Add cal command (#1739)

* Add cal command

* Fix docmentation to show commands on two lines

* Use bullet points on flag documentation for cal

* Dereference day before calling string method

* Silence Clippy warning regarding a function with too many arguments

* Update cal flag descriptions and documentation

* Add some tests for the cal command

crates/nu-cli/src/cli.rs

@@ -251,6 +251,7 @@ pub fn create_default_context(
             whole_stream_command(Touch),
             whole_stream_command(Cpy),
             whole_stream_command(Date),
+            whole_stream_command(Cal),
             whole_stream_command(Calc),
             whole_stream_command(Mkdir),
             whole_stream_command(Move),

crates/nu-cli/src/commands.rs

@@ -8,6 +8,7 @@ pub(crate) mod alias;
 pub(crate) mod append;
 pub(crate) mod args;
 pub(crate) mod autoview;
+pub(crate) mod cal;
 pub(crate) mod calc;
 pub(crate) mod cd;
 pub(crate) mod classified;
@@ -128,6 +129,7 @@ pub(crate) use command::{whole_stream_command, Command, UnevaluatedCallInfo, Who
 
 pub(crate) use alias::Alias;
 pub(crate) use append::Append;
+pub(crate) use cal::Cal;
 pub(crate) use calc::Calc;
 pub(crate) use compact::Compact;
 pub(crate) use config::Config;

crates/nu-cli/src/commands/cal.rs

@@ -0,0 +1,261 @@
+use crate::prelude::*;
+use chrono::{DateTime, Datelike, Local, NaiveDate};
+use nu_errors::ShellError;
+use nu_protocol::Dictionary;
+
+use crate::commands::WholeStreamCommand;
+use indexmap::IndexMap;
+use nu_protocol::{Signature, SyntaxShape, UntaggedValue, Value};
+
+pub struct Cal;
+
+impl WholeStreamCommand for Cal {
+    fn name(&self) -> &str {
+        "cal"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("cal")
+            .switch(
+                "month-names",
+                "Display the month names instead of integers",
+                Some('m'),
+            )
+            .named(
+                "year",
+                SyntaxShape::Int,
+                "Display a year-long calendar for the specified year",
+                Some('y'),
+            )
+    }
+
+    fn usage(&self) -> &str {
+        "Display a calendar."
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        cal(args, registry)
+    }
+}
+
+pub fn cal(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let args = args.evaluate_once(registry)?;
+    let mut calendar_vec_deque = VecDeque::new();
+    let tag = args.call_info.name_tag.clone();
+
+    let (current_year, current_month, current_day) = get_current_date();
+    let should_show_month_names = args.has("month-names");
+
+    if args.has("year") {
+        let mut day_value: Option<u32> = Some(current_day);
+        let year_option = args.get("year");
+        let mut year_value = current_year as u64;
+
+        if let Some(year) = year_option {
+            if let Ok(year_u64) = year.as_u64() {
+                year_value = year_u64;
+            }
+
+            if year_value != current_year as u64 {
+                day_value = None
+            }
+        }
+
+        add_year_to_table(
+            &mut calendar_vec_deque,
+            &tag,
+            year_value as i32,
+            current_year,
+            current_month,
+            day_value,
+            should_show_month_names,
+        );
+    } else {
+        let (day_start_offset, number_of_days_in_month, _) =
+            get_month_information(current_year, current_month, current_year);
+
+        add_month_to_table(
+            &mut calendar_vec_deque,
+            &tag,
+            current_year,
+            current_month,
+            Some(current_day),
+            day_start_offset,
+            number_of_days_in_month as usize,
+            should_show_month_names,
+        );
+    }
+
+    Ok(futures::stream::iter(calendar_vec_deque).to_output_stream())
+}
+
+fn get_current_date() -> (i32, u32, u32) {
+    let local_now: DateTime<Local> = Local::now();
+
+    let current_year: i32 = local_now.date().year();
+    let current_month: u32 = local_now.date().month();
+    let current_day: u32 = local_now.date().day();
+
+    (current_year, current_month, current_day)
+}
+
+fn add_year_to_table(
+    mut calendar_vec_deque: &mut VecDeque<Value>,
+    tag: &Tag,
+    mut selected_year: i32,
+    current_year: i32,
+    current_month: u32,
+    current_day_option: Option<u32>,
+    should_show_month_names: bool,
+) {
+    for month_number in 1..=12 {
+        let (day_start_offset, number_of_days_in_month, chosen_date_is_valid) =
+            get_month_information(selected_year, month_number, current_year);
+
+        if !chosen_date_is_valid {
+            selected_year = current_year;
+        }
+
+        let mut new_current_day_option: Option<u32> = None;
+
+        if let Some(current_day) = current_day_option {
+            if month_number == current_month {
+                new_current_day_option = Some(current_day)
+            }
+        }
+
+        add_month_to_table(
+            &mut calendar_vec_deque,
+            &tag,
+            selected_year,
+            month_number,
+            new_current_day_option,
+            day_start_offset,
+            number_of_days_in_month,
+            should_show_month_names,
+        );
+    }
+}
+
+#[allow(clippy::too_many_arguments)]
+fn add_month_to_table(
+    calendar_vec_deque: &mut VecDeque<Value>,
+    tag: &Tag,
+    year: i32,
+    month: u32,
+    _current_day_option: Option<u32>, // Can be used in the future to display current day
+    day_start_offset: usize,
+    number_of_days_in_month: usize,
+    should_show_month_names: bool,
+) {
+    let day_limit = number_of_days_in_month + day_start_offset;
+    let mut day_count: usize = 1;
+
+    let days_of_the_week = [
+        "sunday",
+        "monday",
+        "tuesday",
+        "wednesday",
+        "thurday",
+        "friday",
+        "saturday",
+    ];
+
+    while day_count <= day_limit {
+        let mut indexmap = IndexMap::new();
+
+        indexmap.insert("year".to_string(), UntaggedValue::int(year).into_value(tag));
+
+        let month_value = if should_show_month_names {
+            UntaggedValue::string(get_month_name(month)).into_value(tag)
+        } else {
+            UntaggedValue::int(month).into_value(tag)
+        };
+
+        indexmap.insert("month".to_string(), month_value);
+
+        for day in &days_of_the_week {
+            let value = if (day_count <= day_limit) && (day_count > day_start_offset) {
+                UntaggedValue::int(day_count - day_start_offset).into_value(tag)
+            } else {
+                UntaggedValue::nothing().into_value(tag)
+            };
+
+            indexmap.insert((*day).to_string(), value);
+
+            day_count += 1;
+        }
+
+        calendar_vec_deque
+            .push_back(UntaggedValue::Row(Dictionary::from(indexmap)).into_value(tag));
+    }
+}
+
+fn get_month_name(month_number: u32) -> String {
+    let month_name = match month_number {
+        1 => "january",
+        2 => "february",
+        3 => "march",
+        4 => "april",
+        5 => "may",
+        6 => "june",
+        7 => "july",
+        8 => "august",
+        9 => "september",
+        10 => "october",
+        11 => "november",
+        _ => "december",
+    };
+
+    month_name.to_string()
+}
+
+fn get_month_information(
+    selected_year: i32,
+    month: u32,
+    current_year: i32,
+) -> (usize, usize, bool) {
+    let (naive_date, chosen_date_is_valid_one) =
+        get_safe_naive_date(selected_year, month, current_year);
+    let weekday = naive_date.weekday();
+    let (days_in_month, chosen_date_is_valid_two) =
+        get_days_in_month(selected_year, month, current_year);
+
+    (
+        weekday.num_days_from_sunday() as usize,
+        days_in_month,
+        chosen_date_is_valid_one && chosen_date_is_valid_two,
+    )
+}
+
+fn get_days_in_month(selected_year: i32, month: u32, current_year: i32) -> (usize, bool) {
+    // Chrono does not provide a method to output the amount of days in a month
+    // This is a workaround taken from the example code from the Chrono docs here:
+    // https://docs.rs/chrono/0.3.0/chrono/naive/date/struct.NaiveDate.html#example-30
+    let (adjusted_year, adjusted_month) = if month == 12 {
+        (selected_year + 1, 1)
+    } else {
+        (selected_year, month + 1)
+    };
+
+    let (naive_date, chosen_date_is_valid) =
+        get_safe_naive_date(adjusted_year, adjusted_month, current_year);
+
+    (naive_date.pred().day() as usize, chosen_date_is_valid)
+}
+
+fn get_safe_naive_date(
+    selected_year: i32,
+    selected_month: u32,
+    current_year: i32,
+) -> (NaiveDate, bool) {
+    if let Some(naive_date) = NaiveDate::from_ymd_opt(selected_year, selected_month, 1) {
+        return (naive_date, true);
+    }
+
+    (NaiveDate::from_ymd(current_year, selected_month, 1), false)
+}

crates/nu-cli/tests/commands/cal.rs

@@ -0,0 +1,39 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn cal_february_2020_leap_year() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        cal -my 2020 | where month == "february" | to json
+        "#
+    ));
+
+    let cal_february_json = r#"[{"year":2020,"month":"february","sunday":null,"monday":null,"tuesday":null,"wednesday":null,"thurday":null,"friday":null,"saturday":1},{"year":2020,"month":"february","sunday":2,"monday":3,"tuesday":4,"wednesday":5,"thurday":6,"friday":7,"saturday":8},{"year":2020,"month":"february","sunday":9,"monday":10,"tuesday":11,"wednesday":12,"thurday":13,"friday":14,"saturday":15},{"year":2020,"month":"february","sunday":16,"monday":17,"tuesday":18,"wednesday":19,"thurday":20,"friday":21,"saturday":22},{"year":2020,"month":"february","sunday":23,"monday":24,"tuesday":25,"wednesday":26,"thurday":27,"friday":28,"saturday":29}]"#;
+
+    assert_eq!(actual.out, cal_february_json);
+}
+
+#[test]
+fn cal_friday_the_thirteenths_in_2015() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        cal -ym 2015 | where friday == 13 | count
+        "#
+    ));
+
+    assert!(actual.out.contains("3"));
+}
+
+#[test]
+fn cal_rows_in_2020() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        cal -y 2020 | count
+        "#
+    ));
+
+    assert!(actual.out.contains("62"));
+}

crates/nu-cli/tests/commands/mod.rs

@@ -1,5 +1,6 @@
 mod alias;
 mod append;
+mod cal;
 mod calc;
 mod cd;
 mod compact;