From 42ed5ade294f1c52709886c1f83ff4dccc2c0b2c Mon Sep 17 00:00:00 2001
From: Gabriel Kaszewski <gabrielkaszewski@gmail.com>
Date: Sat, 17 Oct 2026 23:27:28 +0200
Subject: [PATCH] feat(domain): add ProcessTable with create, get, and destroy

---
 crates/domain/src/error.rs         |  1 +
 crates/domain/src/process/mod.rs   | 59 ++++++++++++++++++++++++++++--
 crates/domain/src/process/tests.rs | 52 ++++++++++++++++++++++++++
 3 files changed, 109 insertions(+), 3 deletions(-)

diff --git a/crates/domain/src/error.rs b/crates/domain/src/error.rs
index 6272965..134cd86 100644
--- a/crates/domain/src/error.rs
+++ b/crates/domain/src/error.rs
@@ -9,4 +9,5 @@ pub enum KernelError {
     InvalidProcess(ProcessId),
     WouldBlock,
     TooManyThreadsInProcess,
+    TooManyProcesses,
 }
diff --git a/crates/domain/src/process/mod.rs b/crates/domain/src/process/mod.rs
index cf9c0f2..c717ed8 100644
--- a/crates/domain/src/process/mod.rs
+++ b/crates/domain/src/process/mod.rs
@@ -3,13 +3,14 @@ use types::{
     id::{ProcessId, ThreadId},
 };
 
-use crate::capability::CapabilityTable;
+use crate::{capability::CapabilityTable, error::KernelError};
 
 #[cfg(test)]
 #[path = "tests.rs"]
 mod tests;
 
 pub const MAX_THREADS_PER_PROCESS: usize = 4;
+pub const MAX_PROCESSES: usize = 64;
 
 pub struct Process {
     id: ProcessId,
@@ -48,12 +49,12 @@ impl Process {
         self.fault_handler
     }
 
-    pub fn add_thread(&mut self, thread: ThreadId) -> Result<(), crate::error::KernelError> {
+    pub fn add_thread(&mut self, thread: ThreadId) -> Result<(), KernelError> {
         let slot = self
             .threads
             .iter_mut()
             .find(|s| s.is_none())
-            .ok_or(crate::error::KernelError::TooManyThreadsInProcess)?;
+            .ok_or(KernelError::TooManyThreadsInProcess)?;
         *slot = Some(thread);
         Ok(())
     }
@@ -71,3 +72,55 @@ impl Process {
         self.threads.iter().filter_map(|s| *s)
     }
 }
+
+pub struct ProcessTable {
+    processes: [Option<Process>; MAX_PROCESSES],
+}
+
+impl ProcessTable {
+    pub fn new() -> Self {
+        Self {
+            processes: [const { None }; MAX_PROCESSES],
+        }
+    }
+
+    pub fn create(
+        &mut self,
+        capabilities: CapabilityTable,
+        fault_handler: Option<CapSlot>,
+    ) -> Result<ProcessId, KernelError> {
+        let idx = self
+            .processes
+            .iter()
+            .position(|s| s.is_none())
+            .ok_or(KernelError::TooManyProcesses)?;
+
+        let id = ProcessId::from_raw(idx as u16);
+        self.processes[idx] = Some(Process::new(id, capabilities, fault_handler));
+        Ok(id)
+    }
+
+    pub fn get(&self, id: ProcessId) -> Result<&Process, KernelError> {
+        let idx = id.raw() as usize;
+        self.processes
+            .get(idx)
+            .and_then(|s| s.as_ref())
+            .ok_or(KernelError::InvalidProcess(id))
+    }
+
+    pub fn get_mut(&mut self, id: ProcessId) -> Result<&mut Process, KernelError> {
+        let idx = id.raw() as usize;
+        self.processes
+            .get_mut(idx)
+            .and_then(|s| s.as_mut())
+            .ok_or(KernelError::InvalidProcess(id))
+    }
+
+    pub fn destroy(&mut self, id: ProcessId) -> Result<Process, KernelError> {
+        let idx = id.raw() as usize;
+        self.processes
+            .get_mut(idx)
+            .and_then(|s| s.take())
+            .ok_or(KernelError::InvalidProcess(id))
+    }
+}
diff --git a/crates/domain/src/process/tests.rs b/crates/domain/src/process/tests.rs
index 3071dcc..8de051d 100644
--- a/crates/domain/src/process/tests.rs
+++ b/crates/domain/src/process/tests.rs
@@ -76,3 +76,55 @@ fn capabilities_mut_accessible() {
     let mut p = test_process(0);
     let _caps = p.capabilities_mut();
 }
+
+// --- ProcessTable tests ---
+
+#[test]
+fn table_create_and_lookup() {
+    let mut table = ProcessTable::new();
+    let id = table.create(CapabilityTable::new(), None).unwrap();
+    assert_eq!(table.get(id).unwrap().id(), id);
+}
+
+#[test]
+fn table_create_returns_unique_ids() {
+    let mut table = ProcessTable::new();
+    let a = table.create(CapabilityTable::new(), None).unwrap();
+    let b = table.create(CapabilityTable::new(), None).unwrap();
+    assert_ne!(a, b);
+}
+
+#[test]
+fn table_destroy_then_get_fails() {
+    let mut table = ProcessTable::new();
+    let id = table.create(CapabilityTable::new(), None).unwrap();
+    table.destroy(id).unwrap();
+    assert!(table.get(id).is_err());
+}
+
+#[test]
+fn table_full_returns_error() {
+    let mut table = ProcessTable::new();
+    for _ in 0..MAX_PROCESSES {
+        table.create(CapabilityTable::new(), None).unwrap();
+    }
+    assert!(table.create(CapabilityTable::new(), None).is_err());
+}
+
+#[test]
+fn table_destroy_reuses_slot() {
+    let mut table = ProcessTable::new();
+    let id = table.create(CapabilityTable::new(), None).unwrap();
+    table.destroy(id).unwrap();
+    let new_id = table.create(CapabilityTable::new(), None).unwrap();
+    assert_eq!(id, new_id);
+}
+
+#[test]
+fn table_get_mut_allows_modification() {
+    let mut table = ProcessTable::new();
+    let id = table.create(CapabilityTable::new(), None).unwrap();
+    let p = table.get_mut(id).unwrap();
+    p.add_thread(thread(0)).unwrap();
+    assert_eq!(table.get(id).unwrap().thread_ids().count(), 1);
+}