<?php
namespace Psalm\Checker\Statements\Expression\Fetch;

use PhpParser;
use Psalm\Checker\Statements\ExpressionChecker;
use Psalm\Checker\StatementsChecker;
use Psalm\CodeLocation;
use Psalm\Context;
use Psalm\Issue\InvalidScope;
use Psalm\Issue\PossiblyUndefinedGlobalVariable;
use Psalm\Issue\PossiblyUndefinedVariable;
use Psalm\Issue\UndefinedGlobalVariable;
use Psalm\Issue\UndefinedVariable;
use Psalm\IssueBuffer;
use Psalm\Type;

class VariableFetchChecker
{
    /**
     * @param   StatementsChecker               $statements_checker
     * @param   PhpParser\Node\Expr\Variable    $stmt
     * @param   Context                         $context
     * @param   bool                            $passed_by_reference
     * @param   Type\Union|null                 $by_ref_type
     * @param   bool                            $array_assignment
     *
     * @return  false|null
     */
    public static function analyze(
        StatementsChecker $statements_checker,
        PhpParser\Node\Expr\Variable $stmt,
        Context $context,
        $passed_by_reference = false,
        Type\Union $by_ref_type = null,
        $array_assignment = false
    ) {
        if ($stmt->name === 'this') {
            if ($statements_checker->isStatic()) {
                if (IssueBuffer::accepts(
                    new InvalidScope(
                        'Invalid reference to $this in a static context',
                        new CodeLocation($statements_checker->getSource(), $stmt)
                    ),
                    $statements_checker->getSuppressedIssues()
                )) {
                    return false;
                }

                return null;
            } elseif (!isset($context->vars_in_scope['$this'])) {
                if (IssueBuffer::accepts(
                    new InvalidScope(
                        'Invalid reference to $this in a non-class context',
                        new CodeLocation($statements_checker->getSource(), $stmt)
                    ),
                    $statements_checker->getSuppressedIssues()
                )) {
                    return false;
                }

                return null;
            }

            $stmt->inferredType = clone $context->vars_in_scope['$this'];

            return null;
        }

        if (!$context->check_variables) {
            if (is_string($stmt->name)) {
                $var_name = '$' . $stmt->name;

                if (!$context->hasVariable($var_name)) {
                    $context->vars_in_scope[$var_name] = Type::getMixed();
                    $context->vars_possibly_in_scope[$var_name] = true;
                    $stmt->inferredType = Type::getMixed();
                } else {
                    $stmt->inferredType = clone $context->vars_in_scope[$var_name];
                }
            } else {
                $stmt->inferredType = Type::getMixed();
            }

            return null;
        }

        if (in_array(
            $stmt->name,
            [
                'GLOBALS',
                '_SERVER',
                '_GET',
                '_POST',
                '_FILES',
                '_COOKIE',
                '_SESSION',
                '_REQUEST',
                '_ENV',
            ],
            true
        )
        ) {
            $stmt->inferredType = Type::getArray();

            return null;
        }

        if (!is_string($stmt->name)) {
            return ExpressionChecker::analyze($statements_checker, $stmt->name, $context);
        }

        if ($passed_by_reference && $by_ref_type) {
            ExpressionChecker::assignByRefParam($statements_checker, $stmt, $by_ref_type, $context);

            return null;
        }

        $var_name = '$' . $stmt->name;

        if (!$context->hasVariable($var_name)) {
            if (!isset($context->vars_possibly_in_scope[$var_name]) ||
                !$statements_checker->getFirstAppearance($var_name)
            ) {
                if ($array_assignment) {
                    // if we're in an array assignment, let's assign the variable
                    // because PHP allows it

                    $context->vars_in_scope[$var_name] = Type::getArray();
                    $context->vars_possibly_in_scope[$var_name] = true;

                    // it might have been defined first in another if/else branch
                    if (!$statements_checker->hasVariable($var_name)) {
                        $statements_checker->registerVariable(
                            $var_name,
                            new CodeLocation($statements_checker, $stmt)
                        );
                    }
                } elseif (!$context->inside_isset) {
                    if ($context->is_global) {
                        if (IssueBuffer::accepts(
                            new UndefinedGlobalVariable(
                                'Cannot find referenced variable ' . $var_name . ' in global scope',
                                new CodeLocation($statements_checker->getSource(), $stmt)
                            ),
                            $statements_checker->getSuppressedIssues()
                        )) {
                            return false;
                        }

                        $stmt->inferredType = Type::getMixed();

                        return null;
                    }

                    IssueBuffer::add(
                        new UndefinedVariable(
                            'Cannot find referenced variable ' . $var_name,
                            new CodeLocation($statements_checker->getSource(), $stmt)
                        )
                    );

                    $stmt->inferredType = Type::getMixed();

                    return false;
                }
            }

            $first_appearance = $statements_checker->getFirstAppearance($var_name);

            if ($first_appearance && !$context->inside_isset) {
                if ($context->is_global) {
                    if (IssueBuffer::accepts(
                        new PossiblyUndefinedGlobalVariable(
                            'Possibly undefined global variable ' . $var_name . ', first seen on line ' .
                                $first_appearance->getLineNumber(),
                            new CodeLocation($statements_checker->getSource(), $stmt)
                        ),
                        $statements_checker->getSuppressedIssues()
                    )) {
                        return false;
                    }
                } else {
                    if (IssueBuffer::accepts(
                        new PossiblyUndefinedVariable(
                            'Possibly undefined variable ' . $var_name . ', first seen on line ' .
                                $first_appearance->getLineNumber(),
                            new CodeLocation($statements_checker->getSource(), $stmt)
                        ),
                        $statements_checker->getSuppressedIssues()
                    )) {
                        return false;
                    }
                }
            }
        } else {
            $stmt->inferredType = clone $context->vars_in_scope[$var_name];
        }

        return null;
    }
}