// SPDX-License-Identifier: MIT

#include "link/output.hpp"

#include <algorithm>
#include <deque>
#include <errno.h>
#include <inttypes.h>
#include <optional>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tuple>
#include <variant>
#include <vector>

#include "diagnostics.hpp"
#include "extern/utf8decoder.hpp"
#include "helpers.hpp"
#include "linkdefs.hpp"
#include "platform.hpp"
#include "util.hpp"

#include "link/main.hpp"
#include "link/section.hpp"
#include "link/symbol.hpp"
#include "link/warning.hpp"

static constexpr size_t BANK_SIZE = 0x4000;

static FILE *outputFile;
static FILE *overlayFile;
static FILE *symFile;
static FILE *mapFile;

struct SortedSymbol {
	Symbol const *sym;
	uint16_t addr;
	uint16_t parentAddr;
};

struct SortedSections {
	std::deque<Section const *> sections;
	std::deque<Section const *> zeroLenSections;
};

static std::deque<SortedSections> sections[SECTTYPE_INVALID];

// Defines the order in which types are output to the sym and map files
static SectionType typeMap[SECTTYPE_INVALID] = {
    SECTTYPE_ROM0,
    SECTTYPE_ROMX,
    SECTTYPE_VRAM,
    SECTTYPE_SRAM,
    SECTTYPE_WRAM0,
    SECTTYPE_WRAMX,
    SECTTYPE_OAM,
    SECTTYPE_HRAM,
};

void out_AddSection(Section const &section) {
	static uint32_t const maxNbBanks[SECTTYPE_INVALID] = {
	    1,          // SECTTYPE_WRAM0
	    2,          // SECTTYPE_VRAM
	    UINT32_MAX, // SECTTYPE_ROMX
	    1,          // SECTTYPE_ROM0
	    1,          // SECTTYPE_HRAM
	    7,          // SECTTYPE_WRAMX
	    UINT32_MAX, // SECTTYPE_SRAM
	    1,          // SECTTYPE_OAM
	};

	uint32_t targetBank = section.bank - sectionTypeInfo[section.type].firstBank;
	if (targetBank >= maxNbBanks[section.type]) {
		fatal(
		    "Section \"%s\" has an invalid bank range (%" PRIu32 " > %" PRIu32 ")",
		    section.name.c_str(),
		    section.bank,
		    maxNbBanks[section.type] - 1
		);
	}
	if (sections[section.type].size() <= targetBank) {
		sections[section.type].resize(targetBank + 1);
	}

	// Insert section while keeping the list sorted by increasing org
	std::deque<Section const *> &bankSections =
	    section.size ? sections[section.type][targetBank].sections
	                 : sections[section.type][targetBank].zeroLenSections;
	auto pos = bankSections.begin();
	while (pos != bankSections.end() && (*pos)->org < section.org) {
		++pos;
	}
	bankSections.insert(pos, &section);
}

Section const *out_OverlappingSection(Section const &section) {
	uint32_t bank = section.bank - sectionTypeInfo[section.type].firstBank;

	for (Section const *ptr : sections[section.type][bank].sections) {
		if (ptr->org < section.org + section.size && section.org < ptr->org + ptr->size) {
			return ptr;
		}
	}
	return nullptr;
}

// Performs sanity checks on the overlay file.
// Returns the number of ROM banks in the overlay file.
static uint32_t checkOverlaySize() {
	if (!overlayFile) {
		return 0;
	}

	std::optional<uint64_t> overlaySize = seekSize(overlayFile);

	if (!overlaySize.has_value()) {
		warnx("Overlay file is not seekable, cannot check if properly formed");
		return 0;
	}

	if (*overlaySize % BANK_SIZE) {
		warnx("Overlay file does not have a size multiple of 0x4000");
	} else if (options.is32kMode && *overlaySize != 0x8000) {
		warnx("Overlay is not exactly 0x8000 bytes large");
	}
	if (*overlaySize < 0x8000) {
		warnx("Overlay is less than 0x8000 bytes large");
	}

	return (*overlaySize + BANK_SIZE - 1) / BANK_SIZE;
}

// Expand `sections[SECTTYPE_ROMX]` to cover all the overlay banks.
// This ensures that `writeROM` will output each bank, even if some are not
// covered by any sections.
static void coverOverlayBanks(uint32_t nbOverlayBanks) {
	// 2 if options.is32kMode, 1 otherwise
	uint32_t nbRom0Banks = sectionTypeInfo[SECTTYPE_ROM0].size / BANK_SIZE;
	// Discount ROM0 banks to avoid outputting too much
	uint32_t nbUncoveredBanks =
	    nbOverlayBanks >= nbRom0Banks
	            && nbOverlayBanks - nbRom0Banks > sections[SECTTYPE_ROMX].size()
	        ? nbOverlayBanks - nbRom0Banks
	        : 0;

	if (nbUncoveredBanks > sections[SECTTYPE_ROMX].size()) {
		for (uint32_t i = sections[SECTTYPE_ROMX].size(); i < nbUncoveredBanks; ++i) {
			sections[SECTTYPE_ROMX].emplace_back();
		}
	}
}

static uint8_t getNextFillByte() {
	if (overlayFile) {
		int c = getc(overlayFile);
		if (c != EOF) {
			return c;
		}

		if (static bool warned = false; !options.hasPadValue && !warned) {
			warnx("Output is larger than overlay file, but no padding value was specified");
			warned = true;
		}
	}

	return options.padValue;
}

static void
    writeBank(std::deque<Section const *> *bankSections, uint16_t baseOffset, uint16_t size) {
	uint16_t offset = 0;

	if (bankSections) {
		for (Section const *section : *bankSections) {
			assume(section->offset == 0);
			// Output padding up to the next SECTION
			while (offset + baseOffset < section->org) {
				putc(getNextFillByte(), outputFile);
				++offset;
			}

			// Output the section itself
			assume(section->size == section->data.size());
			fwrite(section->data.data(), 1, section->size, outputFile);
			offset += section->size;

			if (!overlayFile) {
				continue;
			}
			// Skip bytes even with pipes
			for (uint16_t i = 0; i < section->size; ++i) {
				getc(overlayFile);
			}
		}
	}

	if (!options.disablePadding) {
		while (offset < size) {
			putc(getNextFillByte(), outputFile);
			++offset;
		}
	}
}

static void writeROM() {
	if (options.outputFileName) {
		char const *outputFileName = options.outputFileName->c_str();
		if (*options.outputFileName != "-") {
			outputFile = fopen(outputFileName, "wb");
		} else {
			outputFileName = "<stdout>";
			(void)setmode(STDOUT_FILENO, O_BINARY);
			outputFile = stdout;
		}
		if (!outputFile) {
			fatal("Failed to open output file \"%s\": %s", outputFileName, strerror(errno));
		}
	}
	Defer closeOutputFile{[&] {
		if (outputFile) {
			xfclose(outputFile);
		}
	}};

	if (options.overlayFileName) {
		char const *overlayFileName = options.overlayFileName->c_str();
		if (*options.overlayFileName != "-") {
			overlayFile = fopen(overlayFileName, "rb");
		} else {
			overlayFileName = "<stdin>";
			(void)setmode(STDIN_FILENO, O_BINARY);
			overlayFile = stdin;
		}
		if (!overlayFile) {
			fatal("Failed to open overlay file \"%s\": %s", overlayFileName, strerror(errno));
		}
	}
	Defer closeOverlayFile{[&] {
		if (overlayFile) {
			xfclose(overlayFile);
		}
	}};

	uint32_t nbOverlayBanks = checkOverlaySize();

	if (nbOverlayBanks > 0) {
		coverOverlayBanks(nbOverlayBanks);
	}

	if (outputFile) {
		writeBank(
		    !sections[SECTTYPE_ROM0].empty() ? &sections[SECTTYPE_ROM0][0].sections : nullptr,
		    sectionTypeInfo[SECTTYPE_ROM0].startAddr,
		    sectionTypeInfo[SECTTYPE_ROM0].size
		);

		for (uint32_t i = 0; i < sections[SECTTYPE_ROMX].size(); ++i) {
			writeBank(
			    &sections[SECTTYPE_ROMX][i].sections,
			    sectionTypeInfo[SECTTYPE_ROMX].startAddr,
			    sectionTypeInfo[SECTTYPE_ROMX].size
			);
		}
	}
}

static void writeSymName(std::string const &name, FILE *file) {
	for (char const *ptr = name.c_str(); *ptr != '\0';) {
		// Output legal ASCII characters as-is
		if (char c = *ptr; continuesIdentifier(c)) {
			putc(c, file);
			++ptr;
			continue;
		}

		// Output illegal characters using Unicode escapes ('\u' or '\U')
		// Decode the UTF-8 codepoint; or at least attempt to
		Utf8Decoder decoder;
		do {
			if (decoder.update(*ptr++) != UTF8_REJECT) {
				continue;
			}
			// This sequence was invalid; emit a U+FFFD, and recover
			decoder.codepoint = 0xFFFD;
			// Skip continuation bytes
			// A NUL byte does not qualify, so we're good
			while ((*ptr & 0xC0) == 0x80) {
				++ptr;
			}
			break;
		} while (decoder.state != UTF8_ACCEPT);
		fprintf(
		    file, decoder.codepoint <= 0xFFFF ? "\\u%04" PRIx32 : "\\U%08" PRIx32, decoder.codepoint
		);
	}
}

// Comparator function for `std::stable_sort` to sort symbols
static bool compareSymbols(SortedSymbol const &sym1, SortedSymbol const &sym2) {
	std::string const &sym1_name = sym1.sym->name;
	std::string const &sym2_name = sym2.sym->name;
	bool sym1_local = sym1_name.find('.') != std::string::npos;
	bool sym2_local = sym2_name.find('.') != std::string::npos;

	// First, sort by address
	// Second, sort by locality (global before local)
	// Third, sort by parent address
	// Fourth, sort by name
	return std::tie(sym1.addr, sym1_local, sym1.parentAddr, sym1_name)
	       < std::tie(sym2.addr, sym2_local, sym2.parentAddr, sym2_name);
}

static void forEachSortedSection(
    SortedSections const &bankSections, Procedure<Section const &> auto callback
) {
	for (Section const *sect : bankSections.zeroLenSections) {
		for (Section const &piece : sect->pieces()) {
			callback(piece);
		}
	}
	for (Section const *sect : bankSections.sections) {
		for (Section const &piece : sect->pieces()) {
			callback(piece);
		}
	}
}

static void writeSymBank(SortedSections const &bankSections, SectionType type, uint32_t bank) {
	uint32_t nbSymbols = 0;

	forEachSortedSection(bankSections, [&](Section const &sect) {
		nbSymbols += sect.symbols.size();
	});

	if (!nbSymbols) {
		return;
	}

	std::vector<SortedSymbol> symList;

	symList.reserve(nbSymbols);

	forEachSortedSection(bankSections, [&symList](Section const &sect) {
		for (Symbol const *sym : sect.symbols) {
			// Don't output symbols that begin with an illegal character
			if (sym->name.empty() || !startsIdentifier(sym->name[0])) {
				continue;
			}
			assume(std::holds_alternative<Label>(sym->data));
			uint16_t addr = static_cast<uint16_t>(std::get<Label>(sym->data).offset + sect.org);
			uint16_t parentAddr = addr;
			if (auto pos = sym->name.find('.'); pos != std::string::npos) {
				std::string parentName = sym->name.substr(0, pos);
				if (Symbol const *parentSym = sym_GetSymbol(parentName);
				    parentSym && std::holds_alternative<Label>(parentSym->data)) {
					Label const &parentLabel = std::get<Label>(parentSym->data);
					Section const &parentSection = *parentLabel.section;
					parentAddr = static_cast<uint16_t>(parentLabel.offset + parentSection.org);
				}
			}
			symList.push_back({.sym = sym, .addr = addr, .parentAddr = parentAddr});
		}
	});

	std::stable_sort(RANGE(symList), compareSymbols);

	uint32_t symBank = bank + sectionTypeInfo[type].firstBank;

	for (SortedSymbol &sym : symList) {
		fprintf(symFile, "%02" PRIx32 ":%04" PRIx16 " ", symBank, sym.addr);
		writeSymName(sym.sym->name, symFile);
		putc('\n', symFile);
	}
}

static void writeEmptySpace(uint16_t begin, uint16_t end) {
	if (begin < end) {
		uint16_t len = end - begin;

		fprintf(
		    mapFile,
		    "\tEMPTY: $%04x-$%04x ($%04" PRIx16 " byte%s)\n",
		    begin,
		    end - 1,
		    len,
		    len == 1 ? "" : "s"
		);
	}
}

static void writeSectionName(std::string const &name, FILE *file) {
	for (char c : name) {
		// Escape characters that need escaping
		switch (c) {
		case '\n':
			fputs("\\n", file);
			break;
		case '\r':
			fputs("\\r", file);
			break;
		case '\t':
			fputs("\\t", file);
			break;
		case '\\':
		case '"':
			putc('\\', file);
			[[fallthrough]];
		default:
			putc(c, file);
			break;
		}
	}
}

uint16_t forEachSection(SortedSections const &sectList, Procedure<Section const &> auto callback) {
	uint16_t used = 0;
	auto section = sectList.sections.begin();
	auto zeroLenSection = sectList.zeroLenSections.begin();
	while (section != sectList.sections.end() || zeroLenSection != sectList.zeroLenSections.end()) {
		// Pick the lowest section by address out of the two
		auto &pickedSection = section == sectList.sections.end()                 ? zeroLenSection
		                      : zeroLenSection == sectList.zeroLenSections.end() ? section
		                      : (*section)->org < (*zeroLenSection)->org         ? section
		                                                                         : zeroLenSection;
		used += (*pickedSection)->size;
		callback(**pickedSection);
		++pickedSection;
	}
	return used;
}

static void writeMapSymbols(Section const &sect) {
	bool announced = true;
	for (Section const &piece : sect.pieces()) {
		for (Symbol *sym : piece.symbols) {
			// Don't output symbols that begin with an illegal character
			if (sym->name.empty() || !startsIdentifier(sym->name[0])) {
				continue;
			}
			// Announce this "piece" before its contents
			if (!announced) {
				assume(sect.modifier == piece.modifier);
				if (sect.modifier == SECTION_UNION) {
					fputs("\t         ; Next union\n", mapFile);
				} else if (sect.modifier == SECTION_FRAGMENT) {
					fputs("\t         ; Next fragment\n", mapFile);
				}
				announced = true;
			}
			assume(std::holds_alternative<Label>(sym->data));
			uint16_t addr = static_cast<uint16_t>(std::get<Label>(sym->data).offset + sect.org);
			// Space matches "\tSECTION: $xxxx ..."
			fprintf(mapFile, "\t         $%04" PRIx16 " = ", addr);
			writeSymName(sym->name, mapFile);
			putc('\n', mapFile);
		}
		announced = false;
	}
}

static void writeMapBank(SortedSections const &sectList, SectionType type, uint32_t bank) {
	fprintf(
	    mapFile,
	    "\n%s bank #%" PRIu32 ":\n",
	    sectionTypeInfo[type].name.c_str(),
	    bank + sectionTypeInfo[type].firstBank
	);

	uint16_t prevEndAddr = sectionTypeInfo[type].startAddr;
	uint16_t used = forEachSection(sectList, [&](Section const &sect) {
		assume(sect.offset == 0);

		writeEmptySpace(prevEndAddr, sect.org);

		assume(sect.org + sect.size <= UINT16_MAX);
		prevEndAddr = sect.org + sect.size;

		fprintf(mapFile, "\tSECTION: $%04" PRIx16, sect.org);
		if (sect.size != 0) {
			fprintf(mapFile, "-$%04x", prevEndAddr - 1);
		}
		fprintf(mapFile, " ($%04" PRIx16 " byte%s) [\"", sect.size, sect.size == 1 ? "" : "s");
		writeSectionName(sect.name, mapFile);
		fputs("\"]\n", mapFile);

		if (!options.noSymInMap) {
			// Also print symbols in the following "pieces"
			writeMapSymbols(sect);
		}
	});

	if (used == 0) {
		fputs("\tEMPTY\n", mapFile);
	} else {
		uint16_t bankEndAddr = sectionTypeInfo[type].startAddr + sectionTypeInfo[type].size;

		writeEmptySpace(prevEndAddr, bankEndAddr);

		uint16_t slack = sectionTypeInfo[type].size - used;

		fprintf(mapFile, "\tTOTAL EMPTY: $%04" PRIx16 " byte%s\n", slack, slack == 1 ? "" : "s");
	}
}

static void writeMapSummary() {
	fputs("SUMMARY:\n", mapFile);

	for (uint8_t i = 0; i < SECTTYPE_INVALID; ++i) {
		SectionType type = typeMap[i];
		uint32_t nbBanks = sections[type].size();

		// Do not output used space for VRAM or OAM
		if (type == SECTTYPE_VRAM || type == SECTTYPE_OAM) {
			continue;
		}

		// Do not output unused section types
		if (nbBanks == 0) {
			continue;
		}

		uint32_t usedTotal = 0;

		for (uint32_t bank = 0; bank < nbBanks; ++bank) {
			usedTotal += forEachSection(sections[type][bank], [](Section const &) {});
		}

		fprintf(
		    mapFile,
		    "\t%s: %" PRIu32 " byte%s used / %zu free",
		    sectionTypeInfo[type].name.c_str(),
		    usedTotal,
		    usedTotal == 1 ? "" : "s",
		    static_cast<size_t>(nbBanks) * sectionTypeInfo[type].size - usedTotal
		);
		if (sectionTypeInfo[type].firstBank != sectionTypeInfo[type].lastBank || nbBanks > 1) {
			fprintf(mapFile, " in %u bank%s", nbBanks, nbBanks == 1 ? "" : "s");
		}
		putc('\n', mapFile);
	}
}

static void writeSym() {
	if (!options.symFileName) {
		return;
	}

	char const *symFileName = options.symFileName->c_str();
	if (*options.symFileName != "-") {
		symFile = fopen(symFileName, "w");
	} else {
		symFileName = "<stdout>";
		(void)setmode(STDOUT_FILENO, O_TEXT); // May have been set to O_BINARY previously
		symFile = stdout;
	}
	if (!symFile) {
		fatal("Failed to open sym file \"%s\": %s", symFileName, strerror(errno));
	}
	Defer closeSymFile{[&] { xfclose(symFile); }};

	fputs("; File generated by rgblink\n", symFile);

	for (uint8_t i = 0; i < SECTTYPE_INVALID; ++i) {
		SectionType type = typeMap[i];

		for (uint32_t bank = 0; bank < sections[type].size(); ++bank) {
			writeSymBank(sections[type][bank], type, bank);
		}
	}

	// Output the exported numeric constants
	static std::vector<Symbol *> constants; // `static` so `sym_ForEach` callback can see it
	constants.clear();
	sym_ForEach([](Symbol &sym) {
		// Symbols are already limited to the exported ones
		if (std::holds_alternative<int32_t>(sym.data)) {
			constants.push_back(&sym);
		}
	});
	// Numeric constants are ordered by value, then by name
	std::sort(RANGE(constants), [](Symbol *sym1, Symbol *sym2) -> bool {
		return std::tie(std::get<int32_t>(sym1->data), sym1->name)
		       < std::tie(std::get<int32_t>(sym2->data), sym2->name);
	});
	for (Symbol *sym : constants) {
		uint32_t val = static_cast<uint32_t>(std::get<int32_t>(sym->data));
		int width = val < 0x100 ? 2 : val < 0x10000 ? 4 : 8;
		fprintf(symFile, "%0*" PRIx32 " ", width, val);
		writeSymName(sym->name, symFile);
		putc('\n', symFile);
	}
}

static void writeMap() {
	if (!options.mapFileName) {
		return;
	}

	char const *mapFileName = options.mapFileName->c_str();
	if (*options.mapFileName != "-") {
		mapFile = fopen(mapFileName, "w");
	} else {
		mapFileName = "<stdout>";
		(void)setmode(STDOUT_FILENO, O_TEXT); // May have been set to O_BINARY previously
		mapFile = stdout;
	}
	if (!mapFile) {
		fatal("Failed to open map file \"%s\": %s", mapFileName, strerror(errno));
	}
	Defer closeMapFile{[&] { xfclose(mapFile); }};

	writeMapSummary();

	for (uint8_t i = 0; i < SECTTYPE_INVALID; ++i) {
		SectionType type = typeMap[i];

		for (uint32_t bank = 0; bank < sections[type].size(); ++bank) {
			writeMapBank(sections[type][bank], type, bank);
		}
	}
}

void out_WriteFiles() {
	writeROM();
	writeSym();
	writeMap();
}
