add an option to specify local timezone

src/calendar.rs

@@ -7,7 +7,6 @@ use std::fmt;
 pub enum CalendarError {
     UnknownTimezone(String),
     WrongTimeFormat,
-    WrongDateFormat,
     TimezoneConversionFailed(String),
 }
 
@@ -16,7 +15,6 @@ impl fmt::Display for CalendarError {
         let message = match *self {
             Self::UnknownTimezone(ref tz) => format!("Unknown timezone: {}", tz),
             Self::WrongTimeFormat => "Wrong time format".to_string(),
-            Self::WrongDateFormat => "Wrong date format".to_string(),
             Self::TimezoneConversionFailed(ref tz) => {
                 format!("Could not convert time to timezone: {}", tz)
             }
@@ -28,6 +26,11 @@ impl fmt::Display for CalendarError {
 
 impl Error for CalendarError {}
 
+pub struct SimpleTimezone {
+    pub name: String,
+    pub offset: FixedOffset,
+}
+
 fn create_calendar_strings(time: &NaiveTime, padding_hrs: i8) -> Vec<String> {
     let start = -padding_hrs;
     let end = padding_hrs;
@@ -37,32 +40,61 @@ fn create_calendar_strings(time: &NaiveTime, padding_hrs: i8) -> Vec<String> {
         .collect()
 }
 
+pub fn get_local_timezone_offset(
+    time: &NaiveTime,
+    timezone: &String,
+) -> Result<SimpleTimezone, CalendarError> {
+    if timezone == "Local" {
+        Ok(SimpleTimezone {
+            name: "Local".to_string(),
+            offset: Local::now()
+                .with_time(time.clone())
+                .single()
+                .ok_or(CalendarError::WrongTimeFormat)?
+                .offset()
+                .clone(),
+        })
+    } else {
+        let offset = timezone
+            .parse::<Tz>()
+            .map_err(|_| CalendarError::UnknownTimezone(timezone.to_string()))?
+            .offset_from_utc_datetime(&Utc::now().naive_utc());
+
+        Ok(SimpleTimezone {
+            name: timezone.to_string(),
+            offset: offset.fix(),
+        })
+    }
+}
+
 pub fn create_timetable(
-    target_time: &String,
+    target_time: &NaiveTime,
-    target_date: &String,
+    target_date: &NaiveDate,
+    local_timezone: &FixedOffset,
     in_timezone: &String,
     padding_hrs: i8,
 ) -> Result<Vec<String>, CalendarError> {
+    let datetime = local_timezone.from_local_datetime(&NaiveDateTime::new(
+        target_date.clone(),
+        target_time.clone(),
+    ));
+    let time_in_timezone = if in_timezone == "Local" {
+        Local::now()
+            .with_time(target_time.clone())
+            .single()
+            .ok_or(CalendarError::WrongTimeFormat)?
+            .naive_local()
+    } else {
         let parsed_timezone = in_timezone
             .parse::<Tz>()
             .map_err(|_| CalendarError::UnknownTimezone(in_timezone.clone()))?;
 
-    let parsed_time = if let Ok(hour) = target_time.parse::<u32>() {
+        datetime
-        NaiveTime::from_hms_opt(hour, 0, 0).ok_or(CalendarError::WrongTimeFormat)?
-    } else {
-        NaiveTime::parse_from_str(target_time, "%H:%M")
-            .map_err(|_| CalendarError::WrongTimeFormat)?
-    };
-
-    let parsed_date = NaiveDate::parse_from_str(target_date, "%d-%m-%Y")
-        .or_else(|_| NaiveDate::parse_from_str(target_date, "%d-%m"))
-        .map_err(|_| CalendarError::WrongDateFormat)?;
-
-    let datetime = Local.from_local_datetime(&NaiveDateTime::new(parsed_date, parsed_time));
-    let time_in_timezone = datetime
             .single()
             .ok_or(CalendarError::TimezoneConversionFailed(in_timezone.clone()))?
-        .with_timezone(&parsed_timezone);
+            .with_timezone(&parsed_timezone)
+            .naive_local()
+    };
 
     Ok(create_calendar_strings(
         &time_in_timezone.time(),

src/cli.rs

@@ -1,5 +1,13 @@
-use super::calendar::create_timetable;
+use crate::calendar::CalendarError;
+
+use super::calendar::{create_timetable, get_local_timezone_offset, get_todays_date};
+
+use chrono::NaiveDate;
+use chrono::NaiveTime;
 use clap::Parser;
+use std::error::Error;
+use std::fmt;
+use std::iter;
 
 #[derive(Parser, Debug)]
 #[command(version, about, long_about = None)]
@@ -10,19 +18,78 @@ pub struct Args {
     #[arg(short, long)]
     pub date: Option<String>,
 
+    #[arg(short, long, default_value = "Local")]
+    pub local: String,
+
     pub time: String,
 }
 
-pub fn print_timezones(timezones: &Vec<String>, time: &String, date: &String) {
+#[derive(PartialEq, Debug)]
-    let max_len = timezones.iter().map(|t| t.len()).max().unwrap_or(0) as u32;
+pub enum CliError {
-    for timezone in timezones {
+    CouldNotParseTime,
+    CouldNotParseDate,
+    CouldNoGenerateTimetable(CalendarError),
+}
+
+impl fmt::Display for CliError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let message = match *self {
+            Self::CouldNotParseTime => "Couldn't parse time".to_string(),
+            Self::CouldNotParseDate => "Couldn't parse date".to_string(),
+            Self::CouldNoGenerateTimetable(ref er) => {
+                format!("Could not generate timetable: {}", er)
+            }
+        };
+
+        f.write_str(&message)
+    }
+}
+
+impl Error for CliError {}
+
+pub fn print_timezones(
+    timezones: &Vec<String>,
+    time: &String,
+    date: Option<&String>,
+    local_timezone: &String,
+) -> Result<(), CliError> {
+    let todays_date = &get_todays_date();
+    let date = date.unwrap_or(todays_date);
+
+    let parsed_time = if let Ok(hour) = time.parse::<u32>() {
+        NaiveTime::from_hms_opt(hour, 0, 0).ok_or(CliError::CouldNotParseTime)?
+    } else {
+        NaiveTime::parse_from_str(time, "%H:%M").map_err(|_| CliError::CouldNotParseTime)?
+    };
+
+    let parsed_date = NaiveDate::parse_from_str(date, "%d-%m-%Y")
+        .or_else(|_| NaiveDate::parse_from_str(date, "%d-%m"))
+        .map_err(|_| CliError::CouldNotParseDate)?;
+
+    let local_timezone_offset = &get_local_timezone_offset(&parsed_time, local_timezone)
+        .map_err(|e| CliError::CouldNoGenerateTimetable(e))?;
+
+    let all_timezones: Vec<&String> = iter::once(&local_timezone_offset.name)
+        .chain(timezones)
+        .collect();
+
+    let max_len = all_timezones.iter().map(|t| t.len()).max().unwrap_or(0) as u32;
+
+    for timezone in all_timezones {
         let name_padding = (0..(max_len - timezone.len() as u32))
             .map(|_| " ".to_string())
             .collect::<Vec<String>>()
             .join("");
-        match create_timetable(time, date, timezone, 5) {
+        match create_timetable(
+            &parsed_time,
+            &parsed_date,
+            &local_timezone_offset.offset,
+            timezone,
+            5,
+        ) {
             Ok(timetable) => println!("{}:{}\t{}", timezone, name_padding, timetable.join("\t")),
             Err(error) => panic!("Failed: {}", error),
         }
     }
+    Ok(())
 }

src/main.rs

@@ -1,7 +1,6 @@
 mod calendar;
 mod cli;
 
-use calendar::get_todays_date;
 use clap::Parser;
 use cli::{Args, print_timezones};
 
@@ -9,7 +8,10 @@ fn main() {
     let args = Args::parse();
 
     if args.timezone.len() > 0 {
-        let date = args.date.unwrap_or(get_todays_date());
+        let res = print_timezones(&args.timezone, &args.time, args.date.as_ref(), &args.local);
-        print_timezones(&args.timezone, &args.time, &date);
+
+        if let Err(error) = res {
+            println!("Error: {}", error);
+        }
     }
 }