#include <cstdio>
#include <cstring>
#include <cerrno>
#include <cstdint>
#include <vector>
#include <map>
#include <utility>

#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#include "common.hh"

struct TreHeader { // little endian
  char magic[4]; // == "XTRE"
  uint32_t unknown;
  uint32_t table1Ofs;
  uint32_t table2Ofs;
  uint32_t table3Ofs;
  uint32_t dataOfs;
} __attribute__((__packed__));

struct Table1Entry { // little endian
  uint32_t crc;
  uint32_t table3Ptr;
} __attribute__((__packed__));

struct Table2EntryHead {
  uint8_t len;
}  __attribute__((__packed__));

struct Table2EntryTail { // little endian
  uint32_t table3Ptr;
} __attribute__((__packed__));

struct Table3Entry { // little endian
  unsigned dataPtr:32;
  //  unsigned unknown1:8;
  unsigned length:24;
  unsigned unknown2:8;
} __attribute__((__packed__));

class TreFile {
public:
  TreFile(std::string const& filename) {
    FILEUPtr file{fopen(filename.c_str(), "rb")};
    if (!file)
      throw POSIXException{errno, "Could not open "s + filename};

    struct stat statBuf;
  
    if (fstat(fileno(file.get()), &statBuf) != 0)
      throw POSIXException(errno, "Could not stat");

    construct_(file.get(), 0, statBuf.st_size);
  }

  TreFile(FILE* file, off_t start, off_t length) {
    construct_(file, start, length);
  }
  
  void printStructure() {
    printf("Table 1: %lu entries\n", table1_.size());
    printf("Table 2: %lu entries\n", table2_.size());
    printf("Table 3: %lu entries\n", table3_.size());

    printf("Files by CRC:\n");
    for(auto const& ent : table1_) {
      printf("\t%.8x -> (ofs %.8x, len %.8x)\n", ent.first,
	     std::get<0>(table3_[ent.second]),
	     std::get<1>(table3_[ent.second]));
    }

    printf("Files by Name:\n");
    for(auto const& ent : table2_) {
      printf("\t%s -> (ofs %.8x, len %.8x)\n", ent.first.c_str(),
	     std::get<0>(table3_[ent.second]),
	     std::get<1>(table3_[ent.second]));
    }
  }
  
private:
  void construct_(FILE* file, off_t start, size_t length) {
    if (length < sizeof(TreHeader))
      throw FormatException{"Size < header size"};
    
    if (fseeko(file, start, SEEK_SET) != 0) {
      throw POSIXException(errno, "Could not seek");
    }
 
    TreHeader header;
    if (fread(&header, sizeof(TreHeader), 1, file) != 1)
      throw POSIXException{errno, "Could not read header"};

    if (memcmp(header.magic, "XTRE", 4) != 0)
      throw FormatException{"Wrong magic, not a TRE?"};
    
    if ((header.table1Ofs > length) ||
	(header.table2Ofs > length) ||
	(header.table3Ofs > length) ||
	(header.dataOfs > length))
      throw FormatException{"Table offset exceeds length"};

    if ((header.table1Ofs > header.table2Ofs) ||
	(header.table2Ofs > header.table3Ofs) ||
	(header.table3Ofs > header.dataOfs))
      throw FormatException{"Table offsets not in ascending order"};

    const size_t numTable1Entries = (header.table2Ofs-header.table1Ofs)/sizeof(Table1Entry);
    const size_t numTable3Entries = (header.dataOfs-header.table3Ofs)/sizeof(Table3Entry);
    
    printf("Table 1: start %u, length %u (%lu entries)\n",
	   header.table1Ofs, header.table2Ofs-header.table1Ofs,
	   numTable1Entries);
    printf("Table 2: start %u, length %u\n",
	   header.table2Ofs, header.table3Ofs-header.table2Ofs);
    printf("Table 3: start %u, length %u (%lu entries)\n",
	   header.table3Ofs, header.dataOfs-header.table3Ofs,
	   numTable3Entries);
    printf("Data: start %u, length %lu\n",
	   header.dataOfs, length - header.dataOfs);
    
    // Read Table 3
    if (fseeko(file, start+header.table3Ofs, SEEK_SET) != 0) {
      throw POSIXException{errno, "Could not seek"};
    }

    table3_.reserve(numTable3Entries);
    for (size_t i = 0;i < numTable3Entries;++i) {
      Table3Entry entry;
      if (fread(&entry, sizeof(Table3Entry), 1, file) != 1)
	throw POSIXException{errno, "Could not read"};

      if ((entry.dataPtr > length) ||
	  (entry.dataPtr < header.dataOfs))
	throw FormatException{"Data pointer out of range"};

      if ((entry.dataPtr + entry.length) > length) {
	fprintf(stderr, "Data length exceeds file length: %.8x %.8x\n", entry.dataPtr, entry.length);
	//throw FormatException{"Data length exceeds file length"};
      }
      
      table3_.push_back(std::make_tuple(static_cast<uint32_t>(entry.dataPtr),
					static_cast<uint32_t>(entry.length)));
    }

    // Read Table 2
    if (fseeko(file, start+header.table2Ofs, SEEK_SET) != 0) {
      throw POSIXException{errno, "Could not seek"};
    }

    std::map<size_t, uint32_t> table2Pos;
    
    size_t pos = header.table2Ofs;
    while(pos < header.table3Ofs) {
      uint8_t nameLen;

      if (fread(&nameLen, 1, 1, file) != 1)
	throw POSIXException{errno, "Could not read"};

      if (pos+nameLen+4 > header.table3Ofs)
	throw FormatException{"Table 2 entry exceeds table "s + std::to_string(nameLen)};
      
      std::vector<char> nameData(nameLen);
      if (fread(nameData.data(), nameLen, 1, file) != 1)
	throw POSIXException{errno, "Could not read"};

      uint32_t table3Ptr;
      if (fread(&table3Ptr, 4, 1, file) != 1)
	throw POSIXException{errno, "Could not read"};

      if ((table3Ptr < header.table3Ofs) ||
	  (table3Ptr >= header.dataOfs)) {
	throw FormatException{"Table3 pointer out of range"};
      }
      
      std::string nameStr{nameData.data(), nameLen};
      size_t table3Index = (table3Ptr - header.table3Ofs)/sizeof(Table3Entry);
      
      auto ins = table2_.emplace(nameStr, table3Index);
      if (!ins.second) {
	if (ins.first->second == table3Index)
	  printf("Duplicate entry for name %s\n", nameStr.c_str());
	else
	  printf("Collision for name %s: prev %lu, new %lu\n", nameStr.c_str(),
		 ins.first->second, table3Index);
      }
      // Store an position-indexed copy of Table2 to resolve Table1->Table2 ptr's
      table2Pos.emplace(pos, table3Ptr);

      pos += 1+nameLen+4;
    }
    
    // Read Table 1
    if (fseeko(file, start+header.table1Ofs, SEEK_SET) != 0) {
      throw POSIXException{errno, "Could not seek"};
    }

    for (size_t i = 0;i < numTable1Entries;++i) {
      Table1Entry entry;
      if (fread(&entry, sizeof(Table1Entry), 1, file) != 1)
	throw POSIXException{errno, "Could not read"};

      if ((entry.crc == 0x00000000) &&
	  (entry.table3Ptr == 0xffffffff))
	continue; // Unused entry
      
      if ((entry.table3Ptr < header.table2Ofs) ||
	  (entry.table3Ptr >= header.dataOfs)) {
	throw FormatException{"Table3 pointer out of range"};
      }

      if (entry.table3Ptr < header.table3Ofs) {
	auto it = table2Pos.find(entry.table3Ptr);
	if (it == table2Pos.end()) {
	  fprintf(stderr, "Table1->Table2 pointer: Table 2 entry not found: crc %.8x ptr %.8x\n",
		  entry.crc, entry.table3Ptr);
	  continue;
	}
	printf("Table1->Table2 pointer resolved: Table 2 %.8x -> Table 3 %.8x\n",
	       entry.table3Ptr, it->second);
	entry.table3Ptr = it->second;
      }

      size_t table3Index = (entry.table3Ptr - header.table3Ofs)/sizeof(Table3Entry);
      auto ins = table1_.emplace(static_cast<uint32_t>(entry.crc), table3Index);
      if (!ins.second) {
	if (ins.first->second == table3Index)
	  printf("Duplicate entry for CRC %.8x\n", entry.crc);
	else
	  printf("Collision for CRC %.8x: prev %lu, new %lu\n", entry.crc, ins.first->second, table3Index);
      }
    }
  }
  
  std::map<uint32_t, size_t> table1_;
  std::map<std::string, size_t> table2_;
  std::vector<std::tuple<uint32_t, uint32_t> > table3_;
};

int main(int argc, char *argv[]) {
  if (argc != 2) {
    fprintf(stderr, "Usage: %s tre-file\n", argv[0]);
    return 1;
  }

  try {
    TreFile file{argv[1]};

    file.printStructure();
  } catch (POSIXException &ex) {
    fprintf(stderr, "%s\n", ex.toString().c_str());
    return 2;
  } catch (FormatException &ex) {
    fprintf(stderr, "%s\n", ex.toString().c_str());
    return 3;
  }
  
  return 0;
}