#include "storage.h"

#include "config.h"

#include <chrono>
#include <iostream>
#include <random>

#include <SQLiteCpp/SQLiteCpp.h>

using namespace std::string_literals;

Storage::Storage(const Config& config):
 m_db(config.getDataPath() + "/whiteboard.db3", SQLite::OPEN_READWRITE | SQLite::OPEN_CREATE),
 m_maxage(config.getMaxage()),

 // Note about VARCHAR(N): "SQLite does not impose any length restrictions" - handled elsewhere in application
 m_stmt_create(m_db, "CREATE TABLE IF NOT EXISTS documents (id VARCHAR(16) PRIMARY KEY, value BLOB, rev INTEGER, cursorpos INTEGER, timestamp BIGINT)"),
 m_stmt_getNumberOfDocuments(m_db, "SELECT COUNT(*) FROM documents"),
 m_stmt_cleanup(m_db, "DELETE FROM documents WHERE timestamp + ? < ?"),
 m_stmt_vacuum(m_db, "VACUUM"),
 m_stmt_exists(m_db, "SELECT id FROM documents WHERE id = ?"),
 m_stmt_getDocument(m_db, "SELECT value FROM documents WHERE id = ?"),
 m_stmt_getRevision(m_db, "SELECT rev FROM documents WHERE id = ?"),
 m_stmt_getCursorPos(m_db, "SELECT cursorpos FROM documents WHERE id = ?"),
 m_stmt_getRow(m_db, "SELECT value, rev, cursorpos FROM documents WHERE id = ?"),
 m_stmt_setDocument(m_db, "UPDATE documents SET value = ?, timestamp = ?, rev = rev + 1 WHERE id = ?"),
 m_stmt_setDocument_new(m_db, "INSERT INTO documents (id, value, rev, cursorpos, timestamp) values (?, ?, ?, ?, ?)"),
 m_stmt_setRevision(m_db, "UPDATE documents SET rev = ? WHERE id = ?"),
 m_stmt_setCursorPos(m_db, "UPDATE documents SET cursorpos = ? WHERE id = ?"),
 m_stmt_setRow(m_db, "INSERT OR REPLACE INTO documents (id, value, rev, cursorpos, timestamp) values (?, ?, ?, ?, ?)"),
 m_stmt_getDbSizeGross(m_db, "SELECT page_count * page_size as size FROM pragma_page_count(), pragma_page_size()"),
 m_stmt_getDbSizeNet(m_db, "SELECT (page_count - freelist_count) * page_size as size FROM pragma_page_count(), pragma_freelist_count(), pragma_page_size()"),
 m_stmt_touchDocument(m_db, "UPDATE documents SET timestamp = ? WHERE id = ?")
{
 CompiledSQL::Guard g{m_stmt_create};
 m_stmt_create.execute();
}

Storage::~Storage()
{
}

uint64_t Storage::getNumberOfDocuments()
{
 CompiledSQL::Guard g{m_stmt_getNumberOfDocuments};
 if (!m_stmt_getNumberOfDocuments.execute())
  throw std::runtime_error("Count not possible");
 
 return m_stmt_getNumberOfDocuments.getColumn<int64_t>(0);
}

uint64_t Storage::dbsize_gross()
{
 CompiledSQL::Guard g{m_stmt_getDbSizeGross};
 if (!m_stmt_getDbSizeGross.execute())
  throw std::runtime_error("DB size count (gross) not possible");
 
 return m_stmt_getDbSizeGross.getColumn<int64_t>(0);
}

uint64_t Storage::dbsize_net()
{
 CompiledSQL::Guard g{m_stmt_getDbSizeNet};
 if (!m_stmt_getDbSizeNet.execute())
  throw std::runtime_error("DB size count (net) not possible");
 
 return m_stmt_getDbSizeNet.getColumn<int64_t>(0);
}

namespace {
 uint64_t unixepoch()
 {
  const auto p1 = std::chrono::system_clock::now();
  return std::chrono::duration_cast<std::chrono::seconds>(p1.time_since_epoch()).count();
 }
} // namespace

void Storage::cleanup()
{
 if (m_maxage != 0) {
  CompiledSQL::Guard g{m_stmt_cleanup};
  m_stmt_cleanup.bind(1, static_cast<int64_t>(m_maxage));
  m_stmt_cleanup.bind(2, static_cast<int64_t>(unixepoch()));
  m_stmt_cleanup.execute();
 }
 
 CompiledSQL::Guard g{m_stmt_vacuum};
 m_stmt_vacuum.execute();
}

bool Storage::exists(const std::string& id)
{
 CompiledSQL::Guard g{m_stmt_exists};
 m_stmt_exists.bind(1, id);

 return m_stmt_exists.execute();
}

std::string Storage::getDocument(const std::string& id)
{
 CompiledSQL::Guard g{m_stmt_getDocument};
 m_stmt_getDocument.bind(1, id);

 if (!m_stmt_getDocument.execute())
  throw std::runtime_error("id "s + id + " not found"s);

 return m_stmt_getDocument.getColumn<std::string>(0);
}

int Storage::getRevision(const std::string& id)
{
 CompiledSQL::Guard g{m_stmt_getRevision};
 m_stmt_getRevision.bind(1, id);

 if (!m_stmt_getRevision.execute())
  throw std::runtime_error("id "s + id + " not found"s);

 return m_stmt_getRevision.getColumn<int>(0);
}

int Storage::getCursorPos(const std::string& id)
{
 CompiledSQL::Guard g{m_stmt_getCursorPos};
 m_stmt_getCursorPos.bind(1, id);

 if (!m_stmt_getCursorPos.execute())
  throw std::runtime_error("id "s + id + " not found"s);

 return m_stmt_getCursorPos.getColumn<int>(0);
}

std::tuple<std::string, int, int> Storage::getRow(const std::string& id)
{
 CompiledSQL::Guard g{m_stmt_getRow};
 m_stmt_getRow.bind(1, id);

 if (!m_stmt_getRow.execute())
  throw std::runtime_error("id "s + id + " not found"s);

 return {m_stmt_getRow.getColumn<std::string>(0), m_stmt_getRow.getColumn<int>(1), m_stmt_getRow.getColumn<int>(2)};
}
 
void Storage::setDocument(const std::string& id, const std::string& document)
{
 CompiledSQL::Guard g{m_stmt_setDocument};
 m_stmt_setDocument.bind(1, document);
 m_stmt_setDocument.bind(2, static_cast<int64_t>(unixepoch()));
 m_stmt_setDocument.bind(3, id);

 if (!m_stmt_setDocument.execute()) {
  CompiledSQL::Guard g{m_stmt_setDocument_new};
  m_stmt_setDocument_new.bind(1, id);
  m_stmt_setDocument_new.bind(2, document);
  m_stmt_setDocument_new.bind(3, 0);
  m_stmt_setDocument_new.bind(4, 0);
  m_stmt_setDocument_new.bind(5, static_cast<int64_t>(unixepoch()));
  if (!m_stmt_setDocument_new.execute())
   throw std::runtime_error("Unable to create document with id "s + id);
 }
}

void Storage::setRevision(const std::string& id, int rev)
{
 CompiledSQL::Guard g{m_stmt_setRevision};
 m_stmt_setRevision.bind(1, rev);
 m_stmt_setRevision.bind(2, id);

 if (!m_stmt_setRevision.execute())
  throw std::runtime_error("Unable to set revision for id "s + id);
}

void Storage::setCursorPos(const std::string& id, int cursorPos)
{
 CompiledSQL::Guard g{m_stmt_setCursorPos};
 m_stmt_setCursorPos.bind(1, cursorPos);
 m_stmt_setCursorPos.bind(2, id);

 if (!m_stmt_setCursorPos.execute())
  throw std::runtime_error("Unable to set cursor position for id "s + id);
}

void Storage::setRow(const std::string& id, const std::string& document, int rev, int cursorPos)
{
 CompiledSQL::Guard g{m_stmt_setRow};
 m_stmt_setRow.bind(1, id);
 m_stmt_setRow.bind(2, document);
 m_stmt_setRow.bind(3, rev);
 m_stmt_setRow.bind(4, cursorPos);
 m_stmt_setRow.bind(5, static_cast<int64_t>(unixepoch()));
 if (!m_stmt_setRow.execute())
  throw std::runtime_error("Unable to insert row with id "s + id);
}

uint32_t checksum32(const std::string& s)
{
 uint32_t result{0};
 for (unsigned int i = 0; i < s.size(); i++) {
  result = ((result >> 1) | ((result & 1) << 31)) ^ (s[i] & 0xFF);
 }
 return result & 0x7FFFFFFF;
}

std::string Storage::generate_id()
{
 static std::random_device r;
 static std::default_random_engine e1(r());
 static std::uniform_int_distribution<int> uniform_dist(0, 35);

 // limit tries
 for (int j = 0; j < 100000; j++) {
  std::string result;
  for (int i = 0; i < 6; i++) {
   char c{static_cast<char>('0' + uniform_dist(e1))};
   if (c > '9')
    c = c - '9' - 1 + 'a';
   result.push_back(c);
  }

  if (!exists(result))
   return result;
 }

 return "endofcodes";
}

void Storage::touchDocument(const std::string& id)
{
 CompiledSQL::Guard g{m_stmt_touchDocument};
 m_stmt_touchDocument.bind(1, static_cast<int64_t>(unixepoch()));
 m_stmt_touchDocument.bind(2, id);
 if (!m_stmt_touchDocument.execute())
  throw std::runtime_error("Unable to touch document with id "s + id);
}