<?php

namespace gullevek\AmazonIncentives\AWS;

use gullevek\AmazonIncentives\Client\Client;
use gullevek\AmazonIncentives\Config\Config;
use gullevek\AmazonIncentives\Exceptions\AmazonErrors;
use gullevek\AmazonIncentives\Debug\AmazonDebug;
use gullevek\AmazonIncentives\Response\CancelResponse;
use gullevek\AmazonIncentives\Response\CreateBalanceResponse;
use gullevek\AmazonIncentives\Response\CreateResponse;

class AWS
{
	/** @var string What AWS Service to use: Gift Card on Demand (GCOD) */
	public const SERVICE_NAME = 'AGCODService';
	/** @var string */
	public const ACCEPT_HEADER = 'accept';
	/** @var string content-type */
	public const CONTENT_HEADER = 'content-type';
	/** @var string */
	public const HOST_HEADER = 'host';
	/** @var string */
	public const X_AMZ_DATE_HEADER = 'x-amz-date';
	/** @var string */
	public const X_AMZ_TARGET_HEADER = 'x-amz-target';
	/** @var string */
	public const AUTHORIZATION_HEADER = 'Authorization';
	/** @var string type of encryption type */
	public const AWS_SHA256_ALGORITHM = 'AWS4-HMAC-SHA256';
	/** @var string key type to use */
	public const KEY_QUALIFIER = 'AWS4';
	/** @var string */
	public const TERMINATION_STRING = 'aws4_request';
	/** @var string Service to use: Create Gift Card */
	public const CREATE_GIFT_CARD_SERVICE = 'CreateGiftCard';
	/** @var string Service to use: Cancle Gift Card */
	public const CANCEL_GIFT_CARD_SERVICE = 'CancelGiftCard';
	/** @var string Service to use: Get Available Funds */
	public const GET_AVAILABLE_FUNDS_SERVICE = 'GetAvailableFunds';

	/** @var Config Configuration class with all settings */
	private $config;

	/**
	 * Initialize the main AWS class. This class prepares and sends all the actions
	 * and returns reponses as defined in in the CreateResponse class
	 *
	 * @param Config $config
	 */
	public function __construct(Config $config)
	{
		$this->config = $config;
		AmazonDebug::writeLog([__METHOD__ => date('Y-m-d H:m:s.u')]);
	}

	/**
	 * Bug a gift card
	 *
	 * @param  float          $amount      Amount to buy a gifr card in set currencty
	 * @param  string|null    $creation_id Override creation id, if not set will
	 *                                     be created automatically. If not valid error
	 *                                     will be thrown
	 * @return CreateResponse              Object with AWS response data
	 *
	 * @throws AmazonErrors
	 */
	public function getCode(float $amount, ?string $creation_id = null): CreateResponse
	{
		$service_operation = self::CREATE_GIFT_CARD_SERVICE;
		$payload = $this->getGiftCardPayload($amount, $creation_id);
		$canonical_request = $this->getCanonicalRequest($service_operation, $payload);
		$date_time_string = $this->getTimestamp();
		AmazonDebug::writeLog(['call' => __METHOD__]);
		$result = json_decode($this->makeRequest(
			$payload,
			$canonical_request,
			$service_operation,
			$date_time_string
		), true);
		return new CreateResponse($result);
	}

	/**
	 * Cancle an ordered gift card, only possible within the the time limit
	 *
	 * @param  string         $creation_request_id Previously created creation request id
	 * @param  string         $gift_card_id        Previously created gift card id
	 * @return CancelResponse                      Object with AWS response data
	 *
	 * @throws AmazonErrors
	 */
	public function cancelCode(string $creation_request_id, string $gift_card_id): CancelResponse
	{
		$service_operation = self::CANCEL_GIFT_CARD_SERVICE;
		$payload = $this->getCancelGiftCardPayload($creation_request_id, $gift_card_id);
		$canonical_request = $this->getCanonicalRequest($service_operation, $payload);
		$date_time_string = $this->getTimestamp();
		AmazonDebug::writeLog(['call' => __METHOD__]);
		$result = json_decode($this->makeRequest(
			$payload,
			$canonical_request,
			$service_operation,
			$date_time_string
		), true);
		return new CancelResponse($result);
	}

	/**
	 * Get current account funds
	 *
	 * @return CreateBalanceResponse Object with AWS response data
	 *
	 * @throws AmazonErrors
	 */
	public function getBalance(): CreateBalanceResponse
	{
		$service_operation = self::GET_AVAILABLE_FUNDS_SERVICE;
		$payload = $this->getAvailableFundsPayload();
		$canonical_request = $this->getCanonicalRequest($service_operation, $payload);
		$date_time_string = $this->getTimestamp();
		AmazonDebug::writeLog(['call' => __METHOD__]);
		$result = json_decode($this->makeRequest(
			$payload,
			$canonical_request,
			$service_operation,
			$date_time_string
		), true);
		return new CreateBalanceResponse($result);
	}

	/**
	 * General request method for all actions
	 * Calls the Client class that actually runs the json request
	 * For service_operation valid data see AWS GCOD documentation
	 *
	 * @param  string $payload           The data needed for this request
	 * @param  string $canonical_request Header data to send for this request
	 * @param  string $service_operation Service operation. CREATE_GIFT_CARD_SERVICE,
	 *                                   CANCEL_GIFT_CARD_SERVICE or
	 *                                   GET_AVAILABLE_FUNDS_SERVICE constant values
	 * @param  string $date_time_string  Ymd\THis\Z encoded timestamp, getTimestamp()
	 * @return string                    Request result as string, json data
	 */
	public function makeRequest(
		string $payload,
		string $canonical_request,
		string $service_operation,
		string $date_time_string
	): string {
		// debug
		AmazonDebug::writeLog([__METHOD__ => [
			'Operation' => $service_operation,
			'Payload' => $payload,
			'Cannonical Request' => $canonical_request,
			'Date Time String' => $date_time_string

		]]);
		$KEY_QUALIFIER = self::KEY_QUALIFIER;
		$canonical_request_hash = $this->buildHash($canonical_request);
		$string_to_sign = $this->buildStringToSign($canonical_request_hash);
		$authorization_value = $this->buildAuthSignature($string_to_sign);

		$secret_key = $this->config->getSecret();
		$endpoint = $this->config->getEndpoint();
		$region_name = $this->getRegion();

		$SERVICE_NAME = 'AGCODService';
		$service_target = 'com.amazonaws.agcod.' . $SERVICE_NAME . '.' . $service_operation;
		$date_string = $this->getDateString();

		$signature_aws_key = $KEY_QUALIFIER . $secret_key;

		$k_date = $this->hmac($date_string, $signature_aws_key);
		$k_date_hexis = $this->hmac($date_string, $signature_aws_key, false);
		$k_region = $this->hmac($region_name, $k_date);
		$k_region_hexis = $this->hmac($region_name, $k_date, false);
		$k_service_hexis = $this->hmac($SERVICE_NAME, $k_region, false);

		AmazonDebug::writeLog([__METHOD__ => [
			'Date' => $k_date_hexis,
			'Region' => $k_region_hexis,
			'Service' => $k_service_hexis,
		]]);

		$url = 'https://' . $endpoint . '/' . $service_operation;
		$headers = $this->buildHeaders(
			$payload,
			$authorization_value,
			$date_time_string,
			$service_target
		);
		return (new Client())->request($url, $headers, $payload);
	}

	/**
	 * Build the headers used in the makeRequest method.
	 * These are the HTML headers used with curl
	 *
	 * @param  string       $payload             Paylout to create this header for
	 * @param  string       $authorization_value Auth string
	 * @param  string       $date_time_string    Ymd\THis\Z encoded timestamp, getTimestamp()
	 * @param  string       $service_target      Target service in the agcod string:
	 *                                           Value like com.amazonaws.agcod.<sn>.<so>
	 * @return array<mixed>                      Header data as array for curl request
	 */
	public function buildHeaders(
		string $payload,
		string $authorization_value,
		string $date_time_string,
		string $service_target
	): array {
		$ACCEPT_HEADER = self::ACCEPT_HEADER;
		$X_AMZ_DATE_HEADER = self::X_AMZ_DATE_HEADER;
		$X_AMZ_TARGET_HEADER = self::X_AMZ_TARGET_HEADER;
		$AUTHORIZATION_HEADER = self::AUTHORIZATION_HEADER;
		return [
			'Content-Type:' . $this->getContentType(),
			'Content-Length: ' . strlen($payload),
			$AUTHORIZATION_HEADER . ':' . $authorization_value,
			$X_AMZ_DATE_HEADER . ':' . $date_time_string,
			$X_AMZ_TARGET_HEADER . ':' . $service_target,
			$ACCEPT_HEADER . ':' . $this->getContentType()
		];
	}

	/**
	 * The request string build with the actauly request data created by
	 * getCanonicalRequest(). This string is used in the auth signature call
	 *
	 * @param  string $canonical_request_hash sha256 hash to build from
	 * @return string                         String to send to buildAuthSignature()
	 */
	public function buildStringToSign($canonical_request_hash): string
	{
		$AWS_SHA256_ALGORITHM = self::AWS_SHA256_ALGORITHM;
		$TERMINATION_STRING = self::TERMINATION_STRING;
		$SERVICE_NAME = self::SERVICE_NAME;
		$region_name = $this->getRegion();
		$date_time_string = $this->getTimestamp();
		$date_string = $this->getDateString();
		$string_to_sign = "$AWS_SHA256_ALGORITHM\n"
			. "$date_time_string\n"
			. "$date_string/$region_name/$SERVICE_NAME/$TERMINATION_STRING\n"
			. "$canonical_request_hash";

		return $string_to_sign;
	}

	/**
	 * Build the authentication signature used in the buildHeaders method
	 *
	 * @param  string $string_to_sign Data to sign, buildStringToSign()
	 * @return string                 Authorized value as string
	 */
	public function buildAuthSignature(string $string_to_sign): string
	{
		$AWS_SHA256_ALGORITHM = self::AWS_SHA256_ALGORITHM;
		$SERVICE_NAME = self::SERVICE_NAME;
		$TERMINATION_STRING = self::TERMINATION_STRING;
		$ACCEPT_HEADER = self::ACCEPT_HEADER;
		$HOST_HEADER = self::HOST_HEADER;
		$X_AMZ_DATE_HEADER = self::X_AMZ_DATE_HEADER;
		$X_AMZ_TARGET_HEADER = self::X_AMZ_TARGET_HEADER;

		$aws_key_id = $this->config->getAccessKey();
		$region_name = $this->getRegion();

		$date_string = $this->getDateString();
		$derived_key = $this->buildDerivedKey();
		// Calculate signature per http://docs.aws.amazon.com/general/latest/gr/sigv4-calculate-signature.html
		$final_signature = $this->hmac($string_to_sign, $derived_key, false);

		// Assemble Authorization Header with signing information
		// per http://docs.aws.amazon.com/general/latest/gr/sigv4-add-signature-to-request.html
		$authorization_value =
			$AWS_SHA256_ALGORITHM
			. ' Credential=' . $aws_key_id
			. '/' . $date_string . '/' . $region_name . '/' . $SERVICE_NAME . '/' . $TERMINATION_STRING . ','
			. ' SignedHeaders='
			. $ACCEPT_HEADER . ';' . $HOST_HEADER . ';' . $X_AMZ_DATE_HEADER . ';' . $X_AMZ_TARGET_HEADER . ','
			. ' Signature='
			. $final_signature;

		return $authorization_value;
	}

	/**
	 * Build the derived key to build the final hmac signature string
	 *
	 * @param  bool   $rawOutput Set to true to create the hash based message
	 *                           authenticator string as normal text string or
	 *                           lowercase hexbits
	 * @return string            Derived key (hmac type)
	 */
	public function buildDerivedKey(bool $rawOutput = true): string
	{
		$KEY_QUALIFIER = self::KEY_QUALIFIER;
		$TERMINATION_STRING = self::TERMINATION_STRING;
		$SERVICE_NAME = self::SERVICE_NAME;

		$aws_secret_key = $this->config->getSecret();
		// Append Key Qualifier, "AWS4", to secret key per
		// shttp://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html
		$signature_aws_key = $KEY_QUALIFIER . $aws_secret_key;
		$region_name = $this->getRegion();
		$date_string = $this->getDateString();

		$k_date = $this->hmac($date_string, $signature_aws_key);
		$k_region = $this->hmac($region_name, $k_date);
		$k_service = $this->hmac($SERVICE_NAME, $k_region);

		// Derived the Signing key (derivedKey aka kSigning)
		return $this->hmac($TERMINATION_STRING, $k_service, $rawOutput);
	}

	/**
	 * get the region based on endpoint
	 * list as of 2021/10/20
	 * WHERE			URL										REGION
	 * North America	https://agcod-v2-gamma.amazon.com		us-east-1
	 * 					https://agcod-v2.amazon.com
	 * (US, CA, MX)
	 * Europe and Asia	https://agcod-v2-eu-gamma.amazon.com	eu-west-1
	 * 					https://agcod-v2-eu.amazon.com
	 * (IT, ES, DE, FR, UK, TR, UAE, KSA, PL, NL, SE)
	 * Far East			https://agcod-v2-fe-gamma.amazon.com	us-west-2
	 * 					https://agcod-v2-fe.amazon.com
	 * (JP, AU, SG)
	 *
	 * CURRENCY
	 * USD for US
	 * EUR for EU (IT, ES, DE, FR, PL, NL, SE)
	 * JPY for JP
	 * CAD for CA
	 * AUD for AU
	 * TRY for TR
	 * AED for UAE
	 * MXN for MX
	 * GBP for UK
	 *
	 * @return string Region string depending on given endpoint url
	 */
	public function getRegion(): string
	{
		$endpoint = $this->config->getEndpoint();
		// default region
		$region_name = 'us-east-1';

		switch ($endpoint) {
			case 'agcod-v2.amazon.com':
			case 'agcod-v2-gamma.amazon.com':
				$region_name = 'us-east-1';
				break;
			case 'agcod-v2-eu.amazon.com':
			case 'agcod-v2-eu-gamma.amazon.com':
				$region_name = 'us-west-1';
				break;
			case 'agcod-v2-fe.amazon.com':
			case 'agcod-v2-fe-gamma.amazon.com':
				$region_name = 'us-west-2';
				break;
		}
		return $region_name;
	}


	/**
	 * The actual data to send as json encoded string for creating a gift card.
	 * The creation request id must be in the format:
	 * <partner_id>_<unique id 13 characters>
	 *
	 * @param  float       $amount      Amount of currencty to create the gift card
	 *                                  request for
	 * @param  string|null $creation_id The creation id, if not set will be created here
	 * @return string                   JSON encoded array to be used as payload
	 *                                  in get gift card call
	 */
	public function getGiftCardPayload(float $amount, ?string $creation_id = null): string
	{
		$payload = [
			'creationRequestId' => $creation_id ?: uniqid($this->config->getPartner() . '_'),
			'partnerId' => $this->config->getPartner(),
			'value' =>
				[
					'currencyCode' => $this->config->getCurrency(),
					'amount' => $amount
				]
		];
		return (json_encode($payload)) ?: '';
	}

	/**
	 * The actual data to send as json encoded string to cancel a created gift card
	 *
	 * @param  string $creation_request_id Creation request id from previous get gift card
	 * @param  string $gift_card_id        Gift card id from previous get gift card
	 * @return string                      JSON encoded array to be used as payload
	 *                                     in cancle gift card call
	 */
	public function getCancelGiftCardPayload(string $creation_request_id, string $gift_card_id): string
	{
		$payload = [
			'creationRequestId' => $creation_request_id,
			'partnerId' => $this->config->getPartner(),
			'gcId' => $gift_card_id
		];
		return (json_encode($payload)) ?: '';
	}

	/**
	 * The actualy data to send as json encoded string for getting the current
	 * account funds
	 *
	 * @return string JSON encoded array to be used as payload in funds call
	 */
	public function getAvailableFundsPayload(): string
	{
		$payload = [
			'partnerId' => $this->config->getPartner(),
		];
		return (json_encode($payload)) ?: '';
	}

	/**
	 * Heeders used in the getCanonicalRequest()
	 *
	 * @param  string $service_operation Service operation code in the service string request
	 *                                   Value is: com.amazonaws.agcod.AGCODService.<so>
	 * @return string                    Header string to be used
	 */
	public function buildCanonicalHeaders(string $service_operation): string
	{
		$ACCEPT_HEADER = self::ACCEPT_HEADER;
		$HOST_HEADER = self::HOST_HEADER;
		$X_AMZ_DATE_HEADER = self::X_AMZ_DATE_HEADER;
		$X_AMZ_TARGET_HEADER = self::X_AMZ_TARGET_HEADER;
		$date_time_string = $this->getTimestamp();
		$endpoint = $this->config->getEndpoint();
		$content_type = $this->getContentType();
		return "$ACCEPT_HEADER:$content_type\n"
			. "$HOST_HEADER:$endpoint\n"
			. "$X_AMZ_DATE_HEADER:$date_time_string\n"
			. "$X_AMZ_TARGET_HEADER:com.amazonaws.agcod.AGCODService.$service_operation";
	}

	/**
	 * Headers used in the get/cancel/funds requests
	 *
	 * @param  string $service_operation Service operation code to be used in header request
	 *                                   and main request call
	 * @param  string $payload           Payload from get/cancle Code or funds call
	 * @return string                    Full POST service request code
	 */
	public function getCanonicalRequest(string $service_operation, string $payload): string
	{
		$HOST_HEADER = self::HOST_HEADER;
		$X_AMZ_DATE_HEADER = self::X_AMZ_DATE_HEADER;
		$X_AMZ_TARGET_HEADER = self::X_AMZ_TARGET_HEADER;
		$ACCEPT_HEADER = self::ACCEPT_HEADER;
		$payload_hash = $this->buildHash($payload);
		$canonical_headers = $this->buildCanonicalHeaders($service_operation);
		$canonical_request = "POST\n"
			. "/$service_operation\n\n"
			. "$canonical_headers\n\n"
			. "$ACCEPT_HEADER;$HOST_HEADER;$X_AMZ_DATE_HEADER;$X_AMZ_TARGET_HEADER\n"
			. "$payload_hash";
		return $canonical_request;
	}

	/**
	 * Build sha256 hash from given data
	 *
	 * @param  string $data Data to be hashed with sha256
	 * @return string       sha256 hash
	 */
	public function buildHash(string $data): string
	{
		return hash('sha256', $data);
	}

	/**
	 * Create a sha256 based Hash-Based Message Authentication Code
	 * with the given key and data
	 *
	 * @param  string $data Data to be hashed with key below
	 * @param  string $key  Key to be used for creating the hash
	 * @param  bool   $raw  Returning data as ascii string or hexibits
	 * @return string       Hash-Based Message Authentication Code
	 */
	public function hmac(string $data, string $key, bool $raw = true): string
	{
		return hash_hmac('sha256', $data, $key, $raw);
	}

	/**
	 * Build timestamp in the format used by AWS services
	 * eg 20211009\T102030\Z
	 *
	 * @return string date string based on current time. Ymd\THis\Z
	 */
	public function getTimestamp()
	{
		return gmdate('Ymd\THis\Z');
	}

	/**
	 * Get only the date string from the getTimestamp
	 * eg 20211009
	 *
	 * @return string Date string YYYYmmdd extracted from getTimestamp()
	 */
	public function getDateString()
	{
		return substr($this->getTimestamp(), 0, 8);
	}

	/**
	 * Fixed content type for submission, is json
	 *
	 * @return string 'application/json' string
	 */
	public function getContentType(): string
	{
		return 'application/json';
	}
}

// __END__