/// <summary>
/// Determines whether the specified expressions are equal.
/// </summary>
/// <param name="x">The first expression to compare.</param>
/// <param name="y">The second expression to compare.</param>
/// <returns><see langword="true" /> if the specified expressions are equal; otherwise, <see langword="false" />.</returns>
/// <exception cref="ArgumentException"><paramref name="x"/> or <paramref name="y"/> are expressions that could not be parsed as a SQL expression.</exception>
public bool Equals(string x, string y)
{
if (x is null && y is null)
{
return(true);
}
if (x is null || y is null)
{
return(false);
}
var tokenizer = new SqliteTokenizer();
var xParseResult = tokenizer.TryTokenize(x);
if (!xParseResult.HasValue)
{
throw new ArgumentException($"Could not parse the '{ nameof(x) }' string as a SQL expression. Given: { x }", nameof(x));
}
var yParseResult = tokenizer.TryTokenize(y);
if (!yParseResult.HasValue)
{
throw new ArgumentException($"Could not parse the '{ nameof(y) }' string as a SQL expression. Given: { y }", nameof(y));
}
var xTokens = xParseResult.Value.ToList();
var yTokens = yParseResult.Value.ToList();
if (xTokens.Count != yTokens.Count)
{
return(false);
}
for (var i = 0; i < xTokens.Count; i++)
{
var xToken = xTokens[i];
var yToken = yTokens[i];
if (!TokensEqual(xToken, yToken))
{
return(false);
}
}
return(true);
}
/// <summary>
/// Retrieves all dependencies for an expression.
/// </summary>
/// <param name="objectName">The name of an object defined by an expression (e.g. a computed column definition).</param>
/// <param name="expression">A SQL expression that may contain dependent object names.</param>
/// <returns>A collection of identifiers found in the expression.</returns>
/// <exception cref="ArgumentNullException"><paramref name="objectName"/> is <c>null</c>. Alternatively, if <paramref name="expression"/> is <c>null</c>, empty or whitespace.</exception>
/// <exception cref="ArgumentException">Thrown when <paramref name="expression"/> could not be parsed as a valid SQL expression.</exception>
/// <remarks>This will also return unqualified identifiers, which may cause ambiguity between object names and column names. Additionally it may return other identifiers, such as aliases or type names.</remarks>
public IReadOnlyCollection <Identifier> GetDependencies(Identifier objectName, string expression)
{
if (objectName == null)
{
throw new ArgumentNullException(nameof(objectName));
}
if (expression.IsNullOrWhiteSpace())
{
throw new ArgumentNullException(nameof(expression));
}
var tokenizer = new SqliteTokenizer();
var tokenizeResult = tokenizer.TryTokenize(expression);
if (!tokenizeResult.HasValue)
{
throw new ArgumentException($"Could not parse the given expression as a SQL expression. Given: { expression }", nameof(expression));
}
var result = new HashSet <Identifier>(Comparer);
var tokens = tokenizeResult.Value;
var next = tokens.ConsumeToken();
while (next.HasValue)
{
var sqlIdentifier = SqliteTokenParsers.QualifiedName(next.Location);
if (sqlIdentifier.HasValue)
{
var dependentIdentifier = sqlIdentifier.Value;
if (!Comparer.Equals(dependentIdentifier.Value, objectName))
{
result.Add(dependentIdentifier.Value);
}
next = sqlIdentifier.Remainder.ConsumeToken();
}
else
{
next = next.Remainder.ConsumeToken();
}
}
return(result);
}
