OTA updates (#96)

## Summary

* Adds support for OTA
  * Gets latest firmware bin from latest GitHub release
* I have noticed it be a little flaky unpacking the JSON and
occasionally failing to start

src/network/OtaUpdater.cpp

@@ -0,0 +1,169 @@
+#include "OtaUpdater.h"
+
+#include <ArduinoJson.h>
+#include <HTTPClient.h>
+#include <Update.h>
+#include <WiFiClientSecure.h>
+
+namespace {
+constexpr char latestReleaseUrl[] = "https://api.github.com/repos/daveallie/crosspoint-reader/releases/latest";
+}
+
+OtaUpdater::OtaUpdaterError OtaUpdater::checkForUpdate() {
+  const std::unique_ptr<WiFiClientSecure> client(new WiFiClientSecure);
+  client->setInsecure();
+  HTTPClient http;
+
+  Serial.printf("[%lu] [OTA] Fetching: %s\n", millis(), latestReleaseUrl);
+
+  http.begin(*client, latestReleaseUrl);
+  http.addHeader("User-Agent", "CrossPoint-ESP32-" CROSSPOINT_VERSION);
+
+  const int httpCode = http.GET();
+  if (httpCode != HTTP_CODE_OK) {
+    Serial.printf("[%lu] [OTA] HTTP error: %d\n", millis(), httpCode);
+    http.end();
+    return HTTP_ERROR;
+  }
+
+  JsonDocument doc;
+  const DeserializationError error = deserializeJson(doc, *client);
+  http.end();
+  if (error) {
+    Serial.printf("[%lu] [OTA] JSON parse failed: %s\n", millis(), error.c_str());
+    return JSON_PARSE_ERROR;
+  }
+
+  if (!doc["tag_name"].is<std::string>()) {
+    Serial.printf("[%lu] [OTA] No tag_name found\n", millis());
+    return JSON_PARSE_ERROR;
+  }
+  if (!doc["assets"].is<JsonArray>()) {
+    Serial.printf("[%lu] [OTA] No assets found\n", millis());
+    return JSON_PARSE_ERROR;
+  }
+
+  latestVersion = doc["tag_name"].as<std::string>();
+
+  for (int i = 0; i < doc["assets"].size(); i++) {
+    if (doc["assets"][i]["name"] == "firmware.bin") {
+      otaUrl = doc["assets"][i]["browser_download_url"].as<std::string>();
+      otaSize = doc["assets"][i]["size"].as<size_t>();
+      totalSize = otaSize;
+      updateAvailable = true;
+      break;
+    }
+  }
+
+  if (!updateAvailable) {
+    Serial.printf("[%lu] [OTA] No firmware.bin asset found\n", millis());
+    return NO_UPDATE;
+  }
+
+  Serial.printf("[%lu] [OTA] Found update: %s\n", millis(), latestVersion.c_str());
+  return OK;
+}
+
+bool OtaUpdater::isUpdateNewer() {
+  if (!updateAvailable || latestVersion.empty() || latestVersion == CROSSPOINT_VERSION) {
+    return false;
+  }
+
+  // semantic version check (only match on 3 segments)
+  const auto updateMajor = stoi(latestVersion.substr(0, latestVersion.find('.')));
+  const auto updateMinor = stoi(
+      latestVersion.substr(latestVersion.find('.') + 1, latestVersion.find_last_of('.') - latestVersion.find('.') - 1));
+  const auto updatePatch = stoi(latestVersion.substr(latestVersion.find_last_of('.') + 1));
+
+  std::string currentVersion = CROSSPOINT_VERSION;
+  const auto currentMajor = stoi(currentVersion.substr(0, currentVersion.find('.')));
+  const auto currentMinor = stoi(currentVersion.substr(
+      currentVersion.find('.') + 1, currentVersion.find_last_of('.') - currentVersion.find('.') - 1));
+  const auto currentPatch = stoi(currentVersion.substr(currentVersion.find_last_of('.') + 1));
+
+  if (updateMajor > currentMajor) {
+    return true;
+  }
+  if (updateMajor < currentMajor) {
+    return false;
+  }
+
+  if (updateMinor > currentMinor) {
+    return true;
+  }
+  if (updateMinor < currentMinor) {
+    return false;
+  }
+
+  if (updatePatch > currentPatch) {
+    return true;
+  }
+  return false;
+}
+
+const std::string& OtaUpdater::getLatestVersion() { return latestVersion; }
+
+OtaUpdater::OtaUpdaterError OtaUpdater::installUpdate(const std::function<void(size_t, size_t)>& onProgress) {
+  if (!isUpdateNewer()) {
+    return UPDATE_OLDER_ERROR;
+  }
+
+  const std::unique_ptr<WiFiClientSecure> client(new WiFiClientSecure);
+  client->setInsecure();
+  HTTPClient http;
+
+  Serial.printf("[%lu] [OTA] Fetching: %s\n", millis(), otaUrl.c_str());
+
+  http.begin(*client, otaUrl.c_str());
+  http.setFollowRedirects(HTTPC_STRICT_FOLLOW_REDIRECTS);
+  http.addHeader("User-Agent", "CrossPoint-ESP32-" CROSSPOINT_VERSION);
+  const int httpCode = http.GET();
+
+  if (httpCode != HTTP_CODE_OK) {
+    Serial.printf("[%lu] [OTA] Download failed: %d\n", millis(), httpCode);
+    http.end();
+    return HTTP_ERROR;
+  }
+
+  // 2. Get length and stream
+  const size_t contentLength = http.getSize();
+
+  if (contentLength != otaSize) {
+    Serial.printf("[%lu] [OTA] Invalid content length\n", millis());
+    http.end();
+    return HTTP_ERROR;
+  }
+
+  // 3. Begin the ESP-IDF Update process
+  if (!Update.begin(otaSize)) {
+    Serial.printf("[%lu] [OTA] Not enough space. Error: %s\n", millis(), Update.errorString());
+    http.end();
+    return INTERNAL_UPDATE_ERROR;
+  }
+
+  this->totalSize = otaSize;
+  Serial.printf("[%lu] [OTA] Update started\n", millis());
+  Update.onProgress([this, onProgress](const size_t progress, const size_t total) {
+    this->processedSize = progress;
+    this->totalSize = total;
+    onProgress(progress, total);
+  });
+  const size_t written = Update.writeStream(*client);
+  http.end();
+
+  if (written == otaSize) {
+    Serial.printf("[%lu] [OTA] Successfully written %u bytes\n", millis(), written);
+  } else {
+    Serial.printf("[%lu] [OTA] Written only %u/%u bytes. Error: %s\n", millis(), written, otaSize,
+                  Update.errorString());
+    return INTERNAL_UPDATE_ERROR;
+  }
+
+  if (Update.end() && Update.isFinished()) {
+    Serial.printf("[%lu] [OTA] Update complete\n", millis());
+    return OK;
+  } else {
+    Serial.printf("[%lu] [OTA] Error Occurred: %s\n", millis(), Update.errorString());
+    return INTERNAL_UPDATE_ERROR;
+  }
+}

src/network/OtaUpdater.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <functional>
+#include <string>
+
+class OtaUpdater {
+  bool updateAvailable = false;
+  std::string latestVersion;
+  std::string otaUrl;
+  size_t otaSize = 0;
+
+ public:
+  enum OtaUpdaterError {
+    OK = 0,
+    NO_UPDATE,
+    HTTP_ERROR,
+    JSON_PARSE_ERROR,
+    UPDATE_OLDER_ERROR,
+    INTERNAL_UPDATE_ERROR,
+    OOM_ERROR,
+  };
+  size_t processedSize = 0;
+  size_t totalSize = 0;
+
+  OtaUpdater() = default;
+  bool isUpdateNewer();
+  const std::string& getLatestVersion();
+  OtaUpdaterError checkForUpdate();
+  OtaUpdaterError installUpdate(const std::function<void(size_t, size_t)>& onProgress);
+};