SyncbaseCore/Source/Row.swift

// Copyright 2016 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

import Foundation

public protocol Row {
  /// Key returns the key for this Row.
  var key: String { get }

  /// FullName returns the object name (encoded) of this Row.
  var fullName: String { get }

  /// Exists returns true only if this Row exists. Insufficient permissions cause
  /// Exists to return false instead of an error.
  /// TODO(ivanpi): Exists may fail with an error if higher levels of hierarchy
  /// do not exist.
  func exists() throws -> Bool

  /**
   Get loads the value stored in this Row into the given value. If the given
   value's type does not match the stored value's type, get will throw an error.

   Expected usage:

   ```
   var isRed: Bool?
   try row.get(&isRed)
   ```
   */
  func get<T: SyncbaseJsonConvertible>(inout value: T?) throws

  /**
   Get returns the value stored in this Row. If the given value's type does not match the
   requested generic type, get will throw an error.

   Expected usage:

   ```
   let isRed: Bool? = try row.get()
   ```
   */
  func get<T: SyncbaseJsonConvertible>() throws -> T?

  /// Put writes the given value for this Row.
  func put(value: SyncbaseJsonConvertible) throws

  /// Delete deletes this Row.
  func delete() throws
}

/// RowRange represents all rows with keys in [start, limit).
/// If limit is "", all rows with keys >= start are included.
public protocol RowRange {
  var start: String { get }
  /// If limit is "", all rows with keys >= start are included.
  var limit: String { get }
}

/// StandardRowRange represents all rows with keys in [start, limit).
/// If limit is "", all rows with keys >= start are included.
public struct StandardRowRange: RowRange {
  public let start: String
  /// If limit is "", all rows with keys >= start are included.
  public let limit: String
}

public struct SingleRow: RowRange {
  public let row: String

  public var start: String {
    return row
  }

  public var limit: String {
    return row + "\0"
  }
}

/// PrefixRange represents all rows with keys that have some prefix.
public struct PrefixRange: RowRange {
  public let prefix: String

  /// Returns the start of the row range for the given prefix.
  public var start: String {
    return prefix
  }

  public var limit: String {
    var utf8 = Array(prefix.utf8)
    while utf8.count > 0 {
      if utf8.last! == 255 {
        utf8.removeLast() // chop off what would otherwise be a trailing \x00
      } else {
        utf8[utf8.count - 1] += 1 // add 1
        break // no carry
      }
    }
    return String(bytes: utf8, encoding: NSUTF8StringEncoding)!
  }
}