import { Readable } from 'node:stream';
import { Agent, fetch as undiciFetch } from 'undici';
import { appendBalanceEvent, createSseBillingTransform } from './sse-billing.mjs';
import { developerToolsFromPolicy } from './capabilities.mjs';
import { evaluateProxyRequest, isNativeH5ApiPath } from './policies.mjs';
import { buildSandboxSessionConstraints } from './user-publish.mjs';
import { reconcileAgentSession } from './session-reconcile.mjs';

const insecureDispatcher = new Agent({
  connect: { rejectUnauthorized: false },
});

function isHttpsTarget(target) {
  return target.startsWith('https://');
}

async function apiFetch(target, apiSecret, pathname, init = {}) {
  const url = new URL(pathname, target);
  const headers = {
    ...(init.headers ?? {}),
    'X-Secret-Key': apiSecret,
  };
  if (init.body && !headers['Content-Type']) {
    headers['Content-Type'] = 'application/json';
  }

  return undiciFetch(url, {
    ...init,
    headers,
    dispatcher: isHttpsTarget(target) ? insecureDispatcher : undefined,
  });
}

async function readJsonBody(req) {
  if (req.method === 'GET' || req.method === 'HEAD') return null;
  const chunks = [];
  for await (const chunk of req) {
    chunks.push(chunk);
  }
  if (chunks.length === 0) return null;
  const raw = Buffer.concat(chunks).toString('utf8');
  if (!raw.trim()) return null;
  return JSON.parse(raw);
}

function sendProxyResponse(res, upstream) {
  res.status(upstream.status);
  upstream.headers.forEach((value, key) => {
    if (key === 'transfer-encoding') return;
    res.setHeader(key, value);
  });
  if (!upstream.body) {
    res.end();
    return;
  }
  Readable.fromWeb(upstream.body).pipe(res);
}

function extractSessionId(req, body) {
  const fromParams = req.params?.sessionId ?? req.params?.id;
  if (fromParams) return fromParams;
  if (body?.session_id) return body.session_id;
  if (body?.sessionId) return body.sessionId;
  return null;
}

export function createTkmindProxy({ apiTarget, apiTargets, apiSecret, userAuth, llmProviderService }) {
  const targets = apiTargets?.length ? apiTargets : apiTarget ? [apiTarget] : [];
  const primaryTarget = targets[0] ?? apiTarget ?? '';
  let rrIdx = 0;

  async function targetHealthy(target) {
    try {
      const upstream = await apiFetch(target, apiSecret, '/status', {
        method: 'GET',
        signal: AbortSignal.timeout(1500),
      });
      return upstream.ok;
    } catch {
      return false;
    }
  }

  async function pickTarget() {
    if (targets.length <= 1) return primaryTarget;
    for (let i = 0; i < targets.length; i += 1) {
      const target = targets[rrIdx];
      rrIdx = (rrIdx + 1) % targets.length;
      if (await targetHealthy(target)) return target;
    }
    return primaryTarget;
  }

  async function resolveTarget(sessionId) {
    if (targets.length <= 1 || !sessionId) return primaryTarget;
    try {
      const node = await userAuth.getSessionNode(sessionId);
      return targets[node] ?? primaryTarget;
    } catch {
      return primaryTarget;
    }
  }

  async function applySessionLlmProvider(sessionId) {
    if (!llmProviderService || !sessionId) return null;
    try {
      const target = await resolveTarget(sessionId);
      return await llmProviderService.applyBestProviderForSession(
        sessionId,
        (url, init) => apiFetch(target, apiSecret, `${url.pathname}${url.search}`, init),
      );
    } catch (err) {
      console.warn(
        'LLM provider apply skipped:',
        err instanceof Error ? err.message : err,
      );
      return null;
    }
  }

  async function applyLocalFallbackForSession(sessionId) {
    if (!llmProviderService || !sessionId) return null;
    const target = await resolveTarget(sessionId);
    return llmProviderService.applyLocalFallbackForSession(
      sessionId,
      (url, init) => apiFetch(target, apiSecret, `${url.pathname}${url.search}`, init),
    );
  }

  const requireUser = async (req, res, next) => {
    try {
      const session = req.userSession;
      if (!session) {
        res.status(401).json({ message: '未登录' });
        return;
      }
      const me = await userAuth.getMe(req.userToken);
      if (!me) {
        res.status(401).json({ message: '登录已过期' });
        return;
      }
      req.currentUser = me;
      next();
    } catch (err) {
      res.status(500).json({ message: err instanceof Error ? err.message : '认证失败' });
    }
  };

  const ensureChatAllowed = async (req, res, next) => {
    const gate = await userAuth.canUseChat(req.currentUser.id);
    if (!gate.ok) {
      res.status(402).json({
        message: gate.message,
        code: gate.code,
        balanceCents: gate.balanceCents,
        minRechargeCents: gate.minRechargeCents,
        suggestedTiers: gate.suggestedTiers,
      });
      return;
    }
    next();
  };

  const handlers = {
    'POST /agent/start': [
      requireUser,
      ensureChatAllowed,
      async (req, res) => {
        try {
          const workingDir = await userAuth.resolveWorkingDir(req.currentUser.id);
          const sessionPolicy = await userAuth.getAgentSessionPolicy(req.currentUser.id);
          const startTarget = await pickTarget();
          const upstream = await apiFetch(startTarget, apiSecret, '/agent/start', {
            method: 'POST',
            body: JSON.stringify({
              working_dir: workingDir,
              enable_context_memory: sessionPolicy.enableContextMemory,
              ...(sessionPolicy.extensionOverrides
                ? { extension_overrides: sessionPolicy.extensionOverrides }
                : {}),
              ...(req.body?.recipe ? { recipe: req.body.recipe } : {}),
            }),
          });
          const text = await upstream.text();
          if (!upstream.ok) {
            res.status(upstream.status).send(text);
            return;
          }
          const session = JSON.parse(text);
          if (session?.id) {
            await userAuth.registerAgentSession(
              req.currentUser.id,
              session.id,
              Math.max(0, targets.indexOf(startTarget)),
            );
            if (sessionPolicy.gooseMode) {
              const modeRes = await apiFetch(startTarget, apiSecret, '/agent/update_session', {
                method: 'POST',
                body: JSON.stringify({
                  session_id: session.id,
                  goose_mode: sessionPolicy.gooseMode,
                }),
              });
              if (!modeRes.ok) {
                const modeText = await modeRes.text().catch(() => '');
                res.status(modeRes.status).send(modeText || '设置会话模式失败');
                return;
              }
            }
            const publishLayout = await userAuth.getUserPublishLayout(req.currentUser.id);
            const api = (pathname, init) => apiFetch(startTarget, apiSecret, pathname, init);
            try {
              await reconcileAgentSession(api, session.id, {
                workingDir,
                sessionPolicy,
                sandboxConstraints: publishLayout?.constraints ?? null,
                userContext: publishLayout
                  ? {
                      userId: req.currentUser.id,
                      displayName: publishLayout.displayName,
                      username: publishLayout.username,
                      slug: publishLayout.slug,
                    }
                  : null,
              });
            } catch (reconcileErr) {
              res.status(500).json({
                message:
                  reconcileErr instanceof Error
                    ? `会话策略同步失败：${reconcileErr.message}`
                    : '会话策略同步失败',
              });
              return;
            }
            await applySessionLlmProvider(session.id);
          }
          res.status(upstream.status).json(session);
        } catch (err) {
          res.status(500).json({ message: err instanceof Error ? err.message : '启动会话失败' });
        }
      },
    ],

    'POST /agent/resume': [
      requireUser,
      ensureChatAllowed,
      async (req, res) => {
        try {
          const sessionId = req.body?.session_id;
          if (!sessionId) {
            res.status(400).json({ message: '缺少 session_id' });
            return;
          }
          const owns = await userAuth.ownsSession(req.currentUser.id, sessionId);
          if (!owns) {
            res.status(403).json({ message: '无权访问该会话' });
            return;
          }

          const resumeTarget = await resolveTarget(sessionId);
          const upstream = await apiFetch(resumeTarget, apiSecret, '/agent/resume', {
            method: 'POST',
            body: JSON.stringify(req.body ?? {}),
          });
          const text = await upstream.text();
          if (!upstream.ok) {
            res.status(upstream.status).send(text);
            return;
          }

          const payload = JSON.parse(text);
          const skipReconcile = req.body?.skip_reconcile === true;
          if (!skipReconcile) {
            const workingDir = await userAuth.resolveWorkingDir(req.currentUser.id);
            const sessionPolicy = await userAuth.getAgentSessionPolicy(req.currentUser.id);
            const publishLayout = await userAuth.getUserPublishLayout(req.currentUser.id);
            try {
              await reconcileAgentSession(
                (pathname, init) => apiFetch(resumeTarget, apiSecret, pathname, init),
                sessionId,
                {
                  workingDir,
                  sessionPolicy,
                  sandboxConstraints: publishLayout?.constraints ?? null,
                  tolerateInvalidWorkingDir: true,
                  userContext: publishLayout
                    ? {
                        userId: req.currentUser.id,
                        displayName: publishLayout.displayName,
                        username: publishLayout.username,
                        slug: publishLayout.slug,
                      }
                    : null,
                },
              );
            } catch (reconcileErr) {
              res.status(500).json({
                message:
                  reconcileErr instanceof Error
                    ? `会话恢复后策略同步失败：${reconcileErr.message}`
                    : '会话恢复后策略同步失败',
              });
              return;
            }
          }

          await applySessionLlmProvider(sessionId);

          res.status(upstream.status).json(payload);
        } catch (err) {
          res.status(500).json({ message: err instanceof Error ? err.message : '恢复会话失败' });
        }
      },
    ],

    'GET /sessions': [
      requireUser,
      async (req, res) => {
        try {
          const owned = await userAuth.listOwnedSessionIds(req.currentUser.id);
          const sessionsById = new Map();
          let healthyTargets = 0;
          let lastFailure = null;

          for (const target of targets) {
            try {
              const upstream = await apiFetch(target, apiSecret, '/sessions', {
                method: 'GET',
                signal: AbortSignal.timeout(3000),
              });
              const text = await upstream.text();
              if (!upstream.ok) {
                lastFailure = text || `upstream ${upstream.status}`;
                continue;
              }
              healthyTargets += 1;
              const payload = JSON.parse(text);
              for (const item of payload.sessions ?? []) {
                if (owned.has(item.id)) sessionsById.set(item.id, item);
              }
            } catch (err) {
              lastFailure = err instanceof Error ? err.message : '读取会话失败';
            }
          }

          if (healthyTargets === 0) {
            res.status(502).json({ message: lastFailure ?? '所有 goose 服务不可用' });
            return;
          }
          if (healthyTargets < targets.length) {
            res.setHeader('X-TKMind-Degraded', '1');
          }
          res.json({ sessions: [...sessionsById.values()] });
        } catch (err) {
          res.status(500).json({ message: err instanceof Error ? err.message : '读取会话失败' });
        }
      },
    ],
  };

  const sessionScoped = (build) => [
    requireUser,
    async (req, res, next) => {
      try {
        const body = req.body ?? (await readJsonBody(req));
        req.body = body;
        const sessionId = extractSessionId(req, body);
        if (!sessionId) {
          res.status(400).json({ message: '缺少 session_id' });
          return;
        }
        const owns = await userAuth.ownsSession(req.currentUser.id, sessionId);
        if (!owns) {
          res.status(403).json({ message: '无权访问该会话' });
          return;
        }
        req.agentSessionId = sessionId;
        await build(req, res, next);
      } catch (err) {
        res.status(500).json({ message: err instanceof Error ? err.message : '请求失败' });
      }
    },
  ];

  const proxySessionEvents = async (req, res, sessionId) => {
    try {
      const pathname = `/sessions/${sessionId}/events`;
      const sessionTarget = await resolveTarget(sessionId);
      const upstream = await apiFetch(sessionTarget, apiSecret, pathname, {
        method: 'GET',
        headers: {
          Accept: 'text/event-stream',
          'Last-Event-ID': req.get('last-event-id') ?? '',
        },
      });

      if (!upstream.ok || !upstream.body) {
        const text = await upstream.text().catch(() => '');
        res.status(upstream.status).send(text);
        return;
      }

      res.status(upstream.status);
      res.setHeader('Content-Type', 'text/event-stream');
      res.setHeader('Cache-Control', 'no-cache');
      res.setHeader('Connection', 'keep-alive');

      let pendingBalance = null;
      const billingTransform = createSseBillingTransform({
        onFinish: async (event) => {
          const result = await userAuth.billSessionUsage(
            req.currentUser.id,
            sessionId,
            event.token_state,
            null,
          );
          if (result.ok && result.costCents > 0 && result.balanceCents != null) {
            pendingBalance = {
              balanceCents: result.balanceCents,
              tokensUsed: result.tokensUsed ?? undefined,
              lastUsage: {
                inputTokens: result.deltaInputTokens ?? 0,
                outputTokens: result.deltaOutputTokens ?? 0,
                costCents: result.costCents,
              },
            };
          }
        },
      });

      const source = Readable.fromWeb(upstream.body);
      billingTransform.on('data', (chunk) => {
        res.write(chunk);
        if (pendingBalance != null) {
          res.write(appendBalanceEvent(pendingBalance));
          pendingBalance = null;
        }
      });
      billingTransform.on('end', () => res.end());
      billingTransform.on('error', () => res.end());
      source.on('error', () => res.end());
      source.pipe(billingTransform);
    } catch (err) {
      res.status(502).json({ message: err instanceof Error ? err.message : 'SSE 代理失败' });
    }
  };

  const proxyFallback = async (req, res) => {
    try {
      const pathname = req.originalUrl.replace(/^\/api/, '') || '/';
      if (isNativeH5ApiPath(pathname)) {
        res.status(404).json({
          message: 'H5 本地接口未找到，请确认服务端已更新并重启',
          code: 'not_found',
        });
        return;
      }
      const policyState = await userAuth.resolveUserPolicies(req.currentUser);
      const capabilityState = await userAuth.resolveUserCapabilities(req.currentUser);
      const gate = evaluateProxyRequest(req.method, pathname, policyState.policies, {
        unrestricted: policyState.unrestricted,
      });
      if (!gate.allowed) {
        res.status(403).json({ message: gate.reason ?? '该 API 已被策略禁止' });
        return;
      }
      if (
        /^\/agent\/harness_(bootstrap|remember)$/.test(pathname) &&
        !capabilityState.unrestricted &&
        !capabilityState.capabilities.context_memory
      ) {
        res.status(403).json({ message: '当前账户未开通项目记忆，无法访问该 API' });
        return;
      }
      const body =
        req.method === 'GET' || req.method === 'HEAD'
          ? undefined
          : req.body
            ? JSON.stringify(req.body)
            : undefined;

      const sessionMatch = pathname.match(/^\/sessions\/([^/]+)/);
      const fallbackTarget =
        req.goosedTarget ??
        (sessionMatch ? await resolveTarget(sessionMatch[1]) : primaryTarget);
      const upstream = await apiFetch(fallbackTarget, apiSecret, pathname, {
        method: req.method,
        body,
        headers: {
          Accept: req.get('accept') ?? '*/*',
          'Last-Event-ID': req.get('last-event-id') ?? '',
        },
      });

      sendProxyResponse(res, upstream);
    } catch (err) {
      res.status(502).json({ message: err instanceof Error ? err.message : '代理失败' });
    }
  };

  return {
    requireUser,
    ensureChatAllowed,
    applySessionLlmProvider,
    applyLocalFallbackForSession,
    handlers,
    sessionScoped,
    proxyFallback,
    proxySessionEvents,
    resolveTarget,
    apiFetch: async (pathname, init) => apiFetch(await pickTarget(), apiSecret, pathname, init),
    apiFetchTo: (target, pathname, init) => apiFetch(target, apiSecret, pathname, init),
  };
}

export function matchHandler(handlers, method, path) {
  const key = `${method.toUpperCase()} ${path}`;
  return handlers[key] ?? null;
}