<?php
namespace DatabaseHelper;

use DatabaseHelper\beans\Column;
use DatabaseHelper\beans\Reference;
use DatabaseHelper\beans\Schema;
use DatabaseHelper\enums\Propagation;
use DatabaseHelper\enums\Type;
use InvalidArgumentException;

class Migration
{
    protected Schema $schema;
    protected array $newCols = [];
    protected array $editCols = [];
    protected array $dropCols = [];
    protected array $addRefs = [];
    protected array $dropRefs = [];

    public function __construct(Schema $table) {
        $this->schema = $table;
    }

    public function column(string $name, Type $type, mixed $default = null, bool $isNullable = false, bool $isUnique = false): Migration {
        $table = $this->schema->name;
        if ($this->schema->existsCol($name))
            throw new InvalidArgumentException("Column '$name' already exists in $table.");

        $col = new Column;
        $col->name = $name;
        $col->type = $type;
        $col->default = $default;
        $col->isUnique = $isUnique;
        $col->isNullable = $isNullable;

        $this->schema->cols[$name] = $col;
        $this->newCols[] = $name;
        return $this;
    }

    public function modify(string $name, Type $type, mixed $default = null, bool $isNullable = false, bool $isUnique = false): Migration {
        $this->schema->reqCol($name);
        $col = $this->schema->getCol($name);

        $col->name = $name;
        $col->type = $type;
        $col->default = $default;
        $col->isNullable = $isNullable;
        $col->isUnique = $isUnique;#

        $this->editCols[$name] = $col;
        return $this;
    }

    public function drop(string $name): Migration {
        unset($this->schema->cols[$name]);
        $this->dropCols[] = $name;
        return $this;
    }

    public function reference(Schema $foreignTable, Propagation $onDelete = Propagation::CASCADE, Propagation $onUpdate = Propagation::CASCADE): Migration {
        if($this->schema->existsRef($foreignTable))
            throw new InvalidArgumentException("Foreign table '$foreignTable->name' is already referenced in '{$this->schema->name}'.");
        $name = $foreignTable->id->name;

        $ref = new Reference;
        $ref->name = $name;
        $ref->onUpdate = $onUpdate;
        $ref->onDelete = $onDelete;

        $this->schema->refs[$name] = $ref;
        $this->addRefs[] = $name;

        return $this;
    }

    public function dereference(Schema $foreignTable): Migration {
        $this->schema->reqRef($foreignTable);
        $name = $foreignTable->id->name;

        unset($this->schema->refs[$name]);
        $this->dropRefs[] = $name;

        return $this;
    }

    public function toSql(): string {
        global $wpdb;
        // We assume that the table name in the schema is not prefixed; add the prefix here.
        $tableName = $wpdb->prefix . $this->schema->name;
        $clauses = [];

        // Process new columns.
        foreach ($this->newCols as $columnName) {
            $col = $this->schema->cols[$columnName];
            $clause = "ADD COLUMN `{$col['name']}` {$col['type']->toString()}";

            $clause .= !$col['isNullable'] ? " NOT NULL" : "";
            $clause .= $col['isUnique'] ? " UNIQUE" : "";

            if (!is_null($col['default'])) {
                $default = is_string($col['default']) ? "'{$col['default']}'" : $col['default'];
                $clause .= " DEFAULT $default";
            }

            $clauses[] = $clause;
        }

        // Process modified columns.
        foreach ($this->editCols as $columnName) {
            $col = $this->schema->cols[$columnName];
            $clause = "MODIFY COLUMN `{$col['name']}` {$col['type']->toString()}";

            $clause .= !$col['isNullable'] ? " NOT NULL" : "";
            $clause .= $col['isUnique'] ? " UNIQUE" : "";

            if (!is_null($col['default'])) {
                $default = is_string($col['default']) ? "'{$col['default']}'" : $col['default'];
                $clause .= " DEFAULT $default";
            }

            $clauses[] = $clause;
        }


        // Process dropped columns.
        foreach ($this->dropCols as $columnName)
            $clauses[] = "DROP COLUMN `$columnName`";

        // Process foreign keys to add.
        foreach ($this->addRefs as $key) {
            $foreignKey = $this->schema->refs[$key];

            $clause = "  ADD CONSTRAINT `fk_{$foreignKey['name']}`";
            $clause .= " FOREIGN KEY (`{$foreignKey['name']}`)";
            $clause .= " REFERENCES `{$foreignKey['table']}` (`{$foreignKey['name']}`)";
            $clause .= " ON DELETE {$foreignKey['onDelete']->toString()}";
            $clause .= " ON UPDATE {$foreignKey['onUpdate']->toString()},\n";

            $clauses[] = $clause;
        }

        // Process foreign keys to drop.
        foreach ($this->dropRefs as $fkName)
            $clauses[] = "DROP FOREIGN KEY `fk_{$fkName}`";

        if (empty($clauses))
            throw new InvalidArgumentException("No migration operations to perform.");

        return "ALTER TABLE `$tableName`\n" . implode(",\n", $clauses) . ";";
    }

    public function migrate(): Schema {
        global $wpdb;
        $sql = $this->toSql();
        $wpdb->query($sql);
        return $this->schema;
    }
}