//===----------------------------------------------------------*- swift -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
// GLKit overlays for Swift
//===----------------------------------------------------------------------===//

@_exported import GLKit // Clang module

// The GLKit headers provide a fairly complete set of types and operations
// that Swift's importer is now able to present in Swift. However, Swift
// still doesn't know yet how to natively expose the elements of these types.
// This overlay generates Swift accessors for the GLKit matrix and vector
// types.

%{
# Each element of the array is a tuple of the element labels and the minimum
# vector length at which to apply them.
vectorElementNames = [
  (['x', 'y', 'z', 'w'], 2),
  (['s', 't', 'p', 'q'], 2),
  (['r', 'g', 'b', 'a'], 3),
]
}%

// Do dirty pointer manipulations to index an opaque struct like an array.
@inline(__always)
public func _indexHomogeneousValue<TTT, T>(_ aggregate: UnsafePointer<TTT>,
                                           _ index: Int) -> T {
  return UnsafeRawPointer(aggregate).load(
    fromByteOffset: index * MemoryLayout<T>.stride, as: T.self)
}

%{
def defineSubscript(Type, limit):
  return """
  public subscript(i: Int) -> Float {{
    @inline(__always)
    get {{
      _precondition(i >= 0, "Negative {0} index out of range")
      _precondition(i < {1}, "{0} index out of range")

      // We can't derive an UnsafePointer from a let binding. Lame.
      var clone = self
      return _indexHomogeneousValue(&clone, i)
    }}
  }}
  """.format(Type, limit)
}%

% for size in [2, 3, 4]:

extension GLKMatrix${size} {
  public typealias _Tuple = (${ ', '.join(['Float'] * (size * size)) })
  public var _tuple: _Tuple {
    @inline(__always) get { return unsafeBitCast(self, to: _Tuple.self) }
  }
  % for i in xrange(0, size):
  %   for j in xrange(0, size):
  public var m${i}${j}: Float {
    @inline(__always) get { return _tuple.${i * size + j} }
  }
  %   end
  % end

  ${ defineSubscript("GLKMatrix" + str(size), size * size) }
}

extension GLKVector${size} {
  public typealias _Tuple = (${ ', '.join(['Float'] * size) })
  public var _tuple: _Tuple {
    @inline(__always) get { return unsafeBitCast(self, to: _Tuple.self) }
  }

  % for (names, minSize) in vectorElementNames:
  %   for i in xrange(0, size if size >= minSize else 0):
  public var ${names[i]}: Float {
    @inline(__always) get { return _tuple.${i} }
  }
  %   end
  % end

  ${ defineSubscript("GLKVector" + str(size), size) }
}

% end

extension GLKQuaternion {
  public typealias _Tuple = (Float, Float, Float, Float)
  public var _tuple: _Tuple {
    @inline(__always) get { return unsafeBitCast(self, to: _Tuple.self) }
  }

  public var v: GLKVector3 {
    @inline(__always) get {
      let (i, j, k, _) = _tuple
      return GLKVector3Make(i, j, k)
    }
  }

  public var s: Float {
    @inline(__always) get { return _tuple.3 }
  }

  public var x: Float {
    @inline(__always) get { return _tuple.0 }
  }
  public var y: Float {
    @inline(__always) get { return _tuple.1 }
  }
  public var z: Float {
    @inline(__always) get { return _tuple.2 }
  }
  public var w: Float {
    @inline(__always) get { return _tuple.3 }
  }

  ${ defineSubscript("GLKQuaternion", 4) }
}