Extract current time from HTTP responses and keep track of it

firmware/Cargo.toml

@@ -44,6 +44,7 @@ overflow-checks = false
 git2 = { version = "0.19", default-features = false }
 
 [dependencies]
+chrono = { version = "0.4", default-features = false, features = ["alloc"] }
 display-interface = "0.5"
 embassy-embedded-hal = "0.2"
 embassy-executor = "0.6"

firmware/src/http.rs

@@ -1,8 +1,10 @@
 use crate::json::{self, FromJson, ToJson};
+use crate::time;
 use crate::wifi::{DnsSocket, TcpClient, TcpConnection, Wifi};
 use alloc::vec::Vec;
+use chrono::{DateTime, Utc};
 use core::convert::Infallible;
-use core::fmt;
+use core::{fmt, str};
 use embedded_io_async::{BufRead, Read};
 use log::debug;
 use reqwless::client::{HttpClient, HttpResource, HttpResourceRequestBuilder};
@@ -212,6 +214,18 @@ impl<'a> Connection<'a> {
         let response = request.send(rx_buf).await?;
         debug!("HTTP: Status {}", response.status.0);
 
+        // Extract current date and time from response
+        let time = response
+            .headers()
+            .find_map(|(k, v)| (k == "Date").then_some(v))
+            .and_then(|v| str::from_utf8(v).ok())
+            .and_then(|s| DateTime::parse_from_rfc2822(s).ok())
+            .map(|d| d.with_timezone(&Utc));
+        if let Some(time) = time {
+            time::set(time);
+        }
+
+        // Check HTTP response status
         if response.status.0 == 401 {
             return Err(Error::Unauthorized);
         } else if response.status.is_server_error() {

firmware/src/main.rs

@@ -50,6 +50,7 @@ mod keypad;
 mod nfc;
 mod pn532;
 mod screen;
+mod time;
 mod ui;
 mod user;
 mod vereinsflieger;

firmware/src/time.rs

@@ -0,0 +1,44 @@
+use chrono::{DateTime, TimeDelta, Utc};
+use core::cell::RefCell;
+use embassy_sync::blocking_mutex::CriticalSectionMutex;
+use log::debug;
+
+/// Calculated time of system start
+static SYSTEM_START_TIME: CriticalSectionMutex<RefCell<Option<DateTime<Utc>>>> =
+    CriticalSectionMutex::new(RefCell::new(None));
+
+/// Time of system start
+fn start_time() -> Option<DateTime<Utc>> {
+    SYSTEM_START_TIME.lock(|sst| *sst.borrow())
+}
+
+/// Set time of system start
+fn set_start_time(time: DateTime<Utc>) {
+    SYSTEM_START_TIME.lock(|sst| {
+        *sst.borrow_mut() = Some(time);
+    });
+}
+
+/// Duration of system run time
+pub fn uptime() -> Option<TimeDelta> {
+    let millis = esp_hal::time::now().duration_since_epoch().to_millis();
+    TimeDelta::try_milliseconds(i64::try_from(millis).ok()?)
+}
+
+/// Current time
+#[allow(dead_code)]
+pub fn now() -> Option<DateTime<Utc>> {
+    if let (Some(start_time), Some(uptime)) = (start_time(), uptime()) {
+        Some(start_time + uptime)
+    } else {
+        None
+    }
+}
+
+/// Set current time by using the given current time to calculate the time of system start
+pub fn set(now: DateTime<Utc>) {
+    if let Some(uptime) = uptime() {
+        set_start_time(now - uptime);
+        debug!("Time: Current time set to {}", now);
+    }
+}