#define GAME_LAUNCH_NAME "testapp"
#ifndef GAME_LAUNCH_NAME
#error Please define your game exe name.
#endif

#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN 1
#include <windows.h>
typedef PROCESS_INFORMATION ProcessType;
typedef HANDLE PipeType;
#define NULLPIPE NULL
#else
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/wait.h>
#include <signal.h>
typedef pid_t ProcessType;
typedef int PipeType;
#define NULLPIPE -1
#endif

#include "steam/steam_api.h"

#define DEBUGPIPE 1
#if DEBUGPIPE
#define dbgpipe printf
#else
static inline void dbgpipe(const char *fmt, ...) {}
#endif

/* platform-specific mainline calls this. */
static int mainline(void);

/* Windows and Unix implementations of this stuff below. */
static void fail(const char *err);
static bool writePipe(PipeType fd, const void *buf, const unsigned int _len);
static int readPipe(PipeType fd, void *buf, const unsigned int _len);
static bool createPipes(PipeType *pPipeParentRead, PipeType *pPipeParentWrite,
                        PipeType *pPipeChildRead, PipeType *pPipeChildWrite);
static void closePipe(PipeType fd);
static bool setEnvVar(const char *key, const char *val);
static bool launchChild(ProcessType *pid);
static int closeProcess(ProcessType *pid);

#ifdef _WIN32
static void fail(const char *err)
{
    MessageBoxA(NULL, err, "ERROR", MB_ICONERROR | MB_OK);
    ExitProcess(1);
} // fail

static bool writePipe(PipeType fd, const void *buf, const unsigned int _len)
{
    const DWORD len = (DWORD) _len;
    DWORD bw = 0;
    return ((WriteFile(fd, buf, len, &bw, NULL) != 0) && (bw == len));
} // writePipe

static int readPipe(PipeType fd, void *buf, const unsigned int _len)
{
    const DWORD len = (DWORD) _len;
    DWORD br = 0;
    return ReadFile(fd, buf, len, &br, NULL) ? (int) br : -1;
} // readPipe

static bool createPipes(PipeType *pPipeParentRead, PipeType *pPipeParentWrite,
                        PipeType *pPipeChildRead, PipeType *pPipeChildWrite)
{
    SECURITY_ATTRIBUTES pipeAttr;

    pipeAttr.nLength = sizeof (pipeAttr);
    pipeAttr.lpSecurityDescriptor = NULL;
    pipeAttr.bInheritHandle = TRUE;
    if (!CreatePipe(pPipeParentRead, pPipeChildWrite, &pipeAttr, 0))
        return 0;

    pipeAttr.nLength = sizeof (pipeAttr);
    pipeAttr.lpSecurityDescriptor = NULL;
    pipeAttr.bInheritHandle = TRUE;
    if (!CreatePipe(pPipeChildRead, pPipeParentWrite, &pipeAttr, 0))
    {
        CloseHandle(*pPipeParentRead);
        CloseHandle(*pPipeChildWrite);
        return 0;
    } // if

    return 1;
} // createPipes

static void closePipe(PipeType fd)
{
    CloseHandle(fd);
} // closePipe

static bool setEnvVar(const char *key, const char *val)
{
    return (SetEnvironmentVariableA(key, val) != 0);
} // setEnvVar

static bool launchChild(ProcessType *pid);
{
    return (CreateProcessW(TEXT(".\\") TEXT(GAME_LAUNCH_NAME) TEXT(".exe"),
                           GetCommandLineW(), NULL, NULL, TRUE, 0, NULL,
                           NULL, NULL, pid) != 0);
} // launchChild

static int closeProcess(ProcessType *pid)
{
    CloseHandle(pid->hProcess);
    CloseHandle(pid->hThread);
    return 0;
} // closeProcess

int CALLBACK WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                     LPSTR lpCmdLine, int nCmdShow)
{
    mainline();
    ExitProcess(0);
    return 0;  // just in case.
} // WinMain


#else  // everyone else that isn't Windows.

static void fail(const char *err)
{
    // !!! FIXME: zenity or something.
    fprintf(stderr, "%s\n", err);
    _exit(1);
} // fail

static bool writePipe(PipeType fd, const void *buf, const unsigned int _len)
{
    const ssize_t len = (ssize_t) _len;
    ssize_t bw;
    while (((bw = write(fd, buf, len)) == -1) && (errno == EINTR)) { /*spin*/ }
    return (bw == len);
} // writePipe

static int readPipe(PipeType fd, void *buf, const unsigned int _len)
{
    const ssize_t len = (ssize_t) _len;
    ssize_t br;
    while (((br = read(fd, buf, len)) == -1) && (errno == EINTR)) { /*spin*/ }
    return (int) br;
} // readPipe

static bool createPipes(PipeType *pPipeParentRead, PipeType *pPipeParentWrite,
                        PipeType *pPipeChildRead, PipeType *pPipeChildWrite)
{
    int fds[2];
    if (pipe(fds) == -1)
        return 0;
    *pPipeParentRead = fds[0];
    *pPipeChildWrite = fds[1];

    if (pipe(fds) == -1)
    {
        close(*pPipeParentRead);
        close(*pPipeChildWrite);
        return 0;
    } // if

    *pPipeChildRead = fds[0];
    *pPipeParentWrite = fds[1];

    return 1;
} // createPipes

static void closePipe(PipeType fd)
{
    close(fd);
} // closePipe

static bool setEnvVar(const char *key, const char *val)
{
    return (setenv(key, val, 1) != -1);
} // setEnvVar

static int GArgc = 0;
static char **GArgv = NULL;

static bool launchChild(ProcessType *pid)
{
    *pid = fork();
    if (*pid == -1)   // failed
        return false;
    else if (*pid != 0)  // we're the parent
        return true;  // we'll let the pipe fail if this didn't work.

    // we're the child.
    GArgv[0] = strdup("./" GAME_LAUNCH_NAME);
    execvp(GArgv[0], GArgv);
    // still here? It failed! Terminate, closing child's ends of the pipes.
    _exit(1);
} // launchChild

static int closeProcess(ProcessType *pid)
{
    int rc = 0;
    while ((waitpid(*pid, &rc, 0) == -1) && (errno == EINTR)) { /*spin*/ }
    if (!WIFEXITED(rc))
        return 1;  // oh well.
    return WEXITSTATUS(rc);
} // closeProcess

int main(int argc, char **argv)
{
    signal(SIGPIPE, SIG_IGN);
    GArgc = argc;
    GArgv = argv;
    return mainline();
} // main

#endif


// THE ACTUAL PROGRAM.

class SteamBridge;

static ISteamUserStats *GSteamStats = NULL;
static ISteamUtils *GSteamUtils = NULL;
static ISteamUser *GSteamUser = NULL;
static AppId_t GAppID = 0;
static uint64 GUserID = 0;
static SteamBridge *GSteamBridge = NULL;

class SteamBridge
{
public:
    SteamBridge(PipeType _fd);
	STEAM_CALLBACK(SteamBridge, OnUserStatsReceived, UserStatsReceived_t, m_CallbackUserStatsReceived);
	STEAM_CALLBACK(SteamBridge, OnUserStatsStored, UserStatsStored_t, m_CallbackUserStatsStored);

private:
    PipeType fd;
};

typedef enum ShimCmd
{
    SHIMCMD_BYE,
    SHIMCMD_PUMP,
    SHIMCMD_REQUESTSTATS,
    SHIMCMD_STORESTATS,
    SHIMCMD_SETACHIEVEMENT,
    SHIMCMD_GETACHIEVEMENT,
    SHIMCMD_RESETSTATS,
    SHIMCMD_SETSTATI,
    SHIMCMD_GETSTATI,
    SHIMCMD_SETSTATF,
    SHIMCMD_GETSTATF,
} ShimCmd;

typedef enum ShimEvent
{
    SHIMEVENT_BYE,
    SHIMEVENT_STATSRECEIVED,
    SHIMEVENT_STATSSTORED,
    SHIMEVENT_SETACHIEVEMENT,
    SHIMEVENT_GETACHIEVEMENT,
    SHIMEVENT_RESETSTATS,
    SHIMEVENT_SETSTATI,
    SHIMEVENT_GETSTATI,
    SHIMEVENT_SETSTATF,
    SHIMEVENT_GETSTATF,
} ShimEvent;

static bool write1ByteCmd(PipeType fd, const uint8 b1)
{
    const uint8 buf[] = { 1, b1 };
    return writePipe(fd, buf, sizeof (buf));
} // write1ByteCmd

static bool write2ByteCmd(PipeType fd, const uint8 b1, const uint8 b2)
{
    const uint8 buf[] = { 2, b1, b2 };
    return writePipe(fd, buf, sizeof (buf));
} // write2ByteCmd

static bool write3ByteCmd(PipeType fd, const uint8 b1, const uint8 b2, const uint8 b3)
{
    const uint8 buf[] = { 3, b1, b2, b3 };
    return writePipe(fd, buf, sizeof (buf));
} // write3ByteCmd


static inline bool writeBye(PipeType fd)
{
    dbgpipe("Parent sending SHIMEVENT_BYE().\n");
    return write1ByteCmd(fd, SHIMEVENT_BYE);
} // writeBye

static inline bool writeStatsReceived(PipeType fd, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_STATSRECEIVED(%sokay).\n", okay ? "" : "!");
    return write2ByteCmd(fd, SHIMEVENT_STATSRECEIVED, okay ? 1 : 0);
} // writeStatsReceived

static inline bool writeStatsStored(PipeType fd, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_STATSSTORED(%sokay).\n", okay ? "" : "!");
    return write2ByteCmd(fd, SHIMEVENT_STATSSTORED, okay ? 1 : 0);
} // writeStatsStored

static bool writeAchievementSet(PipeType fd, const char *name, const bool enable, const bool okay)
{
    uint8 buf[256];
    uint8 *ptr = buf+1;
    dbgpipe("Parent sending SHIMEVENT_SETACHIEVEMENT('%s', %senable, %sokay).\n", name, enable ? "" : "!", okay ? "" : "!");
    *(ptr++) = (uint8) SHIMEVENT_SETACHIEVEMENT;
    *(ptr++) = enable ? 1 : 0;
    *(ptr++) = okay ? 1 : 0;
    strcpy((char *) ptr, name);
    ptr += strlen(name) + 1;
    buf[0] = (uint8) ((ptr-1) - buf);
    return writePipe(fd, buf, buf[0] + 1);
} // writeAchievementSet

static bool writeAchievementGet(PipeType fd, const char *name, const int status, const uint64 time)
{
    uint8 buf[256];
    uint8 *ptr = buf+1;
    dbgpipe("Parent sending SHIMEVENT_GETACHIEVEMENT('%s', status %d, time %llu).\n", name, status, (unsigned long long) time);
    *(ptr++) = (uint8) SHIMEVENT_GETACHIEVEMENT;
    *(ptr++) = (uint8) status;
    memcpy(ptr, &time, sizeof (time));
    ptr += sizeof (time);
    strcpy((char *) ptr, name);
    ptr += strlen(name) + 1;
    buf[0] = (uint8) ((ptr-1) - buf);
    return writePipe(fd, buf, buf[0] + 1);
} // writeAchievementGet

static inline bool writeResetStats(PipeType fd, const bool alsoAch, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_RESETSTATS(%salsoAchievements, %sokay).\n", alsoAch ? "" : "!", okay ? "" : "!");
    return write3ByteCmd(fd, SHIMEVENT_RESETSTATS, alsoAch ? 1 : 0, okay ? 1 : 0);
} // writeResetStats

static bool writeStatThing(PipeType fd, const ShimEvent ev, const char *name, const void *val, const size_t vallen, const bool okay)
{
    uint8 buf[256];
    uint8 *ptr = buf+1;
    *(ptr++) = (uint8) ev;
    *(ptr++) = okay ? 1 : 0;
    memcpy(ptr, val, vallen);
    ptr += vallen;
    strcpy((char *) ptr, name);
    ptr += strlen(name) + 1;
    buf[0] = (uint8) ((ptr-1) - buf);
    return writePipe(fd, buf, buf[0] + 1);
} // writeStatThing

static inline bool writeSetStatI(PipeType fd, const char *name, const int32 val, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_SETSTATI('%s', val %d, %sokay).\n", name, (int) val, okay ? "" : "!");
    return writeStatThing(fd, SHIMEVENT_SETSTATI, name, &val, sizeof (val), okay);
} // writeSetStatI

static inline bool writeSetStatF(PipeType fd, const char *name, const float val, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_SETSTATF('%s', val %f, %sokay).\n", name, val, okay ? "" : "!");
    return writeStatThing(fd, SHIMEVENT_SETSTATF, name, &val, sizeof (val), okay);
} // writeSetStatF

static inline bool writeGetStatI(PipeType fd, const char *name, const int32 val, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_GETSTATI('%s', val %d, %sokay).\n", name, (int) val, okay ? "" : "!");
    return writeStatThing(fd, SHIMEVENT_GETSTATI, name, &val, sizeof (val), okay);
} // writeGetStatI

static inline bool writeGetStatF(PipeType fd, const char *name, const float val, const bool okay)
{
    dbgpipe("Parent sending SHIMEVENT_GETSTATF('%s', val %f, %sokay).\n", name, val, okay ? "" : "!");
    return writeStatThing(fd, SHIMEVENT_GETSTATF, name, &val, sizeof (val), okay);
} // writeGetStatF



SteamBridge::SteamBridge(PipeType _fd)
    : m_CallbackUserStatsReceived( this, &SteamBridge::OnUserStatsReceived )
	, m_CallbackUserStatsStored( this, &SteamBridge::OnUserStatsStored )
	, fd(_fd)
{
} // SteamBridge::SteamBridge

void SteamBridge::OnUserStatsReceived(UserStatsReceived_t *pCallback)
{
	if (GAppID != pCallback->m_nGameID) return;
	if (GUserID != pCallback->m_steamIDUser.ConvertToUint64()) return;
    writeStatsReceived(fd, pCallback->m_eResult == k_EResultOK);
} // SteamBridge::OnUserStatsReceived

void SteamBridge::OnUserStatsStored(UserStatsStored_t *pCallback)
{
	if (GAppID != pCallback->m_nGameID) return;
    writeStatsStored(fd, pCallback->m_eResult == k_EResultOK);
} // SteamBridge::OnUserStatsStored


static bool processCommand(const uint8 *buf, unsigned int buflen, PipeType fd)
{
    if (buflen == 0)
        return true;

    const ShimCmd cmd = (ShimCmd) *(buf++);
    buflen--;

    #if DEBUGPIPE
    if (false) {}
    #define PRINTGOTCMD(x) else if (cmd == x) printf("Parent got " #x ".\n")
    PRINTGOTCMD(SHIMCMD_BYE);
    PRINTGOTCMD(SHIMCMD_PUMP);
    PRINTGOTCMD(SHIMCMD_REQUESTSTATS);
    PRINTGOTCMD(SHIMCMD_STORESTATS);
    PRINTGOTCMD(SHIMCMD_SETACHIEVEMENT);
    PRINTGOTCMD(SHIMCMD_GETACHIEVEMENT);
    PRINTGOTCMD(SHIMCMD_RESETSTATS);
    PRINTGOTCMD(SHIMCMD_SETSTATI);
    PRINTGOTCMD(SHIMCMD_GETSTATI);
    PRINTGOTCMD(SHIMCMD_SETSTATF);
    PRINTGOTCMD(SHIMCMD_GETSTATF);
    #undef PRINTGOTCMD
    else printf("Parent got unknown shimcmd %d.\n", (int) cmd);
    #endif

    switch (cmd)
    {
        case SHIMCMD_PUMP:
            SteamAPI_RunCallbacks();
            break;

        case SHIMCMD_BYE:
            writeBye(fd);
            return false;

        case SHIMCMD_REQUESTSTATS:
            if ((!GSteamStats) || (!GSteamStats->RequestCurrentStats()))
                writeStatsReceived(fd, false);
            // callback later.
            break;

        case SHIMCMD_STORESTATS:
            if ((!GSteamStats) || (!GSteamStats->StoreStats()))
                writeStatsStored(fd, false);
            // callback later.
            break;

        case SHIMCMD_SETACHIEVEMENT:
            if (buflen >= 2)
            {
                const bool enable = (*(buf++) != 0);
                const char *name = (const char *) buf;   // !!! FIXME: buffer overflow possible.
                if (!GSteamStats)
                    writeAchievementSet(fd, name, enable, false);
                else if (enable && !GSteamStats->SetAchievement(name))
                    writeAchievementSet(fd, name, enable, false);
                else if (!enable && !GSteamStats->ClearAchievement(name))
                    writeAchievementSet(fd, name, enable, false);
                else
                    writeAchievementSet(fd, name, enable, true);
            } // if
            break;

        case SHIMCMD_GETACHIEVEMENT:
            if (buflen)
            {
                const char *name = (const char *) buf;   // !!! FIXME: buffer overflow possible.
                bool ach = false;
	            uint32 t = 0;
                if ((GSteamStats) && (GSteamStats->GetAchievementAndUnlockTime(name, &ach, &t)))
                    writeAchievementGet(fd, name, ach ? 1 : 0, t);
	            else
                    writeAchievementGet(fd, name, 2, 0);
            } // if
            break;

        case SHIMCMD_RESETSTATS:
            if (buflen)
            {
                const bool alsoAch = (*(buf++) != 0);
                writeResetStats(fd, alsoAch, (GSteamStats) && (GSteamStats->ResetAllStats(alsoAch)));
            } // if
            break;

        case SHIMCMD_SETSTATI:
            if (buflen >= 5)
            {
                const int32 val = *((int32 *) buf);
                buf += sizeof (int32);
                const char *name = (const char *) buf;   // !!! FIXME: buffer overflow possible.
                writeSetStatI(fd, name, val, (GSteamStats) && (GSteamStats->SetStat(name, val)));
            } // if
            break;

        case SHIMCMD_GETSTATI:
            if (buflen)
            {
                const char *name = (const char *) buf;   // !!! FIXME: buffer overflow possible.
                int32 val = 0;
                if ((GSteamStats) && (GSteamStats->GetStat(name, &val)))
                    writeGetStatI(fd, name, val, true);
                else
                    writeGetStatI(fd, name, 0, false);
            } // if
            break;

        case SHIMCMD_SETSTATF:
            if (buflen >= 5)
            {
                const float val = *((float *) buf);
                buf += sizeof (float);
                const char *name = (const char *) buf;   // !!! FIXME: buffer overflow possible.
                writeSetStatF(fd, name, val, (GSteamStats) && (GSteamStats->SetStat(name, val)));
            } // if
            break;

        case SHIMCMD_GETSTATF:
            if (buflen)
            {
                const char *name = (const char *) buf;   // !!! FIXME: buffer overflow possible.
                float val = 0;
                if ((GSteamStats) && (GSteamStats->GetStat(name, &val)))
                    writeGetStatF(fd, name, val, true);
                else
                    writeGetStatF(fd, name, 0.0f, false);
            } // if
            break;
    } // switch

    return true;  // keep going.
} // processCommand

static void processCommands(PipeType pipeParentRead, PipeType pipeParentWrite)
{
    bool quit = false;
    uint8 buf[256];
    int br;

    // this read blocks.
    while (!quit && ((br = readPipe(pipeParentRead, buf, sizeof (buf))) > 0))
    {
        while (br > 0)
        {
            const int cmdlen = (int) buf[0];
            if ((br-1) >= cmdlen)
            {
                if (!processCommand(buf+1, cmdlen, pipeParentWrite))
                {
                    quit = true;
                    break;
                } // if

                br -= cmdlen + 1;
                if (br > 0)
                    memmove(buf, buf+cmdlen+1, br);
            } // if
            else  // get more data.
            {
                const int morebr = readPipe(pipeParentRead, buf+br, sizeof (buf) - br);
                if (morebr <= 0)
                {
                    quit = true;  // uhoh.
                    break;
                } // if
                br += morebr;
            } // else
        } // while
    } // while
} // processCommands

static bool setEnvironmentVars(PipeType pipeChildRead, PipeType pipeChildWrite)
{
    char buf[64];
    snprintf(buf, sizeof (buf), "%llu", (unsigned long long) pipeChildRead);
    if (!setEnvVar("STEAMSHIM_READHANDLE", buf))
        return false;

    snprintf(buf, sizeof (buf), "%llu", (unsigned long long) pipeChildWrite);
    if (!setEnvVar("STEAMSHIM_WRITEHANDLE", buf))
        return false;

    return true;
} // setEnvironmentVars

static bool initSteamworks(PipeType fd)
{
    // this can fail for many reasons:
    //  - you forgot a steam_appid.txt in the current working directory.
    //  - you don't have Steam running
    //  - you don't own the game listed in steam_appid.txt
    if (!SteamAPI_Init())
        return 0;

    GSteamStats = SteamUserStats();
    GSteamUtils = SteamUtils();
    GSteamUser = SteamUser();

    GAppID = GSteamUtils ? GSteamUtils->GetAppID() : 0;
	GUserID = GSteamUser ? GSteamUser->GetSteamID().ConvertToUint64() : 0;
    GSteamBridge = new SteamBridge(fd);

    return 1;
} // initSteamworks

static void deinitSteamworks(void)
{
    SteamAPI_Shutdown();
    delete GSteamBridge;
    GSteamBridge = NULL;
    GSteamStats = NULL;
    GSteamUtils= NULL;
    GSteamUser = NULL;
} // deinitSteamworks

static int mainline(void)
{
    PipeType pipeParentRead = NULLPIPE;
    PipeType pipeParentWrite = NULLPIPE;
    PipeType pipeChildRead = NULLPIPE;
    PipeType pipeChildWrite = NULLPIPE;
    ProcessType childPid;

    dbgpipe("Parent starting mainline.\n");

    if (!createPipes(&pipeParentRead, &pipeParentWrite, &pipeChildRead, &pipeChildWrite))
        fail("Failed to create application pipes");
    else if (!initSteamworks(pipeParentWrite))
        fail("Failed to initialize Steamworks");
    else if (!setEnvironmentVars(pipeChildRead, pipeChildWrite))
        fail("Failed to set environment variables");
    else if (!launchChild(&childPid))
        fail("Failed to launch application");

    // Close the ends of the pipes that the child will use; we don't need them.
    closePipe(pipeChildRead);
    closePipe(pipeChildWrite);
    pipeChildRead = pipeChildWrite = NULLPIPE;

    dbgpipe("Parent in command processing loop.\n");

    // Now, we block for instructions until the pipe fails (child closed it or
    //  terminated/crashed).
    processCommands(pipeParentRead, pipeParentWrite);

    dbgpipe("Parent shutting down.\n");

    // Close our ends of the pipes.
    writeBye(pipeParentWrite);
    closePipe(pipeParentRead);
    closePipe(pipeParentWrite);

    deinitSteamworks();

    dbgpipe("Parent waiting on child process.\n");

    // Wait for the child to terminate, close the child process handles.
    const int retval = closeProcess(&childPid);

    dbgpipe("Parent exiting mainline (child exit code %d).\n", retval);

    return retval;
} // mainline

// end of steamshim_parent.cpp ...