// dirsearch.cc -- directory searching for gold

#include "gold.h"

#include <cerrno>
#include <sys/types.h>
#include <dirent.h>

#include "gold-threads.h"
#include "dirsearch.h"

namespace
{

// Read all the files in a directory.

class Dir_cache
{
 public:
  Dir_cache(const char* dirname)
    : dirname_(dirname), files_()
  { }

  // Read the files in the directory.
  void read_files();

  // Return whether a file (a base name) is present in the directory.
  bool find(const std::string&) const;

 private:
  // We can not copy this class.
  Dir_cache(const Dir_cache&);
  Dir_cache& operator=(const Dir_cache&);

  const char* dirname_;
  Unordered_set<std::string> files_;
};

void
Dir_cache::read_files()
{
  DIR* d = opendir(this->dirname_);
  if (d == NULL)
    {
      // We ignore directories which do not exist.
      if (errno == ENOENT)
	return;

      char *s = NULL;
      if (asprintf(&s, _("can not read directory %s"), this->dirname_) < 0)
	gold::gold_nomem();
      gold::gold_fatal(s, true);
    }

  dirent* de;
  while ((de = readdir(d)) != NULL)
    this->files_.insert(std::string(de->d_name));

  if (closedir(d) != 0)
    gold::gold_fatal("closedir failed", true);
}

bool
Dir_cache::find(const std::string& basename) const
{
  return this->files_.find(basename) != this->files_.end();
}

// A mapping from directory names to caches.  A lock permits
// concurrent update.  There is no lock for read operations--some
// other mechanism must be used to prevent reads from conflicting with
// writes.

class Dir_caches
{
 public:
  Dir_caches()
    : lock_(), caches_()
  { }

  ~Dir_caches();

  // Add a cache for a directory.
  void add(const char*);

  // Look up a directory in the cache.  This much be locked against
  // calls to Add.
  Dir_cache* lookup(const char*) const;

 private:
  // We can not copy this class.
  Dir_caches(const Dir_caches&);
  Dir_caches& operator=(const Dir_caches&);

  typedef Unordered_map<const char*, Dir_cache*> Cache_hash;

  gold::Lock lock_;
  Cache_hash caches_;
};

Dir_caches::~Dir_caches()
{
  for (Cache_hash::iterator p = this->caches_.begin();
       p != this->caches_.end();
       ++p)
    delete p->second;
}

void
Dir_caches::add(const char* dirname)
{
  {
    gold::Hold_lock hl(this->lock_);
    if (this->lookup(dirname) != NULL)
      return;
  }

  Dir_cache* cache = new Dir_cache(dirname);

  cache->read_files();

  {
    gold::Hold_lock hl(this->lock_);

    std::pair<const char*, Dir_cache*> v(dirname, cache);
    std::pair<Cache_hash::iterator, bool> p = this->caches_.insert(v);
    gold_assert(p.second);
  }
}

Dir_cache*
Dir_caches::lookup(const char* dirname) const
{
  Cache_hash::const_iterator p = this->caches_.find(dirname);
  if (p == this->caches_.end())
    return NULL;
  return p->second;
}

// The caches.

Dir_caches caches;

// A Task to read the directory.

class Dir_cache_task : public gold::Task
{
 public:
  Dir_cache_task(const char* dir, gold::Task_token& token)
    : dir_(dir), token_(token)
  { }

  Is_runnable_type is_runnable(gold::Workqueue*);

  gold::Task_locker* locks(gold::Workqueue*);

  void run(gold::Workqueue*);

 private:
  const char* dir_;
  gold::Task_token& token_;
};

// We can always run the task to read the directory.

gold::Task::Is_runnable_type
Dir_cache_task::is_runnable(gold::Workqueue*)
{
  return IS_RUNNABLE;
}

// Return the locks to hold.  We use a blocker lock to prevent file
// lookups from starting until the directory contents have been read.

gold::Task_locker*
Dir_cache_task::locks(gold::Workqueue* workqueue)
{
  return new gold::Task_locker_block(this->token_, workqueue);
}

// Run the task--read the directory contents.

void
Dir_cache_task::run(gold::Workqueue*)
{
  caches.add(this->dir_);
}

}

namespace gold
{

Dirsearch::Dirsearch()
  : directories_(), token_()
{
}

void
Dirsearch::add(Workqueue* workqueue, const char* d)
{
  this->directories_.push_back(d);
  this->token_.add_blocker();
  workqueue->queue(new Dir_cache_task(d, this->token_));
}

void
Dirsearch::add(Workqueue* workqueue, const General_options::Dir_list& list)
{
  for (General_options::Dir_list::const_iterator p = list.begin();
       p != list.end();
       ++p)
    this->add(workqueue, *p);
}

std::string
Dirsearch::find(const std::string& n1, const std::string& n2) const
{
  gold_assert(!this->token_.is_blocked());

  for (std::list<const char*>::const_iterator p = this->directories_.begin();
       p != this->directories_.end();
       ++p)
    {
      Dir_cache* pdc = caches.lookup(*p);
      gold_assert(pdc != NULL);
      if (pdc->find(n1))
	return std::string(*p) + '/' + n1;
      if (!n2.empty() && pdc->find(n2))
	return std::string(*p) + '/' + n2;
    }

  return std::string();
}

} // End namespace gold.