<?php

namespace App\Services;

use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
use Symfony\Component\ExpressionLanguage\ParsedExpression;

class RuleExpressionService
{
    protected ExpressionLanguage $language;

    /** @var array<string, ParsedExpression> */
    protected array $parsedCache = [];

    public function __construct()
    {
        $this->language = new ExpressionLanguage();
    }

    public function evaluate(string $expr, array $context = [])
    {
        $expr = trim($expr);
        if ($expr === '') {
            return null;
        }

        $names = array_keys($context);
        sort($names);
        $cacheKey = md5($expr . '|' . implode(',', $names));

        if (!isset($this->parsedCache[$cacheKey])) {
            $this->parsedCache[$cacheKey] = $this->language->parse($expr, $names);
        }

        return $this->language->evaluate($this->parsedCache[$cacheKey], $context);
    }

    public function evaluateBoolean(?string $expr, array $context = []): bool
    {
        if ($expr === null || trim($expr) === '') {
            return true;
        }

        return (bool) $this->evaluate($expr, $context);
    }

    /**
     * Compile DSL expression to engine-compatible JSON structure.
     *
     * Supported DSL:
     * - if(condition ? action : action)
     * - sex('F'|'M') -> order["Sex"] == 'F'
     * - set_result(value) -> {"value": value} or {"valueExpr": "value"}
     *
     * @param string $expr The raw DSL expression
     * @return array The compiled structure with valueExpr
     * @throws \InvalidArgumentException If DSL is invalid
     */
    public function compile(string $expr): array
    {
        $expr = trim($expr);
        if ($expr === '') {
            return [];
        }

        // Remove outer parentheses from if(...)
        if (preg_match('/^if\s*\(\s*(.+?)\s*\)$/s', $expr, $m)) {
            $expr = trim($m[1]);
        }

        // Parse: condition ? thenAction : elseAction
        if (!preg_match('/^(.+?)\s*\?\s*(.+?)\s*:\s*(.+)$/s', $expr, $parts)) {
            throw new \InvalidArgumentException('Invalid DSL: expected "if(condition ? action : action)" format');
        }

        $condition = trim($parts[1]);
        $thenAction = trim($parts[2]);
        $elseAction = trim($parts[3]);

        // Compile condition
        $compiledCondition = $this->compileCondition($condition);

        // Compile actions
        $thenCompiled = $this->compileAction($thenAction);
        $elseCompiled = $this->compileAction($elseAction);

        // Build valueExpr combining condition and actions
        $thenValue = $thenCompiled['valueExpr'] ?? json_encode($thenCompiled['value'] ?? null);
        $elseValue = $elseCompiled['valueExpr'] ?? json_encode($elseCompiled['value'] ?? null);

        // Handle string vs numeric values
        if (is_string($thenCompiled['value'] ?? null)) {
            $thenValue = '"' . addslashes($thenCompiled['value']) . '"';
        }
        if (is_string($elseCompiled['value'] ?? null)) {
            $elseValue = '"' . addslashes($elseCompiled['value']) . '"';
        }

        $valueExpr = "({$compiledCondition}) ? {$thenValue} : {$elseValue}";

        return [
            'conditionExpr' => $compiledCondition,
            'valueExpr' => $valueExpr,
            'then' => $thenCompiled,
            'else' => $elseCompiled,
        ];
    }

    /**
     * Compile DSL condition to ExpressionLanguage expression
     */
    private function compileCondition(string $condition): string
    {
        $condition = trim($condition);

        // sex('F') -> order["Sex"] == 'F'
        if (preg_match("/^sex\s*\(\s*['\"]([MF])['\"]\s*\)$/i", $condition, $m)) {
            return 'order["Sex"] == "' . $m[1] . '"';
        }

        // sex == 'F' (alternative syntax)
        if (preg_match('/^\s*sex\s*==\s*[\'"]([MF])[\'"]\s*$/i', $condition, $m)) {
            return 'order["Sex"] == "' . $m[1] . '"';
        }

        // priority('S') -> order["Priority"] == 'S'
        if (preg_match("/^priority\s*\(\s*['\"]([SR])['\"]\s*\)$/i", $condition, $m)) {
            return 'order["Priority"] == "' . $m[1] . '"';
        }

        // priority == 'S' (alternative syntax)
        if (preg_match('/^\s*priority\s*==\s*[\'"]([SR])[\'"]\s*$/i', $condition, $m)) {
            return 'order["Priority"] == "' . $m[1] . '"';
        }

        // age > 18 -> patient["Age"] > 18 (if available) or order["Age"] > 18
        if (preg_match('/^\s*age\s*([<>]=?)\s*(\d+)\s*$/i', $condition, $m)) {
            return 'order["Age"] ' . $m[1] . ' ' . $m[2];
        }

        // If already valid ExpressionLanguage, return as-is
        return $condition;
    }

    /**
     * Compile DSL action to action params
     */
    private function compileAction(string $action): array
    {
        $action = trim($action);

        // set_result(value) -> SET_RESULT action
        if (preg_match('/^set_result\s*\(\s*(.+?)\s*\)$/i', $action, $m)) {
            $value = trim($m[1]);

            // Check if it's a number
            if (is_numeric($value)) {
                return [
                    'type' => 'SET_RESULT',
                    'value' => strpos($value, '.') !== false ? (float) $value : (int) $value,
                    'valueExpr' => $value,
                ];
            }

            // Check if it's a quoted string
            if (preg_match('/^["\'](.+)["\']$/s', $value, $vm)) {
                return [
                    'type' => 'SET_RESULT',
                    'value' => $vm[1],
                    'valueExpr' => '"' . addslashes($vm[1]) . '"',
                ];
            }

            // Complex expression
            return [
                'type' => 'SET_RESULT',
                'valueExpr' => $value,
            ];
        }

        throw new \InvalidArgumentException('Unknown action: ' . $action);
    }
}