<?php

namespace App\Database\Migrations;

use CodeIgniter\Database\Migration;

class EnsureFinancialModelSchoolYears extends Migration
{
    public function up()
    {
        $this->ensureColumn('invoice_lines', 'invoice_id');
        $this->backfillFromParent('invoice_lines', 'invoices', 'invoice_id');

        $this->ensureColumn('refund_payouts', 'refund_id');
        $this->backfillFromParent('refund_payouts', 'refunds', 'refund_id');

        $this->ensureColumn('payment_corrections', 'parent_id');
        $this->backfillFromParent('payment_corrections', 'invoices', 'invoice_id');

        $this->ensureColumn('reimbursement_batch_admin_files', 'batch_id');
        $this->backfillFromParent('reimbursement_batch_admin_files', 'reimbursement_batches', 'batch_id');

        $this->ensureColumn('purchase_orders', 'status');
        $this->backfillCurrentYear('purchase_orders');

        $this->ensureColumn('purchase_order_items', 'purchase_order_id');
        $this->backfillFromParent('purchase_order_items', 'purchase_orders', 'purchase_order_id');
    }

    public function down()
    {
        // school_year is now part of the financial model contract; do not drop it.
    }

    private function ensureColumn(string $table, string $after): void
    {
        if (!$this->db->tableExists($table)) {
            return;
        }

        if (!$this->db->fieldExists('school_year', $table)) {
            $this->forge->addColumn($table, [
                'school_year' => [
                    'type' => 'VARCHAR',
                    'constraint' => 9,
                    'null' => true,
                    'after' => $after,
                ],
            ]);
        }
    }

    private function backfillFromParent(string $childTable, string $parentTable, string $foreignKey): void
    {
        if (
            !$this->db->tableExists($childTable)
            || !$this->db->tableExists($parentTable)
            || !$this->db->fieldExists('school_year', $childTable)
            || !$this->db->fieldExists('school_year', $parentTable)
            || !$this->db->fieldExists($foreignKey, $childTable)
        ) {
            return;
        }

        $this->db->query(sprintf(
            "UPDATE %s child
             INNER JOIN %s parent ON parent.id = child.%s
                SET child.school_year = parent.school_year
              WHERE child.school_year IS NULL OR TRIM(child.school_year) = ''",
            $this->db->escapeIdentifiers($childTable),
            $this->db->escapeIdentifiers($parentTable),
            $this->db->escapeIdentifiers($foreignKey)
        ));

        $this->backfillCurrentYear($childTable);
    }

    private function backfillCurrentYear(string $table): void
    {
        if (!$this->db->tableExists($table) || !$this->db->fieldExists('school_year', $table)) {
            return;
        }

        $this->db->query(
            sprintf(
                'UPDATE %s SET school_year = ? WHERE school_year IS NULL OR TRIM(school_year) = ?',
                $this->db->escapeIdentifiers($table)
            ),
            [$this->currentSchoolYear(), '']
        );

        $this->db->query(sprintf(
            'ALTER TABLE %s MODIFY school_year VARCHAR(9) NOT NULL',
            $this->db->escapeIdentifiers($table)
        ));

        $this->ensureIndex($table);
    }

    private function ensureIndex(string $table): void
    {
        $indexName = 'idx_' . $table . '_school_year';
        if (strlen($indexName) > 64) {
            $indexName = 'idx_' . substr(hash('sha256', $table . '_school_year'), 0, 24);
        }

        $indexes = $this->db->query('SHOW INDEX FROM ' . $this->db->escapeIdentifiers($table))->getResultArray();
        foreach ($indexes as $index) {
            if (($index['Key_name'] ?? '') === $indexName) {
                return;
            }
        }

        $this->db->query(sprintf(
            'CREATE INDEX %s ON %s (school_year)',
            $this->db->escapeIdentifiers($indexName),
            $this->db->escapeIdentifiers($table)
        ));
    }

    private function currentSchoolYear(): string
    {
        if ($this->db->tableExists('school_years')) {
            $row = $this->db->table('school_years')
                ->select('name')
                ->where('status', 'active')
                ->orderBy('id', 'DESC')
                ->get(1)
                ->getRowArray();

            $name = trim((string)($row['name'] ?? ''));
            if (preg_match('/^\d{4}-\d{4}$/', $name) === 1) {
                return $name;
            }
        }

        $year = (int)date('Y');

        return $year . '-' . ($year + 1);
    }
}