<?php
namespace GraphQL;

use GraphQL\Type\Descriptor;
use GraphQL\Type\Definition\AbstractType;
use GraphQL\Type\Definition\Directive;
use GraphQL\Type\Definition\InterfaceType;
use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;
use GraphQL\Type\Definition\UnionType;
use GraphQL\Type\Introspection;
use GraphQL\Utils\TypeInfo;
use GraphQL\Utils\Utils;

/**
 * Schema Definition
 *
 * A Schema is created by supplying the root types of each type of operation:
 * query, mutation (optional) and subscription (optional). A schema definition is
 * then supplied to the validator and executor.
 *
 * Example:
 *
 *     $schema = new GraphQL\Schema([
 *       'query' => $MyAppQueryRootType,
 *       'mutation' => $MyAppMutationRootType,
 *     ]);
 *
 * Note: If an array of `directives` are provided to GraphQL\Schema, that will be
 * the exact list of directives represented and allowed. If `directives` is not
 * provided then a default set of the specified directives (e.g. @include and
 * @skip) will be used. If you wish to provide *additional* directives to these
 * specified directives, you must explicitly declare them. Example:
 *
 *     $mySchema = new GraphQL\Schema([
 *       ...
 *       'directives' => array_merge(GraphQL::getInternalDirectives(), [ $myCustomDirective ]),
 *     ])
 *
 * @package GraphQL
 */
class Schema
{
    /**
     * @var Config
     */
    private $config;

    /**
     * Contains actual descriptor for this schema
     *
     * @var Descriptor
     */
    private $descriptor;

    /**
     * Contains currently resolved schema types
     *
     * @var Type[]
     */
    private $resolvedTypes = [];

    /**
     * True when $resolvedTypes contain all possible schema types
     *
     * @var bool
     */
    private $fullyLoaded = false;

    /**
     * Schema constructor.
     *
     * @param array|Config $config
     */
    public function __construct($config = null)
    {
        if (func_num_args() > 1 || $config instanceof Type) {
            trigger_error(
                'GraphQL\Schema constructor expects config object now instead of types passed as arguments. '.
                'See https://github.com/webonyx/graphql-php/issues/36',
                E_USER_DEPRECATED
            );
            list($queryType, $mutationType, $subscriptionType) = func_get_args() + [null, null, null];

            $config = [
                'query' => $queryType,
                'mutation' => $mutationType,
                'subscription' => $subscriptionType
            ];
        }
        if (is_array($config)) {
            $config = Config::create($config);
        }

        Utils::invariant(
            $config instanceof Config,
            'Schema constructor expects instance of GraphQL\Schema\Config or an array with keys: %s; but got: %s',
            implode(', ', [
                'query',
                'mutation',
                'subscription',
                'types',
                'directives',
                'typeLoader',
                'descriptor'
            ]),
            Utils::getVariableType($config)
        );

        Utils::invariant(
            $config->query instanceof ObjectType,
            "Schema query must be Object Type but got: " . Utils::getVariableType($config->query)
        );

        $this->config = $config;
    }

    /**
     * Returns schema query type
     *
     * @return ObjectType
     */
    public function getQueryType()
    {
        return $this->config->query;
    }

    /**
     * Returns schema mutation type
     *
     * @return ObjectType|null
     */
    public function getMutationType()
    {
        return $this->config->mutation;
    }

    /**
     * Returns schema subscription
     *
     * @return ObjectType|null
     */
    public function getSubscriptionType()
    {
        return $this->config->subscription;
    }

    /**
     * @return Config
     */
    public function getConfig()
    {
        return $this->config;
    }

    /**
     * Returns array of all types in this schema. Keys of this array represent type names, values are instances
     * of corresponding type definitions
     *
     * @return Type[]
     */
    public function getTypeMap()
    {
        if (!$this->fullyLoaded) {
            if ($this->config->descriptor && $this->config->typeLoader) {
                // Following is still faster than $this->collectAllTypes() because it won't init fields
                $typesToResolve = array_diff_key($this->config->descriptor->typeMap, $this->resolvedTypes);
                foreach ($typesToResolve as $typeName => $_) {
                    $this->resolvedTypes[$typeName] = $this->loadType($typeName);
                }
            } else {
                $this->resolvedTypes = $this->collectAllTypes();
            }
            $this->fullyLoaded = true;
        }
        return $this->resolvedTypes;
    }

    /**
     * Returns type by it's name
     *
     * @param string $name
     * @return Type
     */
    public function getType($name)
    {
        return $this->resolveType($name);
    }

    /**
     * Returns serializable schema descriptor which can be passed later
     * to Schema config to enable a set of performance optimizations
     *
     * @return Descriptor
     */
    public function describe()
    {
        if ($this->descriptor) {
            return $this->descriptor;
        }

        $this->resolvedTypes = $this->collectAllTypes();
        $this->fullyLoaded = true;

        $descriptor = new Descriptor();
        $descriptor->version = '1.0';
        $descriptor->created = time();

        foreach ($this->resolvedTypes as $type) {
            if ($type instanceof ObjectType) {
                foreach ($type->getInterfaces() as $interface) {
                    $descriptor->possibleTypeMap[$interface->name][$type->name] = 1;
                }
            } else if ($type instanceof UnionType) {
                foreach ($type->getTypes() as $innerType) {
                    $descriptor->possibleTypeMap[$type->name][$innerType->name] = 1;
                }
            }
            $descriptor->typeMap[$type->name] = 1;
        }

        return $this->descriptor = $descriptor;
    }

    private function collectAllTypes()
    {
        $initialTypes = [
            $this->config->query,
            $this->config->mutation,
            $this->config->subscription,
            Introspection::_schema()
        ];
        if (!empty($this->config->types)) {
            $initialTypes = array_merge($initialTypes, $this->config->types);
        }
        $typeMap = [];
        foreach ($initialTypes as $type) {
            $typeMap = TypeInfo::extractTypes($type, $typeMap);
        }
        return $typeMap + Type::getInternalTypes();
    }

    /**
     * Returns all possible concrete types for given abstract type
     * (implementations for interfaces and members of union type for unions)
     *
     * @param AbstractType $abstractType
     * @return ObjectType[]
     */
    public function getPossibleTypes(AbstractType $abstractType)
    {
        if ($abstractType instanceof UnionType) {
            return $abstractType->getTypes();
        }

        /** @var InterfaceType $abstractType */
        $descriptor = $this->config->descriptor ?: $this->describe();

        $result = [];
        if (isset($descriptor->possibleTypeMap[$abstractType->name])) {
            foreach ($descriptor->possibleTypeMap[$abstractType->name] as $typeName => $_) {
                $result[] = $this->resolveType($typeName);
            }
        }
        return $result;
    }

    /**
     * Accepts name of type or type instance and returns type instance. If type with given name is not loaded yet -
     * will load it first.
     *
     * @param $typeOrName
     * @return Type
     */
    public function resolveType($typeOrName)
    {
        if ($typeOrName instanceof Type) {
            if ($typeOrName->name && !isset($this->resolvedTypes[$typeOrName->name])) {
                $this->resolvedTypes[$typeOrName->name] = $typeOrName;
            }
            return $typeOrName;
        }
        if (!isset($this->resolvedTypes[$typeOrName])) {
            $this->resolvedTypes[$typeOrName] = $this->loadType($typeOrName);
        }
        return $this->resolvedTypes[$typeOrName];
    }

    private function loadType($typeName)
    {
        $typeLoader = $this->config->typeLoader;

        if (!$typeLoader) {
            return $this->defaultTypeLoader($typeName);
        }

        $type = $typeLoader($typeName);
        // TODO: validate returned value
        return $type;
    }

    /**
     * Returns true if object type is concrete type of given abstract type
     * (implementation for interfaces and members of union type for unions)
     *
     * @param AbstractType $abstractType
     * @param ObjectType $possibleType
     * @return bool
     */
    public function isPossibleType(AbstractType $abstractType, ObjectType $possibleType)
    {
        if ($this->config->descriptor) {
            return !empty($this->config->descriptor->possibleTypeMap[$abstractType->name][$possibleType->name]);
        }

        if ($abstractType instanceof InterfaceType) {
            return $possibleType->implementsInterface($abstractType);
        }

        /** @var UnionType $abstractType */
        return $abstractType->isPossibleType($possibleType);
    }

    /**
     * Returns a list of directives supported by this schema
     *
     * @return Directive[]
     */
    public function getDirectives()
    {
        return $this->config->directives ?: GraphQL::getInternalDirectives();
    }

    /**
     * Returns instance of directive by name
     *
     * @param $name
     * @return Directive
     */
    public function getDirective($name)
    {
        foreach ($this->getDirectives() as $directive) {
            if ($directive->name === $name) {
                return $directive;
            }
        }
        return null;
    }

    /**
     * @param $typeName
     * @return Type
     */
    private function defaultTypeLoader($typeName)
    {
        // Default type loader simply fallbacks to collecting all types
        if (!$this->fullyLoaded) {
            $this->resolvedTypes = $this->collectAllTypes();
            $this->fullyLoaded = true;
        }
        if (!isset($this->resolvedTypes[$typeName])) {
            return null;
        }
        return $this->resolvedTypes[$typeName];
    }
}