//
//  MemoryMap.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 25/10/2020.
//  Copyright © 2020 Thomas Harte. All rights reserved.
//

#ifndef Machines_Apple_AppleIIgs_MemoryMap_hpp
#define Machines_Apple_AppleIIgs_MemoryMap_hpp

#include <array>
#include <vector>

#include "../AppleII/LanguageCardSwitches.hpp"
#include "../AppleII/AuxiliaryMemorySwitches.hpp"

namespace Apple {
namespace IIgs {


class MemoryMap {
	public:
		MemoryMap() : auxiliary_switches_(*this), language_card_(*this) {}

		void set_storage(std::vector<uint8_t> &ram, std::vector<uint8_t> &rom) {
			// Keep a pointer for later.
			ram_ = ram.data();

			// Establish bank mapping.
			uint8_t next_region = 0;
			auto region = [&next_region, this]() -> uint8_t {
				assert(next_region != regions.size());
				return next_region++;
			};
			auto set_region = [this](uint8_t bank, uint16_t start, uint16_t end, uint8_t region) {
				assert((end == 0xffff) || !(end&0xff));
				assert(!(start&0xff));

				// Fill in memory map.
				size_t target = size_t((bank << 8) | (start >> 8));
				for(int c = start; c < end; c += 0x100) {
					region_map[target] = region;
					++target;
				}
			};

			// Current beliefs about the IIgs memory map:
			//
			//	* language card banking applies to banks $00, $01, $e0 and $e1;
			//	* auxiliary memory switches apply to banks $00 only;
			//	* shadowing may be enabled only on banks $00 and $01, or on all RAM pages.
			//
			// So banks $00 and $01 need their own divided spaces at the shadowing resolution,
			// all the other fast RAM banks can share a set of divided spaces, $e0 and $e1 need
			// to be able to deal with language card-level division but no further, and the pure
			// ROM pages don't need to be subdivided at all.

			// Reserve region 0 as that for unmapped memory.
			region();

			// Bank $00: all locations potentially affected by the auxiliary switches or the
			// language switches. Which will naturally align with shadowable zones.
			set_region(0x00, 0x0000, 0x0200, region());
			set_region(0x00, 0x0200, 0x0400, region());
			set_region(0x00, 0x0400, 0x0800, region());
			set_region(0x00, 0x0800, 0x2000, region());
			set_region(0x00, 0x2000, 0x4000, region());
			set_region(0x00, 0x4000, 0xc000, region());
			set_region(0x00, 0xc000, 0xc100, region());
			set_region(0x00, 0xc100, 0xc300, region());
			set_region(0x00, 0xc300, 0xc400, region());
			set_region(0x00, 0xc400, 0xc800, region());
			set_region(0x00, 0xc800, 0xd000, region());
			set_region(0x00, 0xd000, 0xe000, region());
			set_region(0x00, 0xe000, 0xffff, region());

			// Bank $01: all locations potentially affected by the language switches, by shadowing,
			// or marked for IO.
			set_region(0x01, 0x0000, 0x0400, region());
			set_region(0x01, 0x0400, 0x0800, region());
			set_region(0x01, 0x0800, 0x0c00, region());
			set_region(0x01, 0x0c00, 0x2000, region());
			set_region(0x01, 0x2000, 0x4000, region());
			set_region(0x01, 0x4000, 0x6000, region());
			set_region(0x01, 0x6000, 0xa000, region());
			set_region(0x01, 0xa000, 0xc000, region());
			set_region(0x01, 0xc000, 0xd000, region());
			set_region(0x01, 0xd000, 0xe000, region());
			set_region(0x01, 0xe000, 0xffff, region());

			// Banks $02–[end of RAM]: all locations potentially affected by shadowing.
			const uint8_t fast_ram_bank_count = uint8_t((ram.size() - 128*1024) / 65536);
			if(fast_ram_bank_count > 2) {
				const uint8_t evens[] = {
					region(),	// 0x0000 – 0x0400.
					region(),	// 0x0400 – 0x0800.
					region(),	// 0x0800 – 0x0c00.
					region(),	// 0x0c00 – 0x2000.
					region(),	// 0x2000 – 0x4000.
					region(),	// 0x4000 – 0x6000.
					region(),	// 0x6000 – [end].
				};
				const uint8_t odds[] = {
					region(),	// 0x0000 – 0x0400.
					region(),	// 0x0400 – 0x0800.
					region(),	// 0x0800 – 0x0c00.
					region(),	// 0x0c00 – 0x2000.
					region(),	// 0x2000 – 0x4000.
					region(),	// 0x4000 – 0x6000.
					region(),	// 0x6000 – 0xa000.
					region(),	// 0xa000 – [end].
				};
				for(uint8_t bank = 0x02; bank < fast_ram_bank_count; bank += 2) {
					set_region(bank, 0x0000, 0x0400, evens[0]);
					set_region(bank, 0x0400, 0x0800, evens[1]);
					set_region(bank, 0x0800, 0x0c00, evens[2]);
					set_region(bank, 0x0c00, 0x2000, evens[3]);
					set_region(bank, 0x2000, 0x4000, evens[4]);
					set_region(bank, 0x4000, 0x6000, evens[5]);
					set_region(bank, 0x6000, 0xffff, evens[6]);

					set_region(bank+1, 0x0000, 0x0400, odds[0]);
					set_region(bank+1, 0x0400, 0x0800, odds[1]);
					set_region(bank+1, 0x0800, 0x0c00, odds[2]);
					set_region(bank+1, 0x0c00, 0x2000, odds[3]);
					set_region(bank+1, 0x2000, 0x4000, odds[4]);
					set_region(bank+1, 0x4000, 0x6000, odds[5]);
					set_region(bank+1, 0x6000, 0xa000, odds[6]);
					set_region(bank+1, 0xa000, 0xffff, odds[7]);
				}
			}

			// [Banks $80–$e0: empty].

			// Banks $e0, $e1: all locations potentially affected by the language switches or marked for IO.
			for(uint8_t c = 0; c < 2; c++) {
				set_region(0xe0 + c, 0x0000, 0xc000, region());
				set_region(0xe0 + c, 0xc000, 0xd000, region());
				set_region(0xe0 + c, 0xd000, 0xffff, region());
			}

			// [Banks $e2–[ROM start]: empty].

			// ROM banks: directly mapped to ROM.
			const uint8_t rom_bank_count = uint8_t(rom.size() >> 16);
			const uint8_t first_rom_bank = uint8_t(0x100 - rom_bank_count);
			const uint8_t rom_region = region();
			for(uint8_t c = 0; c < rom_bank_count; ++c) {
				set_region(first_rom_bank + c, 0x0000, 0xffff, rom_region);
			}

			// Apply proper storage to those banks.
			auto set_storage = [this](uint32_t address, const uint8_t *read, uint8_t *write) {
				// Don't allow the reserved null region to be modified.
				assert(region_map[address >> 8]);

				// Either set or apply a quick bit of testing as to the logic at play.
				auto &region = regions[region_map[address >> 8]];
				if(read) read -= address;
				if(write) write -= address;
				if(!region.read) {
					region.read = read;
					region.write = write;
				} else {
					assert(region.read == read);
					assert(region.write == write);
				}
			};

			// This is highly redundant, but decouples this step from the above.
			for(size_t c = 0; c < 0x800000; c += 0x100) {
				if(c < ram.size() - 128*1024) {
					set_storage(uint32_t(c), &ram[c], &ram[c]);
				}
			}
			uint8_t *const slow_ram = &ram[ram.size() - 0x20000];
			for(size_t c = 0xe00000; c < 0xe20000; c += 0x100) {
				set_storage(uint32_t(c), &slow_ram[c - 0xe00000], &slow_ram[c - 0xe00000]);
			}
			for(uint32_t c = 0; c < uint32_t(rom_bank_count); c++) {
				set_storage((first_rom_bank + c) << 16, &rom[c << 16], nullptr);
			}

			// Apply initial language/auxiliary state. [TODO: including shadowing register].
			set_card_paging();
			set_zero_page_paging();
			set_main_paging();
		}

		// MARK: - Memory banking.
		void set_language_card_paging() {
			const auto language_state = language_card_.state();
			const auto zero_state = auxiliary_switches_.zero_state();

			uint8_t *const ram = zero_state ? &ram_[65536] : ram_;
			const uint8_t *const rom = &regions[region_map[0xffd0]].read[0xffd000];

			// Assumption: the language card regions are unique.
			auto &d0_region = regions[region_map[0x00d0]];
			d0_region.read = (language_state.read ? &ram[language_state.bank1 ? 0xd000 : 0xc000] : rom) - 0xd000;
			if(language_state.write) {
				d0_region.write = nullptr;
			} else {
				d0_region.write = &ram[language_state.bank1 ? 0xd000 : 0xc000] - 0xd000;
			}

			auto &e0_region = regions[region_map[0x00e0]];
			e0_region.read = (language_state.read ? &ram[0xe000] : rom) - 0xd000;
			if(language_state.write) {
				e0_region.write = nullptr;
			} else {
				e0_region.write = ram;
			}

			// TODO: banks other than zero!
		}
		void set_card_paging() {
		}
		void set_zero_page_paging() {
			set_language_card_paging();
		}
		void set_main_paging() {
		}

	private:
		Apple::II::AuxiliaryMemorySwitches<MemoryMap> auxiliary_switches_;
		Apple::II::LanguageCardSwitches<MemoryMap> language_card_;
		uint8_t *ram_ = nullptr;

	public:
		// Memory layout here is done via double indirection; the main loop should:
		//	(i) use the top two bytes of the address to get an index from memory_map_; and
		//	(ii) use that to index the memory_regions table.
		//
		// Pointers are eight bytes at the time of writing, so the extra level of indirection
		// reduces what would otherwise be a 1.25mb table down to not a great deal more than 64kb.
		std::array<uint8_t, 65536> region_map;

		struct Region {
			uint8_t *write = nullptr;
			const uint8_t *read = nullptr;
			uint8_t flags = 0;

			enum Flag: uint8_t {
				IsShadowedE0 = 1 << 0,	// i.e. writes should also be written to bank $e0, and costed appropriately.
				IsShadowedE1 = 1 << 1,	// i.e. writes should also be written to bank $e1, and costed appropriately.
				IsShadowed = IsShadowedE0 | IsShadowedE1,
				Is1Mhz = 1 << 2,		// Both reads and writes should be synchronised with the 1Mhz clock.
				IsIO = 1 << 3,			// Indicates that this region should be checked for soft switches, registers, etc.
			};
		};
		std::array<Region, 47> regions;	// The assert above ensures that this is large enough; there's no
										// doctrinal reason for it to be whatever size it is now, just
										// adjust as required.
};

#define MemoryMapRegion(map, address) map.regions[map.region_map[address >> 8]]
#define MemoryMapRead(region, address, value) *value = region.read ? region.read[address] : 0xff
#define MemoryMapWrite(map, region, address, value) \
	if(region.write) {	\
		region.write[address] = *value;	\
		if(region.flags & (MemoryMap::Region::IsShadowed)) {	\
			const uint32_t shadowed_address = (address & 0xffff) + (uint32_t(0xe1 - (region.flags & MemoryMap::Region::IsShadowedE0)) << 16);	\
			map.regions[map.region_map[shadowed_address >> 8]].write[shadowed_address] = *value;	\
		}	\
	}

}
}

#endif /* MemoryMap_h */