src/net/instaweb/rewriter/public/resource_namer.h

// Copyright 2010 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Author: jmarantz@google.com (Joshua Marantz)

#ifndef NET_INSTAWEB_REWRITER_PUBLIC_RESOURCE_NAMER_H_
#define NET_INSTAWEB_REWRITER_PUBLIC_RESOURCE_NAMER_H_

#include "base/logging.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/base/string_util.h"

namespace net_instaweb {

class Hasher;

// Encapsulates the naming of resource URL leafs.  The class holds the context
// of a single resource, and is not intended for re-use.  We could, of course,
// add a Clear(), but it is a stateful class.
class ResourceNamer {
 public:
  // This determines the overhead imposed on each URL by the ResourceNamer
  // syntax, such as separators.
  static const int kOverhead;

  ResourceNamer() {}
  ~ResourceNamer() {}

  // Encoding and decoding in various formats.

  // Decodes an entire resource name (NAME.pagespeed[.EXPT].ID.HASH[|SIG].EXT),
  // placing the result in the fields in this encoder.
  bool Decode(const StringPiece& encoded_string, int hash_length,
              int signature_length);

  // Calls Decode() passing values of -1, -1 for hash and signature lengths.
  // Hash and signature outputs from this must not be used.
  bool DecodeIgnoreHashAndSignature(StringPiece encoded_string);

  // Encodes the fields in this encoder into an absolute url, with the
  // trailing portion "NAME.pagespeed[.(EXPT|PsolOpts)].ID.HASH[.SIG].EXT".
  GoogleString Encode() const;

  // Encode a key that can used to do a lookup based on an id
  // and the name.  This key can be used to find the hash-code for a
  // resource within the origin TTL.
  //
  // The 'id' is a short code indicating which Instaweb rewriter was
  // used to generate the resource.
  GoogleString EncodeIdName() const;

  // Note: there is no need at this time to decode the name key.

  // Eventual length of name. Gets eventual hash length from passed in hasher
  // and signature_length.
  // Needed by RewriteDriver to check that filenames aren't too long.
  int EventualSize(const Hasher& hasher, int signature_length) const;

  // Simple getters
  StringPiece id() const { return id_; }
  StringPiece options() const { return options_; }
  StringPiece name() const { return name_; }
  StringPiece hash() const { return hash_; }
  StringPiece ext() const { return ext_; }
  StringPiece experiment() const { return experiment_; }
  StringPiece signature() const { return signature_; }

  bool has_experiment() const { return !experiment_.empty(); }
  bool has_options() const { return !options_.empty(); }

  // Simple setters
  void set_id(const StringPiece& p) { p.CopyToString(&id_); }
  void set_options(const StringPiece& opts) { opts.CopyToString(&options_); }
  void set_name(const StringPiece& n) { n.CopyToString(&name_); }
  void set_hash(const StringPiece& h) { h.CopyToString(&hash_); }
  void set_ext(const StringPiece& e) {
    // TODO(jmaessen): Remove check after transitioning to undotted extensions
    // everywhere.
    CHECK(e.empty() || e[0] != '.');
    e.CopyToString(&ext_);
  }
  void set_experiment(const StringPiece& e) { e.CopyToString(&experiment_); }
  void set_signature(const StringPiece& s) { s.CopyToString(&signature_); }

  // Other setter-like operations
  void ClearHash() { hash_.clear(); }
  void CopyFrom(const ResourceNamer& other);

  // Utility functions

  // Name suitable for debugging and logging
  GoogleString PrettyName() const {return  InternalEncode(); }

 private:
  GoogleString InternalEncode() const;
  bool LegacyDecode(const StringPiece& encoded_string);

  GoogleString id_;
  GoogleString options_;
  GoogleString name_;
  GoogleString hash_;
  GoogleString ext_;
  GoogleString experiment_;
  GoogleString signature_;

  DISALLOW_COPY_AND_ASSIGN(ResourceNamer);
};

}  // namespace net_instaweb

#endif  // NET_INSTAWEB_REWRITER_PUBLIC_RESOURCE_NAMER_H_