sile 0.15.5

Simon’s Improved Layout Engine
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local base = require("inputters.base")

local _variant = "epnf"
local parser
local function load_parser ()
   parser = require("inputters.sil-" .. _variant)
end

local inputter = pl.class(base)
inputter._name = "sil"

inputter.order = 50

inputter.appropriate = function (round, filename, doc)
   if not parser then
      load_parser()
   end
   if round == 1 then
      return filename:match(".sil$")
   elseif round == 2 then
      local sniff = doc:sub(1, 100)
      local promising = sniff:match("\\begin") or sniff:match("\\document") or sniff:match("\\sile")
      return promising and inputter.appropriate(3, filename, doc) or false
   elseif round == 3 then
      local status, _ = pcall(parser, doc)
      return status
   end
end

function inputter:_init (options)
   options = options or {}
   if options.variant then
      _variant = options.variant
      load_parser()
   else
      if not parser then
         load_parser()
      end
   end
   -- Save time when parsing strings by only setting up the grammar once per
   -- instantiation then re-using it on every use.
   self._parser = parser
   base._init(self)
end

local linecache = {}
local lno, col, lastpos
local function resetCache ()
   lno = 1
   col = 1
   lastpos = 0
   linecache = { { lno = 1, pos = 1 } }
end

local function getline (str, pos)
   local start = 1
   lno = 1
   if pos > lastpos then
      lno = linecache[#linecache].lno
      start = linecache[#linecache].pos + 1
      col = 1
   else
      for j = 1, #linecache - 1 do
         if linecache[j + 1].pos >= pos then
            lno = linecache[j].lno
            col = pos - linecache[j].pos
            return lno, col
         end
      end
   end
   for i = start, pos do
      if string.sub(str, i, i) == "\n" then
         lno = lno + 1
         col = 1
         linecache[#linecache + 1] = { pos = i, lno = lno }
         lastpos = i
      end
      col = col + 1
   end
   return lno, col
end

local function massage_ast (tree, doc)
   if type(tree) == "string" then
      return tree
   end
   if tree.pos then
      tree.lno, tree.col = getline(doc, tree.pos)
      tree.pos = nil
   end
   SU.debug("inputter", "Processing ID:", tree.id)
   if false or tree.id == "comment" then
      SU.debug("inputter", "Discarding comment:", pl.stringx.strip(tree[1]))
      return {}
   elseif
      false
      or tree.id == "document"
      or tree.id == "braced_content"
      or tree.id == "passthrough_content"
      or tree.id == "braced_passthrough_content"
      or tree.id == "env_passthrough_content"
   then
      SU.debug("inputter", "Re-massage subtree", tree.id)
      return massage_ast(tree[1], doc)
   elseif
      false
      or tree.id == "text"
      or tree.id == "passthrough_text"
      or tree.id == "braced_passthrough_text"
      or tree.id == "env_passthrough_text"
   then
      SU.debug("inputter", "  - Collapse subtree")
      return tree[1]
   elseif false or tree.id == "content" or tree.id == "environment" or tree.id == "command" then
      SU.debug("inputter", "  - Massage in place", tree.id)
      for key, val in ipairs(tree) do
         SU.debug("inputter", "    -", val.id)
         if val.id == "content" then
            SU.splice(tree, key, key, massage_ast(val, doc))
         elseif val.id then -- requiring an id discards nodes with no content such as comments
            tree[key] = massage_ast(val, doc)
         end
      end
      return tree
   end
end

function inputter:parse (doc)
   local status, result = pcall(self._parser, doc)
   if not status then
      return SU.error(([[Unable to parse input document to an AST tree. Parser error:

%s  thrown from document beginning]]):format(pl.stringx.indent(result, 6)))
   end
   resetCache()
   local top = massage_ast(result[1], doc)
   local tree
   -- Content not part of a tagged command could either be part of a document
   -- fragment or junk (e.g. comments, whitespace) outside of a document tag. We
   -- need to either capture the document tag only or decide this is a fragment
   -- and wrap it in a document tag.
   for _, leaf in ipairs(top) do
      if leaf.command and (leaf.command == "document" or leaf.command == "sile") then
         tree = leaf
         break
      end
   end
   -- In the event we didn't isolate a top level document tag above, assume this
   -- is a fragment and wrap it in one.
   if not tree then
      tree = { top, command = "document" }
   end
   -- SU.dump(tree)
   return { tree }
end

return inputter