From b5ee9fb3c438d2b6c86080245b5ea35a4043d237 Mon Sep 17 00:00:00 2001
From: Albert Krewinkel <albert@zeitkraut.de>
Date: Fri, 13 Sep 2024 17:06:00 +0200
Subject: [PATCH] Add `jog` Lua module

---
 src/resources/filters/modules/import_all.lua |   3 +-
 src/resources/filters/modules/jog.lua        | 318 +++++++++++++++++++
 2 files changed, 320 insertions(+), 1 deletion(-)
 create mode 100644 src/resources/filters/modules/jog.lua

diff --git a/src/resources/filters/modules/import_all.lua b/src/resources/filters/modules/import_all.lua
index 1369a183c9..2b97fdef94 100644
--- a/src/resources/filters/modules/import_all.lua
+++ b/src/resources/filters/modules/import_all.lua
@@ -11,6 +11,7 @@ _quarto.modules = {
   dashboard = require("modules/dashboard"),
   filenames = require("modules/filenames"),
   filters = require("modules/filters"),
+  jog = require("modules/jog"),
   license = require("modules/license"),
   lightbox = require("modules/lightbox"),
   mediabag = require("modules/mediabag"),
@@ -20,4 +21,4 @@ _quarto.modules = {
   string = require("modules/string"),
   tablecolwidths = require("modules/tablecolwidths"),
   typst = require("modules/typst")
-}
\ No newline at end of file
+}
diff --git a/src/resources/filters/modules/jog.lua b/src/resources/filters/modules/jog.lua
new file mode 100644
index 0000000000..988e997108
--- /dev/null
+++ b/src/resources/filters/modules/jog.lua
@@ -0,0 +1,318 @@
+--- jog.lua – walk the pandoc AST with context, and with inplace modification.
+---
+--- Copyright: © 2024 Albert Krewinkel, Carlos Scheidegger
+--- License: MIT – see LICENSE for details
+
+local pandoc = require 'pandoc'
+local List   = require 'pandoc.List'
+
+local debug_getmetatable = debug.getmetatable
+
+--- Get the element type; like pandoc.utils.type, but faster.
+local function ptype (x)
+  local mt = debug_getmetatable(x)
+  if mt then
+    local name = mt.__name
+    return name or type(x)
+  else
+    return type(x)
+  end
+end
+
+--- Checks whether the object is a list type.
+local listy_type = {
+  Blocks = true,
+  Inlines = true,
+  List = true,
+}
+
+local function run_filter_function (fn, element, context)
+  if fn == nil then
+    return element
+  end
+
+  local result, continue = fn(element, context)
+  if result == nil then
+    return element, continue
+  else
+    return result, continue
+  end
+end
+
+--- Set of Block and Inline tags that are leaf nodes.
+local leaf_node_tags = {
+  Code = true,
+  CodeBlock = true,
+  HorizontalRule = true,
+  LineBreak = true,
+  Math = true,
+  RawBlock = true,
+  RawInline = true,
+  Space = true,
+  SoftBreak = true,
+  Str = true,
+}
+
+--- Set of Block and Inline tags that have nested items in `.contents` only.
+local content_only_node_tags = {
+  -- Blocks with Blocks content
+  BlockQuote = true,
+  Div = true,
+  Header = true,
+  -- Blocks with Inlines content
+  Para = true,
+  Plain = true,
+  -- Blocks with List content
+  LineBlock = true,
+  BulletList = true,
+  OrderedList = true,
+  DefinitionList = true,
+  -- Inlines with Inlines content
+  Cite = true,
+  Emph = true,
+  Link = true,
+  Quoted = true,
+  SmallCaps = true,
+  Span = true,
+  Strikeout = true,
+  Strong = true,
+  Subscript = true,
+  Superscript = true,
+  Underline = true,
+  -- Inline with Blocks content
+  Note = true,
+}
+
+--- Apply the filter on the nodes below the given element.
+local function recurse (element, tp, jogger)
+  tp = tp or ptype(element)
+  local tag = element.tag
+  if leaf_node_tags[tag] then
+    -- do nothing, cannot traverse any deeper
+  elseif tp == 'table' then
+    for key, value in pairs(element) do
+      element[key] = jogger(value)
+    end
+  elseif content_only_node_tags[tag] or
+         tp == 'Cell' or tp == 'pandoc Cell' then
+    element.content = jogger(element.content)
+  elseif tag == 'Image' then
+    element.caption = jogger(element.caption)
+  elseif tag == 'Table' then
+    element.caption = jogger(element.caption)
+    element.head    = jogger(element.head)
+    element.bodies  = jogger(element.bodies)
+    element.foot    = jogger(element.foot)
+  elseif tag == 'Caption' then
+    element.long = jogger(element.long)
+    element.short = element.short and jogger(element.short)
+  elseif tag == 'Figure' then
+    element.caption = jogger(element.caption)
+    element.content = jogger(element.content)
+  elseif tp == 'Meta' then
+    for key, value in pairs(element) do
+      element[key] = jogger(value)
+    end
+  elseif tp == 'Row' or tp == 'pandoc Row' then
+    element.cells    = jogger(element.cells)
+  elseif tp == 'pandoc TableHead' or tp == 'pandoc TableFoot' or
+         tp == 'TableHead' or tp == 'TableFoot' then
+    element.rows    = jogger(element.rows)
+  elseif tp == 'Blocks' or tp == 'Inlines' then
+    local expected_itemtype = tp == 'Inlines' and 'Inline' or 'Block'
+    local pos = 0
+    local filtered_index = 1
+    local filtered_items = element:map(function (x)
+        return jogger(x)
+    end)
+    local item = filtered_items[filtered_index]
+    local itemtype
+    while item ~= nil do
+      itemtype = ptype(item)
+      if itemtype ~= tp and itemtype ~= expected_itemtype then
+        -- neither the list type nor the list's item type. Try to convert.
+        item = pandoc[tp](item)
+        itemtype = tp
+      end
+      if itemtype == tp then
+        local sublist_index = 1
+        local sublistitem = item[sublist_index]
+        while sublistitem ~= nil do
+          pos = pos + 1
+          element[pos]  = sublistitem
+          sublist_index = sublist_index + 1
+          sublistitem   = item[sublist_index]
+        end
+      else
+        -- not actually a sublist, just an element
+        pos = pos + 1
+        element[pos] = item
+      end
+      filtered_index = filtered_index + 1
+      item = filtered_items[filtered_index]
+    end
+    -- unset remaining indices if the new list is shorter than the old
+    pos = pos + 1
+    while element[pos] do
+      element[pos] = nil
+      pos = pos + 1
+    end
+  elseif tp == 'List' then
+    local i, item = 1, element[1]
+    while item do
+      element[i] = jogger(item)
+      i, item = i+1, element[i+1]
+    end
+  elseif tp == 'Caption' then
+    element.long = jogger(element.long)
+    element.short = element.short and jogger(element.short)
+  elseif tp == 'Pandoc' then
+    element.meta = jogger(element.meta)
+    element.blocks = jogger(element.blocks)
+  else
+    error("Don't know how to traverse " .. (element.t or tp))
+  end
+  return element
+end
+
+local non_joggable_types = {
+  ['Attr'] = true,
+  ['boolean'] = true,
+  ['nil'] = true,
+  ['number'] = true,
+  ['string'] = true,
+}
+
+local function get_filter_function(element, filter, tp)
+  if non_joggable_types[tp] or tp == 'table' then
+    return nil
+  elseif tp == 'Block' then
+    return filter[element.tag] or filter.Block
+  elseif tp == 'Inline' then
+    return filter[element.tag] or filter.Inline
+  else
+    return filter[tp]
+  end
+end
+
+local function make_jogger (filter, context)
+  local is_topdown = filter.traverse == 'topdown'
+  local jogger
+
+  jogger = function (element)
+    if context then
+      context:insert(element)
+    end
+    local tp = ptype(element)
+    local result, continue = nil, true
+    if non_joggable_types[tp] then
+      result = element
+    elseif tp == 'table' then
+      result = recurse(element, tp, jogger)
+    else
+      local fn = get_filter_function(element, filter, tp)
+      if is_topdown then
+        result, continue = run_filter_function(fn, element, context)
+        if continue ~= false then
+          -- the result might have a different type, so use nil
+          result = recurse(result, nil, jogger)
+        end
+      else
+        element = recurse(element, tp, jogger)
+        result = run_filter_function(fn, element, context)
+      end
+    end
+
+    if context then
+      context:remove() -- remove this element from the context
+    end
+    return result
+  end
+  return jogger
+end
+
+local element_name_map = {
+  Cell = 'pandoc Cell',
+  Row = 'pandoc Row',
+  TableHead = 'pandoc TableHead',
+  TableFoot = 'pandoc TableFoot',
+}
+
+--- Function to traverse the pandoc AST with context.
+local function jog(element, filter)
+  local context = filter.context and List{} or nil
+
+  -- Table elements have a `pandoc ` prefix in the name
+  for from, to in pairs(element_name_map) do
+    filter[to] = filter[from]
+  end
+
+  -- Check if we can just call Pandoc and Meta and be done
+  if ptype(element) == 'Pandoc' then
+    local must_recurse = false
+    for name in pairs(filter) do
+      if name:match'^[A-Z]' and name ~= 'Pandoc' and name ~= 'Meta' then
+        must_recurse = true
+        break
+      end
+    end
+    if not must_recurse then
+      element.meta = run_filter_function(filter.Meta, element.meta, context)
+      element = run_filter_function(filter.Pandoc, element, context)
+      return element
+    end
+  end
+
+  -- Create and call traversal function
+  local jog_internal = make_jogger(filter, context)
+  return jog_internal(element)
+end
+
+--- Add `jog` as a method to all pandoc AST elements
+-- This uses undocumented features and might break!
+local function add_method(funname)
+  funname = funname or 'jog'
+  pandoc.Space()          -- init metatable 'Inline'
+  pandoc.HorizontalRule() -- init metatable 'Block'
+  pandoc.Meta{}           -- init metatable 'Meta'
+  pandoc.Pandoc{}         -- init metatable 'Pandoc'
+  pandoc.Blocks{}         -- init metatable 'Blocks'
+  pandoc.Inlines{}        -- init metatable 'Inlines'
+  pandoc.Caption{}        -- init metatable 'Caption'
+  pandoc.Cell{}           -- init metatable 'Cell'
+  pandoc.Row{}            -- init metatable 'Row'
+  pandoc.TableHead{}      -- init metatable 'TableHead'
+  pandoc.TableFoot{}      -- init metatable 'TableFoot'
+  local reg = debug.getregistry()
+  List{
+    'Block', 'Inline', 'Pandoc',
+    'pandoc Cell', 'pandoc Row', 'pandoc TableHead', 'pandoc TableFoot',
+    'Caption', 'Cell', 'Row', 'TableHead', 'TableFoot',
+  }:map(
+    function (name)
+      if reg[name] then
+        reg[name].methods[funname] = jog
+      end
+    end
+  )
+  for name in pairs(listy_type) do
+    if reg[name] then
+      reg[name][funname] = jog
+    end
+  end
+  if reg['Meta'] then
+    reg['Meta'][funname] = jog
+  end
+end
+
+local mt = {
+  __call = function (_, ...)
+    return jog(...)
+  end
+}
+
+local M = setmetatable({}, mt)
+M.jog = jog
+M.add_method = add_method
+
+return M