/*

Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license ( the "Software" ) to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

*/
module derelict.util.loader;

private {
	import std.array : split;
	import std.string : strip;

    import derelict.util.sharedlib;
    import derelict.util.exception;
}

struct SharedLibVersion {
    int major;
    int minor;
    int patch;
}

abstract class SharedLibLoader {
    private {
        string _libNames;
        SharedLib _lib;
    }

    /++
     Constructs a new instance of shared lib loader with a string of one
     or more shared library names to use as default.

     Params:
        libNames =      A string containing one or more comma-separated shared
                        library names.
    +/
    public this( string libNames ) {
        _libNames = libNames;
    }

    public final {
        /++
         Finds and loads a shared library, using this loader's default shared library
         names and default supported shared library version.

         If multiple library names are specified as default, a SharedLibLoadException
         will only be thrown if all of the libraries fail to load. It will be the head
         of an exceptin chain containing one instance of the exception for each library
         that failed.

         Examples:  If this loader supports versions 2.0 and 2.1 of a shared libary,
                    this method will attempt to load 2.1 and will fail if only 2.0
                    is present on the system.

         Throws:    SharedLibLoadException if the shared library or one of its
                    dependencies cannot be found on the file system.
                    SymbolLoadException if an expected symbol is missing from the
                    library.
        +/
        void load() {
            load( _libNames );
        }

        /++
         Finds and loads any version of a shared library greater than or equal to
         the required mimimum version, using this loader's default shared library
         names.

         If multiple library names are specified as default, a SharedLibLoadException
         will only be thrown if all of the libraries fail to load. It will be the head
         of an exceptin chain containing one instance of the exception for each library
         that failed.

         Examples:  If this loader supports versions 2.0 and 2.1 of a shared library,
                    passing a SharedLibVersion with the major field set to 2 and the
                    minor field set to 0 will cause the loader to load version 2.0
                    if version 2.1 is not available on the system.

         Params:
            minRequiredVersion = the minimum version of the library that is acceptable.
                                 Subclasses are free to ignore this.

         Throws:    SharedLibLoadException if the shared library or one of its
                    dependencies cannot be found on the file system.
                    SymbolLoadException if an expected symbol is missing from the
                    library.
        +/
        void load( SharedLibVersion minRequiredVersion ) {
            configureMinimumVersion( minRequiredVersion );
            load();
        }

        /++
         Finds and loads a shared library, using libNames to find the library
         on the file system.

         If multiple library names are specified in libNames, a SharedLibLoadException
         will only be thrown if all of the libraries fail to load. It will be the head
         of an exceptin chain containing one instance of the exception for each library
         that failed.

         Examples:  If this loader supports versions 2.0 and 2.1 of a shared libary,
                    this method will attempt to load 2.1 and will fail if only 2.0
                    is present on the system.

         Params:
            libNames =      A string containing one or more comma-separated shared
                            library names.
         Throws:    SharedLibLoadException if the shared library or one of its
                    dependencies cannot be found on the file system.
                    SymbolLoadException if an expected symbol is missing from the
                    library.
        +/
        void load( string libNames ) {
            assert( libNames !is null );

            auto lnames = libNames.split( "," );
            foreach( ref string l; lnames )
                l = l.strip();

            load( lnames );
        }

        /++
         Finds and loads any version of a shared library greater than or equal to
         the required mimimum version, using libNames to find the library
         on the file system.

         If multiple library names are specified as default, a SharedLibLoadException
         will only be thrown if all of the libraries fail to load. It will be the head
         of an exceptin chain containing one instance of the exception for each library
         that failed.

         Examples:  If this loader supports versions 2.0 and 2.1 of a shared library,
                    passing a SharedLibVersion with the major field set to 2 and the
                    minor field set to 0 will cause the loader to load version 2.0
                    if version 2.1 is not available on the system.

         Params:
            libNames =      A string containing one or more comma-separated shared
                            library names.
            minRequiredVersion = The minimum version of the library that is acceptable.
                                 Subclasses are free to ignore this.

         Throws:    SharedLibLoadException if the shared library or one of its
                    dependencies cannot be found on the file system.
                    SymbolLoadException if an expected symbol is missing from the
                    library.
        +/
        void load( string libNames, SharedLibVersion minRequiredVersion ) {
            configureMinimumVersion( minRequiredVersion );
            load( libNames );
        }

        /++
         Finds and loads a shared library, using libNames to find the library
         on the file system.

         If multiple library names are specified in libNames, a SharedLibLoadException
         will only be thrown if all of the libraries fail to load. It will be the head
         of an exceptin chain containing one instance of the exception for each library
         that failed.


         Params:
            libNames =      An array containing one or more shared library names,
                            with one name per index.

         Throws:    SharedLibLoadException if the shared library or one of its
                    dependencies cannot be found on the file system.
                    SymbolLoadException if an expected symbol is missing from the
                    library.
        +/
        void load( string[] libNames ) {
            _lib.load( libNames );
            loadSymbols();
        }

        /++
         Finds and loads any version of a shared library greater than or equal to
         the required mimimum version, , using libNames to find the library
         on the file system.

         If multiple library names are specified in libNames, a SharedLibLoadException
         will only be thrown if all of the libraries fail to load. It will be the head
         of an exceptin chain containing one instance of the exception for each library
         that failed.

         Examples:  If this loader supports versions 2.0 and 2.1 of a shared library,
                    passing a SharedLibVersion with the major field set to 2 and the
                    minor field set to 0 will cause the loader to load version 2.0
                    if version 2.1 is not available on the system.


         Params:
            libNames =      An array containing one or more shared library names,
                            with one name per index.
            minRequiredVersion = The minimum version of the library that is acceptable.
                                 Subclasses are free to ignore this.

         Throws:    SharedLibLoadException if the shared library or one of its
                    dependencies cannot be found on the file system.
                    SymbolLoadException if an expected symbol is missing from the
                    library.
        +/
        void load( string[] libNames, SharedLibVersion minRequiredVersion ) {
            configureMinimumVersion( minRequiredVersion );
            load( libNames );
        }

        /++
         Unloads the shared library from memory, invalidating all function pointers
         which were assigned a symbol by one of the load methods.
        +/
        void unload() {
            _lib.unload();
        }

        @property {
            /// Returns: true if the shared library is loaded, false otherwise.
            bool isLoaded() {
                return _lib.isLoaded;
            }

            /++
             Sets the callback that will be called when an expected symbol is
             missing from the shared library.

             Params:
                callback =      A delegate that returns a value of type
                                derelict.util.exception.ShouldThrow and accepts
                                a string as the sole parameter.
            +/
            void missingSymbolCallback( MissingSymbolCallbackDg callback ) {
                _lib.missingSymbolCallback = callback;
            }

            /++
             Sets the callback that will be called when an expected symbol is
             missing from the shared library.

             Params:
                callback =      A pointer to a function that returns a value of type
                                derelict.util.exception.ShouldThrow and accepts
                                a string as the sole parameter.
            +/
            void missingSymbolCallback( MissingSymbolCallbackFunc callback ) {
                _lib.missingSymbolCallback = callback;
            }

            /++
             Returns the currently active missing symbol callback.

             This exists primarily as a means to save the current callback before
             setting a new one. It's useful, for example, if the new callback needs
             to delegate to the old one.
            +/
            MissingSymbolCallback missingSymbolCallback() {
                return _lib.missingSymbolCallback;
            }
        }
    }

    protected {
        /++
         Must be implemented by subclasses to load all of the symbols from a
         shared library.

         This method is called by the load methods.
        +/
        abstract void loadSymbols();

        /++
         Allows a subclass to install an exception handler for specific versions
         of a library before loadSymbols is called.

         This method is optional. If the subclass does not implement it, calls to
         any of the overloads of the load method that take a SharedLibVersion will
         cause a compile time assert to fire.
        +/
        void configureMinimumVersion( SharedLibVersion minVersion ) {
            assert( 0, "SharedLibVersion is not supported by this loader." );
        }

        /++
         Subclasses can use this as an alternative to bindFunc, but must bind
         the returned symbol manually.

         bindFunc calls this internally, so it can be overloaded to get behavior
         different from the default.

         Params:
            name =      The name of the symbol to load.doThrow =   If true, a SymbolLoadException will be thrown if the symbol
                        is missing. If false, no exception will be thrown and the
                        ptr parameter will be set to null.
         Throws:        SymbolLoadException if doThrow is true and a the symbol
                        specified by funcName is missing from the shared library.
         Returns:       The symbol matching the name parameter.
        +/
        void* loadSymbol( string name, bool doThrow = true ) {
            return _lib.loadSymbol( name, doThrow );
        }

        /// Returns a reference to the shared library wrapped by this loader.
        final ref SharedLib lib() @property {
            return _lib;
        }

        /++
         Subclasses can use this to bind a function pointer to a symbol in the
         shared library.

         Params:
            ptr =       Pointer to a function pointer that will be used as the bind
                        point.
            funcName =  The name of the symbol to be bound.
            doThrow =   If true, a SymbolLoadException will be thrown if the symbol
                        is missing. If false, no exception will be thrown and the
                        ptr parameter will be set to null.
         Throws:        SymbolLoadException if doThrow is true and a the symbol
                        specified by funcName is missing from the shared library.
        +/
        final void bindFunc( void** ptr, string funcName, bool doThrow = true ) {
            void* func = loadSymbol( funcName, doThrow );
            *ptr = func;
        }
    }
}