dPDF = {}

-- object 1 :: catalog
-- object 2 :: outlines
-- object 3 :: pages

-- TODO:	addPage adds a header and reserves an object space
--			don't necessarily keep space for a font on each page

function dPDF.init()
	dPDF.buffer = ""
	dPDF.pages = 1
	dPDF.outlines = 1
	dPDF.fonts = 1
	
	dPDF.objects = 4
	dPDF.object = {}
	
	dPDF.page = {}
	dPDF.page_content = {}
	dPDF.font_content = {}
end

function dPDF.emit( s )
	dPDF.buffer = dPDF.buffer .. s .. "\n"
end

function dPDF.makeStream( s )
	return "\t<< /Length " .. s:len()+17 .. ">>\nstream\n" .. s .. "\nendstream"
end

function dPDF.addPage()
	print( "wrote page " .. dPDF.pages )
	dPDF.page[dPDF.pages] =
		"<<\t" ..
		"/Type /Page\n" ..
		"\t/Parent 3 0 R\n" ..
		"\t/MediaBox [ 0 0 612 792 ]\n" ..
		"\t/Contents " .. 6 + (dPDF.pages-1)*3 .. " 0 R\n" ..
		"\t/Resources << /ProcSet [/PDF] /Font << /F1 " .. 5+(dPDF.pages-1)*3 .. " 0 R >> >>\n" ..
		">>"

	dPDF.font_content[dPDF.fonts] =
		"<<\t" ..
		"/Type /Font\n" ..
		"\t/Subtype /Type1\n" ..
		"\t/Name /F" .. dPDF.fonts .. "\n" ..
		"\t/BaseFont /Times-Roman\n" ..
		--"\t/Encoding /PDFDocEncoding\n" ..
		"\t/Encoding <</Type /Encoding /Differences [ 2 /scedilla ] >>" ..
		">> "

	dPDF.pages = dPDF.pages + 1
	dPDF.fonts = dPDF.fonts + 1
	dPDF.objects = dPDF.objects + 2
end

function dPDF.addPageContent( i, s )
	dPDF.page_content[i] = dPDF.makeStream( "BT /F1 14 Tf 100 692 Td (" .. s .. ") Tj ET" )
end

function dPDF.addPageContentHex( i, s )
	dPDF.page_content[i] = dPDF.makeStream( "BT /F1 14 Tf 100 692 Td <" .. s .. "> Tj ET" )
end

function dPDF.makeObject( i, s )
	return i .. " 0 obj\n" .. s .. "\nendobj\n"
end

function dPDF.writeContent()

	_offset = {}

	-- write header
	dPDF.emit( "%PDF-1.4" )
	
	-- write catalog
	_offset[1] = dPDF.buffer:len()
	dPDF.emit( dPDF.makeObject( 1, "<<\t/Type /Catalog\n\t/Outlines 2 0 R\n\t/Pages 3 0 R\n>>" ) )
	
	-- write outlines
	_offset[2] = dPDF.buffer:len()
	dPDF.emit( dPDF.makeObject( 2, "<<\t/Type /Outlines\n\t/Count 0\n>>" ) )
	
	-- write page master
	local _pages = ""
	for i = 1, dPDF.pages-1 do
		_pages = _pages .. 4 + 3 * (i-1) .. " 0 R "
	end
	_offset[3] = dPDF.buffer:len()
	dPDF.emit( dPDF.makeObject( 3,
		"<<\t/Type /Pages\n\t/Kids [ " .. _pages .. " ]\n\t/Count " .. dPDF.pages-1 .. "\n>>" ) )
	
	-- write page, page content and font data
	for i = 1, dPDF.pages-1 do
		_offset[4+(i-1)*3] = dPDF.buffer:len()
		dPDF.emit( dPDF.makeObject( 4 + (i-1) * 3, dPDF.page[i] ) )
		_offset[5+(i-1)*3] = dPDF.buffer:len()
		dPDF.emit( dPDF.makeObject( 5 + (i-1) * 3, dPDF.font_content[i] ) )
		_offset[6+(i-1)*3] = dPDF.buffer:len()
		dPDF.emit( dPDF.makeObject( 6 + (i-1) * 3, dPDF.page_content[i] ) )
	end
end

function dPDF.writeXref()
	dPDF.emit( "xref" )
	dPDF.emit( "0 " .. dPDF.objects + 1 )
	dPDF.emit( "0000000000 65535 f" )
	for i = 1, #_offset do
		dPDF.emit( string.format( "%010i 00000 f ", _offset[i] or "666" ) )
	end
end

function dPDF.writePDF()
	dPDF.writeContent()
	dPDF.writeXref()
	dPDF.emit( "trailer << /Size " .. 6+(dPDF.pages-1)*3 .. " /Root 1 0 R >>" )
	dPDF.emit( "startxref\n0+" )
	dPDF.emit( "%%EOF" )
end

function dPDF.outputPDF( s )
	local f = io.open( s, "w" )
	f:write( dPDF.buffer )
	f:close()
end

---------------- TEST
function test()
	dPDF.init()
	dPDF.addPage()
	dPDF.addPage()
	dPDF.addPageContentHex( 1, "02" )
	dPDF.addPageContent( 2, "salut, lume!" )
	dPDF.writePDF()
	dPDF.outputPDF( "lpdf.pdf" )
end

test()