-- create the module's table
local lorom_5volt = {}

-- import required modules
local dict = require "scripts.app.dict"
local dump = require "scripts.app.dump"
local flash = require "scripts.app.flash"
local snes = require "scripts.app.snes"

-- file constants

-- local functions



-- Desc: attempt to read flash rom ID 
-- Pre: snes_init() been called to setup i/o
-- Post:Address left on bus memories disabled
-- Rtn: true if valid flash ID found
local function rom_manf_id( debug )

	local rv
	--enter software mode A14 is highest address bit that needs to be valid
	dict.snes("SNES_SET_BANK", 0x00)

	--/ROMSEL wouldn't normally be low for these addresses..
	--true SNES mapped reads would set A15 high to be in lorom /ROMSEL space
	--but A15 isn't connected to the rom on LOROM so the cart can't see the difference
	--plus A15 doesn't need to be valid to read manf/prod ID anyway..
	dict.snes("SNES_ROM_WR", 0x5555, 0xAA)
	dict.snes("SNES_ROM_WR", 0x2AAA, 0x55)
	dict.snes("SNES_ROM_WR", 0x5555, 0x90)

	--read manf ID
	local manf_id = dict.snes("SNES_ROM_RD", 0x8000)
	if debug then print("attempted read SNES ROM manf ID:", string.format("%X", manf_id)) end

	--read prod ID
	local prod_id = dict.snes("SNES_ROM_RD", 0x8001)
	if debug then print("attempted read SNES ROM prod ID:", string.format("%X", prod_id)) end

	--exit software
	dict.snes("SNES_ROM_WR", 0x0000, 0xF0)

	--return true if detected flash chip
	if (manf_id == 0xBF and prod_id == 0xB7) then
		print("512KByte flash detected")
		return true
	elseif (manf_id == 0xBF and prod_id == 0xB6) then
		print("256KByte flash detected")
		return true
	elseif (manf_id == 0xBF and prod_id == 0xB5) then
		print("128KByte flash detected")
		return true
	else
		return false
	end

end

--dump the SNES ROM starting at the provided bank
--/ROMSEL is always low for this dump
local function dump_rom( file, start_bank, rom_size_KB, debug )

	local KB_per_bank = 32	-- LOROM has 32KB per bank
	local num_reads = rom_size_KB / KB_per_bank
	local read_count = 0
	local addr_base = 0x80	-- $8000 LOROM

	while ( read_count < num_reads ) do

		if debug then print( "dump ROM part ", read_count, " of ", num_reads) end

		--select desired bank
		dict.snes("SNES_SET_BANK", start_bank+read_count)

		dump.dumptofile( file, KB_per_bank, addr_base, "SNESROM_PAGE", false )

		read_count = read_count + 1
	end

end


--write a single byte to SNES ROM flash
--writes to currently selected bank address
local function wr_flash_byte(addr, value, debug)

	if (addr < 0x0000 or addr > 0xFFFF) then
		print("\n  ERROR! flash write to SNES", string.format("$%X", addr), "must be $0000-FFFF \n\n")
		return
	end

	--send unlock command and write byte
	dict.snes("SNES_ROM_WR", 0x5555, 0xAA)
	dict.snes("SNES_ROM_WR", 0x2AAA, 0x55)
	dict.snes("SNES_ROM_WR", 0x5555, 0xA0)
	dict.snes("SNES_ROM_WR", addr, value)

	local rv = dict.snes("SNES_ROM_RD", addr)

	local i = 0

	while ( rv ~= value ) do
		rv = dict.snes("SNES_ROM_RD", addr)
		i = i + 1
	end
	if debug then print(i, "naks, done writing byte.") end
	if debug then print("written value:", string.format("%X",value), "verified value:", string.format("%X",rv)) end

	--TODO handle timeout for problems

	--TODO return pass/fail/info
end


--fast host flash one bank at a time...
--this is controlled from the host side one bank at a time
local function flash_rom(file, rom_size_KB, debug)

	--init_mapper()

	--test some bytes
	--dict.snes("SNES_SET_BANK", 0x00) wr_flash_byte(0x8000, 0xA5, true) wr_flash_byte(0xFFFF, 0x5A, true)
	--dict.snes("SNES_SET_BANK", 0x01) wr_flash_byte(0x8000, 0x15, true) wr_flash_byte(0xFFFF, 0x1A, true)
	--last of 512KB
	--dict.snes("SNES_SET_BANK", 0x0F) wr_flash_byte(0x8000, 0xF5, true) wr_flash_byte(0xFFFF, 0xFA, true)

	print("\nProgramming ROM flash")

	--most of this is overkill for NROM, but it's how we want to handle things for bigger mappers
	local base_addr = 0x8000 --writes occur $8000-9FFF
	local bank_size = 32*1024 --SNES LOROM 32KB per ROM bank
	local buff_size = 1      --number of bytes to write at a time
	local cur_bank = 0
	local total_banks = rom_size_KB*1024/bank_size

	local byte_num --byte number gets reset for each bank
	local byte_str, data, readdata

	while cur_bank < total_banks do

		if (cur_bank %4 == 0) then
			print("writting ROM bank: ", cur_bank, " of ", total_banks-1)
		end

		--select the current bank
		if (cur_bank <= 0xFF) then
			dict.snes("SNES_SET_BANK", cur_bank)
		else
			print("\n\nERROR!!!!  SNES bank cannot exceed 0xFF, it was:", string.format("0x%X",cur_bank))
			return
		end

		--program the entire bank's worth of data

		--[[  This version of the code programs a single byte at a time but doesn't require 
		--	board specific functions in the firmware
		print("This is slow as molasses, but gets the job done")
		byte_num = 0  --current byte within the bank
		while byte_num < bank_size do

			--read next byte from the file and convert to binary
			byte_str = file:read(buff_size)
			data = string.unpack("B", byte_str, 1)

			--write the data
			--SLOWEST OPTION: no firmware specific functions 100% host flash algo:
			--wr_flash_byte(base_addr+byte_num, data, false)   --0.7KBps
			--EASIEST FIRMWARE SPEEDUP: 5x faster, create firmware write byte function:
			dict.snes("FLASH_WR_5V", base_addr+byte_num, data)  --3.8KBps (5.5x faster than above)

			--if (verify) then
			--	readdata = dict.nes("NES_CPU_RD", base_addr+byte_num)
			--	if readdata ~= data then
			--		print("ERROR flashing byte number", byte_num, " in bank",cur_bank, " to flash ", data, readdata)
			--	end
			--end

			byte_num = byte_num + 1
		end
		--]]

		--Have the device write a banks worth of data
		flash.write_file( file, bank_size/1024, "LOROM_5VOLT", "SNESROM", false )

		cur_bank = cur_bank + 1
	end

	print("Done Programming ROM flash")

end


--Cart should be in reset state upon calling this function 
--this function processes all user requests for this specific board/mapper
local function process( test, read, erase, program, verify, dumpfile, flashfile, verifyfile)

	local rv = nil
	local file 

	local snes_mapping = "LOROM"
	--local snes_mapping = "HIROM"

	local ram_size = 0

	--local rom_size = 32
	local rom_size = 512
	--local rom_size = 1024
	--local rom_size = 2048
	--local rom_size = 4096
	--local rom_size = 8192
	--local rom_size = 12288
	--local rom_size = 16384
	

	-- SNES memory map banking
	-- A15 always high for LOROM (A22 is typically low too)
	-- A22 always high for HIROM
	-- A23 splits the map in half
	-- A22 splits it in quarters (between what's typically low half and high half)
	-- b 7  6  5  4 :  3  2  1  0
	-- A23 22 21 20 : 19 18 17 16 
	
	local first_bank --byte that contains A23-16
	
	if (snes_mapping == "LOROM") then
		-- LOROM typically sees the upper half (A15=1) of the first address 0b0000:1000_0000
		first_bank = 0x00
	elseif (snes_mapping == "HIROM") then
		-- HIROM typically sees the last 4MByte as the first addresses = 0b1100:0000_0000
		first_bank = 0xC0
	end


--initialize device i/o for SNES
	dict.io("IO_RESET")
	dict.io("SNES_INIT")


--test cart by reading manf/prod ID
	if test then

		print("\nTesting SNES board");

		--SNES detect HiROM or LoROM & RAM

		--SNES detect if able to read flash ID's
		if not rom_manf_id(true) then
			print("ERROR unable to read flash ID")
			return
		end
	end

--dump the cart to dumpfile
	if read then
		print("\nDumping SNES ROM...")

		file = assert(io.open(dumpfile, "wb"))

		--dump cart into file
		dump_rom(file, first_bank, rom_size, false)

		--close file
		assert(file:close())
		print("DONE Dumping SNES ROM")
	end

--erase the cart
	if erase then

		print("\nErasing PLCC flash");

		local rv = nil

		--WR $AAA:AA $555:55 $AAA:AA
		dict.snes("SNES_SET_BANK", 0x00)

		dict.snes("SNES_ROM_WR", 0x5555, 0xAA)
		dict.snes("SNES_ROM_WR", 0x2AAA, 0x55)
		dict.snes("SNES_ROM_WR", 0x5555, 0x80)
		dict.snes("SNES_ROM_WR", 0x5555, 0xAA)
		dict.snes("SNES_ROM_WR", 0x2AAA, 0x55)
		dict.snes("SNES_ROM_WR", 0x5555, 0x10)
		rv = dict.snes("SNES_ROM_RD", 0x0000)

		local i = 0

		while ( rv ~= 0xFF ) do
			rv = dict.snes("SNES_ROM_RD", 0x8000)
			i = i + 1
		end
		print(i, "naks, done erasing snes rom.");

		--reset flash
		dict.snes("SNES_ROM_WR", 0x0000, 0xF0)

	end


--program flashfile to the cart
	if program then

		--open file
		file = assert(io.open(flashfile, "rb"))
		--determine if auto-doubling, deinterleaving, etc, 
		--needs done to make board compatible with rom

		--flash cart
		flash_rom(file, rom_size, true)

		--close file
		assert(file:close())

	end

--verify flashfile is on the cart
	if verify then
		print("\nPost dumping SNES ROM...")
		--for now let's just dump the file and verify manually

		file = assert(io.open(verifyfile, "wb"))

		--dump cart into file
		dump_rom(file, first_bank, rom_size, false)

		--close file
		assert(file:close())
		print("DONE Post dumping SNES ROM")
	end

	dict.io("IO_RESET")
end


-- global variables so other modules can use them


-- call functions desired to run when script is called/imported


-- functions other modules are able to call
lorom_5volt.process = process

-- return the module's table
return lorom_5volt