From 9dc2947c084e4eaddd9185f5ba70dbf18a6f9bd7 Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Sat, 21 Sep 2024 18:06:12 -0400
Subject: [PATCH] Using an FSM to keep the server straight and detect errors in
 it.

---
 main.cpp | 111 +++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 91 insertions(+), 20 deletions(-)

diff --git a/main.cpp b/main.cpp
index 8142423..abfc11b 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,45 +1,116 @@
+#define FSM_DEBUG 1
 #include <fmt/core.h>
 #include <nlohmann/json.hpp>
 #include <fstream>
 #include "dbc.hpp"
+#include "fsm.hpp"
 
 #define BUF_MAX 1024 * 10
 using namespace fmt;
 using namespace nlohmann;
 
-FILE *run_ffmpeg(const string listen_at, const string bitrate, const string send_to) {
+struct Config {
+  json json_config;
+  string listen_at = "";
+  string bitrate = "";
+  string send_to = "";
+
+  Config(const string json_file) {
+    load(json_file);
+  }
+
+  void load(const string file_name) {
+    std::ifstream infile(file_name);
+    json_config = json::parse(infile);
+
+    listen_at = json_config["listen_at"].template get<string>();
+    bitrate = json_config["bitrate"].template get<string>();
+    send_to = json_config["send_to"].template get<string>();
+  }
+};
+
+FILE *run_ffmpeg(Config &config) {
   string ffmpeg_cmd = format("ffmpeg -listen 1 -i {} -bufsize 3000k  -maxrate {} -flags +global_header  -c:v libx264  -preset veryfast -tune zerolatency  -g:v 60  -vb {} -c:a copy -f flv {}",
-      listen_at, bitrate, bitrate, send_to);
+      config.listen_at,
+      config.bitrate,
+      config.bitrate,
+      config.send_to);
 
   println("RUNNING: {}", ffmpeg_cmd);
 
-  FILE *handle = popen(ffmpeg_cmd.c_str(), "r");
-  dbc::check(handle != nullptr, "failed to start ffmpeg");
-  return handle;
+  return popen(ffmpeg_cmd.c_str(), "r");
 }
 
-json load_config(const string file_name) {
-  std::ifstream infile(file_name);
-  return json::parse(infile);
-}
 
-int main() {
+enum class ServerState {
+  START, READING, STOP, ERROR
+};
+
+enum class ServerEvent {
+  GO
+};
+
+class Server : DeadSimpleFSM<ServerState, ServerEvent> {
+  Config &config;
   FILE *handle = nullptr;
   char buffer[BUF_MAX];
   char *res = nullptr;
-  json config = load_config("config.json");
 
-  const string listen_at = config["listen_at"].template get<string>();
-  const string bitrate = config["bitrate"].template get<string>();
-  const string send_to = config["send_to"].template get<string>();
+public:
 
-  handle = run_ffmpeg(listen_at, bitrate, send_to);
+  Server(Config &config) : config(config) {};
 
-  do {
+  bool stopped() {
+    return in_state(ServerState::STOP) || in_state(ServerState::ERROR);
+  }
+
+  void event(ServerEvent ev) {
+    switch(_state) {
+      FSM_STATE(ServerState, START, ev);
+      FSM_STATE(ServerState, READING, ev);
+      FSM_STATE(ServerState, STOP, ev);
+      FSM_STATE(ServerState, ERROR, ev);
+    }
+  }
+
+  void START(ServerEvent ev) {
+    handle = run_ffmpeg(config);
+    if(handle == nullptr) {
+      state(ServerState::ERROR);
+    } else {
+      state(ServerState::READING);
+    }
+  }
+
+  void READING(ServerEvent ev) {
     res = fgets(buffer, BUF_MAX, handle);
-    print("OUT: {}", res);
-  } while(res != nullptr);
 
-  int rc = pclose(handle);
-  dbc::check(rc == 0, "error closing ffmpeg");
+    if(res == nullptr) {
+      state(ServerState::STOP);
+    } else {
+      state(ServerState::READING);
+    }
+  }
+
+  void STOP(ServerEvent ev) {
+    int rc = pclose(handle);
+    if(rc != 0) {
+      state(ServerState::ERROR);
+    } else {
+      state(ServerState::STOP);
+    }
+  }
+
+  void ERROR(ServerEvent ev) {
+    state(ServerState::ERROR);
+  }
+};
+
+int main() {
+  Config config("config.json");
+  Server server(config);
+
+  while(!server.stopped()) {
+    server.event(ServerEvent::GO);
+  }
 }