--[[
pandoc.lua

Copyright © 2017 Albert Krewinkel

Permission to use, copy, modify, and/or distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright notice
and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
]]

---
-- Lua functions for pandoc scripts.
--
-- @author Albert Krewinkel
-- @copyright © 2017 Albert Krewinkel
-- @license MIT
local M = {
  _VERSION = "0.2.0"
}

------------------------------------------------------------------------
-- The base class for pandoc's AST elements.
-- @type Element
-- @local
local Element = {}

--- Create a new element subtype
-- @local
function Element:make_subtype(o)
  o = o or {}
  setmetatable(o, self)
  self.__index = self
  return o
end

--- Create a new element given its tag and arguments
-- @local
function Element:new(tag, ...)
  local element = { t = tag }
  local content = {...}
  -- special case for unary constructors
  if #content == 1 then
    element.c = content[1]
  -- Don't set 'c' field if no further arguments were given. This is important
  -- for nullary constructors like `Space` and `HorizontalRule`.
  elseif #content > 0 then
    element.c = content
  end
  setmetatable(element, self)
  self.__index = self
  return element
end

--- Create a new constructor
-- @local
-- @param tag Tag used to identify the constructor
-- @param fn Function to be called when constructing a new element
-- @return function that constructs a new element
function Element:create_constructor(tag, fn, accessors)
  local constr = self:make_subtype({tag = tag, getters = {}, setters = {}})

  -- Add accessors to the metatable
  if type(accessors) == "string" then
    constr.getters[accessors] = function(elem)
      return elem.c
    end
    constr.setters[accessors] = function(elem, v)
      elem.c = v
    end
  else
    for i = 1, #(accessors or {}) do
      if type(accessors[i]) == "string" then
        constr.getters[accessors[i]] = function(elem)
          return elem.c[i]
        end
        constr.setters[accessors[i]] = function(elem, v)
          elem.c[i] = v
        end
      else -- only two levels of nesting are supported
        for k, v in ipairs(accessors[i]) do
          constr.getters[v] = function(elem)
            return elem.c[i][k]
          end
          constr.setters[v] = function(elem, v)
            elem.c[i][k] = v
          end
        end
      end
    end
  end

  function constr:new(...)
    local obj = fn(...)
    setmetatable(obj, self)
    self.__index = function(t, k)
      if getmetatable(t).getters[k] then
        return getmetatable(t).getters[k](t)
      elseif k == "t" then
        return getmetatable(t)["tag"]
      else
        return getmetatable(t)[k]
      end
    end
    self.__newindex = function(t, k, v)
      if getmetatable(t).setters[k] then
        getmetatable(t).setters[k](t, v)
      else
        rawset(t, k, v)
      end
    end
    return obj
  end
  self.constructor = self.constructor or {}
  self.constructor[tag] = constr
  return constr
end

--- Calls the constructor, creating a new element.
-- @local
function Element.__call(t, ...)
  return t:new(...)
end

------------------------------------------------------------------------
--- Pandoc Document
-- @section document

--- A complete pandoc document
-- @function Doc
-- @tparam      {Block,...} blocks      document content
-- @tparam[opt] Meta        meta        document meta data
function M.Doc(blocks, meta)
  meta = meta or {}
  return {
    ["blocks"] = blocks,
    ["meta"] = meta,
    ["pandoc-api-version"] = {1,17,0,5},
  }
end


------------------------------------------------------------------------
-- MetaValue
-- @section MetaValue
M.MetaValue = Element:make_subtype{}
M.MetaValue.__call = function(t, ...)
  return t:new(...)
end
--- Meta blocks
-- @function MetaBlocks
-- @tparam {Block,...} blocks blocks

--- Meta inlines
-- @function MetaInlines
-- @tparam {Inline,...} inlines inlines

--- Meta list
-- @function MetaList
-- @tparam {MetaValue,...} meta_values list of meta values

--- Meta map
-- @function MetaMap
-- @tparam table a string-index map of meta values
M.meta_value_types = {
  "MetaBlocks",
  "MetaInlines",
  "MetaList",
  "MetaMap",
}
for i = 1, #M.meta_value_types do
  M[M.meta_value_types[i]] = M.MetaValue:create_constructor(
    M.meta_value_types[i],
    function(content)
      return content
    end
  )
end

--- Creates string to be used in meta data.
-- Does nothing, lua strings are meta strings.
-- @function MetaString
-- @tparam string str string value
function M.MetaString(str)
  return str
end

--- Creates boolean to be used in meta data.
-- Does nothing, lua booleans are meta booleans.
-- @function MetaBool
-- @tparam boolean bool boolean value
function M.MetaBool(bool)
  return bool
end

------------------------------------------------------------------------
-- Blocks
-- @section Block

--- Block elements
M.Block = Element:make_subtype{}
M.Block.__call = function (t, ...)
  return t:new(...)
end

--- Creates a block quote element
-- @function BlockQuote
-- @tparam      {Block,...} content     block content
-- @treturn     Block                   block quote element
M.BlockQuote = M.Block:create_constructor(
  "BlockQuote",
  function(content) return {c = content} end,
  "content"
)

--- Creates a bullet (i.e. unordered) list.
-- @function BulletList
-- @tparam      {{Block,...},...} content     list of items
-- @treturn     Block block quote element
M.BulletList = M.Block:create_constructor(
  "BulletList",
  function(content) return {c = content} end,
  "content"
)

--- Creates a code block element
-- @function CodeBlock
-- @tparam      string      text        code string
-- @tparam[opt] Attributes  attributes  element attributes
-- @treturn     Block                   code block element
M.CodeBlock = M.Block:create_constructor(
  "CodeBlock",
  function(text, attributes) return {c = {attributes, text}} end,
  {{"identifier", "classes", "attributes"}, "text"}
)

--- Creates a definition list, containing terms and their explanation.
-- @function DefinitionList
-- @tparam      {{{Inline,...},{Block,...}},...} content     list of items
-- @treturn     Block block quote element
M.DefinitionList = M.Block:create_constructor(
  "DefinitionList",
  function(content) return {c = content} end,
  "content"
)

--- Creates a div element
-- @function Div
-- @tparam      {Block,...} content     block content
-- @tparam[opt] Attributes  attributes  element attributes
-- @treturn     Block                   code block element
M.Div = M.Block:create_constructor(
  "Div",
  function(content, attributes) return {c = {attributes, content}} end,
  {{"identifier", "classes", "attributes"}, "content"}
)

--- Creates a block quote element.
-- @function Header
-- @tparam      int          level       header level
-- @tparam      Attributes   attributes  element attributes
-- @tparam      {Inline,...} content     inline content
-- @treturn     Block                    header element
M.Header = M.Block:create_constructor(
  "Header",
  function(level, attributes, content)
    return {c = {level, attributes, content}}
  end,
  {"level", {"identifier", "classes", "attributes"}, "content"}
)

--- Creates a horizontal rule.
-- @function HorizontalRule
-- @treturn     Block                   horizontal rule
M.HorizontalRule = M.Block:create_constructor(
  "HorizontalRule",
  function() return {} end
)

--- Creates a line block element.
-- @function LineBlock
-- @tparam      {{Inline,...},...} content    inline content
-- @treturn     Block                   block quote element
M.LineBlock = M.Block:create_constructor(
  "LineBlock",
  function(content) return {c = content} end,
  "content"
)

--- Creates a null element.
-- @function Null
-- @treturn     Block                   null element
M.Null = M.Block:create_constructor(
  "Null",
  function() return {} end
)

--- Creates an ordered list.
-- @function OrderedList
-- @tparam      {{Block,...},...} items list items
-- @param[opt]  listAttributes list parameters
-- @treturn     Block
M.OrderedList = M.Block:create_constructor(
  "OrderedList",
  function(items, listAttributes)
    return {c = {listAttributes,items}}
  end,
  {{"start", "style", "delimiter"}, "content"}
)

--- Creates a para element.
-- @function Para
-- @tparam      {Inline,...} content    inline content
-- @treturn     Block                   block quote element
M.Para = M.Block:create_constructor(
  "Para",
  function(content) return {c = content} end,
  "content"
)

--- Creates a plain element.
-- @function Plain
-- @tparam      {Inline,...} content    inline content
-- @treturn     Block                   block quote element
M.Plain = M.Block:create_constructor(
  "Plain",
  function(content) return {c = content} end,
  "content"
)

--- Creates a raw content block of the specified format.
-- @function RawBlock
-- @tparam      string      format      format of content
-- @tparam      string      text        string content
-- @treturn     Block                   block quote element
M.RawBlock = M.Block:create_constructor(
  "RawBlock",
  function(format, text) return {c = {format, text}} end,
  {"format", "text"}
)

--- Creates a table element.
-- @function Table
-- @tparam      {Inline,...} caption    table caption
-- @tparam      {AlignDefault|AlignLeft|AlignRight|AlignCenter,...} aligns alignments
-- @tparam      {int,...}    widths     column widths
-- @tparam      {Block,...}  headers    header row
-- @tparam      {{Block,...}} rows      table rows
-- @treturn     Block                   block quote element
M.Table = M.Block:create_constructor(
  "Table",
  function(caption, aligns, widths, headers, rows)
    return {c = {caption, aligns, widths, headers, rows}}
  end
)


------------------------------------------------------------------------
-- Inline
-- @section Inline

--- Inline element class
M.Inline = Element:make_subtype{}
M.Inline.__call = function (t, ...)
  return t:new(...)
end

--- Creates a Cite inline element
-- @function Cite
-- @tparam {Inline,...}   content       List of inlines
-- @tparam {Citation,...} citations     List of citations
-- @treturn Inline citations element
M.Cite = M.Inline:create_constructor(
  "Cite",
  function(content, citations) return {c = {citations, content}} end,
  {"citations", "content"}
)

--- Creates a Code inline element
-- @function Code
-- @tparam      string      text        brief image description
-- @tparam[opt] Attributes  attributes  additional attributes
-- @treturn Inline code element
M.Code = M.Inline:create_constructor(
  "Code",
  function(text, attributes) return {c = {attributes, text}} end,
  {{"identifier", "classes", "attributes"}, "text"}
)

--- Creates an inline element representing emphasised text.
-- @function Emph
-- @tparam      {Inline,..} content     inline content
-- @treturn Inline emphasis element
M.Emph = M.Inline:create_constructor(
  "Emph",
  function(content) return {c = content} end,
  "content"
)

--- Creates a Image inline element
-- @function Image
-- @tparam      {Inline,..} caption     text used to describe the image
-- @tparam      string      src         path to the image file
-- @tparam[opt] string      title       brief image description
-- @tparam[opt] Attributes  attributes  additional attributes
-- @treturn Inline image element
M.Image = M.Inline:create_constructor(
  "Image",
  function(caption, src, title, attributes)
    title = title or ""
    attributes = attributes or Attribute.empty
    return {c = {attributes, caption, {src, title}}}
  end,
  {"attributes", "caption", {"src", "title"}}
)

--- Create a LineBreak inline element
-- @function LineBreak
-- @treturn Inline linebreak element
M.LineBreak = M.Inline:create_constructor(
  "LineBreak",
  function() return {} end
)

--- Creates a link inline element, usually a hyperlink.
-- @function Link
-- @tparam      {Inline,..} content     text for this link
-- @tparam      string      target      the link target
-- @tparam[opt] string      title       brief link description
-- @tparam[opt] Attributes  attributes  additional attributes
-- @treturn Inline image element
M.Link = M.Inline:create_constructor(
  "Link",
  function(content, target, title, attributes)
    title = title or ""
    attributes = attributes or Attribute.empty
    return {c = {attributes, content, {target, title}}}
  end,
  {"attributes", "content", {"target", "title"}}
)

--- Creates a Math element, either inline or displayed. It is usually simpler to
-- use one of the specialized functions @{InlineMath} or @{DisplayMath} instead.
-- @function Math
-- @tparam      "InlineMath"|"DisplayMath" mathtype rendering specifier
-- @tparam      string      text        Math content
-- @treturn     Inline                  Math element
M.Math = M.Inline:create_constructor(
  "Math",
  function(mathtype, text)
    return {c = {mathtype, text}}
  end,
  {"mathtype", "text"}
)
--- Creates a DisplayMath element.
-- @function DisplayMath
-- @tparam      string      text        Math content
-- @treturn     Inline                  Math element
M.DisplayMath = M.Inline:create_constructor(
  "DisplayMath",
  function(text) return M.Math("DisplayMath", text) end,
  {"mathtype", "text"}
)
--- Creates an InlineMath inline element.
-- @function InlineMath
-- @tparam      string      text        Math content
-- @treturn     Inline                  Math element
M.InlineMath = M.Inline:create_constructor(
  "InlineMath",
  function(text) return M.Math("InlineMath", text) end,
  {"mathtype", "text"}
)

--- Creates a Note inline element
-- @function Note
-- @tparam      {Block,...} content     footnote block content
M.Note = M.Inline:create_constructor(
  "Note",
  function(content) return {c = content} end,
  "content"
)

--- Creates a Quoted inline element given the quote type and quoted content. It
-- is usually simpler to use one of the specialized functions @{SingleQuoted} or
-- @{DoubleQuoted} instead.
-- @function Quoted
-- @tparam      "DoubleQuote"|"SingleQuote" quotetype type of quotes to be used
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  quoted element
M.Quoted = M.Inline:create_constructor(
  "Quoted",
  function(quotetype, content) return {c = {quotetype, content}} end,
  {"quotetype", "content"}
)
--- Creates a single-quoted inline element.
-- @function SingleQuoted
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  quoted element
-- @see Quoted
M.SingleQuoted = M.Inline:create_constructor(
  "SingleQuoted",
  function(content) return M.Quoted(M.SingleQuote, content) end,
  {"quotetype", "content"}
)
--- Creates a single-quoted inline element.
-- @function DoubleQuoted
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  quoted element
-- @see Quoted
M.DoubleQuoted = M.Inline:create_constructor(
  "DoubleQuoted",
  function(content) return M.Quoted("DoubleQuote", content) end,
  {"quotetype", "content"}
)

--- Creates a RawInline inline element
-- @function RawInline
-- @tparam      string      format      format of the contents
-- @tparam      string      text        string content
-- @treturn     Inline                  raw inline element
M.RawInline = M.Inline:create_constructor(
  "RawInline",
  function(format, text) return {c = {format, text}} end,
  {"format", "text"}
)

--- Creates text rendered in small caps
-- @function SmallCaps
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  smallcaps element
M.SmallCaps = M.Inline:create_constructor(
  "SmallCaps",
  function(content) return {c = content} end,
  "content"
)

--- Creates a SoftBreak inline element.
-- @function SoftBreak
-- @treturn     Inline                  softbreak element
M.SoftBreak = M.Inline:create_constructor(
  "SoftBreak",
  function() return {} end
)

--- Create a Space inline element
-- @function Space
-- @treturn Inline space element
M.Space = M.Inline:create_constructor(
  "Space",
  function() return {} end
)

--- Creates a Span inline element
-- @function Span
-- @tparam      {Inline,..} content     inline content
-- @tparam[opt] Attributes  attributes  additional attributes
-- @treturn Inline span element
M.Span = M.Inline:create_constructor(
  "Span",
  function(content, attributes) return {c = {attributes, content}} end,
  {{"identifier", "classes", "attributes"}, "content"}
)

--- Creates a Str inline element
-- @function Str
-- @tparam      string      text        content
-- @treturn     Inline                  string element
M.Str = M.Inline:create_constructor(
  "Str",
  function(text) return {c = text} end,
  "text"
)

--- Creates text which is striked out.
-- @function Strikeout
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  strikeout element
M.Strikeout = M.Inline:create_constructor(
  "Strikeout",
  function(content) return {c = content} end,
  "content"
)

--- Creates a Strong element, whose text is usually displayed in a bold font.
-- @function Strong
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  strong element
M.Strong = M.Inline:create_constructor(
  "Strong",
  function(content) return {c = content} end,
  "content"
)

--- Creates a Subscript inline element
-- @function Subscript
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  subscript element
M.Subscript = M.Inline:create_constructor(
  "Subscript",
  function(content) return {c = content} end,
  "content"
)

--- Creates a Superscript inline element
-- @function Superscript
-- @tparam      {Inline,..} content     inline content
-- @treturn     Inline                  strong element
M.Superscript = M.Inline:create_constructor(
  "Superscript",
  function(content) return {c = content} end,
  "content"
)


------------------------------------------------------------------------
-- Helpers
-- @section helpers

-- Attributes
M.Attributes = {}
--- Create a new set of attributes (Attr).
-- @function Attributes
-- @tparam      table        key_values table containing string keys and values
-- @tparam[opt] string       id         element identifier
-- @tparam[opt] {string,...} classes    element classes
-- @return element attributes
M.Attributes.__call = function(t, key_values, id, classes)
  id = id or ''
  classes = classes or {}
  local attr = {id, classes, key_values}
  setmetatable(attr, t)
  return attr
end
M.Attributes.__index = function(t, k)
  if rawget(t, k) then
    return rawget(t, k)
  elseif k == "id" then
    if rawget(t, 1) == '' then
      return nil
    else
      return rawget(t, 1)
    end
  elseif k == "class" then
    if #(rawget(t, 2)) == 0 then
      return nil
    else
      return table.concat(t[2], ' ')
    end
  else
    for _, p in ipairs(t[3]) do
      if k == p[1] then
        return p[2]
      end
    end
    return nil
  end
end
M.Attributes.__newindex = function(t, k, v)
  if rawget(t, k) then
    rawset(t, k, v)
  elseif k == "id" then
    rawset(t, 1, v)
  elseif k == "class" then
    if type(v) == "string" then
      rawset(t, 2, {v})
    else
      rawset(t, 2, v)
    end
  else
    for _, p in ipairs(rawget(t, 3)) do
      if k == p[1] then
        p[2] = v
        return
      end
    end
    kv = rawget(t, 3)
    kv[#kv + 1] = {k, v}
    rawset(t, 3, kv)
  end
end
setmetatable(M.Attributes, M.Attributes)


--- Creates a single citation.
-- @function Citation
-- @tparam      string       id       citation identifier (like a bibtex key)
-- @tparam      AuthorInText|SuppressAuthor|NormalCitation mode citation mode
-- @tparam[opt] {Inline,...} prefix   citation prefix
-- @tparam[opt] {Inline,...} suffix   citation suffix
-- @tparam[opt] int          note_num note number
-- @tparam[opt] int          note_num hash number
M.Citation = function(id, mode, prefix, suffix, note_num, hash)
  prefix = prefix or {}
  suffix = suffix or {}
  note_num = note_num or 0
  hash = hash or 0
  return {
    citationId = id,
    citationPrefix = prefix,
    citationSuffix = suffix,
    citationMode = mode,
    citationNoteNum = note_num,
    citationHash = hash,
  }
end


------------------------------------------------------------------------
-- Constants
-- @section constants

--- Author name is mentioned in the text.
-- @see Citation
-- @see Cite
M.AuthorInText = "AuthorInText"

--- Author name is suppressed.
-- @see Citation
-- @see Cite
M.SuppressAuthor = "SuppressAuthor"

--- Default citation style is used.
-- @see Citation
-- @see Cite
M.NormalCitation = "NormalCitation"

--- Table cells aligned left.
-- @see Table
M.AlignLeft = "AlignLeft"

--- Table cells right-aligned.
-- @see Table
M.AlignRight = "AlignRight"

--- Table cell content is centered.
-- @see Table
M.AlignCenter = "AlignCenter"

--- Table cells are alignment is unaltered.
-- @see Table
M.AlignDefault = "AlignDefault"

--- Default list number delimiters are used.
-- @see OrderedList
M.DefaultDelim = "DefaultDelim"

--- List numbers are delimited by a period.
-- @see OrderedList
M.Period = "Period"

--- List numbers are delimited by a single parenthesis.
-- @see OrderedList
M.OneParen = "OneParen"

--- List numbers are delimited by a double parentheses.
-- @see OrderedList
M.TwoParens = "TwoParens"

--- List are numbered in the default style
-- @see OrderedList
M.DefaultStyle = "DefaultStyle"

--- List items are numbered as examples.
-- @see OrderedList
M.Example = "Example"

--- List are numbered using decimal integers.
-- @see OrderedList
M.Decimal = "Decimal"

--- List are numbered using lower-case roman numerals.
-- @see OrderedList
M.LowerRoman = "LowerRoman"

--- List are numbered using upper-case roman numerals
-- @see OrderedList
M.UpperRoman = "UpperRoman"

--- List are numbered using lower-case alphabetic characters.
-- @see OrderedList
M.LowerAlpha = "LowerAlpha"

--- List are numbered using upper-case alphabetic characters.
-- @see OrderedList
M.UpperAlpha = "UpperAlpha"


------------------------------------------------------------------------
-- Helper Functions
-- @section helpers

--- Parse the given string into a Pandoc document.
-- @tparam string markup the markup to be parsed
-- @tparam[opt] string format format specification, defaults to "markdown".
-- @return Doc pandoc document
function M.read(markup, format)
  format = format or "markdown"
  local pd = pandoc.__read(format, markup)
  if type(pd) == "string" then
    error(pd)
  else
    return pd
  end
end

--- Use functions defined in the global namespace to create a pandoc filter.
-- All globally defined functions which have names of pandoc elements are
-- collected into a new table.
-- @return A list of filter functions
-- @usage
-- -- within a file defining a pandoc filter:
-- function Str(text)
--   return pandoc.Str(utf8.upper(text))
-- end
--
-- return {pandoc.global_filter()}
-- -- the above is equivallent to
-- -- return {{Str = Str}}
function M.global_filter()
  local res = {}
  for k, v in pairs(_G) do
    if M.Inline.constructor[k] or M.Block.constructor[k] or M.Block.constructors[k] or k == "Doc" then
      res[k] = v
    end
  end
  return res
end

return M