// dnlib: See LICENSE.txt for more info

using System.Collections.Generic;
using dnlib.DotNet.MD;

namespace dnlib.DotNet.Writer {
	/// <summary>
	/// MD table interface
	/// </summary>
	public interface IMDTable {
		/// <summary>
		/// Gets the table type
		/// </summary>
		Table Table { get; }

		/// <summary>
		/// <c>true</c> if the table is empty
		/// </summary>
		bool IsEmpty { get; }

		/// <summary>
		/// Gets the number of rows in this table
		/// </summary>
		int Rows { get; }

		/// <summary>
		/// Gets/sets a value indicating whether it's sorted
		/// </summary>
		bool IsSorted { get; set; }

		/// <summary>
		/// <c>true</c> if <see cref="SetReadOnly()"/> has been called
		/// </summary>
		bool IsReadOnly { get; }

		/// <summary>
		/// Gets/sets the <see cref="TableInfo"/>
		/// </summary>
		TableInfo TableInfo { get; set; }

		/// <summary>
		/// Called when the table can't be modified any more
		/// </summary>
		void SetReadOnly();
	}

	/// <summary>
	/// Creates rows in a table. Rows can optionally be shared to create a compact table.
	/// </summary>
	/// <typeparam name="TRow">The raw row type</typeparam>
	public sealed class MDTable<TRow> : IMDTable where TRow : struct {
		readonly Table table;
		readonly Dictionary<TRow, uint> cachedDict;
		readonly List<TRow> cached;
		TableInfo tableInfo;
		bool isSorted;
		bool isReadOnly;

		/// <inheritdoc/>
		public Table Table => table;

		/// <inheritdoc/>
		public bool IsEmpty => cached.Count == 0;

		/// <inheritdoc/>
		public int Rows => cached.Count;

		/// <inheritdoc/>
		public bool IsSorted {
			get => isSorted;
			set => isSorted = value;
		}

		/// <inheritdoc/>
		public bool IsReadOnly => isReadOnly;

		/// <inheritdoc/>
		public TableInfo TableInfo {
			get => tableInfo;
			set => tableInfo = value;
		}

		/// <summary>
		/// Gets the value with rid <paramref name="rid"/>
		/// </summary>
		/// <param name="rid">The row ID</param>
		public TRow this[uint rid] {
			get => cached[(int)rid - 1];
			set => cached[(int)rid - 1] = value;
		}

		/// <summary>
		/// Constructor
		/// </summary>
		/// <param name="table">The table type</param>
		/// <param name="equalityComparer">Equality comparer</param>
		public MDTable(Table table, IEqualityComparer<TRow> equalityComparer) {
			this.table = table;
			cachedDict = new Dictionary<TRow, uint>(equalityComparer);
			cached = new List<TRow>();
		}

		/// <inheritdoc/>
		public void SetReadOnly() => isReadOnly = true;

		/// <summary>
		/// Adds a row. If the row already exists, returns a rid to the existing one, else
		/// it's created and a new rid is returned.
		/// </summary>
		/// <param name="row">The row. It's now owned by us and must NOT be modified by the caller.</param>
		/// <returns>The RID (row ID) of the row</returns>
		public uint Add(TRow row) {
			if (isReadOnly)
				throw new ModuleWriterException($"Trying to modify table {table} after it's been set to read-only");
			if (cachedDict.TryGetValue(row, out uint rid))
				return rid;
			return Create(row);
		}

		/// <summary>
		/// Creates a new row even if this row already exists.
		/// </summary>
		/// <param name="row">The row. It's now owned by us and must NOT be modified by the caller.</param>
		/// <returns>The RID (row ID) of the row</returns>
		public uint Create(TRow row) {
			if (isReadOnly)
				throw new ModuleWriterException($"Trying to modify table {table} after it's been set to read-only");
			uint rid = (uint)cached.Count + 1;
			if (!cachedDict.ContainsKey(row))
				cachedDict[row] = rid;
			cached.Add(row);
			return rid;
		}

		/// <summary>
		/// Re-adds all added rows. Should be called if rows have been modified after being
		/// inserted.
		/// </summary>
		public void ReAddRows() {
			if (isReadOnly)
				throw new ModuleWriterException($"Trying to modify table {table} after it's been set to read-only");
			cachedDict.Clear();
			for (int i = 0; i < cached.Count; i++) {
				uint rid = (uint)i + 1;
				var row = cached[i];
				if (!cachedDict.ContainsKey(row))
					cachedDict[row] = rid;
			}
		}

		/// <summary>
		/// Reset the table.
		/// </summary>
		public void Reset() {
			if (isReadOnly)
				throw new ModuleWriterException($"Trying to modify table {table} after it's been set to read-only");
			cachedDict.Clear();
			cached.Clear();
		}
	}
}