bridge.ts

import { buildScoringPrompt, extractJson } from './prompt';
import { validateResponse } from './scoring';
import type { ScoreResponse, Settings } from './types';

export interface BridgeError {
  kind: 'no_bearer' | 'daemon_unreachable' | 'unauthorized' | 'rate_limited' | 'cli_missing' | 'bad_json' | 'unknown';
  message: string;
}

export type BridgeResult =
  | { ok: true; result: ScoreResponse; durationMs: number }
  | { ok: false; error: BridgeError };

export async function scoreDraft(draft: string, settings: Settings): Promise<BridgeResult> {
  if (!settings.bearer) {
    return { ok: false, error: { kind: 'no_bearer', message: 'Set your local agent bearer token in the extension options first.' } };
  }
  const prompt = buildScoringPrompt(draft);
  const url = `${settings.daemonUrl.replace(/\/+$/, '')}/gemini`;
  let resp: Response;
  try {
    resp = await fetch(url, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${settings.bearer}` },
      body: JSON.stringify({ prompt, model: settings.model, timeout_ms: 60000 }),
    });
  } catch (e) {
    return {
      ok: false,
      error: {
        kind: 'daemon_unreachable',
        message: `Cannot reach ${url}. Is your local agent running? (${(e as Error).message})`,
      },
    };
  }
  if (resp.status === 401) {
    return { ok: false, error: { kind: 'unauthorized', message: 'Bearer token rejected by local agent. Check the value in options.' } };
  }
  const payload = (await resp.json().catch(() => null)) as
    | { ok: boolean; text: string; stderr: string; rateLimited: boolean; durationMs: number }
    | null;
  if (!payload) {
    return { ok: false, error: { kind: 'unknown', message: `Local agent returned non-JSON (status ${resp.status}).` } };
  }
  if (payload.rateLimited) {
    return { ok: false, error: { kind: 'rate_limited', message: 'Gemini rate-limited. Try again in a minute.' } };
  }
  if (!payload.ok) {
    if (/gemini-cli not found/i.test(payload.stderr)) {
      return { ok: false, error: { kind: 'cli_missing', message: payload.stderr } };
    }
    return { ok: false, error: { kind: 'unknown', message: payload.stderr || 'Local agent reported failure with no detail.' } };
  }
  let parsed: unknown;
  try {
    parsed = extractJson(payload.text);
  } catch (e) {
    return { ok: false, error: { kind: 'bad_json', message: `Could not parse Gemini response as JSON: ${(e as Error).message}` } };
  }
  if (!validateResponse(parsed)) {
    return { ok: false, error: { kind: 'bad_json', message: 'Gemini response was JSON but did not match expected schema.' } };
  }
  return { ok: true, result: parsed, durationMs: payload.durationMs };
}