using System.Text;
using Strata.SqlTools.SqlBreakdown.Interfaces;
using Strata.SqlTools.SqlBreakdown.Interfaces.QueryEngine;

namespace Strata.SqlTools.SqlBreakdown.Classes;

/// <summary>
/// Manages a collection of multiple SQL breakdown objects and provides parsing for batch SQL statements.
/// </summary>
/// <remarks>
/// This class handles SQL statements containing multiple queries separated by GO statements or semicolons,
/// allowing efficient management and retrieval of multiple SQL breakdowns as a unified collection.
/// Implements ICollection&lt;ISqlBreakdown&gt; to provide standard collection semantics and LINQ support.
/// </remarks>
public class SqlBreakdownCollection : ICollection<ISqlBreakdown>
{
    private readonly List<ISqlBreakdown> _breakdowns;
    private string _separator = "GO";

    /// <summary>
    /// Initializes a new instance of the <see cref="SqlBreakdownCollection"/> class.
    /// </summary>
    public SqlBreakdownCollection()
    {
        _breakdowns = new List<ISqlBreakdown>();
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="SqlBreakdownCollection"/> class with initial breakdowns.
    /// </summary>
    /// <param name="breakdowns">The initial collection of SQL breakdowns.</param>
    public SqlBreakdownCollection(IEnumerable<ISqlBreakdown> breakdowns)
    {
        _breakdowns = new List<ISqlBreakdown>(breakdowns ?? Enumerable.Empty<ISqlBreakdown>());
    }

    /// <summary>
    /// Gets the collection of SQL breakdowns.
    /// </summary>
    public IReadOnlyList<ISqlBreakdown> Breakdowns => _breakdowns.AsReadOnly();

    /// <summary>
    /// Gets the collection of raw SQL statements from all breakdowns.
    /// </summary>
    public IReadOnlyList<string> RawStatements => _breakdowns
        .Where(b => !string.IsNullOrWhiteSpace(b.RawSql))
        .Select(b => b.RawSql!)
        .ToList()
        .AsReadOnly();

    /// <summary>
    /// Gets the count of SQL breakdowns in the collection.
    /// </summary>
    public int Count => _breakdowns.Count;

    /// <summary>
    /// Gets a value indicating whether the collection is empty.
    /// </summary>
    public bool IsEmpty => _breakdowns.Count == 0;

    /// <summary>
    /// Gets a value indicating whether the collection is read-only.
    /// </summary>
    /// <remarks>
    /// This collection is not read-only; items can be added and removed.
    /// </remarks>
    public bool IsReadOnly => false;

    /// <summary>
    /// Gets or sets the separator used for splitting and combining SQL statements.
    /// The default separator is "GO" (common in SQL Server and T-SQL).
    /// You can set this to ";" or other separators based on your SQL dialect.
    /// </summary>
    /// <remarks>
    /// When set, this separator will be used as the default for ParseBatch, GetCombinedSql, and GetBatchSql operations.
    /// Individual method calls can still override this default by providing an explicit separator argument.
    /// </remarks>
    public string Separator
    {
        get => _separator;
        set => _separator = string.IsNullOrWhiteSpace(value) ? "GO" : value;
    }

    /// <summary>
    /// Adds a single SQL breakdown to the collection.
    /// </summary>
    /// <param name="breakdown">The breakdown to add.</param>
    /// <exception cref="ArgumentNullException">Thrown when breakdown is null.</exception>
    public void Add(ISqlBreakdown breakdown)
    {
        if (breakdown == null)
        {
            throw new ArgumentNullException(nameof(breakdown));
        }

        _breakdowns.Add(breakdown);
    }

    /// <summary>
    /// Adds multiple SQL breakdowns to the collection.
    /// </summary>
    /// <param name="breakdowns">The breakdowns to add.</param>
    /// <exception cref="ArgumentNullException">Thrown when breakdowns is null.</exception>
    public void AddRange(IEnumerable<ISqlBreakdown> breakdowns)
    {
        if (breakdowns == null)
        {
            throw new ArgumentNullException(nameof(breakdowns));
        }

        _breakdowns.AddRange(breakdowns);
    }

    /// <summary>
    /// Removes a SQL breakdown from the collection.
    /// </summary>
    /// <param name="breakdown">The breakdown to remove.</param>
    /// <returns>True if the breakdown was removed; otherwise, false.</returns>
    public bool Remove(ISqlBreakdown breakdown)
    {
        return _breakdowns.Remove(breakdown);
    }

    /// <summary>
    /// Removes all SQL breakdowns from the collection.
    /// </summary>
    public void Clear()
    {
        _breakdowns.Clear();
    }

    /// <summary>
    /// Parses a batch SQL statement containing multiple queries and populates the collection.
    /// </summary>
    /// <remarks>
    /// Splits the SQL batch by the configured separator (default: GO) or provided separator argument.
    /// The GO statement is a batch separator commonly used in SQL Server and T-SQL.
    /// Each parsed statement is stored as a RawSqlBreakdown in the collection.
    /// </remarks>
    /// <param name="sqlBatch">The batch SQL statement to parse.</param>
    /// <param name="separator">Optional separator to use for splitting. If null, uses the Separator property.</param>
    /// <exception cref="ArgumentNullException">Thrown when sqlBatch is null.</exception>
    public void ParseBatch(string sqlBatch, string? separator = null)
    {
        if (sqlBatch == null)
        {
            throw new ArgumentNullException(nameof(sqlBatch));
        }

        Clear();

        var effectiveSeparator = separator ?? _separator;

        // Split by configured separator
        var statements = SplitBySeparators(sqlBatch, effectiveSeparator);

        // Create RawSqlBreakdown objects for each statement
        foreach (var statement in statements)
        {
            var trimmed = statement.Trim();
            if (!string.IsNullOrWhiteSpace(trimmed))
            {
                var breakdown = new RawSqlBreakdown { RawSql = trimmed };
                _breakdowns.Add(breakdown);
            }
        }
    }

    /// <summary>
    /// Gets the combined SQL from all breakdowns in the collection.
    /// </summary>
    /// <param name="includeSetupFinish">Whether to include setup and finish clauses for each breakdown.</param>
    /// <param name="separator">The separator to use between SQL statements. If null, uses the Separator property.</param>
    /// <returns>The combined SQL string from all breakdowns.</returns>
    public string GetCombinedSql(bool includeSetupFinish = true, string? separator = null)
    {
        if (_breakdowns.Count == 0)
        {
            return string.Empty;
        }

        var effectiveSeparator = separator ?? _separator;
        var sb = new StringBuilder();

        for (int i = 0; i < _breakdowns.Count; i++)
        {
            var sql = _breakdowns[i].GetSql(includeSetupFinish);
            sb.Append(sql);

            // Add separator between statements (but not after the last one)
            if (i < _breakdowns.Count - 1)
            {
                sb.AppendLine();
                sb.AppendLine(effectiveSeparator);
                sb.AppendLine();
            }
        }

        return sb.ToString();
    }

    /// <summary>
    /// Gets the raw SQL statements as a batch (joined with the configured separator).
    /// </summary>
    /// <param name="separator">The separator to use between SQL statements. If null, uses the Separator property.</param>
    /// <returns>The combined raw SQL statements.</returns>
    public string GetBatchSql(string? separator = null)
    {
        var rawStatements = RawStatements;
        if (rawStatements.Count == 0)
        {
            return string.Empty;
        }

        var effectiveSeparator = separator ?? _separator;
        return string.Join($"{Environment.NewLine}{effectiveSeparator}{Environment.NewLine}", rawStatements);
    }

    /// <summary>
    /// Determines whether the collection contains a specific breakdown.
    /// </summary>
    /// <param name="item">The breakdown to locate.</param>
    /// <returns>True if the breakdown is found; otherwise, false.</returns>
    public bool Contains(ISqlBreakdown item)
    {
        return _breakdowns.Contains(item);
    }

    /// <summary>
    /// Copies the elements of the collection to an array, starting at a particular array index.
    /// </summary>
    /// <param name="array">The destination array.</param>
    /// <param name="arrayIndex">The zero-based index in the array at which copying begins.</param>
    /// <exception cref="ArgumentNullException">Thrown when array is null.</exception>
    /// <exception cref="ArgumentOutOfRangeException">Thrown when arrayIndex is out of range.</exception>
    /// <exception cref="ArgumentException">Thrown when there is not enough space in the array.</exception>
    public void CopyTo(ISqlBreakdown[] array, int arrayIndex)
    {
        _breakdowns.CopyTo(array, arrayIndex);
    }

    /// <summary>
    /// Gets a breakdown at the specified index.
    /// </summary>
    /// <param name="index">The index of the breakdown.</param>
    /// <returns>The breakdown at the specified index.</returns>
    /// <exception cref="ArgumentOutOfRangeException">Thrown when index is out of range.</exception>
    public ISqlBreakdown GetAt(int index)
    {
        if (index < 0 || index >= _breakdowns.Count)
        {
            throw new ArgumentOutOfRangeException(nameof(index), $"Index {index} is out of range for collection with {_breakdowns.Count} items.");
        }

        return _breakdowns[index];
    }

    /// <summary>
    /// Gets the first breakdown matching the given predicate.
    /// </summary>
    /// <param name="predicate">The predicate to match.</param>
    /// <returns>The first matching breakdown, or null if not found.</returns>
    public ISqlBreakdown? FirstOrDefault(Func<ISqlBreakdown, bool> predicate)
    {
        return _breakdowns.FirstOrDefault(predicate ?? throw new ArgumentNullException(nameof(predicate)));
    }

    /// <summary>
    /// Returns an enumerator that iterates through the breakdown collection.
    /// </summary>
    /// <returns>An enumerator for the collection.</returns>
    public IEnumerator<ISqlBreakdown> GetEnumerator()
    {
        return _breakdowns.GetEnumerator();
    }

    /// <summary>
    /// Returns an enumerator that iterates through the breakdown collection.
    /// </summary>
    /// <returns>An enumerator for the collection.</returns>
    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    /// <summary>
    /// Gets the raw statement at the specified index.
    /// </summary>
    /// <param name="index">The index of the raw statement.</param>
    /// <returns>The raw statement at the specified index.</returns>
    /// <exception cref="ArgumentOutOfRangeException">Thrown when index is out of range.</exception>
    public string GetRawStatementAt(int index)
    {
        var rawStatements = RawStatements;
        if (index < 0 || index >= rawStatements.Count)
        {
            throw new ArgumentOutOfRangeException(nameof(index), $"Index {index} is out of range for raw statements collection with {rawStatements.Count} items.");
        }

        return rawStatements[index];
    }

    /// <summary>
    /// Returns the combined SQL string representation of all breakdowns.
    /// </summary>
    /// <returns>The combined SQL string.</returns>
    public override string ToString()
    {
        return GetCombinedSql();
    }

    /// <summary>
    /// Splits SQL batch by the specified separator character/string.
    /// </summary>
    /// <param name="sqlBatch">The SQL batch to split.</param>
    /// <param name="separator">The separator to use for splitting (e.g., "GO" or ";").</param>
    /// <returns>An array of SQL statements.</returns>
    private static string[] SplitBySeparators(string sqlBatch, string separator)
    {
        var statements = new List<string>();
        var currentStatement = new StringBuilder();

        using (var reader = new StringReader(sqlBatch))
        {
            string? line;
            while ((line = reader.ReadLine()) != null)
            {
                // Check if line is a separator statement (case-insensitive for "GO", exact for others, possibly with whitespace)
                var trimmedLine = line.Trim();
                var isSeparator = separator.Equals("GO", StringComparison.OrdinalIgnoreCase)
                    ? trimmedLine.Equals("GO", StringComparison.OrdinalIgnoreCase)
                    : trimmedLine.Equals(separator);

                if (isSeparator)
                {
                    // Save the current statement if it's not empty
                    var statement = currentStatement.ToString().Trim();
                    if (!string.IsNullOrWhiteSpace(statement))
                    {
                        statements.Add(statement);
                    }

                    currentStatement.Clear();
                }
                else
                {
                    // Add line to current statement
                    if (currentStatement.Length > 0)
                    {
                        currentStatement.AppendLine();
                    }

                    currentStatement.Append(line);
                }
            }
        }

        // Add the final statement if it's not empty
        var finalStatement = currentStatement.ToString().Trim();
        if (!string.IsNullOrWhiteSpace(finalStatement))
        {
            statements.Add(finalStatement);
        }

        return statements.ToArray();
    }

    /// <summary>
    /// Gets all unique parameters across all breakdowns in the collection.
    /// </summary>
    /// <remarks>
    /// This aggregates parameters from all QueryBreakdown objects in the collection.
    /// Parameters are uniquely identified by name (case-insensitive comparison).
    /// </remarks>
    /// <returns>A collection of unique parameters from all breakdowns.</returns>
    public IEnumerable<(string Name, object? Value)> GetAllUniqueParameters()
    {
        var parameterDict = new Dictionary<string, object?>(StringComparer.OrdinalIgnoreCase);

        foreach (var breakdown in _breakdowns.OfType<IQueryBreakdown>())
        {
            foreach (var param in breakdown.ParameterList)
            {
                // Add or update parameter (later occurrences override earlier ones)
                parameterDict[param.Name] = param.Value;
            }
        }

        return parameterDict.Select(kvp => (kvp.Key, kvp.Value));
    }

    /// <summary>
    /// Gets a dictionary of all unique parameter names and their values across all breakdowns.
    /// </summary>
    /// <remarks>
    /// This is useful for parameterized query execution where you need all parameters in one place.
    /// Parameters are uniquely identified by name (case-insensitive comparison).
    /// </remarks>
    /// <returns>A dictionary mapping parameter names to their values.</returns>
    public Dictionary<string, object?> GetParameterDictionary()
    {
        var parameters = new Dictionary<string, object?>(StringComparer.OrdinalIgnoreCase);

        foreach (var breakdown in _breakdowns.OfType<IQueryBreakdown>())
        {
            foreach (var param in breakdown.ParameterList)
            {
                parameters[param.Name] = param.Value;
            }
        }

        return parameters;
    }

    /// <summary>
    /// Gets parameter names used in queries that have a specific value.
    /// </summary>
    /// <param name="value">The parameter value to search for.</param>
    /// <returns>Parameter names that have the specified value.</returns>
    public IEnumerable<string> GetParametersWithValue(object? value)
    {
        return GetAllUniqueParameters()
            .Where(p => (p.Value == null && value == null) ||
                       (p.Value != null && p.Value.Equals(value)))
            .Select(p => p.Name);
    }

    /// <summary>
    /// Checks if a parameter with the specified name exists in any breakdown.
    /// </summary>
    /// <param name="parameterName">The parameter name to check.</param>
    /// <returns>True if the parameter exists; otherwise, false.</returns>
    public bool HasParameter(string parameterName)
    {
        if (string.IsNullOrWhiteSpace(parameterName))
        {
            return false;
        }

        return _breakdowns.OfType<IQueryBreakdown>()
            .SelectMany(b => b.ParameterList)
            .Any(p => p.Name.Equals(parameterName, StringComparison.OrdinalIgnoreCase));
    }

    /// <summary>
    /// Gets the value of a parameter by name from the first breakdown that contains it.
    /// </summary>
    /// <param name="parameterName">The parameter name to retrieve.</param>
    /// <param name="value">The parameter value, or null if not found.</param>
    /// <returns>True if the parameter was found; otherwise, false.</returns>
    public bool TryGetParameterValue(string parameterName, out object? value)
    {
        value = null;

        if (string.IsNullOrWhiteSpace(parameterName))
        {
            return false;
        }

        var param = _breakdowns.OfType<IQueryBreakdown>()
            .SelectMany(b => b.ParameterList)
            .FirstOrDefault(p => p.Name.Equals(parameterName, StringComparison.OrdinalIgnoreCase));

        if (param != null)
        {
            value = param.Value;
            return true;
        }

        return false;
    }

    /// <summary>
    /// Gets the count of unique parameters across all breakdowns.
    /// </summary>
    /// <returns>The number of unique parameters.</returns>
    public int GetParameterCount()
    {
        return GetAllUniqueParameters().Count();
    }

    /// <summary>
    /// Gets all parameter names used in the collection (case-insensitive unique list).
    /// </summary>
    /// <returns>An enumerable of unique parameter names.</returns>
    public IEnumerable<string> GetParameterNames()
    {
        return GetAllUniqueParameters().Select(p => p.Name).Distinct(StringComparer.OrdinalIgnoreCase);
    }
}