history with relative time

1 files changed, 113 insertions, 0 deletions

diff --git a/src/date.rs b/src/date.rs
new file mode 100644
index 0000000..149dc79
--- /dev/null
+++ b/src/date.rs
@@ -0,0 +1,113 @@
+use core::fmt;
+use std::{
+    process::Command,
+    time::{Duration, SystemTime},
+};
+
+use crate::BString;
+
+#[derive(Clone)]
+pub struct DateTime {
+    sys: SystemTime,
+}
+
+impl DateTime {
+    pub fn from_unix(unix: u64) -> Self {
+        Self {
+            sys: SystemTime::UNIX_EPOCH + Duration::from_secs(unix),
+        }
+    }
+    pub fn now() -> Self {
+        Self {
+            sys: SystemTime::now(),
+        }
+    }
+    fn format(&self) -> std::io::Result<BString> {
+        let mut out = Command::new("date")
+            .arg("-d")
+            .arg(format!(
+                "@{}",
+                self.sys
+                    .duration_since(SystemTime::UNIX_EPOCH)
+                    .unwrap()
+                    .as_secs()
+            ))
+            .output()?
+            .stdout;
+        while let Some(x) = out.last()
+            && x.is_ascii_whitespace()
+        {
+            out.pop();
+        }
+        Ok(out)
+    }
+
+    fn unix(&self) -> u64 {
+        self.sys
+            .duration_since(SystemTime::UNIX_EPOCH)
+            .unwrap()
+            .as_secs()
+    }
+
+    pub fn relative_to(&self, other: &Self) -> String {
+        let a = self.unix();
+        let b = other.unix();
+
+        let (pre, post, mut diff) = if a < b {
+            ("in ", "", b - a)
+        } else {
+            ("", " ago", a - b)
+        };
+
+        let unit = if diff < 60 {
+            "s"
+        } else if {
+            diff /= 60;
+            diff < 60
+        } {
+            "m"
+        } else if {
+            diff /= 60;
+            diff < 24
+        } {
+            "h"
+        } else if {
+            diff /= 24;
+            diff < 365
+        } {
+            "d"
+        } else {
+            diff /= 365;
+            "y"
+        };
+
+        format!("{pre}{diff}{unit}{post}")
+    }
+
+    pub const fn longest_reasonable_delta() -> usize {
+        7
+    }
+}
+
+#[test]
+fn long_delta() {
+    assert_eq!(
+        DateTime::now()
+            .relative_to(&DateTime {
+                // 30 years ago
+                sys: SystemTime::now() - Duration::from_secs(60 * 60 * 24 * 365 * 30)
+            })
+            .len(),
+        DateTime::longest_reasonable_delta()
+    );
+}
+
+impl fmt::Display for DateTime {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{}",
+            String::from_utf8_lossy(&self.format().unwrap_or_else(|_| Vec::new()))
+        )
+    }
+}