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--
-- Copyright (c) 2021-2024 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 unicode
local bibtex_data
local util
if kpse then
unicode = require("citeproc-unicode")
bibtex_data = require("citeproc-bibtex-data")
util = require("citeproc-util")
else
unicode = require("citeproc.unicode")
bibtex_data = require("citeproc.bibtex-data")
util = require("citeproc.util")
end
local lpeg = require("lpeg")
local latex_parser = nil -- load as needed
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 BibtexEntry { key: string, type: string, fields: table<string, string> }
---@class BibtexData
---@field entries BibtexEntry[]
---@field entries_by_id table<string, BibtexEntry>
---@field strings table<string, string>
---@field preamble string?
---@alias Exception table
---comment
---@param bib_str string
---@param strings table<string, string>?
---@return BibtexData?
---@return Exception[]
function BibtexParser:parse(bib_str, strings)
if strings then
strings = setmetatable({}, {__index = strings})
else
strings = setmetatable({}, {__index = self.strings})
end
if type(bib_str) ~= "string" then
util.error("Invalid string")
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
---@type BibtexData
local res = {
---@type BibtexEntry[]
entries = {},
---@type table<string, BibtexEntry>
entries_by_id = {},
strings = {},
preamble = nil,
}
---@type Exception[]
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, entry)
res.entries_by_id[entry.key] = entry
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
if kpse then
latex_parser = latex_parser or require("citeproc-latex-parser")
else
latex_parser = latex_parser or require("citeproc.latex-parser")
end
value = latex_parser.latex_to_unicode(value)
end
-- if self.name_fields[field] then
-- if self.options.split_names then
-- local value = bibtex_parser.split_names(value)
-- 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<string, string>
---@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 is_biblatex_extended_format = false
if #parts > 0 and (string.match(parts[1], "^[a-zA-Z]+%-?i?%s*=")
or string.match(parts[1], '^"[a-zA-Z]+%-?i?%s*=.*"$')) then
is_biblatex_extended_format = true
end
local name = {}
if is_biblatex_extended_format then
name = bibtex_parser._split_extended_name_format(parts)
elseif #parts == 1 then
name = bibtex_parser._split_first_von_last_parts(parts[1])
elseif #parts == 2 then
name = bibtex_parser._split_von_last_parts(parts[1])
if parts[2] ~= "" then
name.first = parts[2]
end
elseif #parts == 3 then
name = bibtex_parser._split_last_jr_first_parts(parts)
elseif #parts > 3 then
util.error(string.format("Too many commas in name '%s'", str))
name = bibtex_parser._split_last_jr_first_parts(util.slice(parts, 1, 3))
end
return name
end
local function is_lower_word(word)
-- Word is a list of tokens
for _, token in ipairs(word) do
if string.match(token, "^{") then
if string.match(token, "^{\\") then
-- Special characters, level 0
local token_content
if string.match(token, "^{\\%w+") then
token_content = string.gsub(token, "^{\\%w+%s*", "")
else
token_content = string.gsub(token, "^{\\.%s*", "")
end
token_content = string.gsub(token, "}%s*$", "")
for i = 1, #token_content do
local char = string.sub(token_content, i, i)
if unicode.islower(char) then
return true
elseif unicode.isupper(char) then
return false
end
end
end
else
if unicode.islower(token) then
return true
elseif unicode.isupper(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
---@param parts string[]
---@return table<string, string>
function bibtex_parser._split_extended_name_format(parts)
local name = {}
for _, part in ipairs(parts) do
local key, value = string.match(part, "^([a-zA-Z]+%-?i?)%s*=%s*(.-)%s*$")
if not key then
key, value = string.match(part, '^"([a-zA-Z]+%-?i?)%s*=%s*(.-)%s*"%s*$')
end
if not key then
util.error(string.format("Invalid extended name part '%s'", part))
end
if key == "given" then
key = "first"
elseif key == "given-i" then
key = "first-i"
elseif key == "prefix" then
key = "von"
elseif key == "prefix-i" then
key = "von-i"
elseif key == "family" then
key = "last"
elseif key == "family-i" then
key = "last-i"
elseif key == "suffix" then
key = "jr"
elseif key == "suffix-i" then
key = "jr-i"
end
local braced_pattern = P"{" * C(balanced^0) * P"}" * P(-1)
local stripped = braced_pattern:match(value)
if stripped then
value = stripped
end
name[key] = value
end
return name
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
---@param parts string[]
---@return NameDict
function bibtex_parser._split_last_jr_first_parts(parts)
local 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
return name
end
--- Note that BibTeX find crossref in a case-insensitive manner (see
--- `article-crossref` in `xampl.bib`) which is unlike biber/biblatex.
--- This function is case-sensitive.
---@param entry_list BibtexEntry[]
---@param entry_dict table<string, BibtexEntry>?
function bibtex_parser.resolve_crossrefs(entry_list, entry_dict)
if not entry_dict then
entry_dict = {}
for _, entry in ipairs(entry_list) do
entry_dict[entry.key] = entry
end
end
for _, entry in ipairs(entry_list) do
local ref_entry = entry
---@type string?
local ref_key = entry.fields.crossref
while ref_key do
local crossref_entry = entry_dict[ref_key]
if crossref_entry then
ref_entry = crossref_entry
for field, value in pairs(ref_entry.fields) do
if not entry.fields[field] then
entry.fields[field] = value
end
end
ref_key = ref_entry.fields.crossref
else
util.warning(string.format("Didn't find a database entry for crossref '%s' in entry '%s'.", ref_key, ref_entry.key))
ref_entry.fields.crossref = nil
ref_key = nil
end
end
end
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
|