/Spss/SpssCasesCollection.cs

namespace Spss {

	using System;

	using System.Collections;

	using System.Data;



	/// <summary>

	/// Manages the cases in an SPSS data file.  

	/// Supports reading, writing, and appending data.

	/// </summary>

	public sealed class SpssCasesCollection : IEnumerable {

		private int position = -1;



		private int caseCountInWriteMode;



		/// <summary>

		/// Initializes a new instance of the <see cref="SpssCasesCollection"/> class.

		/// </summary>

		/// <param name="document">The hosting document.</param>

		internal SpssCasesCollection(SpssDataDocument document) {

			if (document == null) {

				throw new ArgumentNullException("document");

			}



			this.Document = document;

		}



		/// <summary>

		/// Gets a value indicating whether the set of cases is read only.  

		/// If no cases can be added, changed or removed, IsReadOnly is true.

		/// <seealso cref="IsAppendOnly"/>

		/// </summary>

		public bool IsReadOnly {

			get {

				return Document.AccessMode == SpssFileAccess.Read;

			}

		}



		/// <summary>

		/// Gets a value indicating whether the set of cases can only be appended to.

		/// If no cases can be removed or changed, IsAppendOnly is true.

		/// <seealso cref="IsReadOnly"/>

		/// </summary>

		public bool IsAppendOnly {

			get {

				return this.Document.AccessMode != SpssFileAccess.Read; // Create or Append

			}

		}



		/// <summary>

		/// Gets the SPSS data document whose cases are being managed.

		/// </summary>

		public SpssDataDocument Document { get; private set; }



		/// <summary>

		/// Gets the file handle of the SPSS data document whose cases are being managed.

		/// </summary>

		internal Int32 FileHandle {

			get { return this.Document.Handle; }

		}



		/// <summary>

		/// The number of cases in the document.

		/// </summary>

		public int Count {

			get {

				Int32 casecount = 0;



				// New documents aren't allowed to query cases count, and appended docs

				// report the # of cases there were when the file was first opened.

				if (this.Document.AccessMode != SpssFileAccess.Create) {

					SpssException.ThrowOnFailure(SpssSafeWrapper.spssGetNumberofCasesImpl(this.FileHandle, out casecount), "spssGetNumberofCases");

				}



				return casecount + this.caseCountInWriteMode;

			}

		}



		/// <summary>

		/// Gets or sets the case that SPSS is pointing at to get/set variable data on.

		/// </summary>

		internal int Position {

			get {

				return this.position;

			}



			set {

				if (IsAppendOnly) {

					throw new InvalidOperationException("Not available while in Append mode.");

				}

				if (value < 0) {

					throw new ArgumentOutOfRangeException("Position", value, "Must be a non-negative integer.");

				}

				if (value >= Count) {

					throw new ArgumentOutOfRangeException("Position", value, "Must be less than the number of cases in the file.");

				}

				if (value == position) {

					return; // nothing to do!

				}

				SpssException.ThrowOnFailure(SpssSafeWrapper.spssSeekNextCase(this.FileHandle, value), "spssSeekNextCase");

				SpssException.ThrowOnFailure(SpssSafeWrapper.spssReadCaseRecord(this.FileHandle), "spssReadCaseRecord");

				this.position = value;

			}

		}



		/// <summary>

		/// Gets the case record at a specific 0-based index.

		/// </summary>

		public SpssCase this[int index] {

			get { return new SpssCase(this, index); }

		}



		/// <summary>

		/// Creates a new SPSS case to assign values to.

		/// </summary>

		/// <returns>

		/// The <see cref="SpssCase"/> object used to access the new row.

		/// </returns>

		/// <remarks>

		/// This call must be followed (eventually) with a call to

		/// <see cref="SpssCase.Commit"/> or no new row will actually be added.

		/// </remarks>

		/// <example>

		/// To add a case to an existing SPSS file called mydata.sav, the following code could apply:

		/// <code>

		/// using( SpssDataDocument doc = SpssDataDocument.Open("mydata.sav", SpssFileAccess.Append) )

		/// {

		///		SpssCase Case = doc.Cases.New();

		///		Case["var1"] = 5;

		///		Case["var2"] = 3;

		///		Case["name"] = "Andrew";

		///		Case.Commit();

		///	}

		/// </code>

		/// </example>

		public SpssCase New() {

			if (!IsAppendOnly) {

				throw new InvalidOperationException("Only available in append mode.");

			}



			position = Count;

			return new SpssCase(this, position);

		}



		/// <summary>

		/// Creates a <see cref="DataTable"/> filled with all the data in the SPSS document.

		/// </summary>

		/// <returns>

		/// The created DataTable.

		/// </returns>

		public DataTable ToDataTable() {

			DataTable dt = new DataTable();

			foreach (SpssVariable var in this.Document.Variables) {

				DataColumn dc = new DataColumn(var.Name);

				if (var is SpssStringVariable) {

					dc.DataType = typeof(string);

				} else if (var is SpssNumericVariable) {

					dc.DataType = typeof(double);

				} else if (var is SpssDateVariable) {

					dc.DataType = typeof(DateTime);

				} else {

					throw new NotSupportedException("SPSS variable type " + var.GetType().Name + " is not supported.");

				}

				dt.Columns.Add(dc);

			}



			foreach (SpssCase spssCase in this) {

				DataRow row = dt.NewRow();

				foreach (SpssVariable var in this.Document.Variables) {

					row[var.Name] = spssCase.GetDBValue(var.Name);

				}

				dt.Rows.Add(row);

			}



			return dt;

		}



		/// <summary>

		/// Gets the enumerator that will iterate over all cases in the data file.

		/// </summary>

		IEnumerator IEnumerable.GetEnumerator() {

			if (IsAppendOnly) {

				throw new InvalidOperationException("Not available in append-only mode.");

			}



			return new SpssCasesCollectionEnumerator(this);

		}



		private class SpssCasesCollectionEnumerator : IEnumerator {

			SpssCasesCollection Cases;



			int position;



			/// <summary>

			/// Initializes a new instance of the <see cref="SpssCasesCollectionEnumerator"/> class.

			/// </summary>

			/// <param name="cases">The cases.</param>

			internal SpssCasesCollectionEnumerator(SpssCasesCollection cases) {

				if (cases == null) {

					throw new ArgumentNullException("cases");

				}

				this.Cases = cases;

				this.Reset();

			}



			/// <summary>

			/// Gets the current element in the collection.

			/// </summary>

			/// <returns>

			/// The current element in the collection.

			/// </returns>

			/// <exception cref="T:System.InvalidOperationException">

			/// The enumerator is positioned before the first element of the collection or after the last element.

			/// </exception>

			public SpssCase Current {

				get {

					return this.Cases[position];

				}

			}



			#region IEnumerator Members



			/// <summary>

			/// Advances the enumerator to the next element of the collection.

			/// </summary>

			/// <returns>

			/// true if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.

			/// </returns>

			/// <exception cref="T:System.InvalidOperationException">

			/// The collection was modified after the enumerator was created.

			/// </exception>

			public bool MoveNext() {

				return ++position < Cases.Count;

			}



			/// <summary>

			/// Sets the enumerator to its initial position, which is before the first element in the collection.

			/// </summary>

			/// <exception cref="T:System.InvalidOperationException">

			/// The collection was modified after the enumerator was created.

			/// </exception>

			public void Reset() {

				position = -1;

			}



			/// <summary>

			/// Gets the current element in the collection.

			/// </summary>

			/// <value></value>

			/// <returns>

			/// The current element in the collection.

			/// </returns>

			/// <exception cref="T:System.InvalidOperationException">

			/// The enumerator is positioned before the first element of the collection or after the last element.

			/// </exception>

			object System.Collections.IEnumerator.Current {

				get {

					return this.Current;

				}

			}



			#endregion

		}



		internal void OnCaseCommitted() {

			this.caseCountInWriteMode++;

		}

	}

}