From b03b0b9e48c60195976425cc5b666e1e6cd712ff Mon Sep 17 00:00:00 2001
From: Jaro <jaro@argonaut-constellation.org>
Date: Wed, 29 Mar 2023 11:27:57 +0200
Subject: [PATCH] Prepare pagination for future layout types.

---
 balkon.cabal                                  |  2 +-
 lib/Data/Text/ParagraphLayout.hs              |  2 +-
 .../{ParagraphPagination.hs => Paginable.hs}  | 37 ++++++++++++-------
 3 files changed, 26 insertions(+), 15 deletions(-)
 rename src/Data/Text/ParagraphLayout/Internal/{ParagraphPagination.hs => Paginable.hs} (65%)

diff --git a/balkon.cabal b/balkon.cabal
index f01f83a..7233ebf 100644
--- a/balkon.cabal
+++ b/balkon.cabal
@@ -128,11 +128,11 @@ library balkon-internal
         Data.Text.ParagraphLayout.Internal.Fragment,
         Data.Text.ParagraphLayout.Internal.LineHeight,
         Data.Text.ParagraphLayout.Internal.LinePagination,
+        Data.Text.ParagraphLayout.Internal.Paginable,
         Data.Text.ParagraphLayout.Internal.Paragraph,
         Data.Text.ParagraphLayout.Internal.ParagraphConstruction,
         Data.Text.ParagraphLayout.Internal.ParagraphLayout,
         Data.Text.ParagraphLayout.Internal.ParagraphLine,
-        Data.Text.ParagraphLayout.Internal.ParagraphPagination,
         Data.Text.ParagraphLayout.Internal.Plain,
         Data.Text.ParagraphLayout.Internal.Rect,
         Data.Text.ParagraphLayout.Internal.ResolvedSpan,
diff --git a/lib/Data/Text/ParagraphLayout.hs b/lib/Data/Text/ParagraphLayout.hs
index fa9dcb9..028dd30 100644
--- a/lib/Data/Text/ParagraphLayout.hs
+++ b/lib/Data/Text/ParagraphLayout.hs
@@ -42,8 +42,8 @@ where
 import Data.Text.ParagraphLayout.Internal.Fragment
 import Data.Text.ParagraphLayout.Internal.LineHeight
 import Data.Text.ParagraphLayout.Internal.LinePagination
+import Data.Text.ParagraphLayout.Internal.Paginable
 import Data.Text.ParagraphLayout.Internal.Paragraph
 import Data.Text.ParagraphLayout.Internal.ParagraphLayout
-import Data.Text.ParagraphLayout.Internal.ParagraphPagination
 import Data.Text.ParagraphLayout.Internal.Plain
 import Data.Text.ParagraphLayout.Internal.Span
diff --git a/src/Data/Text/ParagraphLayout/Internal/ParagraphPagination.hs b/src/Data/Text/ParagraphLayout/Internal/Paginable.hs
similarity index 65%
rename from src/Data/Text/ParagraphLayout/Internal/ParagraphPagination.hs
rename to src/Data/Text/ParagraphLayout/Internal/Paginable.hs
index d24dc0a..bb54e34 100644
--- a/src/Data/Text/ParagraphLayout/Internal/ParagraphPagination.hs
+++ b/src/Data/Text/ParagraphLayout/Internal/Paginable.hs
@@ -1,4 +1,8 @@
-module Data.Text.ParagraphLayout.Internal.ParagraphPagination
+module Data.Text.ParagraphLayout.Internal.Paginable
+    (PageOptions(..)
+    ,Paginable
+    ,paginate
+    )
 where
 
 import Data.Int (Int32)
@@ -30,7 +34,7 @@ data PageOptions = PageOptions
 
     }
 
--- | Break a paragraph in order to fit the given pagination constraints.
+-- | Typeclass for layouts that can be broken into pages.
 --
 -- The first component of the output determines whether a page break should
 -- be inserted before the paragraph.
@@ -42,14 +46,21 @@ data PageOptions = PageOptions
 -- The third component of the output will be `Just` the remainder of the
 -- paragraph that can be passed to this function again, or `Nothing` if there
 -- is nothing left to put on further pages.
-paginate :: PageOptions -> ParagraphLayout ->
-    (PageContinuity, ParagraphLayout, Maybe ParagraphLayout)
-paginate opts pl = case paginateLines o w h1 h2 ls of
-    (c, ls1, []) -> (c, mergeLines ls1, Nothing)
-    (c, ls1, ls2) -> (c, mergeLines ls1, Just (mergeLines ls2))
-    where
-        o = pageOrphans opts
-        w = pageWidows opts
-        h1 = pageCurrentHeight opts
-        h2 = pageNextHeight opts
-        ls = cutLines pl
+class Paginable pl where
+    paginate :: PageOptions -> pl -> (PageContinuity, pl, Maybe pl)
+
+instance Line a => Paginable [a] where
+    paginate opts ls = case paginateLines o w h1 h2 ls of
+        (c, p, []) -> (c, p, Nothing)
+        (c, p, rest) -> (c, p, Just rest)
+        where
+            o = pageOrphans opts
+            w = pageWidows opts
+            h1 = pageCurrentHeight opts
+            h2 = pageNextHeight opts
+
+-- | Break a paragraph in order to fit the given pagination constraints.
+instance Paginable ParagraphLayout where
+    paginate opts pl = case paginate opts (cutLines pl) of
+        (c, p, Nothing) -> (c, mergeLines p, Nothing)
+        (c, p, Just rest) -> (c, mergeLines p, Just (mergeLines rest))
-- 
2.30.2