implement the month command

src/commands/month.rs

@@ -1,8 +1,9 @@
 use std::convert::TryFrom;
 use std::io::Write;
+use std::str::FromStr;
 
 use clap::ArgMatches;
-use chrono::{DateTime, Utc, Local, Datelike};
+use chrono::{DateTime, Utc, Local, Datelike, TimeZone};
 use regex::Regex;
 
 use crate::error::{Result, Error};
@@ -10,19 +11,64 @@ use crate::database::Database;
 use crate::formatters::Formatter;
 use crate::config::Config;
 use crate::regex::parse_regex;
-use crate::timeparse::parse_time;
 
 use super::{Command, display::{Sheet, entries_for_display}};
 
-/// Given a local datetime, returns the time of the previous monday's start
-fn beginning_of_month(now: DateTime<Local>) -> DateTime<Utc> {
-    now.date().with_day(1).unwrap().and_hms(0, 0, 0).with_timezone(&Utc)
+/// Given a local datetime, returns the time when the month it belongs started
+fn beginning_of_month(time: DateTime<Local>) -> DateTime<Utc> {
+    time.date().with_day(1).unwrap().and_hms(0, 0, 0).with_timezone(&Utc)
+}
+
+/// Given a datetime compute the time where the previous_month started in UTC
+fn beginning_of_previous_month(time: DateTime<Local>) -> DateTime<Utc> {
+    match time.month() {
+        1 => {
+            Local.ymd(time.year()-1, 12, 1).and_hms(0, 0, 0).with_timezone(&Utc)
+        }
+        n => Local.ymd(time.year(), n-1, 1).and_hms(0, 0, 0).with_timezone(&Utc)
+    }
+}
+
+enum MonthSpec {
+    Last,
+    This,
+    Month(u32),
+}
+
+impl Default for MonthSpec {
+    fn default() -> MonthSpec {
+        MonthSpec::This
+    }
+}
+
+impl FromStr for MonthSpec {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<MonthSpec> {
+        match s.trim().to_lowercase().as_str() {
+            "this" => Ok(MonthSpec::This),
+            "last" => Ok(MonthSpec::Last),
+            "jan" | "january" => Ok(MonthSpec::Month(1)),
+            "feb" | "february" => Ok(MonthSpec::Month(2)),
+            "mar" | "march" => Ok(MonthSpec::Month(3)),
+            "apr" | "april" => Ok(MonthSpec::Month(4)),
+            "may" => Ok(MonthSpec::Month(5)),
+            "jun" | "june" => Ok(MonthSpec::Month(6)),
+            "jul" | "july" => Ok(MonthSpec::Month(7)),
+            "aug" | "august" => Ok(MonthSpec::Month(8)),
+            "sep" | "september" => Ok(MonthSpec::Month(9)),
+            "oct" | "october" => Ok(MonthSpec::Month(10)),
+            "nov" | "november" => Ok(MonthSpec::Month(11)),
+            "dic" | "december" => Ok(MonthSpec::Month(12)),
+            _ => Err(Error::InvalidMonthSpec(s.into())),
+        }
+    }
 }
 
 #[derive(Default)]
 pub struct Args {
     ids: bool,
-    end: Option<DateTime<Utc>>,
+    month: MonthSpec,
     format: Formatter,
     grep: Option<Regex>,
     sheet: Option<Sheet>,
@@ -34,7 +80,7 @@ impl<'a> TryFrom<&'a ArgMatches<'a>> for Args {
     fn try_from(matches: &'a ArgMatches) -> Result<Args> {
         Ok(Args {
             ids: matches.is_present("ids"),
-            end: matches.value_of("end").map(|s| parse_time(s)).transpose()?,
+            month: matches.value_of("month").map(|s| s.parse()).transpose()?.unwrap_or(MonthSpec::This),
             format: matches.value_of("format").unwrap().parse()?,
             grep: matches.value_of("grep").map(parse_regex).transpose()?,
             sheet: matches.value_of("sheet").map(|s| s.parse()).transpose()?,
@@ -53,8 +99,38 @@ impl<'a> Command<'a> for MonthCommand {
         O: Write,
         E: Write,
     {
-        let start = beginning_of_month(Local::now());
+        let now = Local::now();
 
-        entries_for_display(Some(start), args.end, args.sheet, db, out, err, args.format, args.ids, args.grep)
+        let (start, end) = match args.month {
+            MonthSpec::This => (beginning_of_month(now), Utc::now()),
+            MonthSpec::Last => {
+                (beginning_of_previous_month(now), beginning_of_month(now))
+            },
+            MonthSpec::Month(month) => {
+                if month < now.month() {
+                    // the specified month is in the current year
+                    (
+                        Local.ymd(now.year(), month, 1).and_hms(0, 0, 0).with_timezone(&Utc),
+                        if month < 12 {
+                            Local.ymd(now.year(), month+1, 1).and_hms(0, 0, 0).with_timezone(&Utc)
+                        } else {
+                            Local.ymd(now.year()+1, 1, 1).and_hms(0, 0, 0).with_timezone(&Utc)
+                        }
+                    )
+                } else {
+                    // use previous year
+                    (
+                        Local.ymd(now.year() - 1, month, 1).and_hms(0, 0, 0).with_timezone(&Utc),
+                        if month < 12 {
+                            Local.ymd(now.year() - 1, month + 1, 1).and_hms(0, 0, 0).with_timezone(&Utc)
+                        } else {
+                            Local.ymd(now.year(), 1, 1).and_hms(0, 0, 0).with_timezone(&Utc)
+                        }
+                    )
+                }
+            },
+        };
+
+        entries_for_display(Some(start), Some(end), args.sheet, db, out, err, args.format, args.ids, args.grep)
     }
 }

src/error.rs

@@ -51,6 +51,9 @@ pub enum Error {
 
     #[error("The provided regex '{0}' could not be parsed")]
     InvalidRegex(String),
+
+    #[error("Could not understand '{0}' as a month specifier. Try 'this', 'last', or any month name like 'january' or 'nov'")]
+    InvalidMonthSpec(String),
 }
 
 pub type Result<T> = result::Result<T, Error>;

src/main.rs

@@ -183,10 +183,25 @@ fn main() {
             .visible_alias("m")
             .about("Display entries starting this month")
             .arg(ids_arg.clone())
-            .arg(end_arg.clone())
             .arg(format_arg.clone())
             .arg(grep_arg.clone())
             .arg(sheet_arg.clone())
+            .arg(Arg::with_name("month")
+                .long("month").short("m")
+                .takes_value(true).value_name("TIME")
+                .aliases(&["s", "start"])
+                .possible_values(&[
+                    "this", "last", "jan", "january", "feb", "february", "mar",
+                    "march", "apr", "april", "may", "jun", "june", "jul",
+                    "july", "aug", "august", "sep", "september", "oct",
+                    "october", "nov", "november", "dic", "december",
+                ])
+                .hide_possible_values(true)
+                .help(
+                    "Include entries of the specified month instead of the \
+                    current month"
+                )
+            )
         )
 
         .subcommand(SubCommand::with_name("in")