Design command data types

This design went through a few iterations, and this won't be the last.

src/commands.rs

@@ -0,0 +1,87 @@
+use chrono::{NaiveDate, NaiveDateTime, NaiveTime};
+
+#[derive(Debug)]
+struct DateDelta {
+    years: i32,
+    months: i32,
+    weeks: i32,
+    days: i32,
+}
+
+#[derive(Debug)]
+struct TimeDelta {
+    hours: i32,
+    minutes: i32,
+}
+
+#[derive(Debug)]
+enum EndDate {
+    Fixed(NaiveDate),
+    Delta(DateDelta),
+}
+
+#[derive(Debug)]
+enum EndTime {
+    Fixed(NaiveTime),
+    Delta(TimeDelta),
+}
+
+#[derive(Debug)]
+struct DateSpec {
+    start: NaiveDate,
+    end: Option<EndDate>,
+    repeat: Option<DateDelta>,
+}
+
+#[derive(Debug)]
+struct TimeSpec {
+    start: NaiveTime,
+    end: Option<EndTime>,
+}
+
+#[derive(Debug)]
+struct WhenSpec {
+    date: DateSpec,
+    time: Option<TimeSpec>,
+}
+
+#[derive(Debug)]
+struct Done {
+    refering_to: Option<NaiveDate>,
+    created_at: Option<NaiveDateTime>,
+}
+
+#[derive(Debug)]
+struct Task {
+    title: String,
+    when: Option<WhenSpec>,
+    desc: Option<String>,
+    dones: Vec<Done>,
+}
+
+#[derive(Debug)]
+struct Note {
+    title: String,
+    when: WhenSpec,
+    desc: Option<String>,
+}
+
+#[derive(Debug)]
+enum BirthdaySpec {
+    Date(NaiveDate),
+    DateWithoutYear { month: u8, day: u8 },
+}
+
+#[derive(Debug)]
+struct Birthday {
+    title: String,
+    when: BirthdaySpec,
+    desc: Option<String>,
+}
+
+#[derive(Debug)]
+enum Command {
+    Task(Task),
+    Note(Note),
+    Birthday(Birthday),
+}

src/main.rs

@@ -1,3 +1,5 @@
+mod commands;
+
 fn main() {
     println!("Hello, world!");
 }