From 30af956fab6228913bc9876db8961180e28643c9 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Wed, 28 Apr 2021 23:36:50 +0100
Subject: [PATCH] PosOffTableError: Introduce

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 daemon/api.rs    |  4 ++--
 src/gamestate.rs | 20 ++++++++++++--------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/daemon/api.rs b/daemon/api.rs
index e4a3c058..6b62f955 100644
--- a/daemon/api.rs
+++ b/daemon/api.rs
@@ -486,8 +486,8 @@ api_route!{
       let logents = vec![];
       match self.0.clamped(gs.table_size) {
         Ok(pos) => gpc.pos = pos,
-        Err(pos) => {
-          gpc.pos = pos;
+        Err(pote) => {
+          gpc.pos = pote.clamped;
           throw!(ApiPieceOpError::PartiallyProcessed(
             PieceOpError::PosOffTable,
             logents,
diff --git a/src/gamestate.rs b/src/gamestate.rs
index 08b926b7..31931b0a 100644
--- a/src/gamestate.rs
+++ b/src/gamestate.rs
@@ -316,30 +316,34 @@ impl Timestamp {
   }
 }
 
-pub trait ClampTable: Sized {
-  fn clamped(self, range: Self) -> Result<Self, Self>;
+#[derive(Error,Debug,Copy,Clone)]
+pub struct PosOffTableError<T:Debug> { pub clamped: T }
+display_as_debug!{PosOffTableError<T>, <T:Debug>}
+
+pub trait ClampTable: Sized+Debug {
+  fn clamped(self, range: Self) -> Result<Self, PosOffTableError<Self>>;
 }
 
 impl ClampTable for Coord {
-  fn clamped(self, range: Coord) -> Result<Coord, Coord> {
-    if self < 0     { return Err(0,   ) }
-    if self > range { return Err(range) }
+  fn clamped(self, range: Coord) -> Result<Coord, PosOffTableError<Coord>> {
+    if self < 0     { return Err(PosOffTableError{ clamped: 0,    }) }
+    if self > range { return Err(PosOffTableError{ clamped: range }) }
     return Ok(self)
   }
 }
 
 impl ClampTable for Pos {
-  fn clamped(self, range: Pos) -> Result<Pos, Pos> {
+  fn clamped(self, range: Pos) -> Result<Pos, PosOffTableError<Pos>> {
     let mut output = ArrayVec::new();
     let mut ok = true;
     for (&pos, &rng) in izip!(self.coords.iter(), range.coords.iter()) {
       output.push(match pos.clamped(rng) {
         Ok(pos) => pos,
-        Err(pos) => { ok = false; pos },
+        Err(e) => { ok = false; e.clamped },
       })
     }
     let output = PosC{ coords: output.into_inner().unwrap() };
-    if ok { Ok(output) } else { Err(output) }
+    if ok { Ok(output) } else { Err(PosOffTableError { clamped: output }) }
   }
 }
 
-- 
2.30.2