<?php

namespace App\Database\Migrations;

use CodeIgniter\Database\Migration;

class FinancialReimbursementPoHardening extends Migration
{
    public function up()
    {
        $this->ensureReimbursementInvariants();
        $this->ensurePurchaseOrderInvariants();
    }

    public function down()
    {
        if ($this->db->tableExists('reimbursements')) {
            $this->dropIndexIfExists('reimbursements', 'uniq_reimbursement_active_expense');
            if ($this->db->fieldExists('active_expense_id', 'reimbursements')) {
                $this->forge->dropColumn('reimbursements', 'active_expense_id');
            }
        }
        $this->dropIndexIfExists('reimbursement_batches', 'uniq_reimbursement_batch_year_sequence');
        $this->dropIndexIfExists('reimbursement_batch_items', 'uniq_reimbursement_batch_item_active_expense');
    }

    private function ensureReimbursementInvariants(): void
    {
        if (!$this->db->tableExists('reimbursements')) {
            return;
        }

        try {
            $this->forge->modifyColumn('reimbursements', [
                'status' => [
                    'type' => 'ENUM',
                    'constraint' => ['pending', 'approved', 'paid', 'rejected', 'reversed', 'Pending', 'Approved', 'Paid', 'Rejected', 'Reversed'],
                    'default' => 'pending',
                    'null' => false,
                ],
            ]);
        } catch (\Throwable $e) {
            throw new \RuntimeException('Could not normalize reimbursement statuses: ' . $e->getMessage(), 0, $e);
        }

        if (!$this->db->fieldExists('active_expense_id', 'reimbursements')) {
            try {
                $this->db->query(
                    "ALTER TABLE reimbursements
                        ADD active_expense_id INT
                        GENERATED ALWAYS AS (
                            CASE
                                WHEN expense_id IS NOT NULL
                                 AND LOWER(status) NOT IN ('reversed','rejected','cancelled','canceled','voided')
                                THEN expense_id
                                ELSE NULL
                            END
                        ) STORED"
                );
            } catch (\Throwable $e) {
                throw new \RuntimeException('Could not add reimbursement active_expense_id generated column: ' . $e->getMessage(), 0, $e);
            }
        }

        $this->createIndexIfMissing('reimbursements', 'uniq_reimbursement_active_expense', 'CREATE UNIQUE INDEX uniq_reimbursement_active_expense ON reimbursements (active_expense_id)');
        $this->createIndexIfMissing('reimbursement_batches', 'uniq_reimbursement_batch_year_sequence', 'CREATE UNIQUE INDEX uniq_reimbursement_batch_year_sequence ON reimbursement_batches (school_year, yearly_batch_number)');
        $this->createIndexIfMissing('reimbursement_batch_items', 'uniq_reimbursement_batch_item_active_expense', 'CREATE UNIQUE INDEX uniq_reimbursement_batch_item_active_expense ON reimbursement_batch_items (batch_id, expense_id)');
    }

    private function ensurePurchaseOrderInvariants(): void
    {
        if (!$this->db->tableExists('purchase_order_items')) {
            return;
        }

        try {
            $this->forge->modifyColumn('purchase_order_items', [
                'quantity' => [
                    'type' => 'INT',
                    'constraint' => 11,
                    'null' => false,
                ],
                'received_qty' => [
                    'type' => 'INT',
                    'constraint' => 11,
                    'default' => 0,
                    'null' => false,
                ],
                'unit_cost' => [
                    'type' => 'DECIMAL',
                    'constraint' => '10,2',
                    'default' => 0,
                    'null' => false,
                ],
            ]);
        } catch (\Throwable $e) {
            throw new \RuntimeException('Could not tighten purchase order item columns: ' . $e->getMessage(), 0, $e);
        }

        try {
            $this->db->query(
                'ALTER TABLE purchase_order_items
                    ADD CONSTRAINT chk_po_item_quantities
                    CHECK (quantity > 0 AND received_qty >= 0 AND received_qty <= quantity AND unit_cost >= 0)'
            );
        } catch (\Throwable $e) {
            throw new \RuntimeException('Could not add purchase order quantity check: ' . $e->getMessage(), 0, $e);
        }
    }

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

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

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

        throw new \RuntimeException('Required index ' . $indexName . ' was not created.');
    }

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

        try {
            $indexes = $this->db->query('SHOW INDEX FROM ' . $this->db->escapeIdentifiers($table))->getResultArray();
            foreach ($indexes as $index) {
                if (($index['Key_name'] ?? '') === $indexName) {
                    $this->db->query('DROP INDEX ' . $this->db->escapeIdentifiers($indexName) . ' ON ' . $this->db->escapeIdentifiers($table));
                    return;
                }
            }
        } catch (\Throwable $e) {
            log_message('warning', 'Could not drop index ' . $indexName . ': ' . $e->getMessage());
        }
    }
}