rewrite datetime parsing

src/datetime.rs

@@ -1,10 +1,106 @@
-use chrono::{DateTime, FixedOffset};
+use chrono::{DateTime, FixedOffset, NaiveDate};
-use nom::IResult;
+use nom::{
+    IResult,
+    bytes::complete::take_while_m_n,
+    character::is_digit,
+};
 use crate::misc_token;
 
-pub fn section(input: &str) -> IResult<&str, DateTime<FixedOffset>> {
+///  date-time       =   [ day-of-week "," ] date time [CFWS]
+///  @FIXME: if parsing fails, Option::None is silently returned...
+pub fn section(input: &str) -> IResult<&str, Option<DateTime<FixedOffset>>> {
+    let (input, (_, date, time, _) = tuple((
+        opt(terminated(day_of_week), tag(",")),
+        date, time,
+        opt(cfws)))(input)?;
+
+
+
+
+
+
     // @FIXME want to extract datetime our way in the future
     // to better handle obsolete/bad cases instead of returning raw text.
     let (input, raw_date) = misc_token::unstructured(input)?;
     Ok((input, DateTime::parse_from_rfc2822(&raw_date).unwrap()))
 }
+
+///    day-of-week     =   ([FWS] day-name) / obs-day-of-week
+fn day_of_week(input: &str) -> IResult<&str, &str> {
+    alt((day_of_week_strict, obs_day_of_week))(input)
+}
+
+fn day_of_week_strict(input: &str) -> IResult<&str, &str> {
+    preceded(opt(fws), day_name)(input)
+}
+
+fn obs_day_of_week(input: &str) -> IResult<&str, &str> {
+    delimited(obs(cfws), day_name, obs(cfws))(input)
+}
+
+///   day-name        =   "Mon" / "Tue" / "Wed" / "Thu" /
+///                       "Fri" / "Sat" / "Sun"
+
+fn day_name(input: &str) -> IResult<&str, &str> {
+    alt((
+        tag_no_case("Mon"),
+        tag_no_case("Tue"),
+        tag_no_case("Wed"),
+        tag_no_case("Thu"),
+        tag_no_case("Fri"),
+        tag_no_case("Sat"),
+        tag_no_case("Sun"),
+    ))(input)
+}
+
+///    date            =   day month year
+fn date(input: &str) -> IResult<&str, Option<NaiveDate>> {
+   map(
+       tuple((day, month, year)),
+       |(d, m, y)| NaiveDate::from_ymd_opt(y, m, d)
+    )(input)
+}
+
+///    day             =   ([FWS] 1*2DIGIT FWS) / obs-day
+///    obs-day         =   [CFWS] 1*2DIGIT [CFWS]
+fn day(input: &str) -> IResult<&str, u32> {
+    alt((day_strict, obs_day))(input)
+}
+
+fn day_strict(input: &str) -> IResult<&str, u32) {
+    delimited(opt(fws), day_digit, fws)(input)
+}
+
+fn obs_day(input: &str) -> IResult<&str, u32) {
+    delimited(opt(cfws), day_digit, opt(cfws))(input)
+}
+
+fn day_digit(input: &str) -> IRresult<&str, u32) {
+    map(take_while_m_n(1, 2, is_digit), |d| d.parse::<u32>().unwrap())(input)
+}
+
+///  month           =   "Jan" / "Feb" / "Mar" / "Apr" /
+///                      "May" / "Jun" / "Jul" / "Aug" /
+///                      "Sep" / "Oct" / "Nov" / "Dec"
+fn month(input: &str) -> IResult<&str, u32) {
+    alt((
+        value(1, tag_no_case("Jan")),
+        value(2, tag_no_case("Feb")),
+        value(3, tag_no_case("Mar")),
+        value(4, tag_no_case("Apr")),
+        value(5, tag_no_case("May")),
+        value(6, tag_no_case("Jun")),
+        value(7, tag_no_case("Jul")),
+        value(8, tag_no_case("Aug")),
+        value(9, tag_no_case("Sep")),
+        value(10, tag_no_case("Oct")),
+        value(11, tag_no_case("Nov")),
+        value(12, tag_no_case("Dec")),
+    ))(input)
+}
+
+///   year            =   (FWS 4*DIGIT FWS) / obs-year
+///   obs-year        =   [CFWS] 2*DIGIT [CFWS]
+fn year(input: &str) -> IResult<&str, i32> {
+    alt((
+}