<?php
namespace GraphQL\Server;

use GraphQL\Error\Error;
use GraphQL\Error\FormattedError;
use GraphQL\Error\InvariantViolation;
use GraphQL\Executor\ExecutionResult;
use GraphQL\Executor\Executor;
use GraphQL\Executor\Promise\Adapter\SyncPromiseAdapter;
use GraphQL\Executor\Promise\Promise;
use GraphQL\Executor\Promise\PromiseAdapter;
use GraphQL\Language\AST\DocumentNode;
use GraphQL\Language\Parser;
use GraphQL\Utils\AST;
use GraphQL\Utils\Utils;
use GraphQL\Validator\DocumentValidator;

/**
 * Class Helper
 * Contains functionality that could be re-used by various server implementations
 *
 * @package GraphQL\Server
 */
class Helper
{
    /**
     * Executes GraphQL operation with given server configuration and returns execution result
     * (or promise when promise adapter is different from SyncPromiseAdapter)
     *
     * @param ServerConfig $config
     * @param OperationParams $op
     *
     * @return ExecutionResult|Promise
     */
    public function executeOperation(ServerConfig $config, OperationParams $op)
    {
        $promiseAdapter = $config->getPromiseAdapter() ?: Executor::getPromiseAdapter();
        $result = $this->promiseToExecuteOperation($promiseAdapter, $config, $op);

        if ($promiseAdapter instanceof SyncPromiseAdapter) {
            $result = $promiseAdapter->wait($result);
        }

        return $result;
    }

    /**
     * Executes batched GraphQL operations with shared promise queue
     * (thus, effectively batching deferreds|promises of all queries at once)
     *
     * @param ServerConfig $config
     * @param OperationParams[] $operations
     * @return ExecutionResult[]|Promise
     */
    public function executeBatch(ServerConfig $config, array $operations)
    {
        $promiseAdapter = $config->getPromiseAdapter() ?: Executor::getPromiseAdapter();
        $result = [];

        foreach ($operations as $operation) {
            $result[] = $this->promiseToExecuteOperation($promiseAdapter, $config, $operation);
        }

        $result = $promiseAdapter->all($result);

        // Wait for promised results when using sync promises
        if ($promiseAdapter instanceof SyncPromiseAdapter) {
            $result = $promiseAdapter->wait($result);
        }
        return $result;
    }

    /**
     * @param PromiseAdapter $promiseAdapter
     * @param ServerConfig $config
     * @param OperationParams $op
     * @return Promise
     */
    private function promiseToExecuteOperation(PromiseAdapter $promiseAdapter, ServerConfig $config, OperationParams $op)
    {
        try {
            $errors = $this->validateOperationParams($op);

            if (!empty($errors)) {
                return $promiseAdapter->createFulfilled(
                    new ExecutionResult(null, $errors)
                );
            }

            $doc = $op->queryId ? static::loadPersistedQuery($config, $op) : $op->query;

            if (!$doc instanceof DocumentNode) {
                $doc = Parser::parse($doc);
            }
            if ($op->isReadOnly() && AST::getOperation($doc, $op->operation) !== 'query') {
                throw new Error("GET supports only query operation");
            }

            $validationErrors = DocumentValidator::validate(
                $config->getSchema(),
                $doc,
                $this->resolveValidationRules($config, $op)
            );

            if (!empty($validationErrors)) {
                $result = $promiseAdapter->createFulfilled(
                    new ExecutionResult(null, $validationErrors)
                );
            } else {
                $result = Executor::promiseToExecute(
                    $promiseAdapter,
                    $config->getSchema(),
                    $doc,
                    $config->getRootValue(),
                    $config->getContext(),
                    $op->variables,
                    $op->operation,
                    $config->getDefaultFieldResolver()
                );
            }
        } catch (Error $e) {
            $result = $promiseAdapter->createFulfilled(
                new ExecutionResult(null, [$e])
            );
        }

        $applyErrorFormatting = function (ExecutionResult $result) use ($config) {
            if ($config->getDebug()) {
                $errorFormatter = function($e) {
                    return FormattedError::createFromException($e, true);
                };
            } else {
                $errorFormatter = $config->getErrorFormatter();
            }
            $result->setErrorFormatter($errorFormatter);
            return $result;
        };

        return $result->then($applyErrorFormatting);
    }

    /**
     * @param ServerConfig $config
     * @param OperationParams $op
     * @return mixed
     * @throws Error
     * @throws InvariantViolation
     */
    public function loadPersistedQuery(ServerConfig $config, OperationParams $op)
    {
        if (!$op->queryId) {
            throw new InvariantViolation("Could not load persisted query: queryId is not set");
        }

        // Load query if we got persisted query id:
        $loader = $config->getPersistentQueryLoader();

        if (!$loader) {
            throw new Error("Persisted queries are not supported by this server");
        }

        $source = $loader($op->queryId, $op);

        if (!is_string($source) && !$source instanceof DocumentNode) {
            throw new InvariantViolation(sprintf(
                "Persistent query loader must return query string or instance of %s but got: %s",
                DocumentNode::class,
                Utils::printSafe($source)
            ));
        }

        return $source;
    }

    /**
     * @param ServerConfig $config
     * @param OperationParams $params
     * @return array
     */
    public function resolveValidationRules(ServerConfig $config, OperationParams $params)
    {
        // Allow customizing validation rules per operation:
        $validationRules = $config->getValidationRules();

        if (is_callable($validationRules)) {
            $validationRules = $validationRules($params);

            if (!is_array($validationRules)) {
                throw new InvariantViolation(sprintf(
                    "Expecting validation rules to be array or callable returning array, but got: %s",
                    Utils::printSafe($validationRules)
                ));
            }
        }

        return $validationRules;
    }

    /**
     * Parses HTTP request and returns GraphQL QueryParams contained in this request.
     * For batched requests it returns an array of QueryParams.
     *
     * This function doesn't check validity of these params.
     *
     * If $readRawBodyFn argument is not provided - will attempt to read raw request body from php://input stream
     *
     * @param callable|null $readRawBodyFn
     * @return OperationParams|OperationParams[]
     * @throws Error
     */
    public function parseHttpRequest(callable $readRawBodyFn = null)
    {
        $method = isset($_SERVER['REQUEST_METHOD']) ? $_SERVER['REQUEST_METHOD'] : null;

        if ($method === 'GET') {
            $result = OperationParams::create($_GET, true);
        } else if ($method === 'POST') {
            $contentType = isset($_SERVER['CONTENT_TYPE']) ? $_SERVER['CONTENT_TYPE'] : null;

            if (stripos($contentType, 'application/graphql') !== false) {
                $rawBody =  $readRawBodyFn ? $readRawBodyFn() : $this->readRawBody();
                $result = OperationParams::create(['query' => $rawBody ?: '']);
            } else if (stripos($contentType, 'application/json') !== false) {
                $rawBody = $readRawBodyFn ? $readRawBodyFn() : $this->readRawBody();
                $body = json_decode($rawBody ?: '', true);

                if (json_last_error()) {
                    throw new Error("Could not parse JSON: " . json_last_error_msg());
                }
                if (!is_array($body)) {
                    throw new Error(
                        "GraphQL Server expects JSON object or array, but got " .
                        Utils::printSafeJson($body)
                    );
                }
                if (isset($body[0])) {
                    $result = [];
                    foreach ($body as $index => $entry) {
                        $op = OperationParams::create($entry);
                        $result[] = $op;
                    }
                } else {
                    $result = OperationParams::create($body);
                }
            } else if (stripos($contentType, 'application/x-www-form-urlencoded') !== false) {
                $result = OperationParams::create($_POST);
            } else if (null === $contentType) {
                throw new Error('Missing "Content-Type" header');
            } else {
                throw new Error("Unexpected content type: " . Utils::printSafeJson($contentType));
            }
        } else {
            throw new Error('HTTP Method "' . $method . '" is not supported');
        }
        return $result;
    }

    /**
     * @return bool|string
     */
    public function readRawBody()
    {
        return file_get_contents('php://input');
    }

    /**
     * Checks validity of operation params and returns array of errors (empty array when params are valid)
     *
     * @param OperationParams $params
     * @return Error[]
     */
    public function validateOperationParams(OperationParams $params)
    {
        $errors = [];
        if (!$params->query && !$params->queryId) {
            $errors[] = new Error('GraphQL Request must include at least one of those two parameters: "query" or "queryId"');
        }
        if ($params->query && $params->queryId) {
            $errors[] = new Error('GraphQL Request parameters "query" and "queryId" are mutually exclusive');
        }

        if ($params->query !== null && (!is_string($params->query) || empty($params->query))) {
            $errors[] = new Error(
                'GraphQL Request parameter "query" must be string, but got ' .
                Utils::printSafeJson($params->query)
            );
        }
        if ($params->queryId !== null && (!is_string($params->queryId) || empty($params->queryId))) {
            $errors[] = new Error(
                'GraphQL Request parameter "queryId" must be string, but got ' .
                Utils::printSafeJson($params->queryId)
            );
        }

        if ($params->operation !== null && (!is_string($params->operation) || empty($params->operation))) {
            $errors[] = new Error(
                'GraphQL Request parameter "operation" must be string, but got ' .
                Utils::printSafeJson($params->operation)
            );
        }
        if ($params->variables !== null && (!is_array($params->variables) || isset($params->variables[0]))) {
            $errors[] = new Error(
                'GraphQL Request parameter "variables" must be object or JSON string parsed to object, but got ' .
                Utils::printSafeJson($params->getOriginalInput('variables'))
            );
        }
        return $errors;
    }
}