feat(parser): planning parsing

src/elements/mod.rs

@@ -3,6 +3,8 @@ pub(crate) mod dyn_block;
 pub(crate) mod fn_def;
 pub(crate) mod keyword;
 pub(crate) mod list;
+pub(crate) mod planning;
 pub(crate) mod rule;
 
 pub use self::keyword::Key;
+pub use self::planning::Planning;

src/elements/planning.rs

@@ -0,0 +1,65 @@
+use crate::objects::timestamp::{self, Timestamp};
+use memchr::memchr;
+
+#[cfg_attr(test, derive(PartialEq))]
+#[derive(Debug)]
+pub struct Planning<'a> {
+    deadline: Option<Timestamp<'a>>,
+    scheduled: Option<Timestamp<'a>>,
+    closed: Option<Timestamp<'a>>,
+}
+
+impl<'a> Planning<'a> {
+    pub(crate) fn parse(text: &'a str) -> Option<(Planning<'a>, usize)> {
+        let (text, off) = memchr(b'\n', text.as_bytes())
+            .map(|i| (text[..i].trim(), i + 1))
+            .unwrap_or_else(|| (text.trim(), text.len()));
+
+        let mut words = text.split_ascii_whitespace();
+        let (mut deadline, mut scheduled, mut closed) = (None, None, None);
+
+        while let Some(word) = words.next() {
+            let next = words.next()?;
+
+            macro_rules! set_timestamp {
+                ($timestamp:expr) => {
+                    if $timestamp.is_none() {
+                        $timestamp = if next.starts_with('<') {
+                            Some(
+                                timestamp::parse_active(next)
+                                    .or_else(|| timestamp::parse_diary(next))?
+                                    .0,
+                            )
+                        } else if next.starts_with('[') {
+                            Some(timestamp::parse_inactive(next)?.0)
+                        } else {
+                            return None;
+                        }
+                    } else {
+                        return None;
+                    }
+                };
+            }
+
+            match word {
+                "DEADLINE:" => set_timestamp!(deadline),
+                "SCHEDULED:" => set_timestamp!(scheduled),
+                "CLOSED:" => set_timestamp!(closed),
+                _ => (),
+            }
+        }
+
+        if deadline.is_none() && scheduled.is_none() && closed.is_none() {
+            None
+        } else {
+            Some((
+                Planning {
+                    deadline,
+                    scheduled,
+                    closed,
+                },
+                off,
+            ))
+        }
+    }
+}