<?php

namespace Doctrine\DBAL\Schema;

use Doctrine\DBAL\Platforms\AbstractPlatform;

use function array_merge;

/**
 * Differences between two schemas.
 *
 * The object contains the operations to change the schema stored in $fromSchema
 * to a target schema.
 */
class SchemaDiff
{
    /** @var Schema|null */
    public $fromSchema;

    /**
     * All added namespaces.
     *
     * @var string[]
     */
    public $newNamespaces = [];

    /**
     * All removed namespaces.
     *
     * @var string[]
     */
    public $removedNamespaces = [];

    /**
     * All added tables.
     *
     * @var Table[]
     */
    public $newTables = [];

    /**
     * All changed tables.
     *
     * @var TableDiff[]
     */
    public $changedTables = [];

    /**
     * All removed tables.
     *
     * @var Table[]
     */
    public $removedTables = [];

    /** @var Sequence[] */
    public $newSequences = [];

    /** @var Sequence[] */
    public $changedSequences = [];

    /** @var Sequence[] */
    public $removedSequences = [];

    /** @var ForeignKeyConstraint[] */
    public $orphanedForeignKeys = [];

    /**
     * Constructs an SchemaDiff object.
     *
     * @internal The diff can be only instantiated by a {@see Comparator}.
     *
     * @param Table[]     $newTables
     * @param TableDiff[] $changedTables
     * @param Table[]     $removedTables
     */
    public function __construct($newTables = [], $changedTables = [], $removedTables = [], ?Schema $fromSchema = null)
    {
        $this->newTables     = $newTables;
        $this->changedTables = $changedTables;
        $this->removedTables = $removedTables;
        $this->fromSchema    = $fromSchema;
    }

    /**
     * The to save sql mode ensures that the following things don't happen:
     *
     * 1. Tables are deleted
     * 2. Sequences are deleted
     * 3. Foreign Keys which reference tables that would otherwise be deleted.
     *
     * This way it is ensured that assets are deleted which might not be relevant to the metadata schema at all.
     *
     * @return list<string>
     */
    public function toSaveSql(AbstractPlatform $platform)
    {
        return $this->_toSql($platform, true);
    }

    /** @return list<string> */
    public function toSql(AbstractPlatform $platform)
    {
        return $this->_toSql($platform, false);
    }

    /**
     * @param bool $saveMode
     *
     * @return list<string>
     */
    protected function _toSql(AbstractPlatform $platform, $saveMode = false)
    {
        $sql = [];

        if ($platform->supportsSchemas()) {
            foreach ($this->newNamespaces as $newNamespace) {
                $sql[] = $platform->getCreateSchemaSQL($newNamespace);
            }
        }

        if ($platform->supportsForeignKeyConstraints() && $saveMode === false) {
            foreach ($this->orphanedForeignKeys as $orphanedForeignKey) {
                $sql[] = $platform->getDropForeignKeySQL($orphanedForeignKey, $orphanedForeignKey->getLocalTable());
            }
        }

        if ($platform->supportsSequences() === true) {
            foreach ($this->changedSequences as $sequence) {
                $sql[] = $platform->getAlterSequenceSQL($sequence);
            }

            if ($saveMode === false) {
                foreach ($this->removedSequences as $sequence) {
                    $sql[] = $platform->getDropSequenceSQL($sequence);
                }
            }

            foreach ($this->newSequences as $sequence) {
                $sql[] = $platform->getCreateSequenceSQL($sequence);
            }
        }

        $sql = array_merge($sql, $platform->getCreateTablesSQL($this->newTables));

        if ($saveMode === false) {
            $sql = array_merge($sql, $platform->getDropTablesSQL($this->removedTables));
        }

        foreach ($this->changedTables as $tableDiff) {
            $sql = array_merge($sql, $platform->getAlterTableSQL($tableDiff));
        }

        return $sql;
    }
}
