disclosure-bureau/web/lib/chat/openrouter.ts

/**
 * OpenRouter provider — OpenAI-compatible chat completions.
 *
 * Exports:
 *   sendOnce()        — non-streaming, single call (no tools)
 *   streamWithTools() — streaming + tool-call loop (Pattern C)
 *
 * The tool-call loop runs locally:
 *   1. Call model with messages + tools, stream=true.
 *   2. Read SSE deltas: text → emit `text_delta`; tool_calls → buffer args by id.
 *   3. When finish_reason='tool_calls': execute handlers locally, push results
 *      back as tool messages, call model again. Repeat until finish='stop'.
 *   4. When done: emit `done`.
 *
 * Free models (May 2026):
 *   deepseek/deepseek-v4-flash:free            — primary, solid tool calling
 *   nvidia/nemotron-3-super-120b-a12b:free     — fallback
 */
import type { AGUIEvent } from "./agui";
import { TOOL_DEFINITIONS, TOOL_HANDLERS, type ToolHandlerContext } from "./tools";

const PRIMARY = process.env.OPENROUTER_MODEL || "deepseek/deepseek-v4-flash:free";
const FALLBACK = process.env.OPENROUTER_FALLBACK_MODEL || "nvidia/nemotron-3-super-120b-a12b:free";
const ENDPOINT = "https://openrouter.ai/api/v1/chat/completions";

type OAMsg =
  | { role: "system" | "user"; content: string }
  | { role: "assistant"; content?: string | null; tool_calls?: OAToolCall[] }
  | { role: "tool"; content: string; tool_call_id: string; name?: string };

interface OAToolCall {
  id: string;
  type: "function";
  function: { name: string; arguments: string };
}

interface OADelta {
  role?: string;
  content?: string;
  tool_calls?: Array<{
    index: number;
    id?: string;
    type?: string;
    function?: { name?: string; arguments?: string };
  }>;
}

interface OAStreamChunk {
  choices?: Array<{
    delta?: OADelta;
    finish_reason?: string | null;
    message?: { role: string; content?: string | null; tool_calls?: OAToolCall[] };
  }>;
  usage?: { prompt_tokens?: number; completion_tokens?: number; total_tokens?: number };
  model?: string;
  error?: { message?: string };
}

function headers() {
  const apiKey = process.env.OPENROUTER_API_KEY;
  if (!apiKey) throw new Error("OPENROUTER_API_KEY not set");
  return {
    "Authorization": `Bearer ${apiKey}`,
    "Content-Type": "application/json",
    "HTTP-Referer": process.env.NEXT_PUBLIC_SITE_URL || "https://disclosure.top",
    "X-Title": "The Disclosure Bureau",
  };
}

export interface SendOnceReq {
  system: string;
  messages: Array<{ role: "user" | "assistant" | "system"; content: string }>;
  maxTokens?: number;
}

/** Non-streaming single shot — used by claude-code fallback path and tests. */
export async function sendOnce(req: SendOnceReq, model = PRIMARY): Promise<{
  content: string;
  model: string;
  tokensIn?: number;
  tokensOut?: number;
}> {
  const body = {
    model,
    messages: [
      { role: "system", content: req.system },
      ...req.messages.slice(-20),
    ],
    max_tokens: req.maxTokens ?? 1024,
  };
  const res = await fetch(ENDPOINT, {
    method: "POST",
    headers: headers(),
    body: JSON.stringify(body),
  });
  if (!res.ok) {
    const txt = await res.text();
    const err = new Error(`openrouter HTTP ${res.status}: ${txt.slice(0, 300)}`);
    if (res.status === 429 || res.status === 402) {
      (err as Error & { isRateLimit?: boolean }).isRateLimit = true;
    }
    throw err;
  }
  const data = await res.json();
  if (data.error) throw new Error(`openrouter error: ${data.error.message}`);
  return {
    content: data.choices?.[0]?.message?.content ?? "",
    model: data.model ?? model,
    tokensIn: data.usage?.prompt_tokens,
    tokensOut: data.usage?.completion_tokens,
  };
}

/* ─── Pattern C: streaming + tool-call loop ─────────────────────────────── */

export interface StreamRequest {
  system: string;
  history: Array<{ role: "user" | "assistant"; content: string }>;
  userTurn: string;
  ctx: ToolHandlerContext;
  maxTurns?: number; // max tool-call loop iterations
}

export interface StreamCallbacks {
  emit: (ev: AGUIEvent) => void;
}

/**
 * Stream with tool-call loop. Returns the final assistant content (assembled
 * across deltas + after all tool calls resolved) plus token usage.
 *
 * The caller is responsible for closing the SSE stream after this resolves.
 */
export async function streamWithTools(
  req: StreamRequest,
  cb: StreamCallbacks,
): Promise<{
  content: string;
  model: string;
  tokensIn: number;
  tokensOut: number;
  toolCalls: Array<{ name: string; args: Record<string, unknown>; result: unknown }>;
}> {
  const maxTurns = req.maxTurns ?? 5;
  const messages: OAMsg[] = [
    { role: "system", content: req.system },
    ...req.history.map((m): OAMsg => ({
      role: m.role,
      content: m.content,
    })),
    { role: "user", content: req.userTurn },
  ];

  let assembledText = "";
  let totalIn = 0;
  let totalOut = 0;
  let modelUsed = PRIMARY;
  const toolTrace: Array<{ name: string; args: Record<string, unknown>; result: unknown }> = [];

  for (let turn = 0; turn < maxTurns; turn++) {
    // Run one round.
    let model = PRIMARY;
    let res: Response;
    try {
      res = await openrouterStreamCall(messages, model);
    } catch (e) {
      if ((e as Error & { isRateLimit?: boolean }).isRateLimit) {
        model = FALLBACK;
        res = await openrouterStreamCall(messages, model);
      } else throw e;
    }
    modelUsed = model;

    if (!res.body) throw new Error("openrouter: no response body");
    const { roundText, finishReason, toolCalls, usage } = await readSSE(res.body, cb);
    assembledText += roundText;
    totalIn += usage?.prompt_tokens ?? 0;
    totalOut += usage?.completion_tokens ?? 0;

    if (finishReason === "tool_calls" && toolCalls.length > 0) {
      // Append the assistant's tool-call turn to message history
      messages.push({
        role: "assistant",
        content: roundText || null,
        tool_calls: toolCalls,
      });
      // Execute each tool locally
      for (const tc of toolCalls) {
        let argsObj: Record<string, unknown> = {};
        try { argsObj = JSON.parse(tc.function.arguments || "{}"); }
        catch { /* malformed — pass empty */ }
        cb.emit({ type: "tool_start", id: tc.id, name: tc.function.name, args: argsObj });
        const handler = TOOL_HANDLERS[tc.function.name];
        const t0 = Date.now();
        let result: unknown;
        try {
          if (!handler) throw new Error(`unknown tool: ${tc.function.name}`);
          result = await handler(argsObj, req.ctx);
        } catch (e) {
          result = { error: e instanceof Error ? e.message : String(e) };
        }
        const dt = Date.now() - t0;
        cb.emit({ type: "tool_result", id: tc.id, result, durationMs: dt });
        toolTrace.push({ name: tc.function.name, args: argsObj, result });

        // Surface navigate_to as a UI event the frontend can render as a button
        if (tc.function.name === "navigate_to") {
          const target = String(argsObj.target ?? "");
          const label = String(argsObj.label ?? target);
          if (target.startsWith("/")) {
            cb.emit({ type: "navigate", target, label });
          }
        }

        // Append the tool result for the model
        messages.push({
          role: "tool",
          tool_call_id: tc.id,
          name: tc.function.name,
          content: JSON.stringify(result).slice(0, 8000),
        });
      }
      // Continue loop — model will see tool results and produce next turn
      continue;
    }

    // No tool calls → done
    break;
  }

  return {
    content: assembledText,
    model: modelUsed,
    tokensIn: totalIn,
    tokensOut: totalOut,
    toolCalls: toolTrace,
  };
}

async function openrouterStreamCall(messages: OAMsg[], model: string): Promise<Response> {
  const body = {
    model,
    messages,
    tools: TOOL_DEFINITIONS,
    tool_choice: "auto",
    stream: true,
    max_tokens: 1024,
  };
  const res = await fetch(ENDPOINT, {
    method: "POST",
    headers: headers(),
    body: JSON.stringify(body),
  });
  if (!res.ok) {
    const txt = await res.text();
    const err = new Error(`openrouter HTTP ${res.status}: ${txt.slice(0, 300)}`);
    if (res.status === 429 || res.status === 402) {
      (err as Error & { isRateLimit?: boolean }).isRateLimit = true;
    }
    throw err;
  }
  return res;
}

/**
 * Read OpenRouter SSE stream. Emits text_delta events via cb.emit. Returns
 * assembled text, finish_reason, accumulated tool_calls, and usage.
 */
async function readSSE(
  body: ReadableStream<Uint8Array>,
  cb: StreamCallbacks,
): Promise<{
  roundText: string;
  finishReason: string | null;
  toolCalls: OAToolCall[];
  usage?: { prompt_tokens?: number; completion_tokens?: number };
}> {
  const reader = body.getReader();
  const decoder = new TextDecoder();
  let buffer = "";
  let roundText = "";
  let finishReason: string | null = null;
  // tool_calls arrive as deltas across many chunks; accumulate by index.
  const toolBufs: Record<number, { id: string; name: string; args: string }> = {};
  let usage: { prompt_tokens?: number; completion_tokens?: number } | undefined;

  for (;;) {
    const { value, done } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });

    // SSE messages are separated by \n\n
    let idx: number;
    while ((idx = buffer.indexOf("\n\n")) !== -1) {
      const raw = buffer.slice(0, idx);
      buffer = buffer.slice(idx + 2);

      // Each message may have multiple lines; we care about "data: ..."
      for (const line of raw.split("\n")) {
        if (!line.startsWith("data: ")) continue;
        const payload = line.slice(6).trim();
        if (payload === "[DONE]") {
          return { roundText, finishReason, toolCalls: collectToolCalls(toolBufs), usage };
        }
        let chunk: OAStreamChunk;
        try { chunk = JSON.parse(payload); }
        catch { continue; }
        if (chunk.error) throw new Error(`openrouter stream error: ${chunk.error.message}`);
        if (chunk.usage) usage = chunk.usage;

        const choice = chunk.choices?.[0];
        if (!choice) continue;
        const d = choice.delta ?? {};
        if (typeof d.content === "string" && d.content) {
          roundText += d.content;
          cb.emit({ type: "text_delta", delta: d.content });
        }
        if (Array.isArray(d.tool_calls)) {
          for (const tc of d.tool_calls) {
            const slot = (toolBufs[tc.index] ??= { id: "", name: "", args: "" });
            if (tc.id) slot.id = tc.id;
            if (tc.function?.name) slot.name = tc.function.name;
            if (tc.function?.arguments) slot.args += tc.function.arguments;
          }
        }
        if (choice.finish_reason) finishReason = choice.finish_reason;
      }
    }
  }
  return { roundText, finishReason, toolCalls: collectToolCalls(toolBufs), usage };
}

function collectToolCalls(bufs: Record<number, { id: string; name: string; args: string }>): OAToolCall[] {
  return Object.values(bufs)
    .filter((b) => b.id && b.name)
    .map((b) => ({
      id: b.id,
      type: "function" as const,
      function: { name: b.name, arguments: b.args || "{}" },
    }));
}