#include <string>
#include <err.h>
#include <unistd.h>
#include <sysexits.h>
#include <stdlib.h>
#include <fcntl.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>

#include <type_traits>
#include <vector>
#include <algorithm>
#include <iterator>

#include "obj816.h"
#include "zrdz_disassembler.h"

#include "endian.h"

#ifndef O_BINARY
#define O_BINARY 0
#endif


/* not documented */
#ifndef SEC_DATA
#define SEC_DATA 0x80
#endif


struct {
	bool S = false;
	bool g = false;
	bool n = false;
} flags;



template<class T>
void swap_if(T &t, std::false_type) {}

void swap_if(uint8_t &, std::true_type) {}

void swap_if(uint16_t &value, std::true_type) {
	value = __builtin_bswap16(value);
}

void swap_if(uint32_t &value, std::true_type) {
	value = __builtin_bswap32(value);
}

void swap_if(uint64_t &value, std::true_type) {
	value = __builtin_bswap64(value);
}



template<class T>
void le_to_host(T &value) {
	swap_if(value, std::integral_constant<bool, endian::native == endian::big>{});
}

void usage() {
	exit(EX_USAGE);
}

#pragma pack(push, 1)
struct Header {
	uint32_t magic;				/* magic number for detection */
	uint16_t version;			/* version number of object format */
	uint8_t filetype;			/* file type, object or library */
};

#pragma pack(pop)




template<class T>
uint8_t read_8(T &iter) {
	uint8_t tmp = *iter;
	++iter;
	return tmp;
}

template<class T>
uint16_t read_16(T &iter) {
	uint16_t tmp = 0;

	tmp |= *iter << 0;
	++iter;
	tmp |= *iter << 8;
	++iter;
	return tmp;
}

template<class T>
uint32_t read_32(T &iter) {
	uint32_t tmp = 0;

	tmp |= *iter << 0;
	++iter;
	tmp |= *iter << 8;
	++iter;
	tmp |= *iter << 16;
	++iter;
	tmp |= *iter << 24;
	++iter;


	return tmp;
}

template<class T>
std::string read_cstring(T &iter) {
	std::string s;
	for(;;) {
		uint8_t c = *iter;
		++iter;
		if (!c) break;
		s.push_back(c);
	}
	return s;
}


template<class T>
std::string read_pstring(T &iter) {
	std::string s;
	unsigned  size = *iter;
	++iter;
	s.reserve(size);
	while (size--) {
		uint8_t c = *iter;
		++iter;
		s.push_back(c);
	}
	return s;
}


std::vector<section> read_sections(const std::vector<uint8_t> &section_data) {

	std::vector<section> sections;
	auto iter = section_data.begin();
	while (iter != section_data.end()) {

		section s;

		s.number = read_8(iter);
		s.flags = read_8(iter);
		s.size = read_32(iter);
		s.org = read_32(iter);

		if (!(s.flags & SEC_NONAME)) s.name = read_cstring(iter);

		sections.emplace_back(std::move(s));
	}
	return sections;
}


std::vector<symbol> read_symbols(const std::vector<uint8_t> &symbol_data) {

	std::vector<symbol> symbols;

	auto iter = symbol_data.begin();
	while (iter != symbol_data.end()) {
		symbol s;
		s.type = read_8(iter);
		s.flags = read_8(iter);
		s.section = read_8(iter);
		s.offset = s.type == S_UND ? 0 : read_32(iter);
		s.name = read_cstring(iter);


		symbols.emplace_back(std::move(s));
	}

	return symbols;
}

bool dump_obj(const char *name, int fd)
{
	Mod_head h;
	ssize_t ok;

	ok = read(fd, &h, sizeof(h));
	if (ok == 0) return false;

	if (ok != sizeof(h))
		errx(EX_DATAERR, "%s is not an object file", name);


	le_to_host(h.h_magic);
	le_to_host(h.h_version);
	le_to_host(h.h_filtyp);
	le_to_host(h.h_namlen);
	le_to_host(h.h_recsize);
	le_to_host(h.h_secsize);
	le_to_host(h.h_symsize);
	le_to_host(h.h_optsize);
	le_to_host(h.h_tot_secs);
	le_to_host(h.h_num_secs);
	le_to_host(h.h_num_syms);

	assert(h.h_magic == MOD_MAGIC);
	assert(h.h_version == 1);
	assert(h.h_filtyp == 1);

	// now read the name (h_namlen includes 0 terminator.)
	std::vector<char> oname;
	oname.resize(h.h_namlen);
	ok = read(fd, oname.data(), h.h_namlen);
	if (ok != h.h_namlen) errx(EX_DATAERR, "%s", name);


	// records [until record_eof]

	std::vector<uint8_t> data;
	data.resize(h.h_recsize);
	ok = read(fd, data.data(), h.h_recsize);
	if (ok != h.h_recsize) errx(EX_DATAERR, "%s records truncated", name);


	std::vector<uint8_t> section_data;
	section_data.resize(h.h_secsize);
	ok = read(fd, section_data.data(), h.h_secsize);
	if (ok != h.h_secsize) errx(EX_DATAERR, "%s sections truncated", name);


	std::vector<uint8_t> symbol_data;
	symbol_data.resize(h.h_symsize);
	ok = read(fd, symbol_data.data(), h.h_symsize);
	if (ok != h.h_symsize) errx(EX_DATAERR, "%s symbols truncated", name);

	if (h.h_optsize) lseek(fd, h.h_optsize, SEEK_CUR);


	zrdz_disassembler d(read_sections(section_data), read_symbols(symbol_data));

	uint8_t op = REC_END;
	unsigned line = 0;


	d.front_matter(std::string(oname.data()));

	auto iter = data.begin();
	while (iter != data.end()) {


		op = read_8(iter);
		if (op == 0) break;
		if (op < 0xf0) {
			auto end = iter + op;
			while (iter != end) {
				d(*iter++);
			}
			continue;
		}

		switch(op) {

			case REC_RELEXP:
			case REC_EXPR:
				{

					// todo -- pass the relative flag to ()
					// so it can verify it's appropriate for the opcode.

					// todo -- move all this stuff to a separate function.
					uint8_t size = read_8(iter);

					std::vector<std::string> stack;

					// todo -- need to keep operation for precedence?
					// this ignores all precedence...

					for(;;) {
						uint8_t op = read_8(iter);
						if (op == OP_END) break;
						switch (op) {
							case OP_LOC: {
								uint8_t section = read_8(iter);
								uint32_t offset = read_32(iter);


								std::string name;
								if (flags.n) {
									name = d.section_name(section) + "+" + d.to_x(offset, 4, '$');
								} else {
									name = d.location_name(section, offset);
								}
								stack.emplace_back(std::move(name));
								break;
							}

							case OP_VAL:
								stack.push_back(d.to_x(read_32(iter), 4, '$'));
								break;

							case OP_SYM: {
								uint16_t symbol = read_16(iter);
								stack.emplace_back(d.symbol_name(symbol));
								break;
							}

							// unary operatos
							case OP_NOT:
							case OP_NEG:
							case OP_FLP: {
								static const std::string ops[] = {
									".NOT.", "-", "\\"
								};

								if (stack.empty()) errx(EX_DATAERR, "%s : stack underflow error", name);
								std::string a = std::move(stack.back()); stack.pop_back();
								std::string b(ops[op-10]);
								stack.emplace_back(b + a);
								break;
							}

							// binary operators
							case OP_EXP:
							case OP_MUL:
							case OP_DIV:
							case OP_MOD:
							case OP_SHR:
							case OP_SHL:
							case OP_ADD:
							case OP_SUB:
							case OP_AND:
							case OP_OR:
							case OP_XOR:
							case OP_EQ:
							case OP_GT:
							case OP_LT:
							case OP_UGT:
							case OP_ULT: {
								static const std::string ops[] = {
									"**", "*", "/", ".MOD.", ">>", "<<", "+", "-", "&", "|", "^", "=", ">", "<", ".UGT.", ".ULT."

								};
								if (stack.size() < 2) errx(EX_DATAERR, "%s : stack underflow error", name);
								std::string a = std::move(stack.back()); stack.pop_back();
								std::string b = std::move(stack.back()); stack.pop_back();
								stack.emplace_back(b + ops[op-20] + a);
								break;
							}
							default:
								errx(EX_DATAERR, "%s: unknown expression opcode %02x", name, op);

						}
					}
					if (stack.size() != 1) errx(EX_DATAERR, "%s stack overflow error.", name);
					d(stack.front(), size);
				}
				break;

			case REC_DEBUG:
				{
					d.flush();
					uint16_t size = read_16(iter);

					auto end = iter + size;
					while (iter < end) {
						uint8_t op = read_8(iter);
						switch(op) {
							case D_LONGA_ON:
								d.set_m(true);
								d.emit("", "longa", "on");
								break;
							case D_LONGA_OFF:
								d.set_m(false);
								d.emit("", "longa", "off");
								break;
							case D_LONGI_ON:
								d.set_x(true);
								d.emit("", "longi", "on");
								break;
							case D_LONGI_OFF:
								d.set_x(false);
								d.emit("", "longi", "off");
								break;
							case D_C_FILE: {
								std::string file = read_cstring(iter);
								line = read_16(iter);
								std::string tmp = file + ", " + std::to_string(line);
								d.emit("", ".file", tmp);
								break;
							}
							case D_C_LINE: {
								line = read_16(iter);
								d.emit("",".line", std::to_string(line));
								break;
							}
							case D_C_BLOCK: {
								uint16_t block = read_16(iter);
								d.emit("",".block", std::to_string(block));
								break;
							}
							case D_C_ENDBLOCK: {
								uint16_t block = read_16(iter);
								d.emit("",".endblock", std::to_string(block));
								break;
							}
							case D_C_FUNC: {
								uint16_t arg = read_16(iter);
								d.emit("",".function", std::to_string(arg));
								break;								
							}
							case D_C_ENDFUNC: {
								uint16_t line = read_16(iter);
								uint16_t local_offset = read_16(iter);
								uint16_t arg_offset = read_16(iter);
								std::string tmp;
								tmp = std::to_string(line) + ", "
									+ std::to_string(local_offset) + ", "
									+ std::to_string(arg_offset);
								d.emit("",".endfunc", tmp);
								break;
							}

							// etag? reserved for enums but not actually used?
							case D_C_STAG:
							case D_C_ETAG:
							case D_C_UTAG: {
								const char *kOpNames[] = { ".stag", ".etag", ".utag" };
								const char *opname = kOpNames[op - D_C_STAG];

								std::string name = read_cstring(iter);
								uint16_t size = read_16(iter);
								uint16_t tag = read_16(iter);

								std::string tmp;
								tmp = name + ", " + std::to_string(size) + ", " + std::to_string(tag);
								d.emit("", opname, tmp);
								break;
							}
							case D_C_EOS: {
								d.emit("", ".eos");
								break; 
							}

							case D_C_MEMBER:
							case D_C_SYM: {
								// warning - i don't fully understand this one..
								std::string name = read_cstring(iter);
								uint8_t version = read_8(iter); //???
								uint32_t value;
								if (version == 0) value = read_16(iter); // symbol
								if (version == 1) value = read_32(iter); // numeric value.
								assert(version == 0 || version == 1);
								uint32_t type = read_32(iter);
								uint8_t klass = read_8(iter);
								uint16_t size = read_16(iter);


								const char *opname = ".sym";
								if (op == D_C_MEMBER) opname = ".member";


								std::string attr;

								if (version == 0) {
									std::string svalue;
									svalue = d.symbol_name(value);

									attr = name + ", " + svalue;
								}

								if (version == 1) {
									attr = name + ", " + std::to_string(value);
								}

								attr += ", " + std::to_string(type);
								attr += ", " + std::to_string(klass);
								attr += ", " + std::to_string(size);


								/*
								 * type bits 1 ... 5 are T_xxxx
								 * then 3 bits of DT_xxx (repeatedly)
								 *
								 * eg, char ** = (DT_PTR << 11) + (DT_PTR << 8) + T_CHAR
								 */
								int t = type & 0x1f;
								if ((t == T_STRUCT) || (t == T_UNION)) {
									uint16_t tag = read_16(iter);
									attr += ", " + std::to_string(tag);
								}

								// need to do it until t == 0 for
								// multidimensional arrays.
								for ( t = type >> 5; t; t >>= 3) {
									if ((t & 0x07) == DT_ARY) {
										uint16_t dim = read_16(iter);
										attr += ", " + std::to_string(dim);
									}
								}


								d.emit("", opname, attr);

								break;
							}

							default:
								errx(EX_DATAERR, "%s: unknown debug opcode %02x (%d)", name, op, op);
								break;

						}
					}
				}
				break;

			case REC_SECT: {
				uint8_t sec = read_8(iter);
				d.set_section(sec);
				break;
			}

			case REC_ORG: {
				d.flush();
				uint32_t org = read_32(iter);
				d.emit("", ".org", d.to_x(org, 4, '$'));
				d.set_pc(org);
				break;
			}

			case REC_SPACE: {
				uint16_t count = read_16(iter);
				d.space(count);
				break;
			}

			case REC_LINE: {
				// bump line counter, no argument.
				d.flush();
				++line;
				break;
			}
			default:
				d.flush();
				errx(EX_DATAERR, "%s: unknown opcode %02x", name, op);
		}
	}


	unsigned f = 0;
	if (flags.S) f |= 0x01;
	d.back_matter(f);

	if (iter != data.end() || op != REC_END) errx(EX_DATAERR, "%s records ended early", name);



	return true;
}



void dump_lib(const char *name, int fd)
{
	Lib_head h;
	ssize_t ok;

	ok = read(fd, &h, sizeof(h));
	if (ok != sizeof(h))
		errx(EX_DATAERR, "%s is not an object file", name);


	le_to_host(h.l_magic);
	le_to_host(h.l_version);
	le_to_host(h.l_filtyp);
	le_to_host(h.l_modstart);
	le_to_host(h.l_numsyms);
	le_to_host(h.l_symsize);
	le_to_host(h.l_numfiles);

	assert(h.l_magic == MOD_MAGIC);
	assert(h.l_version == 1);
	assert(h.l_filtyp == 2);

	printf("; library %s\n\n", name);
	/*
	printf("; modstart      : $%04x\n", h.l_modstart);
	printf("; number symbols: $%04x\n", h.l_numsyms);
	printf("; number files  : $%04x\n", h.l_numfiles);
	printf("\n");
	*/

	std::vector<uint8_t> data;
	long count = h.l_modstart - sizeof(h);
	if (count < 0) errx(EX_DATAERR, "%s", name);
	data.resize(count);
	ok = read(fd, data.data(), count);
	if (ok != count) errx(EX_DATAERR, "%s truncated", name);


	// files
	printf("; files:\n");
	auto iter = data.begin();
	for (int i = 0; i < h.l_numfiles; ++i) {
		uint16_t file_number = read_16(iter);
		std::string s = read_pstring(iter);
		printf("; $%02x %s\n", file_number, s.c_str());
	}
	printf("\n");

	// symbols
	printf("; symbols:\n");
	auto name_iter = iter + h.l_numsyms * 8;
	for (int i = 0; i < h.l_numsyms; ++i) {
		uint16_t name_offset = read_16(iter);
		uint16_t file_number = read_16(iter);
		uint32_t offset = read_32(iter);
		auto tmp = name_iter + name_offset;
		std::string name = read_pstring(tmp);

		printf("; $%04x %s\n", i, name.c_str());
		//printf("name offset: %02x\n", name_offset);
		//printf("file_number  : $%02x\n", file_number);
		//printf("module offset: $%04x\n", offset); 
	}
	printf("\n");
}

void dump(const char *name) {
	Header h;
	int fd;
	ssize_t ok;

	fd = open(name, O_RDONLY | O_BINARY);
	if (fd < 0) err(EX_NOINPUT, "Unable to open %s", name);


	ok = read(fd, &h, sizeof(h));
	if (ok != sizeof(h))
		errx(EX_DATAERR, "%s is not an object file", name);

	le_to_host(h.magic);
	le_to_host(h.version);
	le_to_host(h.filetype);

	if (h.magic != MOD_MAGIC || h.version != 1 || h.filetype > 2)
		errx(EX_DATAERR, "%s is not an object file", name);

	lseek(fd, 0, SEEK_SET);
	if (h.filetype == 2) dump_lib(name, fd);

	// files may contain multiple modules.
	while (dump_obj(name, fd)) /* ... */;

	close(fd);
}

int main(int argc, char **argv) {

	int c;
	while ((c = getopt(argc, argv, "Sgn")) != -1) {
			switch(c) {
				case 'S': flags.S = true; break;
				case 'g': flags.g = true; break;
				case 'n': flags.n = true; break;
				default: exit(EX_USAGE); break;
			}
	}

	argv += optind;
	argc -= optind;

	if (argc == 0) usage();

	for (int i = 0; i < argc; ++i) {
		dump(argv[i]);
	}

	return 0;
}