Don't use random pages for "related"

3 files changed, 54 insertions, 25 deletions

diff --git a/scripts/metadata.lua b/scripts/metadata.lua
index 49a9c55..9c8a964 100644
--- a/scripts/metadata.lua
+++ b/scripts/metadata.lua
@@ -130,6 +130,7 @@ end
 
 function process_base(build, meta)
     meta.namespace = prep_namespace(meta.namespace)
+    meta.id = meta.namespace.full:gsub("^.*/(.-)$", "%1")
     meta.file_out = utils.stringify(meta.file_out)
     meta.unlisted = meta.unlisted or (meta.draft and build.mode ~= "dev")
     meta.redirect = meta.url and true
@@ -164,6 +165,24 @@ function process(global, build, meta)
     resolve_dates(meta)
 end
 
+function find_pos(meta)
+    for _, p in pairs(meta.pages.by_id) do
+        p.parent = meta
+        find_pos(p)
+        p.parent = nil
+    end
+
+    if not meta.parent then return end
+
+    local pages = meta.parent.list_order == "date_desc" and meta.parent.pages.date_desc or meta.parent.pages.all
+    local _, index = pages:find(meta.id)
+
+    if index == nil then return end
+
+    meta.prev = index >= 2 and pages[index - 1] or nil
+    meta.next = index <= #pages - 1 and pages[index + 1] or nil
+end
+
 function Meta(meta)
     local build = {}
 
@@ -180,6 +199,7 @@ function Meta(meta)
 
     find_depth(meta)
     process(meta, build, meta)
+    find_pos(meta)
 
     return meta
 end
diff --git a/scripts/page.lua b/scripts/page.lua
index dcbb36f..7378bfc 100644
--- a/scripts/page.lua
+++ b/scripts/page.lua
@@ -130,32 +130,35 @@ function generate_list(meta)
     end
 end
 
+function deref_page(pages)
+    return function(ref)
+        return pages[utils.stringify(ref)]
+    end
+end
+
 function generate_related(meta)
     if not meta.parent then return nil end
 
-    meta = meta.parent
+    local deref = deref_page(meta.parent.pages.by_id)
 
-    local items = meta.pages.random:take(2):map(function (p) return d1_page_to_list_item(p) end)
+    meta.prev = meta.prev and d1_page_to_list_item(deref(meta.prev))
+    meta.next = meta.next and d1_page_to_list_item(deref(meta.next))
 
-    if #items == 0 then return nil end
+    if not meta.prev and not meta.next then return nil end
 
     return {
-        url = meta.url,
-        layout = meta.list_layout,
-        items = items
+        url = meta.parent.url,
+        layout = meta.parent.list_layout,
+        prev = meta.prev,
+        next = meta.next
     }
 end
 
-function deref_page(pages)
-    return function(ref)
-        return pages[utils.stringify(ref)]
-    end
-end
-
 function process_pages(meta)
-    meta.pages.all = meta.pages.all:filterMap(deref_page(meta.pages.by_id))
-    meta.pages.date_desc = meta.pages.date_desc:filterMap(deref_page(meta.pages.by_id))
-    meta.pages.random = meta.pages.all :clone():shuffle()
+    local deref = deref_page(meta.pages.by_id)
+
+    meta.pages.all = meta.pages.all:filterMap(deref)
+    meta.pages.date_desc = meta.pages.date_desc:filterMap(deref)
 end
 
 function resolve_urls(global, build, meta)
@@ -179,6 +182,7 @@ function resolve_urls(global, build, meta)
 end
 
 function process_base(meta)
+    meta.id = utils.stringify(meta.id)
     meta.depth = tonumber(utils.stringify(meta.depth))
     meta.file_out = utils.stringify(meta.file_out)
     meta.url = utils.stringify(meta.url)
@@ -187,6 +191,8 @@ function process_base(meta)
     meta.list_order = meta.list_order and utils.stringify(meta.list_order)
     meta.position = meta.position and tonumber(utils.stringify(meta.position))
     meta.thumbnail = meta.thumbnail and utils.stringify(meta.thumbnail)
+    meta.prev = meta.prev and utils.stringify(meta.prev)
+    meta.next = meta.next and utils.stringify(meta.next)
 end
 
 function process(global, build, meta, dir)
@@ -207,7 +213,6 @@ function process(global, build, meta, dir)
 end
 
 function prune_pages(meta, up, down)
-    meta.pages.random = pandoc.List()
     meta.pages.by_id = {}
 
     if down == 0 then
@@ -231,8 +236,6 @@ function prune(meta, up, down)
 end
 
 function Meta(meta)
-    math.randomseed(os.time())
-
     local build = {}
 
     for key, value in pairs(meta) do
@@ -254,7 +257,7 @@ function Meta(meta)
 
     meta = meta.tree
 
-    local parts = utils.stringify(build.namespace):split('/'):skip(1)
+    local parts = build.namespace:split('/'):skip(1)
     for i = 1, #parts do
         local part = parts[i]
         local p = meta.pages.by_id[part]
diff --git a/templates/partials/related.html b/templates/partials/related.html
index b0d3f61..7d29c7a 100644
--- a/templates/partials/related.html
+++ b/templates/partials/related.html
@@ -14,19 +14,25 @@ $if(related)$
             </header>
             <div class="l-card-list__cards l-card-list__cards--$related.layout.id$">
                 $if(related.layout.is_grid-2)$
-                    $related.items:partials/grid_card()$
+                    $related.prev:partials/grid_card()$
+                    $related.next:partials/grid_card()$
                 $elseif(related.layout.is_grid-3)$
-                    $related.items:partials/grid_card()$
+                    $related.prev:partials/grid_card()$
+                    $related.next:partials/grid_card()$
                 $elseif(related.layout.is_gallery-2)$
-                    $related.items:partials/gallery_card()$
+                    $related.prev:partials/gallery_card()$
+                    $related.next:partials/gallery_card()$
                 $elseif(related.layout.is_gallery-3)$
-                    $related.items:partials/gallery_card()$
+                    $related.prev:partials/gallery_card()$
+                    $related.next:partials/gallery_card()$
                 $else$
                     <div class="u-d-contents u-d-none@sm-lo">
-                        $related.items:partials/list_card()$
+                        $related.prev:partials/list_card()$
+                        $related.next:partials/list_card()$
                     </div>
                     <div class="u-d-contents u-d-none@sm-hi">
-                        $related.items:partials/grid_card()$
+                        $related.prev:partials/grid_card()$
+                        $related.next:partials/grid_card()$
                     </div>
                 $endif$
             </div>