#ifndef RESULTSOURCEMAPPING_H
#define RESULTSOURCEMAPPING_H

#include <libpq-fe.h>

#include <vector>

class PgDatabaseCatalog;

namespace Pgsql {
    class Result;
}

/// The table column a result column is read from, as reported by libpq (PQftable/PQftablecol).
/// tableOid is InvalidOid and attnum is 0 for expression columns.
struct ResultColumnSource {
    Oid tableOid = InvalidOid;
    int attnum = 0;
};

/// The primary key of a table, attnums in key order.
struct TablePrimaryKey {
    Oid tableOid = InvalidOid;
    std::vector<int> attnums;
};

/// Maps the columns of a query result to the table columns they come from and decides which
/// cells can be edited. A cell is editable when it maps to a user column of a table whose full
/// primary key is present in the result and which is not ambiguous.
class ResultSourceMapping {
public:
    ResultSourceMapping(std::vector<ResultColumnSource> columns, const std::vector<TablePrimaryKey> &primaryKeys);

    int columnCount() const;
    /// Table the column is read from, InvalidOid for expression columns.
    Oid tableOid(int col) const;
    /// attnum of the column in its table, 0 for expression columns.
    int attnum(int col) const;
    bool isEditable(int col) const;
    /// Result column indices holding the primary key of the table, in key order.
    /// Empty when the table is not editable.
    std::vector<int> primaryKeyColumns(Oid tableOid) const;

private:
    struct TableInfo {
        Oid tableOid = InvalidOid;
        bool editable = false;
        std::vector<int> pkColumns;
    };

    std::vector<ResultColumnSource> m_columns;
    std::vector<TableInfo> m_tables;

    const TableInfo *findTable(Oid tableOid) const;
};

/// Builds the mapping for a query result, looking up the primary keys of the source tables in the catalog.
ResultSourceMapping createResultSourceMapping(const Pgsql::Result &result, const PgDatabaseCatalog &catalog);


#endif // RESULTSOURCEMAPPING_H