<?php

namespace App\Services;

use App\Models\Product;
use InvalidArgumentException;

class FormulaPriceService
{
    /** ضریب تبدیل مثقال به گرم — قابل استفاده در فرمول با MG */
    public const MG = 4.331802;

    public const DEFAULT_FORMULA = '((P)/MG)*W+100000';

    public static function isEnabled(?Product $product): bool
    {
        if (! Product::hasPriceFormulaColumns()) {
            return false;
        }

        return (bool) ($product?->price_formula_enabled);
    }

    public static function isTvEnabled(?Product $product): bool
    {
        if (! Product::hasTvPriceFormulaColumns()) {
            return false;
        }

        return (bool) ($product?->show_on_tv) && (bool) ($product?->tv_price_formula_enabled);
    }

    /**
     * @param  array<string, mixed>|null  $mazanehRow
     */
    public static function calculateTvForProduct(Product $product, ?array $mazanehRow): ?int
    {
        if (! self::isTvEnabled($product) || $mazanehRow === null) {
            return null;
        }

        if (array_key_exists('active', $mazanehRow) && $mazanehRow['active'] == false) {
            return null;
        }

        $p = (float) ($mazanehRow['price'] ?? 0);
        if ($p <= 0) {
            return null;
        }

        $formula = trim((string) ($product->tv_price_formula ?? ''));
        if ($formula === '') {
            $formula = self::DEFAULT_FORMULA;
        }

        return self::evaluate($formula, $p, self::resolveWeight($product->amount ?? 0));
    }

    /**
     * P = قیمت وسط مرجع (بدون تفاوت ارائه‌دهنده / بدون price_offset_percent)
     *
     * @param  array<string, mixed>|null  $mazanehRow
     */
    public static function calculateForProduct(Product $product, ?array $mazanehRow): ?int
    {
        if (! self::isEnabled($product) || $mazanehRow === null) {
            return null;
        }

        if (array_key_exists('active', $mazanehRow) && $mazanehRow['active'] == false) {
            return null;
        }

        $p = (float) ($mazanehRow['price'] ?? 0);
        if ($p <= 0) {
            return null;
        }

        $formula = trim((string) ($product->price_formula ?? ''));
        if ($formula === '') {
            $formula = self::DEFAULT_FORMULA;
        }

        return self::evaluate($formula, $p, self::resolveWeight($product->amount ?? 0));
    }

    public static function resolveWeight(float $amount): float
    {
        return $amount == 0.0 ? 1.0 : (float) $amount;
    }

    public static function evaluate(string $formula, float $p, float $w): ?int
    {
        $formula = trim($formula);
        if ($formula === '') {
            return null;
        }

        try {
            $result = self::evaluateExpression($formula, [
                'P' => $p,
                'W' => $w,
                'MG' => self::MG,
            ]);
        } catch (InvalidArgumentException $e) {
            return null;
        }

        if (! is_finite($result)) {
            return null;
        }

        return (int) round($result);
    }

    /**
     * @param  array<string, float>  $variables
     */
    private static function evaluateExpression(string $expression, array $variables): float
    {
        $tokens = self::tokenize($expression);
        $position = 0;
        $result = self::parseExpression($tokens, $position, $variables);

        if ($position < count($tokens)) {
            throw new InvalidArgumentException('Invalid formula syntax');
        }

        return $result;
    }

    /**
     * @return array<int, array{type: string, value: string}>
     */
    private static function tokenize(string $expression): array
    {
        $expression = str_replace(['×', '÷'], ['*', '/'], $expression);
        $expression = preg_replace('/\s+/', '', $expression) ?? '';

        if ($expression === '' || ! preg_match('/^[0-9A-Za-z_.,+\-*\/()]+$/', $expression)) {
            throw new InvalidArgumentException('Invalid formula characters');
        }

        preg_match_all('/([0-9]+(?:\.[0-9]+)?|[A-Za-z_][A-Za-z0-9_]*|[+\-*\/(),])/', $expression, $matches);

        if (($matches[0] ?? []) === [] || implode('', $matches[0]) !== $expression) {
            throw new InvalidArgumentException('Invalid formula syntax');
        }

        $tokens = [];
        foreach ($matches[0] as $part) {
            if (preg_match('/^[0-9]/', $part)) {
                $tokens[] = ['type' => 'number', 'value' => $part];
            } elseif (preg_match('/^[A-Za-z_]/', $part)) {
                $tokens[] = ['type' => 'ident', 'value' => strtoupper($part)];
            } else {
                $tokens[] = ['type' => 'op', 'value' => $part];
            }
        }

        return $tokens;
    }

    /**
     * @param  array<int, array{type: string, value: string}>  $tokens
     * @param  array<string, float>  $variables
     */
    private static function parseExpression(array $tokens, int &$position, array $variables): float
    {
        $value = self::parseTerm($tokens, $position, $variables);

        while ($position < count($tokens) && in_array($tokens[$position]['value'], ['+', '-'], true)) {
            $operator = $tokens[$position]['value'];
            $position++;
            $right = self::parseTerm($tokens, $position, $variables);
            $value = $operator === '+' ? $value + $right : $value - $right;
        }

        return $value;
    }

    /**
     * @param  array<int, array{type: string, value: string}>  $tokens
     * @param  array<string, float>  $variables
     */
    private static function parseTerm(array $tokens, int &$position, array $variables): float
    {
        $value = self::parseFactor($tokens, $position, $variables);

        while ($position < count($tokens) && in_array($tokens[$position]['value'], ['*', '/'], true)) {
            $operator = $tokens[$position]['value'];
            $position++;
            $right = self::parseFactor($tokens, $position, $variables);
            if ($operator === '/') {
                if (abs($right) < 1e-12) {
                    throw new InvalidArgumentException('Division by zero');
                }
                $value /= $right;
            } else {
                $value *= $right;
            }
        }

        return $value;
    }

    /**
     * @param  array<int, array{type: string, value: string}>  $tokens
     * @param  array<string, float>  $variables
     */
    private static function parseFactor(array $tokens, int &$position, array $variables): float
    {
        if ($position >= count($tokens)) {
            throw new InvalidArgumentException('Unexpected end of formula');
        }

        $token = $tokens[$position];

        if ($token['type'] === 'number') {
            $position++;

            return (float) $token['value'];
        }

        if ($token['type'] === 'ident') {
            $position++;
            $name = $token['value'];

            if ($position < count($tokens) && $tokens[$position]['value'] === '(') {
                $position++;
                $args = [];

                if ($position >= count($tokens) || $tokens[$position]['value'] !== ')') {
                    $args[] = self::parseExpression($tokens, $position, $variables);

                    while ($position < count($tokens) && $tokens[$position]['value'] === ',') {
                        $position++;
                        $args[] = self::parseExpression($tokens, $position, $variables);
                    }
                }

                if ($position >= count($tokens) || $tokens[$position]['value'] !== ')') {
                    throw new InvalidArgumentException('Missing closing parenthesis');
                }
                $position++;

                return self::applyFunction($name, $args);
            }

            if (! array_key_exists($name, $variables)) {
                throw new InvalidArgumentException("Unknown variable: {$name}");
            }

            return (float) $variables[$name];
        }

        if ($token['value'] === '(') {
            $position++;
            $value = self::parseExpression($tokens, $position, $variables);
            if ($position >= count($tokens) || $tokens[$position]['value'] !== ')') {
                throw new InvalidArgumentException('Missing closing parenthesis');
            }
            $position++;

            return $value;
        }

        if ($token['value'] === '-') {
            $position++;

            return -self::parseFactor($tokens, $position, $variables);
        }

        if ($token['value'] === '+') {
            $position++;

            return self::parseFactor($tokens, $position, $variables);
        }

        throw new InvalidArgumentException('Invalid formula syntax');
    }

    /**
     * @param  list<float>  $args
     */
    private static function applyFunction(string $name, array $args): float
    {
        if ($args === []) {
            throw new InvalidArgumentException("Invalid arguments for {$name}");
        }

        $value = (float) $args[0];
        $precision = isset($args[1]) ? (int) $args[1] : 0;

        return match ($name) {
            'ROUND' => (float) round($value, $precision),
            'FLOOR' => self::floorPrecision($value, $precision),
            'CEIL', 'CEILING' => self::ceilPrecision($value, $precision),
            default => throw new InvalidArgumentException("Unknown function: {$name}"),
        };
    }

    private static function floorPrecision(float $value, int $precision): float
    {
        $factor = 10 ** $precision;

        return floor($value * $factor) / $factor;
    }

    private static function ceilPrecision(float $value, int $precision): float
    {
        $factor = 10 ** $precision;

        return ceil($value * $factor) / $factor;
    }
}