/* -----------------------------------------------------------------------------
Copyright 2019-2021 Kevin P. Barry

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: Kevin P. Barry [ta0kira@gmail.com]

// Read at the current position.
//
// Params:
// - #x: The value type to be read.
@value interface ReadCurrent<|#x> {
  // Return the value at the current position.
  readCurrent () -> (#x)
}

// Write at the current position.
//
// Params:
// - #x: The value type to be written.
@value interface WriteCurrent<#x|> {
  // Write the value at the current position and return self.
  writeCurrent (#x) -> (#self)
}

// Forward iteration.
@value interface IterateForward {
  // Return a copy that has been moved forward once. (Do not mutate self.)
  //
  // Notes:
  // - This should crash if pastForwardEnd() is true.
  forward () -> (#self)
  // Returns true iff no more forward movement is possible.
  pastForwardEnd () -> (Bool)
}

// Reverse iteration.
@value interface IterateReverse {
  // Return a copy that has been moved in reverse once. (Do not mutate self.)
  //
  // Notes:
  // - This should crash if pastReverseEnd() is true.
  reverse () -> (#self)
  // Returns true iff no more reverse movement is possible.
  pastReverseEnd () -> (Bool)
}

// Iterator for forward/reverse reading.
@value interface ReadIterator<|#x> {
  refines ReadCurrent<#x>
  refines IterateForward
  refines IterateReverse
}

// Iterator for forward/reverse writing.
@value interface WriteIterator<#x|> {
  refines WriteCurrent<#x>
  refines IterateForward
  refines IterateReverse
}

// Iterator for forward/reverse reading and writing.
@value interface Iterator<#x> {
  refines ReadIterator<#x>
  refines WriteIterator<#x>
}

// Automatic read iteration from ReadAt.
//
// Params:
// - #x: The value type to be read.
concrete AutoReadIterator<#x> {
  refines ReadIterator<#x>

  // Create an iterator from a ReadAt.
  @category from<#y> (ReadAt<#y>) -> (AutoReadIterator<#y>)
  // Create an iterator from a ReadAt starting at an offset.
  @category fromOffset<#y> (ReadAt<#y>,Int) -> (AutoReadIterator<#y>)
}

// Automatic write iteration from WriteAt.
//
// Params:
// - #x: The value type to be written.
concrete AutoWriteIterator<#x> {
  refines WriteIterator<#x>

  // Create an iterator from a WriteAt.
  @category from<#y> (WriteAt<#y>) -> (AutoWriteIterator<#y>)
  // Create an iterator from a WriteAt starting at an offset.
  @category fromOffset<#y> (WriteAt<#y>,Int) -> (AutoWriteIterator<#y>)
}

// Automatic read/write iteration from ReadAt&WriteAt.
//
// Params:
// - #x: The value type to be read/written.
concrete AutoIterator<#x> {
  refines Iterator<#x>

  // Create an iterator from a ReadAt&WriteAt.
  @category from<#y> ([ReadAt<#y>&WriteAt<#y>]) -> (AutoIterator<#y>)
  // Create an iterator from a ReadAt&WriteAt starting at an offset.
  @category fromOffset<#y> ([ReadAt<#y>&WriteAt<#y>],Int) -> (AutoIterator<#y>)
}