// file      : cutl/xml/parser.hxx
// copyright : Copyright (c) 2009-2017 Code Synthesis Tools CC
// license   : MIT; see accompanying LICENSE file

#ifndef CUTL_XML_PARSER_HXX
#define CUTL_XML_PARSER_HXX

#include <map>
#include <vector>
#include <string>
#include <iosfwd>
#include <cstddef> // std::size_t
#include <cassert>

#include <cutl/details/config.hxx> // LIBCUTL_EXTERNAL_EXPAT

#ifndef LIBCUTL_EXTERNAL_EXPAT
#  include <cutl/details/expat/expat.h>
#else
#  include <expat.h>
#endif

// We only support UTF-8 expat.
//
#ifdef XML_UNICODE
#  error UTF-16 expat (XML_UNICODE defined) is not supported
#endif

#include <cutl/xml/qname.hxx>
#include <cutl/xml/exception.hxx>

#include <cutl/details/export.hxx>

namespace cutl
{
  namespace xml
  {
    class parser;

    struct LIBCUTL_EXPORT parsing: exception
    {
      virtual
      ~parsing () throw ();

      parsing (const std::string& name,
               unsigned long long line,
               unsigned long long column,
               const std::string& description);

      parsing (const parser&, const std::string& description);

      const std::string&
      name () const {return name_;}

      unsigned long long
      line () const {return line_;}

      unsigned long long
      column () const {return column_;}

      const std::string&
      description () const {return description_;}

      virtual const char*
      what () const throw ();

    private:
      void
      init ();

    private:
      std::string name_;
      unsigned long long line_;
      unsigned long long column_;
      std::string description_;
      std::string what_;
    };

    class LIBCUTL_EXPORT parser
    {
    public:
      ~parser ();

      typedef xml::qname qname_type;
      typedef unsigned short feature_type;

      // If both receive_attributes_event and receive_attributes_map are
      // specified, then receive_attributes_event is assumed.
      //
      static const feature_type receive_elements = 0x0001;
      static const feature_type receive_characters = 0x0002;
      static const feature_type receive_attributes_map = 0x0004;
      static const feature_type receive_attributes_event = 0x0008;
      static const feature_type receive_namespace_decls = 0x0010;

      static const feature_type receive_default = receive_elements |
                                                  receive_characters |
                                                  receive_attributes_map;

      // Parse std::istream. Input name is used in diagnostics to identify
      // the document being parsed. std::ios_base::failure exception is
      // used to report io errors (badbit and failbit).
      //
      parser (std::istream&,
              const std::string& input_name,
              feature_type = receive_default);

      const std::string&
      input_name () const {return iname_;}

      // Parsing events.
      //
    public:
      enum event_type
      {
        // If adding new events, also update the stream insertion operator.
        //
        start_element,
        end_element,
        start_attribute,
        end_attribute,
        characters,
        start_namespace_decl,
        end_namespace_decl,
        eof
      };

      event_type
      next ()
      {
        if (state_ == state_next)
          return next_ (false);
        else
        {
          // If we previously peeked at start/end_element, then adjust
          // state accordingly.
          //
          switch (event_)
          {
          case end_element:
            {
              if (!element_state_.empty () &&
                  element_state_.back ().depth == depth_)
                pop_element ();

              depth_--;
              break;
            }
          case start_element:
            {
              depth_++;
              break;
            }
          default:
            break;
          }

          state_ = state_next;
          return event_;
        }
      }

      // Get the next event and make sure that it's what's expected. If it
      // is not, then throw an appropriate parsing exception.
      //
      void
      next_expect (event_type);

      void
      next_expect (event_type, const qname_type& qname);

      void
      next_expect (event_type, const std::string& name);

      void
      next_expect (event_type, const std::string& ns, const std::string& name);

      event_type
      peek ()
      {
        if (state_ == state_peek)
          return event_;
        else
        {
          event_type e (next_ (true));
          state_ = state_peek; // Set it after the call to next_().
          return e;
        }
      }

      // Return the even that was last returned by the call to next() or
      // peek().
      //
      event_type
      event () {return event_;}

      // Event data.
      //
    public:
      const qname_type& qname () const {return *pqname_;}

      const std::string& namespace_ () const {return pqname_->namespace_ ();}
      const std::string& name () const {return pqname_->name ();}
      const std::string& prefix () const {return pqname_->prefix ();}

      const std::string& value () const {return *pvalue_;}

      unsigned long long line () const {return line_;}
      unsigned long long column () const {return column_;}

      // Attribute map lookup. If attribute is not found, then the version
      // without the default value throws an appropriate parsing exception
      // while the version with the default value returns that value.
      //
      // Note also that there is no attribute(ns,name) version since it
      // would conflict with attribute(name,dv) (qualified attributes
      // are not very common).
      //
      // Attribute map is valid throughout at the "element level" until
      // end_element and not just during start_element. As a special case,
      // the map is still valid after peek() that returned end_element until
      // this end_element event is retrieved with next().
      //
      const std::string&
      attribute (const std::string& name) const;

      template <typename T>
      T
      attribute (const std::string& name) const;

      std::string
      attribute (const std::string& name, const std::string& dv) const;

      template <typename T>
      T
      attribute (const std::string& name, const T& dv) const;

      const std::string&
      attribute (const qname_type& qname) const;

      template <typename T>
      T
      attribute (const qname_type& qname) const;

      std::string
      attribute (const qname_type& qname, const std::string& dv) const;

      template <typename T>
      T
      attribute (const qname_type& qname, const T& dv) const;

      bool
      attribute_present (const std::string& name) const;

      bool
      attribute_present (const qname_type& qname) const;

      // Low-level attribute map access. Note that this API assumes
      // all attributes are handled.
      //
      struct attribute_value_type
      {
        std::string value;
        mutable bool handled;
      };

      typedef std::map<qname_type, attribute_value_type> attribute_map_type;

      const attribute_map_type&
      attribute_map () const;

      // Optional content processing.
      //
    public:
      enum content_type
      {
                 //  element   characters  whitespaces
        empty,   //    no          no        ignored
        simple,  //    no          yes       preserved
        complex, //    yes         no        ignored
        mixed    //    yes         yes       preserved
      };

      // Note that you cannot get/set content while peeking.
      //
      void
      content (content_type c)
      {
        assert (state_ == state_next);

        if (!element_state_.empty () && element_state_.back ().depth == depth_)
          element_state_.back ().content = c;
        else
          element_state_.push_back (element_entry (depth_, c));
      }

      content_type
      content () const
      {
        assert (state_ == state_next);

        return
          !element_state_.empty () && element_state_.back ().depth == depth_
          ? element_state_.back ().content
          : mixed;
      }

    private:
      static void XMLCALL
      start_element_ (void*, const XML_Char*, const XML_Char**);

      static void XMLCALL
      end_element_ (void*, const XML_Char*);

      static void XMLCALL
      characters_ (void*, const XML_Char*, int);

      static void XMLCALL
      start_namespace_decl_ (void*, const XML_Char*, const XML_Char*);

      static void XMLCALL
      end_namespace_decl_ (void*, const XML_Char*);

    private:
      event_type
      next_ (bool peek);

      event_type
      next_body ();

      void
      handle_error ();

    private:
      std::istream& is_;
      const std::string iname_;
      feature_type feature_;

      XML_Parser p_;
      std::size_t depth_;
      enum {state_next, state_peek} state_;
      event_type event_;
      event_type queue_;

      qname_type qname_;
      std::string value_;

      // These are used to avoid copying when we are handling attributes
      // and namespace decls.
      //
      const qname_type* pqname_;
      const std::string* pvalue_;

      unsigned long long line_;
      unsigned long long column_;

      // Attributes as events.
      //
      struct attribute_type
      {
        qname_type qname;
        std::string value;
      };

      typedef std::vector<attribute_type> attributes;

      attributes attr_;
      attributes::size_type attr_i_; // Index of the current attribute.

      // Namespace declarations.
      //
      typedef std::vector<qname_type> namespace_decls;

      namespace_decls start_ns_;
      namespace_decls::size_type start_ns_i_; // Index of the current decl.

      namespace_decls end_ns_;
      namespace_decls::size_type end_ns_i_; // Index of the current decl.

      // Element state consisting of the content model and attribute map.
      //
      struct element_entry
      {
        element_entry (std::size_t d, content_type c = mixed)
            : depth (d), content (c), attr_unhandled_ (0) {}

        std::size_t depth;
        content_type content;
        attribute_map_type attr_map_;
        mutable attribute_map_type::size_type attr_unhandled_;
      };

      typedef std::vector<element_entry> element_state;
      std::vector<element_entry> element_state_;

      // Empty attribute map to return when an element has no attributes.
      //
      const attribute_map_type empty_attr_map_;

      // Return the element entry corresponding to the current depth, if
      // exists, and NULL otherwise.
      //
      const element_entry*
      get_element () const;

      void
      pop_element ();
    };

    LIBCUTL_EXPORT
    std::ostream&
    operator<< (std::ostream&, parser::event_type);
  }
}

#include <cutl/xml/parser.ixx>
#include <cutl/xml/parser.txx>

#endif // CUTL_XML_PARSER_HXX