// =================================================================================================
//
//	Starling Framework
//	Copyright Gamua GmbH. All Rights Reserved.
//
//	This program is free software. You can redistribute and/or modify it
//	in accordance with the terms of the accompanying license agreement.
//
// =================================================================================================

package starling.rendering
{
    import flash.display3D.VertexBuffer3D;
    import flash.utils.Dictionary;

    import starling.core.Starling;
    import starling.utils.StringUtil;

    /** Describes the memory layout of VertexData instances, as used for every single vertex.
     *
     *  <p>The format is set up via a simple String. Here is an example:</p>
     *
     *  <listing>
     *  format = VertexDataFormat.fromString("position:float2, color:bytes4");</listing>
     *
     *  <p>This String describes two attributes: "position" and "color". The keywords after
     *  the colons depict the format and size of the data that each attribute uses; in this
     *  case, we store two floats for the position (taking up the x- and y-coordinates) and four
     *  bytes for the color. (The available formats are the same as those defined in the
     *  <code>Context3DVertexBufferFormat</code> class:
     *  <code>float1, float2, float3, float4, bytes4</code>.)</p>
     *
     *  <p>You cannot create a VertexData instance with its constructor; instead, you must use the
     *  static <code>fromString</code>-method. The reason for this behavior: the class maintains
     *  a cache, and a call to <code>fromString</code> will return an existing instance if an
     *  equivalent format has already been created in the past. That saves processing time and
     *  memory.</p>
     *
     *  <p>VertexDataFormat instances are immutable, i.e. they are solely defined by their format
     *  string and cannot be changed later.</p>
     *
     *  @see VertexData
     */
    public class VertexDataFormat
    {
        private var _format:String;
        private var _vertexSize:int;
        private var _attributes:Vector.<VertexDataAttribute>;

        // format cache
        private static var sFormats:Dictionary = new Dictionary();

        /** Don't use the constructor, but call <code>VertexDataFormat.fromString</code> instead.
         *  This allows for efficient format caching. */
        public function VertexDataFormat()
        {
            _attributes = new Vector.<VertexDataAttribute>();
        }

        /** Creates a new VertexDataFormat instance from the given String, or returns one from
         *  the cache (if an equivalent String has already been used before).
         *
         *  @param format
         *
         *  Describes the attributes of each vertex, consisting of a comma-separated
         *  list of attribute names and their format, e.g.:
         *
         *  <pre>"position:float2, texCoords:float2, color:bytes4"</pre>
         *
         *  <p>This set of attributes will be allocated for each vertex, and they will be
         *  stored in exactly the given order.</p>
         *
         *  <ul>
         *    <li>Names are used to access the specific attributes of a vertex. They are
         *        completely arbitrary.</li>
         *    <li>The available formats can be found in the <code>Context3DVertexBufferFormat</code>
         *        class in the <code>flash.display3D</code> package.</li>
         *    <li>Both names and format strings are case-sensitive.</li>
         *    <li>Always use <code>bytes4</code> for color data that you want to access with the
         *        respective methods.</li>
         *    <li>Furthermore, the attribute names of colors should include the string "color"
         *        (or the uppercase variant). If that's the case, the "alpha" channel of the color
         *        will automatically be initialized with "1.0" when the VertexData object is
         *        created or resized.</li>
         *  </ul>
         */
        public static function fromString(format:String):VertexDataFormat
        {
            if (format in sFormats) return sFormats[format];
            else
            {
                var instance:VertexDataFormat = new VertexDataFormat();
                instance.parseFormat(format);

                var normalizedFormat:String = instance._format;

                if (normalizedFormat in sFormats)
                    instance = sFormats[normalizedFormat];

                sFormats[format] = instance;
                sFormats[normalizedFormat] = instance;

                return instance;
            }
        }

        /** Creates a new VertexDataFormat instance by appending the given format string
         *  to the current instance's format. */
        public function extend(format:String):VertexDataFormat
        {
            return fromString(_format + ", " + format);
        }

        // query methods

        /** Returns the size of a certain vertex attribute in bytes. */
        public function getSize(attrName:String):int
        {
            return getAttribute(attrName).size;
        }

        /** Returns the size of a certain vertex attribute in 32 bit units. */
        public function getSizeIn32Bits(attrName:String):int
        {
            return getAttribute(attrName).size / 4;
        }

        /** Returns the offset (in bytes) of an attribute within a vertex. */
        public function getOffset(attrName:String):int
        {
            return getAttribute(attrName).offset;
        }

        /** Returns the offset (in 32 bit units) of an attribute within a vertex. */
        public function getOffsetIn32Bits(attrName:String):int
        {
            return getAttribute(attrName).offset / 4;
        }

        /** Returns the format of a certain vertex attribute, identified by its name.
         *  Typical values: <code>float1, float2, float3, float4, bytes4</code>. */
        public function getFormat(attrName:String):String
        {
            return getAttribute(attrName).format;
        }

        /** Returns the name of the attribute at the given position within the vertex format. */
        public function getName(attrIndex:int):String
        {
            return _attributes[attrIndex].name;
        }

        /** Indicates if the format contains an attribute with the given name. */
        public function hasAttribute(attrName:String):Boolean
        {
            var numAttributes:int = _attributes.length;

            for (var i:int=0; i<numAttributes; ++i)
                if (_attributes[i].name == attrName) return true;

            return false;
        }

        // context methods

        /** Specifies which vertex data attribute corresponds to a single vertex shader
         *  program input. This wraps the <code>Context3D</code>-method with the same name,
         *  automatically replacing <code>attrName</code> with the corresponding values for
         *  <code>bufferOffset</code> and <code>format</code>. */
        public function setVertexBufferAt(index:int, buffer:VertexBuffer3D, attrName:String):void
        {
            var attribute:VertexDataAttribute = getAttribute(attrName);
            Starling.context.setVertexBufferAt(index, buffer, attribute.offset / 4, attribute.format);
        }

        // parsing

        private function parseFormat(format:String):void
        {
            if (format != null && format != "")
            {
                _attributes.length = 0;
                _format = "";

                var parts:Array = format.split(",");
                var numParts:int = parts.length;
                var offset:int = 0;

                for (var i:int=0; i<numParts; ++i)
                {
                    var attrDesc:String = parts[i];
                    var attrParts:Array = attrDesc.split(":");

                    if (attrParts.length != 2)
                        throw new ArgumentError("Missing colon: " + attrDesc);

                    var attrName:String = StringUtil.trim(attrParts[0]);
                    var attrFormat:String = StringUtil.trim(attrParts[1]);

                    if (attrName.length == 0 || attrFormat.length == 0)
                        throw new ArgumentError(("Invalid format string: " + attrDesc));

                    var attribute:VertexDataAttribute =
                        new VertexDataAttribute(attrName, attrFormat, offset);

                    offset += attribute.size;

                    _format += (i == 0 ? "" : ", ") + attribute.name + ":" + attribute.format;
                    _attributes[_attributes.length] = attribute; // avoid 'push'
                }

                _vertexSize = offset;
            }
            else
            {
                _format = "";
            }
        }

        /** Returns the normalized format string. */
        public function toString():String
        {
            return _format;
        }

        // internal methods

        /** @private */
        internal function getAttribute(attrName:String):VertexDataAttribute
        {
            var i:int, attribute:VertexDataAttribute;
            var numAttributes:int = _attributes.length;

            for (i=0; i<numAttributes; ++i)
            {
                attribute = _attributes[i];
                if (attribute.name == attrName) return attribute;
            }

            return null;
        }

        /** @private */
        internal function get attributes():Vector.<VertexDataAttribute>
        {
            return _attributes;
        }

        // properties

        /** Returns the normalized format string. */
        public function get formatString():String
        {
            return _format;
        }

        /** The size (in bytes) of each vertex. */
        public function get vertexSize():int
        {
            return _vertexSize;
        }

        /** The size (in 32 bit units) of each vertex. */
        public function get vertexSizeIn32Bits():int
        {
            return _vertexSize / 4;
        }

        /** The number of attributes per vertex. */
        public function get numAttributes():int
        {
            return _attributes.length;
        }
    }
}