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-- Lua LSP Plugin to automatically recognize types for Pandoc Lua filter callbacks
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local kBlockElements = {
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  ['BlockQuote'] = true,
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  ['BulletList'] = true,
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  ['CodeBlock'] = true,
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  ['DefinitionList'] = true,
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  ['Div'] = true,
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  ['Header'] = true,
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  ['HorizontalRule'] = true,
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  ['LineBlock'] = true,
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  ['OrderedList'] = true,
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  ['Para'] = true,
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  ['Plain'] = true,
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  ['RawBlock'] = true,
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  ['Table'] = true
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}
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local kInlineElements = {
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  ['Cite'] = true,
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  ['Code'] = true,
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  ['Emph'] = true,
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  ['Image'] = true,
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  ['LineBreak'] = true,
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  ['Link'] = true,
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  ['Math'] = true,
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  ['Note'] = true,
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  ['Quote'] = true,
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  ['RawInline'] = true,
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  ['SmallCaps'] = true,
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  ['SoftBreak'] = true,
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  ['Space'] = true,
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  ['Span'] = true,
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  ['Str'] = true,
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  ['Strikeout'] = true,
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  ['Strong'] = true,
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  ['Superscript'] = true,
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  ['Subscript'] = true,
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  ['Underline'] = true
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}
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local kListElements = {
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  ['Blocks'] = true,
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  ['Inlines'] = true
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}
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local kTopLevelElements = {
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  ['Meta'] = true,
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  ['Pandoc'] = true
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}
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---@param newline boolean
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---@param start integer
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---@param leading string
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---@param elType string
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---@param elVar string
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---@return { start: integer, finish: integer, prefix: string } | nil
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local functionDiff = function(newline, start, leading, elType, elVar)
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  -- determine return type and tweak elType
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  local returnType = nil
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  if kBlockElements[elType] ~= nil then
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    returnType = 'pandoc.Block|pandoc.List|nil'
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  elseif kInlineElements[elType] ~= nil then
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    returnType = 'pandoc.Inline|pandoc.List|nil'
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  elseif kListElements[elType] ~= nil then
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    elType = 'List'
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    returnType = 'pandoc.List|nil'
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  elseif kTopLevelElements[elType] ~= nil then
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    returnType = 'pandoc.' .. elType .. '|nil'
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  end
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  -- if this is one of ours then return it
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  if returnType ~= nil then
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    -- handle variation between beginning of file and beginning of line
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    local prefix = ''
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    local finish = nil
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    if newline then
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      start = start - 1
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      finish = start
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      prefix = '\n'
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    else
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      finish = start - 1
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    end
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    -- provide the diff w/ requisite start and finish
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    return {
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      start = start,
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      finish = finish,
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      text = (prefix .. '%s---@param %s pandoc.%s\n%s---@return %s\n'):format(
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        leading,elVar,elType,leading,returnType
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      )
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    }
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  else
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    return nil
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  end
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end
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---@param uri string
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---@param text string
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function OnSetText(uri, text)
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  -- manage list of diffs
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  local diffs = {}
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  local addDiff = function(diff)
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    if diff then
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      diffs[#diffs+1] = diff
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    end
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  end
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  local patterns = {
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    -- Div = function(el)
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    '()([\t ]*)(%w+)%s*=%s*function%((%w+)%)',
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    -- function Div(el)
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    '()([\t ]*)function%s+(%w+)%((%w+)%)'  
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  }
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  for _, pattern in pairs(patterns) do
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    -- patterns in file (after first line)
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    for start, leading, elType, elVar in text:gmatch('\n' .. pattern) do
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      addDiff(functionDiff(true, start --[[@as integer]], leading, elType, elVar))
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    end
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     -- pattern on first line
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     local start, leading, elType, elVar = text:match('^' .. pattern)
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     if start ~= nil then
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       addDiff(functionDiff(false, start, leading, elType, elVar))
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     end
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  end
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  return diffs     
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end
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