//go:build !lint

package sds

/*
	#include <libsds.h>
	#include <stdio.h>
	#include <stdlib.h>

	extern void sdsGlobalEventCallback(int ret, char* msg, size_t len, void* userData);

	typedef struct {
		int ret;
		char* msg;
		size_t len;
		void* ffiWg;
	} SdsResp;

	static void* allocResp(void* wg) {
		SdsResp* r = calloc(1, sizeof(SdsResp));
		r->ffiWg = wg;
		return r;
	}

	static void freeResp(void* resp) {
		if (resp != NULL) {
			free(resp);
		}
	}

	static char* getMyCharPtr(void* resp) {
		if (resp == NULL) {
			return NULL;
		}
		SdsResp* m = (SdsResp*) resp;
		return m->msg;
	}

	static size_t getMyCharLen(void* resp) {
		if (resp == NULL) {
			return 0;
		}
		SdsResp* m = (SdsResp*) resp;
		return m->len;
	}

	static int getRet(void* resp) {
		if (resp == NULL) {
			return 0;
		}
		SdsResp* m = (SdsResp*) resp;
		return m->ret;
	}

	// resp must be set != NULL in case interest on retrieving data from the callback
	void SdsGoCallback(int ret, char* msg, size_t len, void* resp);

	static void* cGoSdsNewReliabilityManager(void* resp) {
		// We pass NULL because we are not interested in retrieving data from this callback
		void* ret = SdsNewReliabilityManager((SdsCallBack) SdsGoCallback, resp);
		return ret;
	}

	static void cGoSdsSetEventCallback(void* rmCtx) {
		// The 'sdsGlobalEventCallback' Go function is shared amongst all possible Reliability Manager instances.

		// Given that the 'sdsGlobalEventCallback' is shared, we pass again the
		// rmCtx instance but in this case is needed to pick up the correct method
		// that will handle the event.

		// In other words, for every call libsds makes to sdsGlobalEventCallback,
		// the 'userData' parameter will bring the context of the rm that registered
		// that sdsGlobalEventCallback.

		// This technique is needed because cgo only allows to export Go functions and not methods.

		SdsSetEventCallback(rmCtx, (SdsCallBack) sdsGlobalEventCallback, rmCtx);
	}

	static void cGoSdsCleanupReliabilityManager(void* rmCtx, void* resp) {
		SdsCleanupReliabilityManager(rmCtx, (SdsCallBack) SdsGoCallback, resp);
	}

	static void cGoSdsResetReliabilityManager(void* rmCtx, void* resp) {
		SdsResetReliabilityManager(rmCtx, (SdsCallBack) SdsGoCallback, resp);
	}

	static void cGoSdsWrapOutgoingMessage(void* rmCtx,
					void* message,
	                    		size_t messageLen,
	                    		const char* messageId,
				const char* channelId,
				void* resp) {
		SdsWrapOutgoingMessage(rmCtx,
				message,
				messageLen,
				messageId,
				channelId,
				(SdsCallBack) SdsGoCallback,
				resp);
	}
	static void cGoSdsUnwrapReceivedMessage(void* rmCtx,
									void* message,
                    				size_t messageLen,
									void* resp) {
		SdsUnwrapReceivedMessage(rmCtx,
						message,
						messageLen,
						(SdsCallBack) SdsGoCallback,
						resp);
	}

	static void cGoSdsMarkDependenciesMet(void* rmCtx,
					char** messageIDs,
	                    		size_t count,
					const char* channelId,
					void* resp) {
		SdsMarkDependenciesMet(rmCtx,
				messageIDs,
				count,
				channelId,
				(SdsCallBack) SdsGoCallback,
				resp);
	}

	static void cGoSdsStartPeriodicTasks(void* rmCtx, void* resp) {
		SdsStartPeriodicTasks(rmCtx, (SdsCallBack) SdsGoCallback, resp);
	}

*/
import "C"
import (
	"encoding/json"
	"errors"
	"strconv"
	"strings"
	"sync"
	"unsafe"

	errorspkg "github.com/pkg/errors"
	"go.uber.org/zap"
)

var (
	errEmptyReliabilityManager = errors.New("empty reliability manager")
)

//export SdsGoCallback
func SdsGoCallback(ret C.int, msg *C.char, len C.size_t, resp unsafe.Pointer) {
	if resp != nil {
		m := (*C.SdsResp)(resp)
		m.ret = ret
		m.msg = msg
		m.len = len
		wg := (*sync.WaitGroup)(m.ffiWg)
		wg.Done()
	}
}

func NewReliabilityManager(logger *zap.Logger) (*ReliabilityManager, error) {
	if logger == nil {
		logger = zap.NewNop()
	}

	rm := &ReliabilityManager{
		logger: logger,
	}

	rm.logger.Info("creating new reliability manager")

	wg := sync.WaitGroup{}

	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	if C.getRet(resp) != C.RET_OK {
		errMsg := C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
		return nil, errors.New(errMsg)
	}

	wg.Add(1)
	rm.rmCtx = C.cGoSdsNewReliabilityManager(resp)
	wg.Wait()

	C.cGoSdsSetEventCallback(rm.rmCtx)
	registerReliabilityManager(rm)

	rm.logger.Debug("successfully created reliability manager")
	return rm, nil
}

//export sdsGlobalEventCallback
func sdsGlobalEventCallback(callerRet C.int, msg *C.char, len C.size_t, userData unsafe.Pointer) {
	msgStr := C.GoStringN(msg, C.int(len))
	rm, ok := rmRegistry[userData] // userData contains rm's ctx
	if !ok {
		return
	}

	if callerRet == C.RET_OK {
		rm.OnEvent(msgStr)
	} else {
		rm.OnCallbackError(int(callerRet), msgStr)
	}
}

func (rm *ReliabilityManager) Cleanup() error {
	if rm == nil {
		return errEmptyReliabilityManager
	}

	rm.logger.Debug("cleaning up reliability manager")

	wg := sync.WaitGroup{}
	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	wg.Add(1)
	C.cGoSdsCleanupReliabilityManager(rm.rmCtx, resp)
	wg.Wait()

	if C.getRet(resp) == C.RET_OK {
		unregisterReliabilityManager(rm)
		rm.logger.Debug("cleaned up reliability manager")
		return nil
	}

	errMsg := "error CleanupReliabilityManager: " + C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
	return errors.New(errMsg)
}

func (rm *ReliabilityManager) Reset() error {
	if rm == nil {
		return errEmptyReliabilityManager
	}

	rm.logger.Debug("resetting reliability manager")

	wg := sync.WaitGroup{}
	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	wg.Add(1)
	C.cGoSdsResetReliabilityManager(rm.rmCtx, resp)
	wg.Wait()

	if C.getRet(resp) == C.RET_OK {
		rm.logger.Debug("successfully resetted reliability manager")
		return nil
	}

	errMsg := "error ResetReliabilityManager: " + C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
	return errors.New(errMsg)
}

func (rm *ReliabilityManager) WrapOutgoingMessage(message []byte, messageId MessageID, channelId string) ([]byte, error) {
	if rm == nil {
		return nil, errEmptyReliabilityManager
	}

	logger := rm.logger.With(zap.String("messageId", string(messageId)))
	logger.Debug("wrapping outgoing message", zap.String("messageId", string(messageId)))

	wg := sync.WaitGroup{}
	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	cMessageId := C.CString(string(messageId))
	defer C.free(unsafe.Pointer(cMessageId))

	var cMessagePtr unsafe.Pointer
	if len(message) > 0 {
		cMessagePtr = C.CBytes(message) // C.CBytes allocates memory that needs to be freed
		defer C.free(cMessagePtr)
	} else {
		cMessagePtr = nil
	}
	cMessageLen := C.size_t(len(message))

	cChannelId := C.CString(channelId)
	defer C.free(unsafe.Pointer(cChannelId))

	wg.Add(1)
	C.cGoSdsWrapOutgoingMessage(rm.rmCtx, cMessagePtr, cMessageLen, cMessageId, cChannelId, resp)
	wg.Wait()

	if C.getRet(resp) == C.RET_OK {
		resStr := C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
		if resStr == "" {
			logger.Debug("received empty res string for messageId")
			return nil, nil
		}
		logger.Debug("successfully wrapped message")

		parts := strings.Split(resStr, ",")
		bytes := make([]byte, len(parts))

		for i, part := range parts {
			n, err := strconv.Atoi(strings.TrimSpace(part))
			if err != nil {
				panic(err)
			}
			bytes[i] = byte(n)
		}

		return bytes, nil
	}

	errMsg := "error WrapOutgoingMessage: " + C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
	return nil, errors.New(errMsg)
}

func (rm *ReliabilityManager) UnwrapReceivedMessage(message []byte) (*UnwrappedMessage, error) {
	if rm == nil {
		return nil, errEmptyReliabilityManager
	}

	wg := sync.WaitGroup{}
	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	var cMessagePtr unsafe.Pointer
	if len(message) > 0 {
		cMessagePtr = C.CBytes(message) // C.CBytes allocates memory that needs to be freed
		defer C.free(cMessagePtr)
	} else {
		cMessagePtr = nil
	}
	cMessageLen := C.size_t(len(message))

	wg.Add(1)
	C.cGoSdsUnwrapReceivedMessage(rm.rmCtx, cMessagePtr, cMessageLen, resp)
	wg.Wait()

	if C.getRet(resp) == C.RET_OK {
		resStr := C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
		if resStr == "" {
			rm.logger.Debug("received empty res string")
			return nil, nil
		}
		rm.logger.Debug("successfully unwrapped message")

		unwrappedMessage := UnwrappedMessage{}
		err := json.Unmarshal([]byte(resStr), &unwrappedMessage)
		if err != nil {
			return nil, errorspkg.Wrap(err, "failed to unmarshal unwrapped message")
		}

		return &unwrappedMessage, nil
	}

	errMsg := "error UnwrapReceivedMessage: " + C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
	return nil, errors.New(errMsg)
}

// MarkDependenciesMet informs the library that dependencies are met
func (rm *ReliabilityManager) MarkDependenciesMet(messageIDs []MessageID, channelId string) error {
	if rm == nil {
		return errEmptyReliabilityManager
	}

	if len(messageIDs) == 0 {
		return nil // Nothing to do
	}

	wg := sync.WaitGroup{}
	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	// Convert Go string slice to C array of C strings (char**)
	cMessageIDs := make([]*C.char, len(messageIDs))
	for i, id := range messageIDs {
		cMessageIDs[i] = C.CString(string(id))
		defer C.free(unsafe.Pointer(cMessageIDs[i])) // Ensure each CString is freed
	}

	// Create a pointer (**C.char) to the first element of the slice
	var cMessageIDsPtr **C.char
	if len(cMessageIDs) > 0 {
		cMessageIDsPtr = &cMessageIDs[0]
	} else {
		cMessageIDsPtr = nil // Handle empty slice case
	}

	wg.Add(1)
	cChannelId := C.CString(channelId)
	defer C.free(unsafe.Pointer(cChannelId))

	// Pass the pointer variable (cMessageIDsPtr) directly, which is of type **C.char
	C.cGoSdsMarkDependenciesMet(rm.rmCtx, cMessageIDsPtr, C.size_t(len(messageIDs)), cChannelId, resp)
	wg.Wait()

	if C.getRet(resp) == C.RET_OK {
		rm.logger.Debug("successfully marked dependencies as met")
		return nil
	}

	errMsg := "error MarkDependenciesMet: " + C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
	return errors.New(errMsg)
}

func (rm *ReliabilityManager) StartPeriodicTasks() error {
	if rm == nil {
		return errEmptyReliabilityManager
	}

	rm.logger.Debug("starting periodic tasks")

	wg := sync.WaitGroup{}
	var resp = C.allocResp(unsafe.Pointer(&wg))
	defer C.freeResp(resp)

	wg.Add(1)
	C.cGoSdsStartPeriodicTasks(rm.rmCtx, resp)
	wg.Wait()

	if C.getRet(resp) == C.RET_OK {
		rm.logger.Debug("successfully started periodic tasks")
		return nil
	}

	errMsg := "error StartPeriodicTasks: " + C.GoStringN(C.getMyCharPtr(resp), C.int(C.getMyCharLen(resp)))
	return errors.New(errMsg)
}