api/index.js

import express from "express";
import { createOpencodeClient } from "@opencode-ai/sdk";
import { spawn } from "child_process";
import { fileURLToPath } from "url";
import path from "path";

const __dirname = path.dirname(fileURLToPath(import.meta.url));
process.env.PATH = `${path.join(__dirname, "..", "bin")}:${process.env.PATH ?? ""}`;

process.env.HOME = "/tmp";
if (process.env.OPENCODE_AUTH && !process.env.OPENCODE_AUTH_CONTENT) {
  process.env.OPENCODE_AUTH_CONTENT = Buffer.from(process.env.OPENCODE_AUTH, "base64").toString("utf8");
}

const DEFAULT_MODEL = "opencode/big-pickle";
const POOL = parseInt(process.env.OPENCODE_WORKERS || "4", 10);

const L = (...a) => console.log(`[PROXY] ${new Date().toISOString()}`, ...a);
const E = (...a) => console.error(`[PROXY] ${new Date().toISOString()}`, ...a);

function toModel(m) {
  if (!m) return undefined;
  if (typeof m === "object") return m;
  const i = m.indexOf("/");
  return i === -1 ? { providerID: "opencode", modelID: m } : { providerID: m.slice(0, i), modelID: m.slice(i + 1) };
}

/* ── Worker pool ──────────────────────────────────────────────── */

let _workers = [];
let _next = 0;
let _ready = null;

async function _spawn(i) {
  const port = 4096 + i;
  const proc = spawn("opencode", ["serve", "--hostname=127.0.0.1", `--port=${port}`, "--print-logs"], {
    env: { ...process.env, OPENCODE_CONFIG_CONTENT: "{}" },
  });
  let log = "";
  let resolved = false;
  const cap = (c) => { log += c.toString(); };
  proc.stdout?.on("data", cap);
  proc.stderr?.on("data", cap);
  proc.on("spawn", () => L("pool: worker", i, "pid", proc.pid));
  proc.on("exit", (code) => {
    E("pool: worker", i, "exited code", code, "- respawning in 2s");
    if (_workers[i]) _workers[i].alive = false;
    setTimeout(() => _spawn(i), 2000).unref();
  });

  const url = await new Promise((resolve, reject) => {
    const timer = setTimeout(() => { proc.kill("SIGKILL"); reject(new Error("timeout\n" + log.slice(-2000))); }, 90000);
    const check = () => {
      if (resolved) return;
      const m = log.match(/on\s+(https?:\/\/[^\s]+)/);
      if (m) { resolved = true; clearTimeout(timer); L("pool: worker", i, "ready at", m[1]); resolve(m[1]); }
    };
    proc.stdout?.on("data", check);
    proc.stderr?.on("data", check);
    proc.on("exit", (code) => { clearTimeout(timer); if (!resolved) reject(new Error(`exited ${code}\n` + log.slice(-2000))); });
    proc.on("error", (e) => { clearTimeout(timer); reject(e); });
  });
  const client = createOpencodeClient({ baseUrl: url });
  _workers[i] = { client, proc, index: i, alive: true };
  L("pool: worker", i, "online");
}

async function _boot() {
  L("pool: spawning", POOL, "workers");
  await Promise.allSettled(Array.from({ length: POOL }, (_, i) => _spawn(i).catch(e => E("pool: worker", i, "spawn failed:", e.message))));
  const n = _workers.filter(w => w?.alive).length;
  L("pool: ready", n, "/", POOL);
}

async function _pool() {
  if (!_ready) _ready = _boot();
  await _ready;
}

async function getClient() {
  await _pool();
  for (let t = 0; t < POOL * 2; t++) {
    const i = _next++ % POOL;
    const w = _workers[i];
    if (w && w.alive && !w.proc.killed) return w.client;
  }
  await new Promise(r => setTimeout(r, 1000));
  return getClient();
}

async function withOpencode(fn) {
  const client = await getClient();
  try {
    return await fn(client);
  } catch (e) {
    const isConnErr = e?.code === "ECONNREFUSED" || e?.code === "ECONNRESET" || (e?.message && e.message.includes("fetch failed"));
    if (isConnErr) {
      for (const w of _workers) {
        if (w && w.client === client) { w.alive = false; break; }
      }
      L("withOpencode: retrying with another worker");
      const client2 = await getClient();
      return await fn(client2);
    }
    throw e;
  }
}

/* ── Express ──────────────────────────────────────────────────── */

const app = express();
app.use(express.json({ limit: "10mb" }));
app.use((req, res, next) => {
  res.setHeader("Access-Control-Allow-Origin", "*");
  res.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS");
  res.setHeader("Access-Control-Allow-Headers", req.headers["access-control-request-headers"] || "*");
  res.setHeader("Access-Control-Max-Age", "86400");
  if (req.method === "OPTIONS") return res.status(204).end();
  next();
});

app.use((req, _res, next) => {
  const size = req.headers["content-length"] ? `${req.headers["content-length"]}b` : "unknown";
  L("request:", req.method, req.originalUrl, "from", req.headers.origin || req.ip, "body", size);
  next();
});

app.get("/health", async (_req, res) => {
  L("GET /health");
  try { await withOpencode(() => ({ ok: true })); res.json({ ok: true }); }
  catch (e) { E("GET /health:", e); res.status(500).json({ error: String(e) }); }
});

app.post("/prompt", async (req, res) => {
  const { parts, model, sessionId, system, tools, agent, noReply } = req.body || {};
  if (!parts) return res.status(400).json({ error: "parts required" });
  L("POST /prompt:", model || DEFAULT_MODEL, "session", sessionId || "(new)");
  try {
    const out = await withOpencode(async (c) => {
      const created = sessionId ? { data: { id: sessionId } } : await c.session.create({ body: {} });
      const result = await c.session.prompt({
        path: { id: created.data.id },
        body: { parts, model: toModel(model || DEFAULT_MODEL), system, tools, agent, noReply },
      });
      return { sessionId: created.data.id, ok: !result.error, data: result.data, error: result.error };
    });
    res.json(out);
  } catch (e) { E("POST /prompt:", e); res.status(500).json({ error: String(e) }); }
});

function openaiText(data) {
  return (data?.parts ?? []).filter((p) => p.type === "text").map((p) => p.text).join("");
}
function openaiReasoning(data) {
  return (data?.parts ?? []).filter((p) => p.type === "reasoning").map((p) => p.text).join("");
}
function openaiUsage(info) {
  const t = info?.tokens ?? {};
  return { prompt_tokens: t.input ?? 0, completion_tokens: t.output ?? 0, total_tokens: t.total ?? (t.input ?? 0) + (t.output ?? 0) };
}

app.post("/v1/chat/completions", async (req, res) => {
  const { model, messages, stream, system: sysArg, sessionId } = req.body || {};
  if (!messages) return res.status(400).json({ error: { message: "messages required", type: "invalid_request_error" } });
  const flat = (c) => typeof c === "string" ? c : (c ?? []).map((x) => x.text ?? x).join("");
  const system = [sysArg, ...messages.filter((m) => m.role === "system").map((m) => flat(m.content))].filter(Boolean).join("\n");
  const convo = messages.filter((m) => m.role !== "system");
  if (!convo.some((m) => m.role === "user")) return res.status(400).json({ error: { message: "no user message", type: "invalid_request_error" } });
  const text = convo.length === 1
    ? flat(convo[0].content)
    : convo.map((m) => `${m.role === "assistant" ? "Assistant" : "User"}: ${flat(m.content)}`).join("\n\n");
  const parts = [{ type: "text", text }];
  const modelId = model || DEFAULT_MODEL;
  const id = "chatcmpl-" + Math.random().toString(36).slice(2);
  const created = Date.now() / 1000 | 0;
  L("POST /v1/chat/completions:", "model", modelId, "stream", Boolean(stream), "messages", messages.length);

  if (!stream) {
    try {
      const out = await withOpencode(async (c) => {
        const s = sessionId ? { data: { id: sessionId } } : await c.session.create({ body: {} });
        const result = await c.session.prompt({ path: { id: s.data.id }, body: { parts, model: toModel(modelId), system } });
        return result.error ? { error: result.error } : { data: result.data };
      });
      if (out.error) return res.status(500).json({ error: { message: JSON.stringify(out.error), type: "server_error" } });
      const data = out.data, content = openaiText(data), reasoning = openaiReasoning(data), usage = openaiUsage(data.info);
      L("chat: ok, chars", content.length);
      const message = { role: "assistant", content, ...(reasoning ? { reasoning_content: reasoning } : {}) };
      return res.json({ id, object: "chat.completion", created, model: modelId, choices: [{ index: 0, message, finish_reason: "stop" }], usage });
    } catch (e) { E("chat:", e); return res.status(500).json({ error: { message: String(e), type: "server_error" } }); }
  }

  res.setHeader("Content-Type", "text/event-stream");
  res.setHeader("Cache-Control", "no-cache");
  res.setHeader("Connection", "keep-alive");
  L("chat(stream): starting");

  let client;
  try { client = await getClient(); }
  catch (e) { E("chat(stream): get client failed:", e); return res.status(500).json({ error: { message: String(e), type: "server_error" } }); }

  let sentRole = false;
  const chunk = (delta) => {
    if (!sentRole) delta = { role: "assistant", ...delta };
    sentRole = true;
    res.write(`data: ${JSON.stringify({ id, object: "chat.completion.chunk", created, model: modelId, choices: [{ index: 0, delta }] })}\n\n`);
  };
  let sid;
  try {
    const made = sessionId ? { data: { id: sessionId } } : await client.session.create({ body: {} });
    sid = made.data.id;
    L("chat(stream): session", sid);
  } catch (e) { E("chat(stream): session create failed:", e); return res.status(500).json({ error: { message: String(e), type: "server_error" } }); }

  const ac = new AbortController();
  req.on("close", () => { ac.abort(); L("chat(stream): client disconnected"); });
  let readyResolve;
  const ready = new Promise((r) => { readyResolve = r; });
  let fullText = "";
  let deltaCount = 0;
  const pump = (async () => {
    try {
      const sse = await client.global.event({ signal: ac.signal });
      for await (const ev of sse.stream) {
        readyResolve();
        const p = ev?.payload ?? ev;
        const t = p?.type;
        if (t === "message.part.delta") {
          if (p.properties?.sessionID === sid && p.properties?.delta) {
            if (p.properties.field === "text") chunk({ content: p.properties.delta });
            else if (p.properties.field === "reasoning") chunk({ reasoning_content: p.properties.delta });
            deltaCount++;
          }
          continue;
        }
        if (t === "message.part.updated") {
          const part = p.properties?.part;
          if (!part || part.sessionID !== sid || (part.type !== "text" && part.type !== "reasoning")) continue;
          let delta = p.properties?.delta;
          if (!delta) delta = (part.text ?? "").slice(fullText.length);
          if (delta) { fullText += delta; chunk(part.type === "reasoning" ? { reasoning_content: delta } : { content: delta }); deltaCount++; }
          continue;
        }
        if (t === "message.updated") {
          const info = p.properties?.info;
          if (info?.role === "assistant" && info?.finish) { ac.abort(); return; }
        }
      }
    } catch (e) { E("chat(stream): pump error:", e); }
  })();
  await Promise.race([ready, new Promise((r) => setTimeout(r, 1000))]);
  try {
    await client.session.prompt({ path: { id: sid }, body: { parts, model: toModel(modelId), system } });
    L("chat(stream): prompt sent");
  } catch (e) {
    E("chat(stream): prompt failed:", e);
    chunk({ content: "\n[error] " + String(e) });
  } finally {
    await Promise.race([pump, new Promise((r) => setTimeout(r, 2000))]);
    L("chat(stream): done, deltas", deltaCount, "chars", fullText.length);
    ac.abort();
    await pump.catch(() => {});
  }
  res.write(`data: ${JSON.stringify({ choices: [{ index: 0, delta: {}, finish_reason: "stop" }] })}\n\n`);
  res.write("data: [DONE]\n\n");
  res.end();
});

app.all("*", (req, res) => { L("404:", req.method, req.originalUrl); res.status(404).json({ error: "not found" }); });

app.use((err, _req, res, _next) => {
  E("unhandled error:", err);
  if (res.headersSent) return;
  res.status(500).json({ error: { message: String(err?.message ?? err), type: "server_error" } });
});

export default app;