<?php
namespace Psalm\Type;

use Psalm\Type\Atomic\TInt;
use Psalm\Type\Atomic\TScalar;
use function array_pop;
use function array_shift;
use function count;
use function explode;
use function implode;
use function ksort;
use Psalm\Codebase;
use Psalm\CodeLocation;
use Psalm\Internal\Analyzer\StatementsAnalyzer;
use Psalm\Internal\Type\AssertionReconciler;
use Psalm\Issue\DocblockTypeContradiction;
use Psalm\Issue\PsalmInternalError;
use Psalm\Issue\RedundantCondition;
use Psalm\Issue\RedundantConditionGivenDocblockType;
use Psalm\Issue\RedundantPropertyInitializationCheck;
use Psalm\Issue\TypeDoesNotContainNull;
use Psalm\Issue\TypeDoesNotContainType;
use Psalm\IssueBuffer;
use Psalm\Type;
use Psalm\Type\Atomic\TEmpty;
use Psalm\Type\Atomic\TMixed;
use Psalm\Type\Atomic\TNamedObject;
use Psalm\Type\Atomic\TNull;
use Psalm\Type\Atomic\TObject;
use Psalm\Type\Atomic\TString;
use Psalm\Type\Atomic\TTemplateParam;
use function str_replace;
use function str_split;
use function strpos;
use function strtolower;
use function substr;
use function preg_match;
use function preg_quote;
use function array_merge;

class Reconciler
{
    /** @var array<string, array<int, string>> */
    private static $broken_paths = [];

    /**
     * Takes two arrays and consolidates them, removing null values from existing types where applicable
     *
     * @param  array<string, array<array<int, string>>> $new_types
     * @param  array<string, array<array<int, string>>> $active_new_types - types we can complain about
     * @param  array<string, Type\Union> $existing_types
     * @param  array<string, bool>       $changed_var_ids
     * @param  array<string, bool>       $referenced_var_ids
     * @param  array<string, array<string, Type\Union>> $template_type_map
     *
     * @return array<string, Type\Union>
     */
    public static function reconcileKeyedTypes(
        array $new_types,
        array $active_new_types,
        array $existing_types,
        array &$changed_var_ids,
        array $referenced_var_ids,
        StatementsAnalyzer $statements_analyzer,
        array $template_type_map = [],
        bool $inside_loop = false,
        ?CodeLocation $code_location = null,
        bool $negated = false
    ): array {
        if (!$new_types) {
            return $existing_types;
        }

        $suppressed_issues = $statements_analyzer->getSuppressedIssues();

        $old_new_types = $new_types;

        $new_types = self::addNestedAssertions($new_types, $existing_types);

        // make sure array keys come after base keys
        ksort($new_types);

        $codebase = $statements_analyzer->getCodebase();

        foreach ($new_types as $key => $new_type_parts) {
            if (strpos($key, '::')
                && !strpos($key, '$')
                && !strpos($key, '[')
            ) {
                continue;
            }

            $has_negation = false;
            $has_isset = false;
            $has_inverted_isset = false;
            $has_falsyish = false;
            $has_empty = false;
            $has_count_check = false;
            $is_equality = ($old_new_types[$key] ?? null) === $new_type_parts;

            foreach ($new_type_parts as $new_type_part_parts) {
                foreach ($new_type_part_parts as $new_type_part_part) {
                    switch ($new_type_part_part[0]) {
                        case '!':
                            $has_negation = true;
                            break;
                    }

                    $has_isset = $has_isset
                        || $new_type_part_part === 'isset'
                        || $new_type_part_part === '=isset'
                        || $new_type_part_part === 'array-key-exists'
                        || $new_type_part_part === '=string-array-access';

                    $has_empty = $has_empty || $new_type_part_part === 'empty';

                    $has_falsyish = $has_falsyish
                        || $new_type_part_part === 'empty'
                        || $new_type_part_part === 'falsy';

                    $is_equality = $is_equality
                        && $new_type_part_part[0] === '='
                        && $new_type_part_part !== '=isset';

                    $has_inverted_isset = $has_inverted_isset || $new_type_part_part === '!isset';

                    $has_count_check = $has_count_check
                        || $new_type_part_part === 'non-empty-countable';
                }
            }

            $did_type_exist = isset($existing_types[$key]);

            $has_object_array_access = false;

            $result_type = isset($existing_types[$key])
                ? clone $existing_types[$key]
                : self::getValueForKey(
                    $codebase,
                    $key,
                    $existing_types,
                    $new_types,
                    $code_location,
                    $has_isset,
                    $has_inverted_isset,
                    $has_empty,
                    $inside_loop,
                    $has_object_array_access
                );

            if ($result_type && empty($result_type->getAtomicTypes())) {
                throw new \InvalidArgumentException('Union::$types cannot be empty after get value for ' . $key);
            }

            $before_adjustment = $result_type ? clone $result_type : null;

            $failed_reconciliation = 0;

            foreach ($new_type_parts as $offset => $new_type_part_parts) {
                $orred_type = null;

                foreach ($new_type_part_parts as $new_type_part_part) {
                    if ($new_type_part_part[0] === '>') {
                        /** @var array<string, array<int, array<int, string>>> */
                        $data = \json_decode(substr($new_type_part_part, 1), true);

                        $existing_types = self::reconcileKeyedTypes(
                            $data,
                            $data,
                            $existing_types,
                            $changed_var_ids,
                            $referenced_var_ids,
                            $statements_analyzer,
                            $template_type_map,
                            $inside_loop,
                            $code_location,
                            $negated
                        );

                        $new_type_part_part = '!falsy';
                    }

                    $result_type_candidate = AssertionReconciler::reconcile(
                        $new_type_part_part,
                        $result_type ? clone $result_type : null,
                        $key,
                        $statements_analyzer,
                        $inside_loop,
                        $template_type_map,
                        $code_location
                            && isset($referenced_var_ids[$key])
                            && isset($active_new_types[$key][$offset])
                            ? $code_location
                            : null,
                        $suppressed_issues,
                        $failed_reconciliation,
                        $negated
                    );

                    if (!$result_type_candidate->getAtomicTypes()) {
                        $result_type_candidate->addType(new TEmpty);
                    }

                    $orred_type = $orred_type
                        ? Type::combineUnionTypes(
                            $result_type_candidate,
                            $orred_type,
                            $codebase
                        )
                        : $result_type_candidate;
                }

                $result_type = $orred_type;
            }

            if (!$result_type) {
                throw new \UnexpectedValueException('$result_type should not be null');
            }

            if (!$did_type_exist && $result_type->isEmpty()) {
                continue;
            }

            if (($statements_analyzer->data_flow_graph instanceof \Psalm\Internal\Codebase\TaintFlowGraph
                    && (!$result_type->hasScalarType())
                        || ($result_type->hasString() && !$result_type->hasLiteralString()))
                || $statements_analyzer->data_flow_graph instanceof \Psalm\Internal\Codebase\VariableUseGraph
            ) {
                if ($before_adjustment && $before_adjustment->parent_nodes) {
                    $result_type->parent_nodes = $before_adjustment->parent_nodes;
                } elseif (!$did_type_exist && $code_location) {
                    $result_type->parent_nodes = $statements_analyzer->getParentNodesForPossiblyUndefinedVariable(
                        $key
                    );
                }
            }

            if ($before_adjustment && $before_adjustment->by_ref) {
                $result_type->by_ref = true;
            }

            $type_changed = !$before_adjustment || !$result_type->equals($before_adjustment);

            if ($type_changed || $failed_reconciliation) {
                $changed_var_ids[$key] = true;

                if (substr($key, -1) === ']' && !$has_inverted_isset && !$has_empty && !$is_equality) {
                    $key_parts = self::breakUpPathIntoParts($key);
                    self::adjustTKeyedArrayType(
                        $key_parts,
                        $existing_types,
                        $changed_var_ids,
                        $result_type
                    );
                } elseif ($key !== '$this') {
                    foreach ($existing_types as $new_key => $_) {
                        if ($new_key === $key) {
                            continue;
                        }

                        if (!isset($new_types[$new_key])
                            && preg_match('/' . preg_quote($key, '/') . '[\]\[\-]/', $new_key)
                        ) {
                            unset($existing_types[$new_key]);
                        }
                    }
                }
            } elseif (!$has_negation && !$has_falsyish && !$has_isset) {
                $changed_var_ids[$key] = true;
            }

            if ($failed_reconciliation === 2) {
                $result_type->failed_reconciliation = true;
            }

            if (!$has_object_array_access) {
                $existing_types[$key] = $result_type;
            }
        }

        return $existing_types;
    }

    /**
     * This generates a list of extra assertions for an assertion on a nested key.
     *
     * For example  ['$a[0]->foo->bar' => 'isset']
     *
     * generates the assertions
     *
     * [
     *     '$a' => '=int-or-string-array-access',
     *     '$a[0]' => '=isset',
     *     '$a[0]->foo' => '=isset',
     *     '$a[0]->foo->bar' => 'isset' // original assertion
     * ]
     *
     * @param array<string, array<array<int, string>>> $new_types
     * @param array<string, Type\Union> $existing_types
     *
     * @return array<string, array<array<int, string>>>
     */
    private static function addNestedAssertions(array $new_types, array $existing_types) : array
    {
        foreach ($new_types as $nk => $type) {
            if (strpos($nk, '[') || strpos($nk, '->')) {
                if ($type[0][0] === '=isset'
                    || $type[0][0] === '!=empty'
                    || $type[0][0] === 'isset'
                    || $type[0][0] === '!empty'
                ) {
                    $key_parts = Reconciler::breakUpPathIntoParts($nk);

                    if (!$key_parts) {
                        throw new \UnexpectedValueException('There should be some key parts');
                    }

                    $base_key = array_shift($key_parts);

                    if ($base_key[0] !== '$' && count($key_parts) > 2 && $key_parts[0] === '::$') {
                        $base_key .= array_shift($key_parts);
                        $base_key .= array_shift($key_parts);
                    }

                    if (!isset($existing_types[$base_key]) || $existing_types[$base_key]->isNullable()) {
                        if (!isset($new_types[$base_key])) {
                            $new_types[$base_key] = [['=isset']];
                        } else {
                            $new_types[$base_key][] = ['=isset'];
                        }
                    }

                    while ($key_parts) {
                        $divider = array_shift($key_parts);

                        if ($divider === '[') {
                            $array_key = array_shift($key_parts);
                            array_shift($key_parts);

                            $new_base_key = $base_key . '[' . $array_key . ']';

                            if (strpos($array_key, '\'') !== false) {
                                $new_types[$base_key][] = ['=string-array-access'];
                            } else {
                                $new_types[$base_key][] = ['=int-or-string-array-access'];
                            }

                            $base_key = $new_base_key;

                            continue;
                        }

                        if ($divider === '->') {
                            $property_name = array_shift($key_parts);
                            $new_base_key = $base_key . '->' . $property_name;

                            if (!isset($new_types[$base_key])) {
                                $new_types[$base_key] = [['=isset']];
                            }

                            $base_key = $new_base_key;
                        } else {
                            break;
                        }

                        if (!$key_parts) {
                            break;
                        }

                        if (!isset($new_types[$base_key])) {
                            $new_types[$base_key] = [['!~bool'], ['!~int'], ['=isset']];
                        } else {
                            $new_types[$base_key][] = ['!~bool'];
                            $new_types[$base_key][] = ['!~int'];
                            $new_types[$base_key][] = ['=isset'];
                        }
                    }
                }

                if ($type[0][0] === 'array-key-exists') {
                    $key_parts = Reconciler::breakUpPathIntoParts($nk);

                    if (count($key_parts) === 4
                        && $key_parts[1] === '['
                        && $key_parts[2][0] !== '\''
                        && !\is_numeric($key_parts[2])
                    ) {
                        if (isset($new_types[$key_parts[2]])) {
                            $new_types[$key_parts[2]][] = ['=in-array-' . $key_parts[0]];
                        } else {
                            $new_types[$key_parts[2]] = [['=in-array-' . $key_parts[0]]];
                        }

                        if ($key_parts[0][0] === '$') {
                            if (isset($new_types[$key_parts[0]])) {
                                $new_types[$key_parts[0]][] = ['=has-array-key-' . $key_parts[2]];
                            } else {
                                $new_types[$key_parts[0]] = [['=has-array-key-' . $key_parts[2]]];
                            }
                        }
                    }
                }
            }
        }

        return $new_types;
    }

    /**
     * @return array<int, string>
     */
    public static function breakUpPathIntoParts(string $path): array
    {
        if (isset(self::$broken_paths[$path])) {
            return self::$broken_paths[$path];
        }

        $chars = str_split($path);

        $string_char = null;
        $escape_char = false;
        $brackets = 0;

        $parts = [''];
        $parts_offset = 0;

        for ($i = 0, $char_count = count($chars); $i < $char_count; ++$i) {
            $char = $chars[$i];

            if ($string_char) {
                if ($char === $string_char && !$escape_char) {
                    $string_char = null;
                }

                if ($char === '\\') {
                    $escape_char = !$escape_char;
                }

                $parts[$parts_offset] .= $char;
                continue;
            }

            switch ($char) {
                case '[':
                case ']':
                    $parts_offset++;
                    $parts[$parts_offset] = $char;
                    ++$parts_offset;

                    if ($char === '[') {
                        $brackets++;
                    } else {
                        $brackets--;
                    }

                    continue 2;

                case '\'':
                case '"':
                    if (!isset($parts[$parts_offset])) {
                        $parts[$parts_offset] = '';
                    }
                    $parts[$parts_offset] .= $char;
                    $string_char = $char;

                    continue 2;

                case ':':
                    if (!$brackets
                        && $i < $char_count - 2
                        && $chars[$i + 1] === ':'
                        && $chars[$i + 2] === '$'
                    ) {
                        ++$i;
                        ++$i;

                        ++$parts_offset;
                        $parts[$parts_offset] = '::$';
                        ++$parts_offset;
                        continue 2;
                    }
                    // fall through

                case '-':
                    if (!$brackets
                        && $i < $char_count - 1
                        && $chars[$i + 1] === '>'
                    ) {
                        ++$i;

                        ++$parts_offset;
                        $parts[$parts_offset] = '->';
                        ++$parts_offset;
                        continue 2;
                    }
                    // fall through

                    // no break
                default:
                    if (!isset($parts[$parts_offset])) {
                        $parts[$parts_offset] = '';
                    }
                    $parts[$parts_offset] .= $char;
            }
        }

        $parts = \array_values($parts);

        self::$broken_paths[$path] = $parts;

        return $parts;
    }

    /**
     * Gets the type for a given (non-existent key) based on the passed keys
     *
     * @param array<string,Type\Union>  $existing_keys
     * @param array<string,mixed>       $new_assertions
     */
    private static function getValueForKey(
        Codebase $codebase,
        string $key,
        array &$existing_keys,
        array $new_assertions,
        ?CodeLocation $code_location,
        bool $has_isset,
        bool $has_inverted_isset,
        bool $has_empty,
        bool $inside_loop,
        bool &$has_object_array_access
    ): ?Union {
        $key_parts = self::breakUpPathIntoParts($key);

        if (count($key_parts) === 1) {
            return isset($existing_keys[$key_parts[0]]) ? clone $existing_keys[$key_parts[0]] : null;
        }

        $base_key = array_shift($key_parts);

        if ($base_key === 'C::A' && isset($existing_keys[$base_key]) && $existing_keys[$base_key]->isMixed()) {
            throw new \Exception("Error Processing Request", 1);
        }

        if ($base_key[0] !== '$' && count($key_parts) > 2 && $key_parts[0] === '::$') {
            $base_key .= array_shift($key_parts);
            $base_key .= array_shift($key_parts);
        }

        if (!isset($existing_keys[$base_key])) {
            if (strpos($base_key, '::')) {
                [$fq_class_name, $const_name] = explode('::', $base_key);

                if (!$codebase->classlikes->classOrInterfaceExists($fq_class_name)) {
                    return null;
                }

                $class_constant = $codebase->classlikes->getClassConstantType(
                    $fq_class_name,
                    $const_name,
                    \ReflectionProperty::IS_PRIVATE,
                    null
                );

                if ($class_constant) {
                    $existing_keys[$base_key] = clone $class_constant;
                } else {
                    return null;
                }
            } else {
                return null;
            }
        }

        while ($key_parts) {
            $divider = array_shift($key_parts);

            if ($divider === '[') {
                $array_key = array_shift($key_parts);
                array_shift($key_parts);

                $new_base_key = $base_key . '[' . $array_key . ']';

                if (!isset($existing_keys[$new_base_key])) {
                    $new_base_type = null;

                    $atomic_types = $existing_keys[$base_key]->getAtomicTypes();

                    while ($atomic_types) {
                        $existing_key_type_part = array_shift($atomic_types);

                        if ($existing_key_type_part instanceof TTemplateParam) {
                            $atomic_types = array_merge($atomic_types, $existing_key_type_part->as->getAtomicTypes());
                            continue;
                        }

                        if ($existing_key_type_part instanceof Type\Atomic\TArray) {
                            if ($has_empty) {
                                return null;
                            }

                            $new_base_type_candidate = clone $existing_key_type_part->type_params[1];

                            if ($new_base_type_candidate->isMixed() && !$has_isset && !$has_inverted_isset) {
                                return $new_base_type_candidate;
                            }

                            if (($has_isset || $has_inverted_isset) && isset($new_assertions[$new_base_key])) {
                                if ($has_inverted_isset && $new_base_key === $key) {
                                    $new_base_type_candidate->addType(new Type\Atomic\TNull);
                                }

                                $new_base_type_candidate->possibly_undefined = true;
                            }
                        } elseif ($existing_key_type_part instanceof Type\Atomic\TList) {
                            if ($has_empty) {
                                return null;
                            }

                            $new_base_type_candidate = clone $existing_key_type_part->type_param;

                            if (($has_isset || $has_inverted_isset) && isset($new_assertions[$new_base_key])) {
                                if ($has_inverted_isset && $new_base_key === $key) {
                                    $new_base_type_candidate->addType(new Type\Atomic\TNull);
                                }

                                $new_base_type_candidate->possibly_undefined = true;
                            }
                        } elseif ($existing_key_type_part instanceof Type\Atomic\TNull
                            || $existing_key_type_part instanceof Type\Atomic\TFalse
                        ) {
                            $new_base_type_candidate = Type::getNull();

                            if ($existing_keys[$base_key]->ignore_nullable_issues) {
                                $new_base_type_candidate->ignore_nullable_issues = true;
                            }
                        } elseif ($existing_key_type_part instanceof Type\Atomic\TClassStringMap) {
                            return Type::getMixed();
                        } elseif ($existing_key_type_part instanceof Type\Atomic\TEmpty
                            || ($existing_key_type_part instanceof Type\Atomic\TMixed
                                && $existing_key_type_part->from_loop_isset)
                        ) {
                            return Type::getMixed($inside_loop);
                        } elseif ($existing_key_type_part instanceof TString) {
                            $new_base_type_candidate = Type::getString();
                        } elseif ($existing_key_type_part instanceof Type\Atomic\TNamedObject
                            && ($has_isset || $has_inverted_isset)
                        ) {
                            $has_object_array_access = true;

                            unset($existing_keys[$new_base_key]);

                            return null;
                        } elseif (!$existing_key_type_part instanceof Type\Atomic\TKeyedArray) {
                            return Type::getMixed();
                        } elseif ($array_key[0] === '$' || ($array_key[0] !== '\'' && !\is_numeric($array_key[0]))) {
                            if ($has_empty) {
                                return null;
                            }

                            $new_base_type_candidate = $existing_key_type_part->getGenericValueType();
                        } else {
                            $array_properties = $existing_key_type_part->properties;

                            $key_parts_key = str_replace('\'', '', $array_key);

                            if (!isset($array_properties[$key_parts_key])) {
                                if ($existing_key_type_part->previous_value_type) {
                                    $new_base_type_candidate = clone $existing_key_type_part->previous_value_type;
                                    $new_base_type_candidate->different = true;
                                } else {
                                    return null;
                                }
                            } else {
                                $new_base_type_candidate = clone $array_properties[$key_parts_key];
                            }
                        }

                        if (!$new_base_type) {
                            $new_base_type = $new_base_type_candidate;
                        } else {
                            $new_base_type = Type::combineUnionTypes(
                                $new_base_type,
                                $new_base_type_candidate,
                                $codebase
                            );
                        }

                        $existing_keys[$new_base_key] = $new_base_type;
                    }
                }

                $base_key = $new_base_key;
            } elseif ($divider === '->' || $divider === '::$') {
                $property_name = array_shift($key_parts);
                $new_base_key = $base_key . $divider . $property_name;

                if (!isset($existing_keys[$new_base_key])) {
                    $new_base_type = null;

                    $atomic_types = $existing_keys[$base_key]->getAtomicTypes();

                    while ($atomic_types) {
                        $existing_key_type_part = array_shift($atomic_types);

                        if ($existing_key_type_part instanceof TTemplateParam) {
                            $atomic_types = array_merge($atomic_types, $existing_key_type_part->as->getAtomicTypes());
                            continue;
                        }

                        if ($existing_key_type_part instanceof TNull) {
                            $class_property_type = Type::getNull();
                        } elseif ($existing_key_type_part instanceof TMixed
                            || $existing_key_type_part instanceof TTemplateParam
                            || $existing_key_type_part instanceof TObject
                            || ($existing_key_type_part instanceof TNamedObject
                                && strtolower($existing_key_type_part->value) === 'stdclass')
                        ) {
                            $class_property_type = Type::getMixed();
                        } elseif ($existing_key_type_part instanceof TNamedObject) {
                            if (!$codebase->classOrInterfaceExists($existing_key_type_part->value)) {
                                $class_property_type = Type::getMixed();
                            } else {
                                if (substr($property_name, -2) === '()') {
                                    $method_id = new \Psalm\Internal\MethodIdentifier(
                                        $existing_key_type_part->value,
                                        strtolower(substr($property_name, 0, -2))
                                    );

                                    if (!$codebase->methods->methodExists($method_id)) {
                                        return null;
                                    }

                                    $declaring_method_id = $codebase->methods->getDeclaringMethodId(
                                        $method_id
                                    );

                                    if ($declaring_method_id === null) {
                                        return null;
                                    }

                                    $declaring_class = $declaring_method_id->fq_class_name;

                                    $method_return_type = $codebase->methods->getMethodReturnType(
                                        $method_id,
                                        $declaring_class,
                                        null,
                                        null
                                    );

                                    if ($method_return_type) {
                                        $class_property_type = \Psalm\Internal\Type\TypeExpander::expandUnion(
                                            $codebase,
                                            clone $method_return_type,
                                            $declaring_class,
                                            $declaring_class,
                                            null
                                        );
                                    } else {
                                        $class_property_type = Type::getMixed();
                                    }
                                } else {
                                    $class_property_type = self::getPropertyType(
                                        $codebase,
                                        $existing_key_type_part->value,
                                        $property_name
                                    );

                                    if (!$class_property_type) {
                                        return null;
                                    }
                                }
                            }
                        } else {
                            $class_property_type = Type::getMixed();
                        }

                        if ($new_base_type instanceof Type\Union) {
                            $new_base_type = Type::combineUnionTypes(
                                $new_base_type,
                                $class_property_type,
                                $codebase
                            );
                        } else {
                            $new_base_type = $class_property_type;
                        }

                        $existing_keys[$new_base_key] = $new_base_type;
                    }
                }

                $base_key = $new_base_key;
            } else {
                return null;
            }
        }

        if (!isset($existing_keys[$base_key])) {
            if ($code_location) {
                IssueBuffer::add(
                    new PsalmInternalError(
                        'Unknown key ' . $base_key,
                        $code_location
                    )
                );
            }

            return null;
        }

        return $existing_keys[$base_key];
    }

    private static function getPropertyType(
        Codebase $codebase,
        string $fq_class_name,
        string $property_name
    ) : ?Type\Union {
        $property_id = $fq_class_name . '::$' . $property_name;

        if (!$codebase->properties->propertyExists($property_id, true)) {
            $declaring_class_storage = $codebase->classlike_storage_provider->get(
                $fq_class_name
            );

            if (isset($declaring_class_storage->pseudo_property_get_types['$' . $property_name])) {
                return clone $declaring_class_storage->pseudo_property_get_types['$' . $property_name];
            }

            return null;
        }

        $declaring_property_class = $codebase->properties->getDeclaringClassForProperty(
            $property_id,
            true
        );

        if ($declaring_property_class === null) {
            return null;
        }

        $class_property_type = $codebase->properties->getPropertyType(
            $property_id,
            false,
            null,
            null
        );

        $declaring_class_storage = $codebase->classlike_storage_provider->get(
            $declaring_property_class
        );

        if ($class_property_type) {
            return \Psalm\Internal\Type\TypeExpander::expandUnion(
                $codebase,
                clone $class_property_type,
                $declaring_class_storage->name,
                $declaring_class_storage->name,
                null
            );
        }

        return Type::getMixed();
    }

    /**
     * @param  string[]     $suppressed_issues
     *
     */
    protected static function triggerIssueForImpossible(
        Union $existing_var_type,
        string $old_var_type_string,
        string $key,
        string $assertion,
        bool $redundant,
        bool $negated,
        CodeLocation $code_location,
        array $suppressed_issues
    ): void {
        $not = $assertion[0] === '!';

        if ($not) {
            $assertion = substr($assertion, 1);
        }

        if ($negated) {
            $redundant = !$redundant;
            $not = !$not;
        }

        $existing_var_atomic_types = $existing_var_type->getAtomicTypes();

        $from_docblock = $existing_var_type->from_docblock
            || (isset($existing_var_atomic_types[$assertion])
                && $existing_var_atomic_types[$assertion]->from_docblock);

        if ($redundant) {
            if ($existing_var_type->from_property && $assertion === 'isset') {
                if (IssueBuffer::accepts(
                    new RedundantPropertyInitializationCheck(
                        'Property type ' . $key . ' with type '
                            . $old_var_type_string . ' should already be set in the constructor',
                        $code_location
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            } elseif ($from_docblock) {
                if (IssueBuffer::accepts(
                    new RedundantConditionGivenDocblockType(
                        'Docblock-defined type ' . $old_var_type_string
                        . ' for ' . $key
                        . ' is ' . ($not ? 'never ' : 'always ') . $assertion,
                        $code_location,
                        $old_var_type_string . ' ' . $assertion
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            } else {
                if (IssueBuffer::accepts(
                    new RedundantCondition(
                        'Type ' . $old_var_type_string
                        . ' for ' . $key
                        . ' is ' . ($not ? 'never ' : 'always ') . $assertion,
                        $code_location,
                        $old_var_type_string . ' ' . $assertion
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            }
        } else {
            if ($from_docblock) {
                if (IssueBuffer::accepts(
                    new DocblockTypeContradiction(
                        'Docblock-defined type ' . $old_var_type_string
                            . ' for ' . $key
                            . ' is ' . ($not ? 'always ' : 'never ') . $assertion,
                        $code_location,
                        $old_var_type_string . ' ' . $assertion
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            } else {
                if ($assertion === 'null' && !$not) {
                    $issue = new TypeDoesNotContainNull(
                        'Type ' . $old_var_type_string
                            . ' for ' . $key
                            . ' is never ' . $assertion,
                        $code_location,
                        $old_var_type_string . ' ' . $assertion
                    );
                } else {
                    $issue = new TypeDoesNotContainType(
                        'Type ' . $old_var_type_string
                            . ' for ' . $key
                            . ' is ' . ($not ? 'always ' : 'never ') . $assertion,
                        $code_location,
                        $old_var_type_string . ' ' . $assertion
                    );
                }

                if (IssueBuffer::accepts(
                    $issue,
                    $suppressed_issues
                )) {
                    // fall through
                }
            }
        }
    }

    /**
     * @param  string[]                  $key_parts
     * @param  array<string,Type\Union>  $existing_types
     * @param  array<string, bool>       $changed_var_ids
     */
    private static function adjustTKeyedArrayType(
        array $key_parts,
        array &$existing_types,
        array &$changed_var_ids,
        Type\Union $result_type
    ): void {
        array_pop($key_parts);
        $array_key = array_pop($key_parts);
        array_pop($key_parts);

        if ($array_key === null) {
            throw new \UnexpectedValueException('Not expecting null array key');
        }

        if ($array_key[0] === '$') {
            return;
        }

        $array_key_offset = $array_key[0] === '\'' || $array_key[0] === '"' ? substr($array_key, 1, -1) : $array_key;

        $base_key = implode($key_parts);

        if (isset($existing_types[$base_key]) && $array_key_offset !== false) {
            foreach ($existing_types[$base_key]->getAtomicTypes() as $base_atomic_type) {
                if ($base_atomic_type instanceof Type\Atomic\TKeyedArray
                    || ($base_atomic_type instanceof Type\Atomic\TArray
                        && !$base_atomic_type->type_params[1]->isEmpty())
                    || $base_atomic_type instanceof Type\Atomic\TList
                    || $base_atomic_type instanceof Type\Atomic\TClassStringMap
                ) {
                    $new_base_type = clone $existing_types[$base_key];

                    if ($base_atomic_type instanceof Type\Atomic\TArray) {
                        $previous_key_type = clone $base_atomic_type->type_params[0];
                        $previous_value_type = clone $base_atomic_type->type_params[1];

                        $base_atomic_type = new Type\Atomic\TKeyedArray(
                            [
                                $array_key_offset => clone $result_type,
                            ],
                            null
                        );

                        if (!$previous_key_type->isEmpty()) {
                            $base_atomic_type->previous_key_type = $previous_key_type;
                        }
                        $base_atomic_type->previous_value_type = $previous_value_type;
                    } elseif ($base_atomic_type instanceof Type\Atomic\TList) {
                        $previous_key_type = Type::getInt();
                        $previous_value_type = clone $base_atomic_type->type_param;

                        $base_atomic_type = new Type\Atomic\TKeyedArray(
                            [
                                $array_key_offset => clone $result_type,
                            ],
                            null
                        );

                        $base_atomic_type->is_list = true;

                        $base_atomic_type->previous_key_type = $previous_key_type;
                        $base_atomic_type->previous_value_type = $previous_value_type;
                    } elseif ($base_atomic_type instanceof Type\Atomic\TClassStringMap) {
                        // do nothing
                    } else {
                        $base_atomic_type = clone $base_atomic_type;
                        $base_atomic_type->properties[$array_key_offset] = clone $result_type;
                    }

                    $new_base_type->addType($base_atomic_type);

                    $changed_var_ids[$base_key . '[' . $array_key . ']'] = true;

                    if ($key_parts[count($key_parts) - 1] === ']') {
                        self::adjustTKeyedArrayType(
                            $key_parts,
                            $existing_types,
                            $changed_var_ids,
                            $new_base_type
                        );
                    }

                    $existing_types[$base_key] = $new_base_type;
                    break;
                }
            }
        }
    }

    protected static function refineArrayKey(Union $key_type) : void
    {
        foreach ($key_type->getAtomicTypes() as $key => $cat) {
            if ($cat instanceof TTemplateParam) {
                self::refineArrayKey($cat->as);
                $key_type->bustCache();
            } elseif ($cat instanceof TScalar || $cat instanceof TMixed) {
                $key_type->removeType($key);
                $key_type->addType(new Type\Atomic\TArrayKey());
            } elseif (!$cat instanceof TString && !$cat instanceof TInt) {
                $key_type->removeType($key);
                $key_type->addType(new Type\Atomic\TArrayKey());
            }
        }

        if (!$key_type->getAtomicTypes()) {
            // this should ideally prompt some sort of error
            $key_type->addType(new Type\Atomic\TArrayKey());
        }
    }
}
