feat(manifest): app manifest + decision crate (strict TOML subset, checked newtypes, capability catalog); docs/apps.md spec

crates/manifest/src/decision.rs

@@ -0,0 +1,59 @@
+//! The owner's decision about one app: what it was granted.
+
+use crate::Error;
+use crate::capability::{Capabilities, Capability};
+use crate::toml;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct Decision {
+    pub granted: Capabilities,
+}
+
+/// Longest decision file `write` produces: the header and every name.
+pub const MAX_TEXT: usize = 512;
+
+impl Decision {
+    pub fn parse(text: &str) -> Result<Self, Error> {
+        let mut granted = None;
+        toml::parse(text, |e| match (e.table, e.key) {
+            ("decision", "granted") if granted.is_none() => {
+                granted = Some(crate::manifest::capabilities(e.value, e.line)?);
+                Ok(())
+            }
+            ("decision", "granted") => Err(Error::Duplicate { line: e.line }),
+            _ => Err(Error::Unknown { line: e.line }),
+        })?;
+        Ok(Self {
+            granted: granted.ok_or(Error::Missing("granted"))?,
+        })
+    }
+
+    /// The file this decision is stored as, in `out`; its length.
+    pub fn write(&self, out: &mut [u8; MAX_TEXT]) -> usize {
+        let mut w = Writer { out, len: 0 };
+        w.put("[decision]\ngranted = [");
+        for (i, c) in self.granted.iter().enumerate() {
+            if i > 0 {
+                w.put(", ");
+            }
+            w.put("\"");
+            w.put(Capability::name(c));
+            w.put("\"");
+        }
+        w.put("]\n");
+        w.len
+    }
+}
+
+struct Writer<'a> {
+    out: &'a mut [u8; MAX_TEXT],
+    len: usize,
+}
+
+impl Writer<'_> {
+    fn put(&mut self, s: &str) {
+        let end = (self.len + s.len()).min(MAX_TEXT);
+        self.out[self.len..end].copy_from_slice(&s.as_bytes()[..end - self.len]);
+        self.len = end;
+    }
+}