '}' : ']';
  let depth = 0;
  let inString = false;
  let escaped = false;

  for (let i = startIndex; i < source.length; i++) {
    const ch = source[i];
    if (inString) {
      if (escaped) {
        escaped = false;
      } else if (ch === '\\') {
        escaped = true;
      } else if (ch === '"') {
        inString = false;
      }
      continue;
    }
    if (ch === '"') {
      inString = true;
      continue;
    }
    if (ch === open) depth += 1;
    else if (ch === close) {
      depth -= 1;
      if (depth === 0) return source.slice(startIndex, i + 1);
    }
  }
  return null;
}

function extractJSONText(text) {
  const stripped = stripOuterFence(text);
  try {
    JSON.parse(stripped);
    return stripped;
  } catch {}

  for (let i = 0; i < stripped.length; i++) {
    if (stripped[i] !== '[' && stripped[i] !== '{') continue;
    const candidate = extractBalancedJSON(stripped, i);
    if (!candidate) continue;
    try {
      JSON.parse(candidate);
      return candidate;
    } catch {}
  }
  return stripped;
}