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|
--
-- Copyright (c) 2021-2023 Zeping Lee
-- Released under the MIT license.
-- Repository: https://github.com/zepinglee/citeproc-lua
--
--[[
A PEG-based implementation of a Bib(La)TeX database (.bib) parser
References notes: scripts/bibtex-parser-notes.md
--]]
-- @module bibtex_parser
local bibtex_parser = {}
local lpeg = require("lpeg")
local unicode = require("unicode")
local bibtex_data = require("citeproc-bibtex-data")
local latex_parser = nil -- load as needed
local util = require("citeproc-util")
local P = lpeg.P
local R = lpeg.R
local S = lpeg.S
local C = lpeg.C
local Cc = lpeg.Cc
local Cf = lpeg.Cf
local Cg = lpeg.Cg
local Cmt = lpeg.Cmt
local Cp = lpeg.Cp
local Ct = lpeg.Ct
local V = lpeg.V
-- Learned from <http://boston.conman.org/2020/06/05.1>.
local function case_insensitive_pattern(str)
local char = R("AZ", "az") / function (c) return P(c:lower()) + P(c:upper()) end
+ P(1) / function (c) return P(c) end
return Cf(char^1, function (a, b) return a * b end):match(str)
end
-- Merge multiple white spaces to one
local function normalize_white_space(str)
local res = string.gsub(str, "%s+", " ")
return res
end
-- Based on the grammar described at <https://github.com/aclements/biblib>.
local function get_bibtex_grammar()
local comment = (1 - P"@")^0
local space = S(" \t\r\n")^0
local comment_cmd = case_insensitive_pattern("comment")
local balanced = P{ "{" * V(1)^0 * "}" + (1 - S"{}") }
local ident = (- R"09") * (R"\x20\x7F" - S" \t\"#%'(),={}")^1
local piece = (P"{" * (balanced^0 / normalize_white_space) * P"}")
+ (P'"' * ((balanced - P'"')^0 / normalize_white_space) * P'"')
+ C(R("09")^1)
+ C(ident) / function (name)
return {
category = "string",
name = string.lower(name),
}
end
local value = Ct(piece * (space * P"#" * space * piece)^0)
local string_body = Cg(ident / string.lower, "name") * space * P"=" * space * Cg(value, "contents")
local string_cmd = Ct(Cg(Cc"string", "category") * case_insensitive_pattern("string") * space * (
P"{" * space * string_body * space * P"}"
+ P"(" * space * string_body * space * P")"
))
local preamble_body = Cg(value, "contents")
local preamble_cmd = Ct(Cg(Cc"preamble", "category") * case_insensitive_pattern("preamble") * space * (
P"{" * space * preamble_body * space * P"}"
+ P"(" * space * preamble_body * space * P")"
))
local key = (1 - S", \t}\r\n")^0
local key_paren = (1 - S", \t\r\n")^0
local field_value_pair = (ident / string.lower) * space * P"=" * space * value -- * record_success_position()
local entry_body = Cf(Ct"" * (P"," * space * Cg(field_value_pair))^0 * (P",")^-1, rawset)
local entry = Ct(Cg(Cc"entry", "category") * Cg(ident / string.lower, "type") * space * (
P"{" * space * Cg(key, "key") * space * Cg(entry_body, "fields")^-1 * space * (P"}")
+ P"(" * space * Cg(key_paren, "key") * space * Cg(entry_body, "fields")^-1 * space * (P")")
))
local command_or_entry = P"@" * space * (comment_cmd + preamble_cmd + string_cmd + entry)
-- The P(-1) causes nil parsing result in case of error.
local bibtex_grammar = Ct(comment * (command_or_entry * comment)^0) * P(-1)
return bibtex_grammar
end
local function concat_strings(pieces, strings)
local value = ""
for _, piece in ipairs(pieces) do
if type(piece) == "string" then
value = value .. piece
elseif type(piece) == "table" and piece.category == "string" then
local piece_str = strings[piece.name]
if piece_str then
value = value .. piece_str
else
util.warning(string.format('String name "%s" is undefined."', piece.name))
end
end
end
value = normalize_white_space(value)
return value
end
-- The parser class
---@class BibtexParser
local BibtexParser = {
grammar = get_bibtex_grammar(),
-- config
strings = {},
options = {
-- allow_escaped_braces = true,
convert_to_unicode = false,
-- common_strings = false,
split_names = false,
split_name_parts = false,
},
-- variables
name_fields = {},
}
---Create a new BibtexParser instance.
---@return BibtexParser
function BibtexParser:new()
local obj = {}
obj.options = util.clone(self.options)
for field, info in ipairs(bibtex_data.fields) do
if info.type == "name" then
obj.name_fields[field] = true
end
end
setmetatable(obj, self)
self.__index = self
return obj
end
---@alias BibtexData table
---@alias Exception table
---comment
---@return BibtexData?, Exception[]?
function BibtexParser:parse(bib_str, strings)
if strings then
strings = setmetatable({}, {__index = strings})
else
strings = setmetatable({}, {__index = self.strings})
end
local bib_objects = self.grammar:match(bib_str)
if not bib_objects then
local error = {
type = "error",
message = "BibTeX parser error.",
}
return nil, {error}
end
local res = {
entries = {},
strings = {},
preamble = nil,
}
local exceptions = {}
for _, object in ipairs(bib_objects) do
if object.category == "entry" then
local entry = self:_make_entry(object, strings)
table.insert(res.entries, object)
elseif object.category == "string" then
local string_value = concat_strings(object.contents, strings)
strings[object.name] = string_value
res.strings[object.name] = string_value
elseif object.category == "preamble" then
local value = concat_strings(object.contents, strings)
if res.preamble then
res.preamble = res.preamble .. "\n" .. value
else
res.preamble = value
end
-- elseif object.category == "comment" then
-- Is this really needed?
elseif object.category == "exception" then
-- TODO
end
end
return res, exceptions
end
function BibtexParser:_make_entry(object, strings)
object.category = nil
for field, value in pairs(object.fields) do
value = concat_strings(value, strings)
if self.options.convert_to_unicode then
latex_parser = latex_parser or require("citeproc-latex-parser")
value = latex_parser.latex_to_unicode(value)
end
if self.name_fields[field] then
if self.options.split_names then
value = bibtex_parser.split_names(value)
if self.options.split_name_parts then
for i, name in ipairs(value) do
value[i] = bibtex_parser.split_name_parts(name)
end
end
end
end
object.fields[field] = value
end
return object
end
-- continuation byte
local utf8_cont = lpeg.R("\128\191")
local utf8_char = lpeg.R("\0\127")
+ lpeg.R("\194\223") * utf8_cont
+ lpeg.R("\224\239") * utf8_cont * utf8_cont
+ lpeg.R("\240\244") * utf8_cont * utf8_cont * utf8_cont
local space_char = S(" \t\r\n")
local space = space_char^1
local white_space = space_char^0
local balanced = P { "{" * V(1) ^ 0 * "}" + (P "\\{" + P "\\}" + 1 - S "{}") }
local utf8_balanced = P { "{" * V(1) ^ 0 * "}" + (P "\\{" + P "\\}" + utf8_char - S "{}") }
-- The case-insensitivity trick is taken from <http://boston.conman.org/2020/06/05.1>.
local function ignore_case(str)
local char = R("AZ", "az") / function (c) return P(c:lower()) + P(c:upper()) end
+ P(1) / function (c) return P(c) end
return Cf(char^1, function (a, b) return a * b end):match(str)
end
---@alias NameDict table
---@alias NameStr string
---Split BibTeX names
---@param str NameStr name field value
---@return NameStr[]
function bibtex_parser.split_names(str)
local delimiter_and = ignore_case("and") * (space + -1)
local name = (balanced - space * delimiter_and)^1
local names = Ct(((white_space * delimiter_and) + C(name))^0)
return names:match(str)
end
---Split BibTeX name parts
---@param str NameStr single name string
---@return NameDict
function bibtex_parser.split_name_parts(str)
str = util.strip(str)
if string.match(str, ",$") then
util.warning(string.format('Name "%s" has has a comma at the end.', str))
str = string.gsub(str, ",$", '')
end
local comma = P","
local comma_part = (balanced - comma)^0
local comma_parts = Ct(C(comma_part) * (comma * white_space * C(comma_part))^0)
local parts = comma_parts:match(str)
local name = {}
if #parts == 1 then
name = bibtex_parser._split_first_von_last_parts(parts[1])
elseif #parts == 2 then
name = bibtex_parser._split_von_last_parts(parts[1])
if parts[2] ~= "" then
name.first = parts[2]
end
elseif #parts == 3 then
name = bibtex_parser._split_von_last_parts(parts[1])
if parts[2] ~= "" then
name.jr = parts[2]
end
if parts[3] ~= "" then
name.first = parts[3]
end
elseif #parts > 3 then
util.warning()
name = bibtex_parser._split_last_jr_fist_parts(util.slice(parts, 1, 3))
else
util.warning()
end
return name
end
local function is_upper_letter(char)
return unicode.utf8.upper(char) == char and unicode.utf8.lower(char) ~= char
end
local function is_lower_letter(char)
return unicode.utf8.lower(char) == char and unicode.utf8.upper(char) ~= char
end
local function is_lower_word(word)
-- Word is a list of tokens
for _, token in ipairs(word) do
if string.match(token, "^{") then
if string.match(token, "^{\\") then
-- Special characters, level 0
local token_content
if string.match(token, "^{\\%w+") then
token_content = string.gsub(token, "^{\\%w+%s*", "")
else
token_content = string.gsub(token, "^{\\.%s*", "")
end
token_content = string.gsub(token, "}%s*$", "")
for i = 1, #token_content do
local char = string.sub(token_content, i, i)
if is_lower_letter(char) then
return true
elseif is_upper_letter(char) then
return false
end
end
end
else
if is_lower_letter(token) then
return true
elseif is_upper_letter(token) then
return false
end
end
end
return false
end
local function join_words_and_seps(words, seps, start, stop)
local tokens = {}
for i = start, stop do
if i > start then
table.insert(tokens, seps[i])
end
for _, token in ipairs(words[i]) do
table.insert(tokens, token)
end
end
local res = table.concat(tokens, "")
if res == "" then
return nil
end
return res
end
function bibtex_parser._split_first_von_last_parts(str)
local word_sep = P"-" + P"~" + P(util.unicode['no-break space'])
local word_tokens = Ct(C(utf8_balanced - space_char - word_sep)^0)
local words_and_seps = Ct(word_tokens * (C(space + word_sep) * word_tokens)^0)
local pieces = words_and_seps:match(str)
local words = {}
local seps = { "" }
for _, piece in ipairs(pieces) do
if type(piece) == "table" then
table.insert(words, piece)
else
table.insert(seps, piece)
end
end
local von_start = 0
local von_stop = 0
local first_stop = #words - 1
local last_start = #words
-- for i, word_or_sep in ipairs(part) do
for i = 1, #words - 1 do
local word = words[i]
if is_lower_word(word) then
if von_start == 0 then
von_start = i
end
von_stop = i
end
end
-- util.debug(von_start)
-- util.debug(von_stop)
local name = {}
if von_stop > 0 then
name.von = join_words_and_seps(words, seps, von_start, von_stop)
last_start = von_stop + 1
first_stop = von_start - 1
end
name.last = join_words_and_seps(words, seps, last_start, #words)
if first_stop > 0 then
name.first = join_words_and_seps(words, seps, 1, first_stop)
end
return name
end
function bibtex_parser._split_von_last_parts(str)
local word_sep = P"-" + P"~" + P(util.unicode['no-break space'])
local word_tokens = Ct(C(utf8_balanced - space_char - word_sep)^0)
local words_and_seps = Ct(word_tokens * (C(space + word_sep) * word_tokens)^0)
local pieces = words_and_seps:match(str)
local words = {}
local seps = {""}
for _, piece in ipairs(pieces) do
if type(piece) == "table" then
table.insert(words, piece)
else
table.insert(seps, piece)
end
end
local von_stop = 0
local last_start = 1
-- for i, word_or_sep in ipairs(part) do
for i = #words - 1, 1, -1 do
local word = words[i]
if is_lower_word(word) then
von_stop = i
break
end
end
local name = {}
if von_stop > 0 then
name.von = join_words_and_seps(words, seps, 1, von_stop)
last_start = von_stop + 1
end
name.last = join_words_and_seps(words, seps, last_start, #words)
return name
end
bibtex_parser._default_parser = BibtexParser:new()
---comment
---@param bib_str string input string
---@param strings table<string, string> strings
---@return BibtexData?, Exception[]?
function bibtex_parser.parse(bib_str, strings)
return bibtex_parser._default_parser:parse(bib_str, strings)
end
bibtex_parser.BibtexParser = BibtexParser
return bibtex_parser
|