From a7a90097a8cf4e866001a436944ebdddeeb646d4 Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Sun, 11 Jun 2023 11:01:15 +0100
Subject: [PATCH] Add sort and cannonicalize

---
 preserves.nimble  |  2 +-
 src/preserves.nim | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/preserves.nimble b/preserves.nimble
index cb5e18d..336760e 100644
--- a/preserves.nimble
+++ b/preserves.nimble
@@ -1,6 +1,6 @@
 # Package
 
-version = "20230607"
+version = "20230611"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"
diff --git a/src/preserves.nim b/src/preserves.nim
index 50ecae4..b5d8d3d 100644
--- a/src/preserves.nim
+++ b/src/preserves.nim
@@ -4,6 +4,7 @@
 import std/[base64, endians, hashes, options, sets, sequtils, streams, tables, typetraits]
 import ./preserves/private/macros
 
+from std/algorithm import sort
 from std/json import escapeJson, escapeJsonUnquoted
 from std/strutils import parseEnum
 import ./preserves/private/dot
@@ -167,6 +168,30 @@ proc `<`*[A, B](x: Preserve[A]; y: Preserve[B]): bool =
       when (not A is void) and (A is B):
         result = x.embed < y.embed
 
+proc cmp*[E](x, y: var Preserve[E]): int =
+  if x == y: 0
+  elif x < y: -1
+  else: 1
+
+proc sort*[E](pr: var Preserve[E]) = sort(pr.sequence, cmp)
+  ## Sort a Preserves array by total ordering.
+
+proc cannonicalize*[E](pr: var Preserve[E]) {.gcsafe.} =
+  ## Cannonicalize a compound Preserves value by total ordering.
+  case pr.kind
+  of pkSequence:
+    apply(pr.sequence, cannonicalize)
+  of pkSet:
+    apply(pr.set, cannonicalize)
+    sort(pr.set)
+  of pkDictionary:
+    apply(pr.dict) do (e: var DictEntry[E]):
+      cannonicalize(e.val)
+    sort(pr.dict) do (x, y: DictEntry[E]) -> int:
+      cmp(x.key, y.key)
+  else:
+    discard
+
 proc hash*(pr: Preserve): Hash =
   ## Produce a `Hash` of `pr` for use with a `HashSet` or `Table`.
   var h = hash(pr.kind.int) !& hash(pr.embedded)