#ifndef SQLCONTEXT_H
#define SQLCONTEXT_H

#include <QString>
#include <vector>

/**
 * Kind of names that are expected at the cursor position.
 */
enum class CompletionKind {
	None,
	Relation,        // schema, table or view name
	Column,          // column name of the relations in scope
	QualifiedColumn, // column after "alias." or "table."
	Schema,
	Function,
	JoinTarget       // complete "table alias ON ..." proposal after JOIN
};

/**
 * Part of the statement the cursor is in.
 */
enum class SqlClause {
	None,
	Select,
	From,
	Join,
	On,
	Where,
	GroupBy,
	OrderBy,
	Having,
	Set,
	Update,
	InsertInto,
	Returning,
	Values
};

/**
 * An item of a FROM clause (or UPDATE/INSERT target, CTE, derived table).
 * Names are normalised: unquoted identifiers are folded to lower case.
 */
struct RelationRef {
	QString schema;
	QString name;  // may be a CTE name or the alias of a derived table
	QString alias;
	bool quoted = false; // name was written as quoted identifier
	bool derived = false; // CTE or sub query, columns are not in the catalog
};

struct SqlContext {
	CompletionKind kind = CompletionKind::None;
	SqlClause clause = SqlClause::None;
	QString prefix;                // identifier text typed so far (without opening quote)
	int prefixStart = 0;           // replace range in document
	int prefixLen = 0;
	QString qualifier;             // text before '.', if any
	QString qualifierSchema;       // for schema.table.
	std::vector<RelationRef> relations; // relations in scope, innermost query first
	bool prefixWasQuoted = false;
};

/**
 * Tolerant analysis of possibly incomplete SQL around the cursor.
 * @param cursorPos position in text (between characters) where completion is requested.
 */
SqlContext analyzeSqlContext(const QString &text, int cursorPos);

#endif // SQLCONTEXT_H