#!/usr/bin/env texlua
-- SPDX-License-Identifier: MIT
-- Copyright (c) 2026 import-citation-cff contributors

local kpse = require("kpse")
kpse.set_program_name("luatex")
local script_directory = arg[0]:match("^(.*[/\\])") or "./"
local lfs = require("lfs")
local windows = package.config:sub(1, 1) == "\\"

-- Kpathsea's Lua searcher does not use package.path. Prefer sibling files in
-- a source checkout; installed modules can fall back to the TeX search path.
local function load_module(name)
  local filename = script_directory .. name .. ".lua"
  if lfs.isfile(filename) then
    package.loaded[name] = dofile(filename)
    return package.loaded[name]
  end
  return require(name)
end

local function read_file(filename)
  local input, message = io.open(filename, "rb")
  if not input then
    error(message, 0)
  end
  local text, read_error = input:read("*a")
  input:close()
  if not text then
    error(read_error, 0)
  end
  return text
end

local function options(arguments)
  local result, positional = {}, false
  local index = 1
  while index <= #arguments do
    local value = arguments[index]
    if not positional and (value == "--help" or value == "-h") then
      return {help = true}
    elseif not positional and value == "--version" then
      return {version = true}
    elseif not positional and value == "--" then
      positional = true
    elseif not positional and (value == "--output" or value == "-o"
      or value:match("^%-%-output=")) then
      if result.output then
        error("--output may be specified only once", 0)
      end
      result.output = value:match("^%-%-output=(.*)$")
      if not result.output then
        index = index + 1
        result.output = arguments[index]
      end
      if not result.output or result.output == "" then
        error("--output requires a filename", 0)
      end
    elseif not positional and value:sub(1, 1) == "-" then
      error("unknown option: " .. value, 0)
    elseif result.input then
      error("expected exactly one input TeX file", 0)
    else
      result.input = value
    end
    index = index + 1
  end
  if not result.input then
    error("expected an input TeX file (see --help)", 0)
  end
  return result
end

local function absolute(filename)
  if windows then
    if not filename:match("^[/\\]") and not filename:match("^%a:[/\\]") then
      filename = lfs.currentdir() .. "/" .. filename
    end
    filename = filename:gsub("\\", "/")
  elseif not filename:match("^/") then
    filename = lfs.currentdir() .. "/" .. filename
  end
  -- A Windows path keeps its drive, as in C:/Users, without a leading slash.
  local drive = windows and filename:match("^%a:") or ""
  local parts = {}
  for part in filename:sub(#drive + 1):gmatch("[^/]+") do
    if part == ".." then
      parts[#parts] = nil
    elseif part ~= "." then
      parts[#parts + 1] = part
    end
  end
  return drive .. "/" .. table.concat(parts, "/")
end

local function protect_input(input, output)
  if absolute(input) == absolute(output) then
    error("refusing to overwrite the input TeX file", 0)
  end
  local original, target = lfs.attributes(input), lfs.attributes(output)
  if original and target and original.ino and original.ino ~= 0
    and original.dev == target.dev and original.ino == target.ino then
    error("refusing to overwrite the input TeX file (same file)", 0)
  end
end

-- Allocate a private directory next to the destination, then rename the
-- complete result into place. A conversion or write failure keeps the old
-- destination intact. No shell commands or global temporary paths are used.
local function write_output(filename, text)
  local directory, basename = filename:match("^(.*[/\\])([^/\\]+)$")
  directory, basename = directory or "./", basename or filename
  local temporary
  for index = 1, 100 do
    local candidate = directory .. "." .. basename .. ".cfflatexpand-"
      .. os.time() .. "-" .. index
    if lfs.mkdir(candidate) then
      temporary = candidate
      break
    end
  end
  if not temporary then
    error("cannot create an output temporary directory beside " .. filename, 0)
  end
  local staged = temporary .. "/output.tex"
  local success, message = pcall(function()
    local output, open_error = io.open(staged, "wb")
    if not output then
      error(open_error, 0)
    end
    local written, write_error = output:write(text)
    local closed, close_error = output:close()
    if not written or not closed then
      error(write_error or close_error, 0)
    end
    local renamed, rename_error = os.rename(staged, filename)
    -- Windows does not rename a file onto an existing one. Move the old
    -- destination into the private directory, and back if the new file
    -- cannot take its place.
    if not renamed and windows and lfs.attributes(filename, "mode") == "file" then
      local previous = temporary .. "/previous.tex"
      if os.rename(filename, previous) then
        renamed, rename_error = os.rename(staged, filename)
        if renamed then
          os.remove(previous)
        else
          os.rename(previous, filename)
        end
      end
    end
    if not renamed then
      error(rename_error, 0)
    end
  end)
  os.remove(staged)
  lfs.rmdir(temporary)
  if not success then
    error(message, 0)
  end
end

local function main()
  local selected = options(arg)
  if selected.help then
    load_module("cfflatex-data")
    io.stdout:write(load_module("cfflatexpand").help)
    return
  end
  if selected.version then
    local filename = script_directory .. "import-citation-cff.sty"
    if not lfs.isfile(filename) then
      filename = kpse.find_file("import-citation-cff.sty", "tex") or filename
    end
    local version = read_file(filename):match(
      "\\ProvidesExplPackage%s*{import%-citation%-cff}%s*{[^}]*}%s*{([^}]+)}")
    if not version then
      error("cannot read the import-citation-cff version from " .. filename, 0)
    end
    io.stdout:write("cfflatexpand (import-citation-cff) " .. version .. "\n")
    return
  end
  if selected.output and selected.output ~= "-" then
    protect_input(selected.input, selected.output)
  end
  load_module("cfflatex-data")
  local expand = load_module("cfflatexpand")
  local function render_authors(model, author_options)
    load_module("cfflatex")
    local document_directory = absolute(selected.input):match("^(.*[/\\])")
    return load_module("cfflatexpand-authors").render(model, author_options,
      script_directory, document_directory)
  end
  local result = expand.transform(read_file(selected.input), selected.input, render_authors)
  if selected.output and selected.output ~= "-" then
    write_output(selected.output, result)
  else
    -- Windows would write each line feed as CR LF, and CR LF as CR CR LF,
    -- which TeX reads as an extra empty line. Write the bytes unchanged.
    lfs.setmode(io.stdout, "binary")
    local success, message = io.stdout:write(result)
    if success then
      success, message = io.stdout:flush()
    end
    if not success then
      error(message, 0)
    end
  end
end

local success, message = pcall(main)
if not success then
  io.stderr:write("cfflatexpand: " .. tostring(message) .. "\n")
  os.exit(1)
end