<?php

namespace Mnml\Interpreter;

use Closure;
use Mnml\Lexer\Lexer;
use Mnml\Lexer\Token;
use Mnml\Lexer\TokenType;
use Mnml\Parser\ArrayMapAccessNode;
use Mnml\Parser\ArrayNode;
use Mnml\Parser\BoolNode;
use Mnml\Parser\CommentNode;
use Mnml\Parser\CompareExpression;
use Mnml\Parser\Condition;
use Mnml\Parser\ConstVariableDeclaration;
use Mnml\Parser\FunctionCall;
use Mnml\Parser\FunctionCallParameter;
use Mnml\Parser\FunctionDefinition;
use Mnml\Parser\FunctionReturn;
use Mnml\Parser\IdentifierNode;
use Mnml\Parser\IfArm;
use Mnml\Parser\IfNode;
use Mnml\Parser\MapNode;
use Mnml\Parser\Node;
use Mnml\Parser\NumberNode;
use Mnml\Parser\OperatorExpression;
use Mnml\Parser\Parenthesis;
use Mnml\Parser\Parser;
use Mnml\Parser\PipeExpression;
use Mnml\Parser\StringNode;
use Mnml\Parser\VariableAssignment;

class Interpreter
{
    private array $nodes;
    
    /**
    * @param Node[] $nodes
    */
    public function __construct(array $nodes)
    {
        $this->nodes = $nodes;
    }

    public function compile(array $parameters): Scope
    {
        $scope = new Scope();

        // add standard library
        $standardLibrary = include dirname(__DIR__) . "/standard.php";
        foreach ($standardLibrary as $identifier => $function) {
            $scope->addExternal($identifier, $function);
        }
        
        foreach ($this->nodes as $currentNode) {
            $value = $this->evaluate($currentNode, $scope);
        }

        return $scope;
    }

    private function evaluate(Node $currentNode, Scope $scope): Node|null|bool
    {
        if ($currentNode instanceof ConstVariableDeclaration) {
            $identifier = $currentNode->identifier;
            $value = new ValueNode(null);

            /*if ($scope->has($identifier)) {
                echo sprintf("%s already declared in current scope." . PHP_EOL, $identifier->token->value);
            }*/ # TODO: problems with recursive functions. clear scope somehow?

            #else {
                if (! is_null($currentNode->expression)) {
                    $value = $this->evaluate($currentNode->expression, $scope);
                }

                $scope->add($identifier, $value);
            #}

            return $value;
        }

        if ($currentNode instanceof VariableAssignment) {
            $identifier = $currentNode->identifier;
            $value = new ValueNode(null);
            
            if ($scope->has($identifier)) {
                $curentValue = $scope->get($identifier)->getValue();
                
                if (is_null($curentValue)) {
                    $value = $this->evaluate($currentNode->expression, $scope);
                    $scope->set($identifier, $value);
                }
                else {
                    echo sprintf("%s already assigned in current scope." . PHP_EOL, $identifier->token->value);
                }
            }
            
            else {
                 echo sprintf("%s is not declared in current scope." . PHP_EOL, $identifier->token->value);                           
            }

            return $value;            
        }
        
        else if ($currentNode instanceof IdentifierNode) {
            $variable = $scope->get($currentNode);

            return $this->evaluate($variable, $scope);
        }

        else if ($currentNode instanceof ArrayMapAccessNode) {
            return $this->evaluateArrayOrMapAccess($currentNode, $scope);
        }

        else if ($currentNode instanceof Parenthesis) {
            return $this->evaluate($currentNode->content, $scope);
        }
        
        else if ($currentNode instanceof OperatorExpression) {
            $left = $this->evaluate($currentNode->left, $scope)->getValue();
            $right = $this->evaluate($currentNode->right, $scope)->getValue();

            if ($currentNode->operator->value == "+") {
                if (is_string($left) and is_string($right)) {
                    return new ValueNode($left . $right);
                }

                return new ValueNode($left + $right);
            }

            else if ($currentNode->operator->value == "-") {
                return new ValueNode($left - $right);
            }
            
            else if ($currentNode->operator->value == "*") {
                return new ValueNode($left * $right);
            }

            else if ($currentNode->operator->value == "**") {
                return new ValueNode(pow($left, $right));
            }

            else if ($currentNode->operator->value == "/") {
                return new ValueNode($left / $right);
            }
            
            else if ($currentNode->operator->value == "%") {
                return new ValueNode($left % $right);
            }
        }
        
        else if ($currentNode instanceof CompareExpression) {
            $left = $this->evaluate($currentNode->left, $scope)->getValue();
            $right = $this->evaluate($currentNode->right, $scope)->getValue();
            
            if ($currentNode->operator->value == "<") {
                return new ValueNode($left < $right);
            }

            else if ($currentNode->operator->value == ">") {
                return new ValueNode($left > $right);
            }

            else if ($currentNode->operator->value == "<=") {
                return new ValueNode($left <= $right);
            }

            else if ($currentNode->operator->value == ">=") {
                return new ValueNode($left >= $right);
            }

            else if ($currentNode->operator->value == "==") {
                return new ValueNode($left == $right);
            }

            else if ($currentNode->operator->value == "!=") {
                return new ValueNode($left != $right);
            }
        }

        else if ($currentNode instanceof IfNode) {
            foreach ($currentNode->arms as $arm) {
                /**@var IfArm $arm*/
                $condition = true;
                if ($arm->condition != null) {
                    $condition = $this->evaluate($arm->condition, $scope)->getValue();
                }

                if ($condition) {
                    return $this->evaluateIfArmBody($arm, $scope);
                }
            }
            
            return null;
        }

        else if ($currentNode instanceof Condition) {
            $left = $this->evaluate($currentNode->left, $scope)->getValue();
            $right = $this->evaluate($currentNode->right, $scope)->getValue();

            if ($currentNode->operator->value == "and") {
                return new ValueNode($left and $right);
            }

            else if ($currentNode->operator->value == "or") {
                return new ValueNode($left or $right);
            }
        }
        
        else if ($currentNode instanceof FunctionDefinition) {
            return $currentNode;
        }

        else if ($currentNode instanceof FunctionCall) {
            $functionDefinition = $scope->get($currentNode->identifier);

            if ($functionDefinition instanceof FunctionDefinition) {
                return $this->evaluateFunction($currentNode->identifier, $functionDefinition, $currentNode->parameters, $scope);
            }
            else if ($functionDefinition instanceof Closure) {
                return $this->evaluateClosure($currentNode->identifier, $functionDefinition, $currentNode->parameters, $scope);
            }

            return $currentNode;
        }

        else if ($currentNode instanceof PipeExpression) {
            $left = $this->evaluate($currentNode->left, $scope);
            
            $pipeScope = new Scope($scope);
            $pipeScope->add(new IdentifierNode(new Token(TokenType::Identifier, "$", "$", 0, 0)), $left);
            
            $right = $this->evaluate($currentNode->right, $pipeScope);

            return $right;
        }

        else if ($currentNode instanceof NumberNode) {
            return $currentNode;
        }

        else if ($currentNode instanceof StringNode) {
            return $currentNode;
        }

        else if ($currentNode instanceof BoolNode) {
            return $currentNode;
        }
        
        else if ($currentNode instanceof ArrayNode) {
            return $currentNode;
        }

        else if ($currentNode instanceof MapNode) {
            return $currentNode;
        }

        else if ($currentNode instanceof ValueNode) {
            return $currentNode;
        }

        else if ($currentNode instanceof CommentNode) {
            return $currentNode;
        }
        
        else if (is_callable($currentNode)) {
            return true;
        }

        else {
            echo sprintf("Compiler Error: Unhandled Node type %s." . PHP_EOL, get_class($currentNode));
            return false;
        }
    }

    private function evaluateArrayOrMapAccess(ArrayMapAccessNode $arrayOrMapAccess, Scope $scope): Node
    {
        $arrayOrMap = $arrayOrMapAccess->arrayOrMap;
        if ($arrayOrMap instanceof IdentifierNode) {
            $arrayOrMap = $this->evaluate($arrayOrMap, $scope);
        }
        
        $accessee = $arrayOrMap;
        
        foreach ($arrayOrMapAccess->items as $item) {
            $evaluation = $this->evaluate($item, $scope)->getValue();

            if ($accessee instanceof ArrayNode) {
                $accessee = $accessee->values[$evaluation];
            }
            else if ($accessee instanceof MapNode) {
                foreach ($accessee->values as $value) {
                    $key = $this->evaluate($value->key, $scope)->getValue();
                    if ($key == $evaluation) {
                        $accessee = $this->evaluate($value->value, $scope);
                        break;
                    }
                }
            }
            else if ($accessee instanceof ValueNode) {
                $accessee = new ValueNode($accessee->getValue()[$evaluation]);
            }
        }

        return $accessee;
    }

    /**
    * @param FunctionCallParameter[] $parameters
    */
    private function evaluateFunction(IdentifierNode $identifier, FunctionDefinition $function, array $parameters, Scope $outerScope): mixed
    {
        $scope = new Scope($outerScope);

        foreach ($parameters as $parameter) {
            /**@var FunctionCallParameter $parameter*/
            $scope->add($parameter->identifier, $this->evaluate($parameter->value, $outerScope));
        }

        foreach ($function->body as $currentNode) {
            if ($currentNode instanceof FunctionReturn) {
                return $this->evaluate($currentNode->returnValue, $scope);
            }

            else if ($currentNode instanceof IfNode) {
                $returnValue = $this->evaluate($currentNode, $scope);

                // return if "if" had a return inside
                if ($returnValue) {
                    return $returnValue;
                }
            }

            else {
                $this->evaluate($currentNode, $scope);
            }
        }

        echo sprintf("Function %s missing return value." . PHP_EOL, $identifier->token->value);
    }

    /**
    * @param FunctionCallParameter[] $parameters
    */
    private function evaluateClosure(IdentifierNode $identifier, Closure $function, array $parameters, Scope $scope): mixed
    {
        $evaluatedParameters = [];
        foreach ($parameters as $parameter) {
            /**@var FunctionCallParameter $parameter*/
            $evaluatedParameters[] = $this->evaluate($parameter->value, $scope)->getValue();
        }

        return new ValueNode(call_user_func_array($function, $evaluatedParameters));
    }

    private function evaluateIfArmBody(IfArm $arm, Scope $outerScope): mixed
    {
        $scope = new Scope($outerScope);
        
        foreach ($arm->body as $currentNode) {
            if ($currentNode instanceof FunctionReturn) {
                return $this->evaluate($currentNode->returnValue, $scope);
            }

            else {
                $this->evaluate($currentNode, $scope);
            }
        }

        return null;
    }
}

class Scope
{
    private ?Scope $outerScope;
    public array $values;

    public function __construct(?Scope $outerScope = null)
    {
        $this->outerScope = $outerScope;
    }

    public function add(IdentifierNode $identifier, mixed $value): void
    {
        $key = $identifier->token->value;
        
        $this->values[$key] = $value;
    }

    public function get(IdentifierNode $identifier): mixed
    {
        $key = $identifier->token->value;
        
        if (isset($this->values[$key])) {
            $value = $this->values[$key];
            if ($value instanceof IdentifierNode and $value->token->value == $key) {}
            else {
                return $this->values[$key];
            }
        }

        if (! isset($this->outerScope)) {
            echo sprintf("Undefined variable \"%s\" at %d:%d" . PHP_EOL, $key, $identifier->token->line, $identifier->token->column);

            return null;
        }
        
        return $this->outerScope->get($identifier);
    }

    public function set(IdentifierNode $identifier, mixed $value): void
    {
        $key = $identifier->token->value;

        if (isset($this->values[$key])) {
            $this->values[$key] = $value;
        }

        else if (isset($this->outerScope)){
            $this->outerScope->set($identifier, $value);
        }

        else {
            echo sprintf("Can't set nonexistent variable %s." . PHP_EOL, $identifier->token->value);            
        }
    }

    public function has(IdentifierNode $identifier): bool
    {
        $has = isset($this->values[$identifier->token->value]);

        if ($has) {
            return $has;
        }

        if (isset($this->outerScope)) {
            return $this->outerScope->has($identifier);
        }

        return false;
    }

    public function addExternal(string $identifier, mixed $value): void
    {
        $this->values[$identifier] = $value;
    }
}

class ValueNode extends Node
{
    public function __construct(private mixed $value)
    {}

    public function getValue(): mixed
    {
        return $this->value;
    }
}