import { spawn } from 'node:child_process';
import {
  resolveDeepseekNoThinkProxyBaseUrl,
} from './deepseek-no-think-proxy.mjs';

export const DEFAULT_HEADROOM_PROXY_PORT = 8787;
export const MEMIND_HEADROOM_MODES = Object.freeze(['off', 'shadow', 'active']);

export const DEFAULT_HEADROOM_EXCLUDED_SKILLS = Object.freeze([
  'static-page-publish',
  'page-data-collect',
  'aider-development',
]);

function normalizeMode(value, fallback = 'off') {
  const raw = String(value ?? fallback).trim().toLowerCase();
  return MEMIND_HEADROOM_MODES.includes(raw) ? raw : fallback;
}

export function resolveHeadroomMode(env = process.env) {
  return normalizeMode(env.MEMIND_HEADROOM_MODE, 'off');
}

export function resolveHeadroomProxyPort(env = process.env) {
  const port = Number(env.MEMIND_HEADROOM_PROXY_PORT ?? DEFAULT_HEADROOM_PROXY_PORT);
  return Number.isFinite(port) && port > 0 ? port : DEFAULT_HEADROOM_PROXY_PORT;
}

export function resolveHeadroomProxyBaseUrl(env = process.env) {
  const explicit = String(env.MEMIND_HEADROOM_PROXY_BASE_URL ?? '').trim();
  if (explicit) return explicit.replace(/\/$/, '');
  const host = String(env.MEMIND_HEADROOM_PROXY_HOST ?? '127.0.0.1').trim() || '127.0.0.1';
  return `http://${host}:${resolveHeadroomProxyPort(env)}/v1`;
}

export function resolveHeadroomUpstreamBaseUrl(env = process.env) {
  const explicit = String(env.MEMIND_HEADROOM_UPSTREAM_BASE_URL ?? '').trim();
  if (explicit) return explicit.replace(/\/$/, '');
  return resolveDeepseekNoThinkProxyBaseUrl(env);
}

export function parseHeadroomExcludedSkills(env = process.env) {
  const raw = String(env.MEMIND_HEADROOM_EXCLUDED_SKILLS ?? '').trim();
  if (!raw) return [...DEFAULT_HEADROOM_EXCLUDED_SKILLS];
  return raw.split(',').map((item) => item.trim()).filter(Boolean);
}

export function isHeadroomEligibleForSkill(skillId, env = process.env) {
  if (resolveHeadroomMode(env) === 'off') return false;
  const skill = String(skillId ?? '').trim();
  if (!skill) return true;
  return !parseHeadroomExcludedSkills(env).includes(skill);
}

/**
 * Decide whether goosed should talk to headroom instead of the direct compat proxy.
 * fail-open: active mode falls back to the original apiUrl when headroom is unreachable.
 */
export function resolveGoosedApiUrlWithHeadroom({
  apiUrl,
  mode = resolveHeadroomMode(),
  headroomReachable = false,
  eligible = true,
  env = process.env,
} = {}) {
  const normalizedMode = normalizeMode(mode, 'off');
  const original = String(apiUrl ?? '').trim();
  if (!original || normalizedMode === 'off' || !eligible) {
    return {
      apiUrl: original,
      mode: normalizedMode,
      routed: false,
      eligible,
    };
  }

  const headroomBase = resolveHeadroomProxyBaseUrl(env);
  if (normalizedMode === 'shadow') {
    return {
      apiUrl: original,
      mode: 'shadow',
      routed: false,
      eligible: true,
      wouldRouteTo: headroomBase,
      upstreamBaseUrl: resolveHeadroomUpstreamBaseUrl(env),
    };
  }

  if (!headroomReachable) {
    return {
      apiUrl: original,
      mode: 'active',
      routed: false,
      eligible: true,
      fallback: 'headroom_unreachable',
      wouldRouteTo: headroomBase,
    };
  }

  return {
    apiUrl: headroomBase,
    mode: 'active',
    routed: true,
    eligible: true,
    upstreamBaseUrl: resolveHeadroomUpstreamBaseUrl(env),
  };
}

export function buildHeadroomRunObservation({ skillId, env = process.env } = {}) {
  const mode = resolveHeadroomMode(env);
  const eligible = isHeadroomEligibleForSkill(skillId, env);
  return {
    mode,
    eligible,
    excludedSkills: parseHeadroomExcludedSkills(env),
    proxyBaseUrl: mode !== 'off' ? resolveHeadroomProxyBaseUrl(env) : null,
    upstreamBaseUrl: mode !== 'off' ? resolveHeadroomUpstreamBaseUrl(env) : null,
  };
}

export async function ensureHeadroomProxyRunning({
  env = process.env,
  spawnImpl = spawn,
  startupWaitMs = 20_000,
} = {}) {
  const baseUrl = resolveHeadroomProxyBaseUrl(env);
  if (await probeHeadroomProxyReachable({ baseUrl, env })) {
    return { started: false, baseUrl, reachable: true };
  }

  const upstream = resolveHeadroomUpstreamBaseUrl(env);
  const port = resolveHeadroomProxyPort(env);
  const host = String(env.MEMIND_HEADROOM_PROXY_HOST ?? '127.0.0.1').trim() || '127.0.0.1';
  const openaiApiRoot = upstream.replace(/\/v1\/?$/, '');

  const child = spawnImpl(
    'headroom',
    ['proxy', '--port', String(port), '--host', host, '--openai-api-url', openaiApiRoot],
    {
      detached: true,
      stdio: 'ignore',
      env: {
        ...process.env,
        ...env,
        OPENAI_TARGET_API_URL: upstream,
        HEADROOM_OUTPUT_SHAPER: '0',
      },
    },
  );
  child.unref?.();

  const deadline = Date.now() + startupWaitMs;
  while (Date.now() < deadline) {
    await new Promise((resolve) => setTimeout(resolve, 1000));
    if (await probeHeadroomProxyReachable({ baseUrl, env })) {
      return { started: true, baseUrl, reachable: true, upstream, port };
    }
  }

  return { started: true, baseUrl, reachable: false, upstream, port };
}

export async function probeHeadroomProxyReachable({
  baseUrl,
  fetchImpl = fetch,
  timeoutMs = 1500,
  env = process.env,
} = {}) {
  const root = String(baseUrl ?? resolveHeadroomProxyBaseUrl(env))
    .trim()
    .replace(/\/v1\/?$/i, '');
  if (!root) return false;

  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), timeoutMs);
  try {
    const response = await fetchImpl(`${root}/v1/models`, {
      method: 'GET',
      signal: controller.signal,
      headers: { Authorization: 'Bearer headroom-probe' },
    });
    // Proxy alive when it responds, even with auth/upstream errors.
    return response.status > 0;
  } catch {
    return false;
  } finally {
    clearTimeout(timer);
  }
}