feat: Implement the prompt module for time (#138)

Add a module which displays the current time in a format requested by
the user. Disabled by default.

src/module.rs

@@ -24,6 +24,7 @@ pub const ALL_MODULES: &[&str] = &[
     "python",
     "ruby",
     "rust",
+    "time",
     "username",
 ];
 

src/modules/mod.rs

@@ -15,6 +15,7 @@ mod package;
 mod python;
 mod ruby;
 mod rust;
+mod time;
 mod username;
 
 #[cfg(feature = "battery")]
@@ -44,6 +45,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
         "jobs" => jobs::module(context),
         "nix_shell" => nix_shell::module(context),
         "hostname" => hostname::module(context),
+        "time" => time::module(context),
 
         _ => {
             eprintln!("Error: Unknown module {}. Use starship module --list to list out all supported modules.", module);

src/modules/time.rs

@@ -0,0 +1,105 @@
+use ansi_term::Color;
+use chrono::offset::TimeZone;
+use chrono::{DateTime, Local};
+
+use super::{Context, Module};
+
+/// Outputs the current time
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("time");
+
+    // Remove when logic for disabled by default exists
+    if module.config_value_bool("disabled").unwrap_or(true) {
+        return None;
+    }
+
+    let module_style = module
+        .config_value_style("style")
+        .unwrap_or_else(|| Color::Yellow.bold());
+    module.set_style(module_style);
+
+    // Load module settings
+    let is_12hr = module.config_value_bool("12hr").unwrap_or(false);
+
+    let default_format = if is_12hr { "%r" } else { "%T" };
+    let time_format = module
+        .config_value_str("format")
+        .unwrap_or(default_format)
+        .to_owned();
+
+    log::trace!(
+        "Timer module is enabled with format string: {}",
+        time_format
+    );
+
+    let local: DateTime<Local> = Local::now();
+    let formatted_time_string = format_time(&time_format, local);
+    module.new_segment("time", &formatted_time_string);
+    module.get_prefix().set_value("at ");
+
+    Some(module)
+}
+
+/// Format a given time into the given string. This function should be referentially
+/// transparent, which makes it easy to test (unlike anything involving the actual time)
+fn format_time(time_format: &str, localtime: DateTime<Local>) -> String {
+    localtime.format(time_format).to_string()
+}
+
+/* Because we cannot do integration tests on the time module, these unit
+tests become extra important */
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const FMT_12: &str = "%r";
+    const FMT_24: &str = "%T";
+
+    #[test]
+    fn test_midnight_12hr() {
+        let time = Local.ymd(2014, 7, 8).and_hms(0, 0, 0);
+        let formatted = format_time(FMT_12, time);
+        assert_eq!(formatted, "12:00:00 AM");
+    }
+
+    #[test]
+    fn test_midnight_24hr() {
+        let time = Local.ymd(2014, 7, 8).and_hms(0, 0, 0);
+        let formatted = format_time(FMT_24, time);
+        assert_eq!(formatted, "00:00:00");
+    }
+
+    #[test]
+    fn test_noon_12hr() {
+        let time = Local.ymd(2014, 7, 8).and_hms(12, 0, 0);
+        let formatted = format_time(FMT_12, time);
+        assert_eq!(formatted, "12:00:00 PM");
+    }
+
+    #[test]
+    fn test_noon_24hr() {
+        let time = Local.ymd(2014, 7, 8).and_hms(12, 0, 0);
+        let formatted = format_time(FMT_24, time);
+        assert_eq!(formatted, "12:00:00");
+    }
+
+    #[test]
+    fn test_arbtime_12hr() {
+        let time = Local.ymd(2014, 7, 8).and_hms(15, 36, 47);
+        let formatted = format_time(FMT_12, time);
+        assert_eq!(formatted, "03:36:47 PM");
+    }
+
+    #[test]
+    fn test_arbtime_24hr() {
+        let time = Local.ymd(2014, 7, 8).and_hms(15, 36, 47);
+        let formatted = format_time(FMT_24, time);
+        assert_eq!(formatted, "15:36:47");
+    }
+
+    fn test_format_with_paren() {
+        let time = Local.ymd(2014, 7, 8).and_hms(15, 36, 47);
+        let formatted = format_time("[%T]", time);
+        assert_eq!(formatted, "[15:36:47]");
+    }
+}

src/print.rs

@@ -29,7 +29,7 @@ const DEFAULT_PROMPT_ORDER: &[&str] = &[
     "line_break",
     "jobs",
     #[cfg(feature = "battery")]
-    "battery",
+    "time",
     "character",
 ];