// derive forecast table name from source tname + version id
function fcTable(tname, versionId) {
    return `pf.fc_${tname}_${versionId}`;
}

// The columns of a relation, from pg_catalog rather than information_schema.
//
// information_schema.columns omits materialized views -- they are not in the
// SQL standard -- so a source built on one looked like it had no columns at
// all: registering it seeded nothing, and creating a version failed with "No
// usable columns in col_meta" while col_meta plainly had thirty-six.
//
// The shape matches what information_schema returned, so mapType and the
// callers did not have to change. data_type is format_type with the modifier
// stripped, which gives the same spelling information_schema uses ('character
// varying', 'numeric'), and the numeric precision and scale are unpacked from
// atttypmod the way information_schema does internally.
//
// Takes $1 = schema, $2 = relation name.
const RELATION_COLUMNS_SQL = `
    SELECT a.attname                                              AS column_name
          ,regexp_replace(format_type(a.atttypid, a.atttypmod), '\\(.*\\)$', '') AS data_type
          ,a.attnum                                               AS ordinal_position
          ,CASE WHEN a.attnotnull THEN 'NO' ELSE 'YES' END        AS is_nullable
          ,CASE WHEN a.atttypid = 'numeric'::regtype AND a.atttypmod > 4
                THEN ((a.atttypmod - 4) >> 16) & 65535 END        AS numeric_precision
          ,CASE WHEN a.atttypid = 'numeric'::regtype AND a.atttypmod > 4
                THEN (a.atttypmod - 4) & 65535 END                AS numeric_scale
    FROM pg_attribute a
    JOIN pg_class     c ON c.oid = a.attrelid
    JOIN pg_namespace n ON n.oid = c.relnamespace
    WHERE TRUE
      AND n.nspname = $1
      AND c.relname = $2
      AND c.relkind IN ('r', 'v', 'm', 'f', 'p')
      AND a.attnum > 0
      AND NOT a.attisdropped
`;

// map a data_type name to a clean postgres column type
function mapType(dataType, numericPrecision, numericScale) {
    switch (dataType) {
        case 'character varying':
        case 'character':
        case 'text':
            return 'text';
        case 'smallint':
        case 'integer':
            return 'integer';
        case 'bigint':
            return 'bigint';
        case 'numeric':
        case 'decimal':
            return (numericPrecision)
                ? `numeric(${numericPrecision}, ${numericScale || 0})`
                : 'numeric';
        case 'real':
        case 'double precision':
            return 'numeric';
        case 'date':
            return 'date';
        case 'timestamp without time zone':
            return 'timestamp';
        case 'timestamp with time zone':
            return 'timestamptz';
        case 'boolean':
            return 'boolean';
        default:
            return 'text';
    }
}

module.exports = { fcTable, mapType, RELATION_COLUMNS_SQL };