diff npc/main.c @ 181:a2720eac50ce

[NPC] Adding JSON RPC protocol for MPC endpoints
author June Park <parkjune1995@gmail.com>
date Fri, 23 Jan 2026 21:07:08 -0800
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/npc/main.c	Fri Jan 23 21:07:08 2026 -0800
@@ -0,0 +1,146 @@
+#include "seobeo/seobeo.h"
+#include <string.h>
+#include <time.h>
+
+static _Atomic uint32_t counter = 0;
+
+static void build_response(char *out, size_t size, const char *id, const char *result) {
+  snprintf(out, size, "{\"jsonrpc\":\"2.0\",\"id\":%s,\"result\":%s}", id, result);
+}
+
+static void build_error(char *out, size_t size, const char *id, int code, const char *msg) {
+  snprintf(out, size,
+    "{\"jsonrpc\":\"2.0\",\"id\":%s,\"error\":{\"code\":%d,\"message\":\"%s\"}}",
+    id, code, msg);
+}
+
+static void handle_initialize(char *out, size_t size, const char *id) {
+  const char *result = "{"
+    "\"protocolVersion\":\"2024-11-05\","
+    "\"capabilities\":{\"tools\":{}},"
+    "\"serverInfo\":{\"name\":\"simple-mcp\",\"version\":\"1.0.0\"}"
+  "}";
+  build_response(out, size, id, result);
+}
+
+static void handle_tools_list(char *out, size_t size, const char *id) {
+  const char *result = "{"
+    "\"tools\":["
+      "{"
+        "\"name\":\"get_time\","
+        "\"description\":\"Get current Unix timestamp\","
+        "\"inputSchema\":{\"type\":\"object\",\"properties\":{}}"
+      "},"
+      "{"
+        "\"name\":\"get_counter\","
+        "\"description\":\"Get and increment a counter\","
+        "\"inputSchema\":{\"type\":\"object\",\"properties\":{}}"
+      "}"
+    "]"
+  "}";
+  build_response(out, size, id, result);
+}
+
+static void handle_tools_call(char *out, size_t size, const char *id, Dowa_JSON_Entry *json) {
+  Dowa_JSON_Value *params_val = Dowa_JSON_Get(json, "params");
+  if (!params_val || params_val->type != DOWA_JSON_OBJECT)
+  {
+    build_error(out, size, id, -32602, "Missing params");
+    return;
+  }
+
+  Dowa_JSON_Entry *params = (Dowa_JSON_Entry *)params_val->object_val;
+  char *tool_name = Dowa_JSON_Get_String(params, "name");
+
+  if (!tool_name) {
+    build_error(out, size, id, -32602, "Missing tool name");
+    return;
+  }
+
+  char result[256];
+  if (strcmp(tool_name, "get_time") == 0) {
+    time_t now = time(NULL);
+    snprintf(result, sizeof(result),
+      "{\"content\":[{\"type\":\"text\",\"text\":\"Current timestamp: %ld\"}]}",
+      (long)now);
+  } else if (strcmp(tool_name, "get_counter") == 0) {
+    uint32_t val = ++counter;
+    snprintf(result, sizeof(result),
+      "{\"content\":[{\"type\":\"text\",\"text\":\"Counter value: %u\"}]}",
+      val);
+  } else {
+    build_error(out, size, id, -32601, "Unknown tool");
+    return;
+  }
+
+  build_response(out, size, id, result);
+}
+
+Seobeo_Request_Entry* HandleMCP(Seobeo_Request_Entry *req, Dowa_Arena *arena)
+{
+  Seobeo_Request_Entry *resp = NULL;
+
+  void *body_kv = Dowa_HashMap_Get_Ptr(req, "Body");
+  if (!body_kv)
+  {
+    char *err = "{\"jsonrpc\":\"2.0\",\"id\":null,\"error\":{\"code\":-32700,\"message\":\"No body\"}}";
+    Dowa_HashMap_Push_Arena(resp, "status", "400", arena);
+    Dowa_HashMap_Push_Arena(resp, "content-type", "application/json", arena);
+    Dowa_HashMap_Push_Arena(resp, "body", err, arena);
+    return resp;
+  }
+
+  const char *body = ((Seobeo_Request_Entry*)body_kv)->value;
+  int32 body_len = strlen(body);
+
+  Dowa_JSON_Value parsed = Dowa_JSON_Parse(body, body_len, arena);
+  if (parsed.type != DOWA_JSON_OBJECT || !parsed.object_val)
+  {
+    char *err = "{\"jsonrpc\":\"2.0\",\"id\":null,\"error\":{\"code\":-32700,\"message\":\"Parse error\"}}";
+    Dowa_HashMap_Push_Arena(resp, "status", "400", arena);
+    Dowa_HashMap_Push_Arena(resp, "content-type", "application/json", arena);
+    Dowa_HashMap_Push_Arena(resp, "body", err, arena);
+    return resp;
+  }
+
+  Dowa_JSON_Entry *json = (Dowa_JSON_Entry *)parsed.object_val;
+  char *method = Dowa_JSON_Get_String(json, "method");
+  Dowa_JSON_Value *id_val = Dowa_JSON_Get(json, "id");
+  char id_buf[32] = "null";
+  if (id_val)
+  {
+    if (id_val->type == DOWA_JSON_NUMBER)
+      snprintf(id_buf, sizeof(id_buf), "%.0f", id_val->num_val);
+    else if (id_val->type == DOWA_JSON_STRING)
+      snprintf(id_buf, sizeof(id_buf), "\"%s\"", id_val->str_val);
+  }
+
+  char *response = Dowa_Arena_Allocate(arena, 2048);
+
+  if (!method)
+    build_error(response, 2048, id_buf, -32600, "Missing method");
+  else if (strcmp(method, "initialize") == 0)
+    handle_initialize(response, 2048, id_buf);
+  else if (strcmp(method, "tools/list") == 0)
+    handle_tools_list(response, 2048, id_buf);
+  else if (strcmp(method, "tools/call") == 0)
+    handle_tools_call(response, 2048, id_buf, json);
+  else if (strcmp(method, "notifications/initialized") == 0)
+    snprintf(response, 2048, "{\"jsonrpc\":\"2.0\",\"id\":%s,\"result\":{}}", id_buf);
+  else
+    build_error(response, 2048, id_buf, -32601, "Method not found");
+
+  Dowa_HashMap_Push_Arena(resp, "status", "200", arena);
+  Dowa_HashMap_Push_Arena(resp, "content-type", "application/json", arena);
+  Dowa_HashMap_Push_Arena(resp, "body", response, arena);
+  return resp;
+}
+
+int main(void) {
+  Seobeo_Router_Init();
+  Seobeo_Router_Register("POST", "/mcp", HandleMCP);
+
+  Seobeo_Log(SEOBEO_INFO, "MCP server running on http://localhost:8080/mcp\n");
+  Seobeo_Web_Server_Start(NULL, "8080", SEOBEO_MODE_FORK, 0);
+  return 0;
+}