<?php

namespace SilverStripe\SQLite;

use SilverStripe\ORM\Queries\SQLAssignmentRow;
use SilverStripe\ORM\Queries\SQLInsert;
use SilverStripe\ORM\Queries\SQLSelect;
use SilverStripe\ORM\Connect\DBQueryBuilder;
use InvalidArgumentException;

/**
 * Builds a SQL query string from a SQLExpression object
 *
 * @package SQLite3
 */
class SQLite3QueryBuilder extends DBQueryBuilder
{

    /**
     * @param SQLInsert $query
     * @param array $parameters
     * @return string
     */
    protected function buildInsertQuery(SQLInsert $query, array &$parameters)
    {
        // Multi-row insert requires SQLite specific syntax prior to 3.7.11
        // For backwards compatibility reasons include the "union all select" syntax

        $nl = $this->getSeparator();
        $into = $query->getInto();

        // Column identifiers
        $columns = $query->getColumns();

        // Build all rows
        $rowParts = array();
        foreach ($query->getRows() as $row) {
            // Build all columns in this row
            /** @var SQLAssignmentRow $row */
            $assignments = $row->getAssignments();
            // Join SET components together, considering parameters
            $parts = array();
            foreach ($columns as $column) {
                // Check if this column has a value for this row
                if (isset($assignments[$column])) {
                    // Assigment is a single item array, expand with a loop here
                    foreach ($assignments[$column] as $assignmentSQL => $assignmentParameters) {
                        $parts[] = $assignmentSQL;
                        $parameters = array_merge($parameters, $assignmentParameters);
                        break;
                    }
                } else {
                    // This row is missing a value for a column used by another row
                    $parts[] = '?';
                    $parameters[] = null;
                }
            }
            $rowParts[] = implode(', ', $parts);
        }
        $columnSQL = implode(', ', $columns);
        $sql = "INSERT INTO {$into}{$nl}($columnSQL){$nl}SELECT " . implode("{$nl}UNION ALL SELECT ", $rowParts);

        return $sql;
    }

    /**
     * Return the LIMIT clause ready for inserting into a query.
     *
     * @param SQLSelect $query The expression object to build from
     * @param array $parameters Out parameter for the resulting query parameters
     * @return string The finalised limit SQL fragment
     */
    public function buildLimitFragment(SQLSelect $query, array &$parameters)
    {
        $nl = $this->getSeparator();

        // Ensure limit is given
        $limit = $query->getLimit();
        if (empty($limit)) {
            return '';
        }

        // For literal values return this as the limit SQL
        if (! is_array($limit)) {
            return "{$nl}LIMIT $limit";
        }

        // Assert that the array version provides the 'limit' key
        if (! array_key_exists('limit', $limit) || ($limit['limit'] !== null && ! is_numeric($limit['limit']))) {
            throw new InvalidArgumentException(
                'SQLite3QueryBuilder::buildLimitSQL(): Wrong format for $limit: '. var_export($limit, true)
            );
        }

        $clause = "{$nl}";
        if ($limit['limit'] !== null) {
            $clause .= "LIMIT {$limit['limit']} ";
        } else {
            $clause .= "LIMIT -1 ";
        }

        if (isset($limit['start']) && is_numeric($limit['start']) && $limit['start'] !== 0) {
            $clause .= "OFFSET {$limit['start']}";
        }
        return $clause;
    }
}