<?php

namespace App\Services\Forms;

use App\Models\FormTemplate;
use App\Models\FormPrintLog;

class MailMergeService
{
    /**
     * Evaluate all fields for a given record and return values array.
     */
    public static function evaluateFields(FormTemplate $template, Model $record): array
    {
        $values = [];

        foreach ($template->fields as $field) {
            $values[$field->code] = self::evaluateSingleField($field, $record, $values);
        }

        return $values;
    }

    protected static function evaluateSingleField($field, Model $record, array $evaluatedValues): mixed
    {
        $config = $field->source_config ?? [];

        return match ($field->source_type) {
            'db_column' => self::getDbColumnValue($record, $config['column'] ?? null),
            'db_relation' => self::getRelationValue($record, $config),
            'formula' => self::evaluateFormula($config['expression'] ?? '', $evaluatedValues),
            'input' => $config['default'] ?? '',
            'static' => $config['value'] ?? '',
            default => '',
        };
    }

    protected static function getDbColumnValue(Model $record, ?string $column): mixed
    {
        if (! $column) return '';
        return $record->{$column} ?? '';
    }

    protected static function getRelationValue(Model $record, array $config): mixed
    {
        $relation = $config['relation'] ?? null;
        $column = $config['column'] ?? null;
        $index = $config['index'] ?? null;

        if (! $relation || ! $column) return '';

        $related = $record->{$relation};

        if (is_null($related)) return '';

        if ($related instanceof \Illuminate\Database\Eloquent\Collection) {
            if ($index !== null) {
                $item = $related->skip($index)->first();
                return $item?->{$column} ?? '';
            }
            return $related->pluck($column)->implode(', ');
        }

        return $related->{$column} ?? '';
    }

    protected static function evaluateFormula(string $expression, array $values): float
    {
        if (empty($expression)) return 0;

        // Thay thế tên biến bằng giá trị
        $evalExpression = $expression;
        foreach ($values as $key => $value) {
            if (is_numeric($value)) {
                $evalExpression = str_replace($key, (float) $value, $evalExpression);
            }
        }

        // Chỉ cho phép số và các phép toán cơ bản
        $evalExpression = preg_replace('/[^0-9.\+\-\*\/\(\)\s]/', '', $evalExpression);

        if (empty($evalExpression)) return 0;

        try {
            // Eval an toàn với chỉ phép toán
            $result = self::safeEval($evalExpression);
            return (float) $result;
        } catch (\Throwable $e) {
            return 0;
        }
    }

    protected static function safeEval(string $expression): float
    {
        // Loại bỏ các hàm nguy hiểm, chỉ giữ phép toán
        $expression = preg_replace('/[^0-9.\+\-\*\/\(\)\s]/', '', $expression);

        if (empty($expression) || preg_match('/[a-zA-Z]/', $expression)) {
            throw new \InvalidArgumentException('Invalid expression');
        }

        // Dùng bc math nếu có, hoặc eval đơn giản
        return (float) eval('return ' . $expression . ';');
    }

    /**
     * Format value theo kiểu field.
     */
    public static function formatValue(mixed $value, string $format, int $decimals = 0): string
    {
        return match ($format) {
            'number' => number_format((float) $value, $decimals, ',', '.'),
            'currency' => number_format((float) $value, 0, ',', '.') . ' VNĐ',
            'percent' => number_format((float) $value, $decimals, ',', '.') . '%',
            'date' => $value ? \Carbon\Carbon::parse($value)->format('d/m/Y') : '',
            default => (string) $value,
        };
    }

    /**
     * Render template with evaluated values.
     */
    public static function render(FormTemplate $template, Model $record): array
    {
        $rawValues = self::evaluateFields($template, $record);

        $formattedValues = [];
        foreach ($template->fields as $field) {
            $code = $field->code;
            $rawValue = $rawValues[$code] ?? '';
            $formattedValues[$code] = self::formatValue(
                $rawValue,
                $field->format,
                $field->decimal_places
            );
        }

        $html = $template->html_template;
        foreach ($formattedValues as $code => $value) {
            $html = str_replace('{{' . $code . '}}', (string) $value, $html);
        }

        return [
            'html' => $html,
            'raw_values' => $rawValues,
            'formatted_values' => $formattedValues,
        ];
    }

    /**
     * Save print log with snapshot.
     */
    public static function savePrintLog(FormTemplate $template, Model $record, array $renderResult, int $userId): FormPrintLog
    {
        return FormPrintLog::create([
            'template_id' => $template->id,
            'target_model' => get_class($record),
            'target_id' => $record->id,
            'target_number' => $record->contract_number ?? $record->code ?? null,
            'snapshot_data' => [
                'raw_values' => $renderResult['raw_values'],
                'formatted_values' => $renderResult['formatted_values'],
            ],
            'rendered_html' => $renderResult['html'],
            'printed_by' => $userId,
            'printed_at' => now(),
        ]);
    }
}