/*

 * @file sqlite3port.c
 * @author Lukasz Skrzypczak (lukasz.skrypczak@mudita.com)
 * @date 21 cze 2018
 * @brief Insert brief information about this file purpose.
 * @copyright Copyright (C) 2018 mudita.com. Based on https://www.sqlite.org/src/doc/trunk/src/test_demovfs.c
 * @details :
 **
 ** This file implements an example of a simple VFS implementation that
 ** omits complex features often not required or not possible on embedded
 ** platforms.  Code is included to buffer writes to the journal file,
 ** which can be a significant performance improvement on some embedded
 ** platforms.
 **
 ** OVERVIEW
 **
 **   The code in this file implements a minimal SQLite VFS that can be
 **   used on Linux and other posix-like operating systems. The following
 **   system calls are used:
 **
 **    File-system: access(), unlink(), getcwd()
 **    File IO:     open(), read(), write(), fsync(), close(), fstat()
 **    Other:       sleep(), usleep(), time()
 **
 **   The following VFS features are omitted:
 **
 **     1. File locking. The user must ensure that there is at most one
 **        connection to each database when using this VFS. Multiple
 **        connections to a single shared-cache count as a single connection
 **        for the purposes of the previous statement.
 **
 **     2. The loading of dynamic extensions (shared libraries).
 **
 **     3. Temporary files. The user must configure SQLite to use in-memory
 **        temp files when using this VFS. The easiest way to do this is to
 **        compile with:
 **
 **          -DSQLITE_TEMP_STORE=3
 **
 **     4. File truncation. As of version 3.6.24, SQLite may run without
 **        a working xTruncate() call, providing the user does not configure
 **        SQLite to use "journal_mode=truncate", or use both
 **        "journal_mode=persist" and ATTACHed databases.
 **
 **   It is assumed that the system uses UNIX-like path-names. Specifically,
 **   that '/' characters are used to separate path components and that
 **   a path-name is a relative path unless it begins with a '/'. And that
 **   no UTF-8 encoded paths are greater than 512 bytes in length.
 **
 ** JOURNAL WRITE-BUFFERING
 **
 **   To commit a transaction to the database, SQLite first writes rollback
 **   information into the journal file. This usually consists of 4 steps:
 **
 **     1. The rollback information is sequentially written into the journal
 **        file, starting at the start of the file.
 **     2. The journal file is synced to disk.
 **     3. A modification is made to the first few bytes of the journal file.
 **     4. The journal file is synced to disk again.
 **
 **   Most of the data is written in step 1 using a series of calls to the
 **   VFS xWrite() method. The buffers passed to the xWrite() calls are of
 **   various sizes. For example, as of version 3.6.24, when committing a
 **   transaction that modifies 3 pages of a database file that uses 4096
 **   byte pages residing on a media with 512 byte sectors, SQLite makes
 **   eleven calls to the xWrite() method to create the rollback journal,
 **   as follows:
 **
 **             Write offset | Bytes written
 **             ----------------------------
 **                        0            512
 **                      512              4
 **                      516           4096
 **                     4612              4
 **                     4616              4
 **                     4620           4096
 **                     8716              4
 **                     8720              4
 **                     8724           4096
 **                    12820              4
 **             ++++++++++++SYNC+++++++++++
 **                        0             12
 **             ++++++++++++SYNC+++++++++++
 **
 **   On many operating systems, this is an efficient way to write to a file.
 **   However, on some embedded systems that do not cache writes in OS
 **   buffers it is much more efficient to write data in blocks that are
 **   an integer multiple of the sector-size in size and aligned at the
 **   start of a sector.
 **
 **   To work around this, the code in this file allocates a fixed size
 **   buffer of SQLITE_DEMOVFS_BUFFERSZ using sqlite3_malloc() whenever a
 **   journal file is opened. It uses the buffer to coalesce sequential
 **   writes into aligned SQLITE_DEMOVFS_BUFFERSZ blocks. When SQLite
 **   invokes the xSync() method to sync the contents of the file to disk,
 **   all accumulated data is written out, even if it does not constitute
 **   a complete block. This means the actual IO to create the rollback
 **   journal for the example transaction above is this:
 **
 **             Write offset | Bytes written
 **             ----------------------------
 **                        0           8192
 **                     8192           4632
 **             ++++++++++++SYNC+++++++++++
 **                        0             12
 **             ++++++++++++SYNC+++++++++++
 **
 **   Much more efficient if the underlying OS is not caching write
 **   operations.
 */

#if !defined(SQLITE_TEST) || SQLITE_OS_UNIX

#include "sqlite3.h"

#include <assert.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
//#include <sys/file.h>
#include <sys/param.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#include <fcntl.h>

#include "FreeRTOS.h"
#include "task.h"
#include "vfs.hpp"
#include "config.h"

/*
 ** Size of the write buffer used by journal files in bytes.
 */
#ifndef SQLITE_ECOPHONEVFS_BUFFERSZ
#define SQLITE_ECOPHONEVFS_BUFFERSZ 8192
#endif

/*
 ** The maximum pathname length supported by this VFS.
 */
#define MAXPATHNAME 512

#define UNUSED(x) ((void)(x))

/*
 ** When using this VFS, the sqlite3_file* handles that SQLite uses are
 ** actually pointers to instances of type EcophoneFile.
 */
typedef struct EcophoneFile EcophoneFile;
struct EcophoneFile
{
    sqlite3_file base; /* Base class. Must be first. */
    vfs::FILE *fd;     /* File descriptor */

    char *aBuffer;             /* Pointer to malloc'd buffer */
    int nBuffer;               /* Valid bytes of data in zBuffer */
    sqlite3_int64 iBufferOfst; /* Offset in file of zBuffer[0] */
};

/*
 ** Write directly to the file passed as the first argument. Even if the
 ** file has a write-buffer (EcophoneFile.aBuffer), ignore it.
 */
static int ecophoneDirectWrite(EcophoneFile *p,   /* File handle */
                               const void *zBuf,  /* Buffer containing data to write */
                               int iAmt,          /* Size of data to write in bytes */
                               sqlite_int64 iOfst /* File offset to write to */
)
{
    size_t nWrite; /* Return value from write() */

    auto fileSize = vfs.filelength(p->fd);
    // vfs_fseek doesn't like offset to be > file size
    if (iOfst >= fileSize)
        iOfst = fileSize;

    if (vfs.fseek(p->fd, iOfst, SEEK_SET) != 0) {
        return SQLITE_IOERR_WRITE;
    }

    nWrite = vfs.fwrite(zBuf, 1, iAmt, p->fd);
    if ((int)nWrite != iAmt) {
        return SQLITE_IOERR_WRITE;
    }

    return SQLITE_OK;
}

/*
 ** Flush the contents of the EcophoneFile.aBuffer buffer to disk. This is a
 ** no-op if this particular file does not have a buffer (i.e. it is not
 ** a journal file) or if the buffer is currently empty.
 */
static int ecophoneFlushBuffer(EcophoneFile *p)
{
    int rc = SQLITE_OK;
    if (p->nBuffer) {
        rc         = ecophoneDirectWrite(p, p->aBuffer, p->nBuffer, p->iBufferOfst);
        p->nBuffer = 0;
    }
    return rc;
}

/*
 ** Close a file.
 */
static int ecophoneClose(sqlite3_file *pFile)
{
    int rc;
    EcophoneFile *p = (EcophoneFile *)pFile;
    rc              = ecophoneFlushBuffer(p);
    sqlite3_free(p->aBuffer);

    vfs.fclose(p->fd);
    return rc;
}

/*
 ** Read data from a file.
 */
static int ecophoneRead(sqlite3_file *pFile, void *zBuf, int iAmt, sqlite_int64 iOfst)
{
    EcophoneFile *p = (EcophoneFile *)pFile;
    int nRead; /* Return value from read() */
    int rc;    /* Return code from ecophoneFlushBuffer() */

    /* Flush any data in the write buffer to disk in case this operation
     ** is trying to read data the file-region currently cached in the buffer.
     ** It would be possible to detect this case and possibly save an
     ** unnecessary write here, but in practice SQLite will rarely read from
     ** a journal file when there is data cached in the write-buffer.
     */
    rc = ecophoneFlushBuffer(p);
    if (rc != SQLITE_OK) {
        return rc;
    }

    // vfs_fseek returns error if desired file position is > file size. To mimic lseek desired position need to be
    // truncated
    auto fileSize = vfs.filelength(p->fd);
    if (p->fd != NULL) {
        if (iOfst >= fileSize)
            iOfst = fileSize;
    }

    if (vfs.fseek(p->fd, iOfst, SEEK_SET) != 0) {
        return SQLITE_IOERR_READ;
    }

    nRead = vfs.fread(zBuf, 1, iAmt, p->fd);

    if (nRead == iAmt) {
        return SQLITE_OK;
    }
    else if (nRead >= 0) {
        return SQLITE_IOERR_SHORT_READ;
    }

    return SQLITE_IOERR_READ;
}

/*
 ** Write data to a crash-file.
 */
static int ecophoneWrite(sqlite3_file *pFile, const void *zBuf, int iAmt, sqlite_int64 iOfst)
{
    EcophoneFile *p = (EcophoneFile *)pFile;

    if (p->aBuffer) {
        char *z         = (char *)zBuf; /* Pointer to remaining data to write */
        int n           = iAmt;         /* Number of bytes at z */
        sqlite3_int64 i = iOfst;        /* File offset to write to */

        while (n > 0) {
            int nCopy; /* Number of bytes to copy into buffer */

            /* If the buffer is full, or if this data is not being written directly
             ** following the data already buffered, flush the buffer. Flushing
             ** the buffer is a no-op if it is empty.
             */
            if (p->nBuffer == SQLITE_ECOPHONEVFS_BUFFERSZ || p->iBufferOfst + p->nBuffer != i) {
                int rc = ecophoneFlushBuffer(p);
                if (rc != SQLITE_OK) {
                    return rc;
                }
            }
            assert(p->nBuffer == 0 || p->iBufferOfst + p->nBuffer == i);
            p->iBufferOfst = i - p->nBuffer;

            /* Copy as much data as possible into the buffer. */
            nCopy = SQLITE_ECOPHONEVFS_BUFFERSZ - p->nBuffer;
            if (nCopy > n) {
                nCopy = n;
            }
            memcpy(&p->aBuffer[p->nBuffer], z, nCopy);
            p->nBuffer += nCopy;

            n -= nCopy;
            i += nCopy;
            z += nCopy;
        }
    }
    else {
        return ecophoneDirectWrite(p, zBuf, iAmt, iOfst);
    }

    return SQLITE_OK;
}

/*
 ** Truncate a file. This is a no-op for this VFS (see header comments at
 ** the top of the file).
 */
static int ecophoneTruncate(sqlite3_file *pFile, sqlite_int64 size)
{
#if 0
    if( ftruncate(((EcophoneFile *)pFile)->fd, size) ) return SQLITE_IOERR_TRUNCATE;
#else
    UNUSED(pFile);
    UNUSED(size);
#endif
    return SQLITE_OK;
}

/*
 ** Sync the contents of the file to the persistent media.
 */
static int ecophoneSync(sqlite3_file *pFile, int flags)
{
    EcophoneFile *p = (EcophoneFile *)pFile;
    int rc;

    UNUSED(flags);

    rc = ecophoneFlushBuffer(p);
    if (rc != SQLITE_OK) {
        return rc;
    }

    // rc = fflush(p->fd);  //FF doesn't have this function
    rc = SQLITE_OK;
    return (rc == 0 ? SQLITE_OK : SQLITE_IOERR_FSYNC);
}

/*
 ** Write the size of the file in bytes to *pSize.
 */
static int ecophoneFileSize(sqlite3_file *pFile, sqlite_int64 *pSize)
{
    EcophoneFile *p = (EcophoneFile *)pFile;
    int rc; /* Return code from fstat() call */

    /* Flush the contents of the buffer to disk. As with the flush in the
     ** ecophoneRead() method, it would be possible to avoid this and save a write
     ** here and there. But in practice this comes up so infrequently it is
     ** not worth the trouble.
     */
    rc = ecophoneFlushBuffer(p);
    if (rc != SQLITE_OK) {
        return rc;
    }

    *pSize = vfs.filelength(p->fd);

    return SQLITE_OK;
}

/*
 ** Locking functions. The xLock() and xUnlock() methods are both no-ops.
 ** The xCheckReservedLock() always indicates that no other process holds
 ** a reserved lock on the database file. This ensures that if a hot-journal
 ** file is found in the file-system it is rolled back.
 */
static int ecophoneLock(sqlite3_file *pFile, int eLock)
{
    UNUSED(pFile);
    UNUSED(eLock);
    return SQLITE_OK;
}

static int ecophoneUnlock(sqlite3_file *pFile, int eLock)
{
    UNUSED(pFile);
    UNUSED(eLock);
    return SQLITE_OK;
}

static int ecophoneCheckReservedLock(sqlite3_file *pFile, int *pResOut)
{
    UNUSED(pFile);
    *pResOut = 0;
    return SQLITE_OK;
}

/*
 ** No xFileControl() verbs are implemented by this VFS.
 */
static int ecophoneFileControl(sqlite3_file *pFile, int op, void *pArg)
{
    UNUSED(pFile);
    UNUSED(op);
    UNUSED(pArg);
    return SQLITE_OK;
}

/*
 ** The xSectorSize() and xDeviceCharacteristics() methods. These two
 ** may return special values allowing SQLite to optimize file-system
 ** access to some extent. But it is also safe to simply return 0.
 */
static int ecophoneSectorSize(sqlite3_file *pFile)
{
    UNUSED(pFile);
    return 0;
}

static int ecophoneDeviceCharacteristics(sqlite3_file *pFile)
{
    UNUSED(pFile);
    return 0;
}

/*
 ** Query the file-system to see if the named file exists, is readable or
 ** is both readable and writable.
 */
static int ecophoneAccess(sqlite3_vfs *pVfs, const char *zPath, int flags, int *pResOut)
{
    vfs::FILE *fd;
    UNUSED(pVfs);

    assert(flags == SQLITE_ACCESS_EXISTS       /* access(zPath, F_OK) */
           || flags == SQLITE_ACCESS_READ      /* access(zPath, R_OK) */
           || flags == SQLITE_ACCESS_READWRITE /* access(zPath, R_OK|W_OK) */
    );

    fd = vfs.fopen(zPath, (const char *)"r");
    if (fd != NULL) {
        if (pResOut)
            *pResOut = flags;
        vfs.fclose(fd);
    }
    else if (pResOut)
        *pResOut = 0;
    return SQLITE_OK;
}

/*
 ** Open a file handle.
 */
#pragma GCC diagnostic ignored "-Wmissing-field-initializers"

static int ecophoneOpen(sqlite3_vfs *pVfs,   /* VFS */
                        const char *zName,   /* File to open, or 0 for a temp file */
                        sqlite3_file *pFile, /* Pointer to EcophoneFile struct to populate */
                        int flags,           /* Input SQLITE_OPEN_XXX flags */
                        int *pOutFlags       /* Output SQLITE_OPEN_XXX flags (or NULL) */
)
{
    UNUSED(pVfs);

    static const sqlite3_io_methods ecophoneio = {
        1,                            /* iVersion */
        ecophoneClose,                /* xClose */
        ecophoneRead,                 /* xRead */
        ecophoneWrite,                /* xWrite */
        ecophoneTruncate,             /* xTruncate */
        ecophoneSync,                 /* xSync */
        ecophoneFileSize,             /* xFileSize */
        ecophoneLock,                 /* xLock */
        ecophoneUnlock,               /* xUnlock */
        ecophoneCheckReservedLock,    /* xCheckReservedLock */
        ecophoneFileControl,          /* xFileControl */
        ecophoneSectorSize,           /* xSectorSize */
        ecophoneDeviceCharacteristics /* xDeviceCharacteristics */
    };

    EcophoneFile *p = (EcophoneFile *)pFile; /* Populate this structure */
    char *aBuf      = 0;

    if (zName == 0) {
        return SQLITE_IOERR;
    }

    if (flags & SQLITE_OPEN_MAIN_JOURNAL) {
        aBuf = (char *)sqlite3_malloc(SQLITE_ECOPHONEVFS_BUFFERSZ);
        if (!aBuf) {
            return SQLITE_NOMEM;
        }
    }

    memset(p, 0, sizeof(EcophoneFile));

    std::string oflags;
    if (flags & SQLITE_OPEN_READONLY) {
        oflags = "r";
    }
    else if ((flags & SQLITE_OPEN_READWRITE) && (flags & SQLITE_OPEN_CREATE)) {

        // check if database specified exists
        p->fd = vfs.fopen(zName, "r");
        if (p->fd == nullptr) {
            // database doesn't exist, create new one with read&write permissions
            oflags = "w+";
        }
        else {
            // database exists, open it with read&write permissions
            vfs.fclose(p->fd);
            oflags = "r+";
        }
    }
    else {
        oflags = "r+";
    }

    p->fd = vfs.fopen(zName, oflags.c_str());
    if (p->fd == nullptr) {
        sqlite3_free(aBuf);
        return SQLITE_CANTOPEN;
    }

    p->aBuffer = aBuf;

    if (pOutFlags) {
        *pOutFlags = flags;
    }
    p->base.pMethods = &ecophoneio;
    return SQLITE_OK;
}

/*
 ** Delete the file identified by argument zPath. If the dirSync parameter
 ** is non-zero, then ensure the file-system modification to delete the
 ** file has been synced to disk before returning.
 */
static int ecophoneDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync)
{
    UNUSED(pVfs);
    int rc; /* Return code */

    rc = vfs.remove(zPath);
    if (rc != 0 /*&& errno==ENOENT*/)
        return SQLITE_OK;

    if (rc == 0 && dirSync) {
        vfs::FILE *dfd;             /* File descriptor open on directory */
        int i;                      /* Iterator variable */
        char zDir[MAXPATHNAME + 1]; /* Name of directory containing file zPath */

        /* Figure out the directory name from the path of the file deleted. */
        sqlite3_snprintf(MAXPATHNAME, zDir, "%q", zPath);
        zDir[MAXPATHNAME] = '\0';
        for (i = strlen(zDir); i > 1 && zDir[i] != '/'; i++)
            ;
        zDir[i] = '\0';

        /* Open a file-descriptor on the directory. Sync. Close. */
        dfd = vfs.fopen(zDir, "D");
        if (dfd == NULL) {
            rc = -1;
        }
        else {
            rc = SQLITE_OK;
            vfs.fclose(dfd);
        }
    }
    return (rc == 0 ? SQLITE_OK : SQLITE_IOERR_DELETE);
}

/*
 ** Argument zPath points to a nul-terminated string containing a file path.
 ** If zPath is an absolute path, then it is copied as is into the output
 ** buffer. Otherwise, if it is a relative path, then the equivalent full
 ** path is written to the output buffer.
 **
 ** This function assumes that paths are UNIX style. Specifically, that:
 **
 **   1. Path components are separated by a '/'. and
 **   2. Full paths begin with a '/' character.
 */
static int ecophoneFullPathname(sqlite3_vfs *pVfs, /* VFS */
                                const char *zPath, /* Input path (possibly a relative path) */
                                int nPathOut,      /* Size of output buffer in bytes */
                                char *zPathOut     /* Pointer to output buffer */
)
{
    UNUSED(pVfs);

    std::string path;
    // absolute path
    if (zPath[0] == '/') {}
    // relative path
    else {
        path = vfs.getcurrdir();
        if (path.empty())
            return SQLITE_IOERR;
    }

    // Current path is "/"
    if (path.size() == 1) {
        sqlite3_snprintf(nPathOut, zPathOut, "%q%q", path.c_str(), zPath);
    }
    else {
        sqlite3_snprintf(nPathOut, zPathOut, "%q/%q", path.c_str(), zPath);
    }

    zPathOut[nPathOut - 1] = '\0';

    return SQLITE_OK;
}

/*
 ** The following four VFS methods:
 **
 **   xDlOpen
 **   xDlError
 **   xDlSym
 **   xDlClose
 **
 ** are supposed to implement the functionality needed by SQLite to load
 ** extensions compiled as shared objects. This simple VFS does not support
 ** this functionality, so the following functions are no-ops.
 */
static void *ecophoneDlOpen(sqlite3_vfs *pVfs, const char *zPath)
{
    UNUSED(pVfs);
    UNUSED(zPath);
    return 0;
}

static void ecophoneDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg)
{
    UNUSED(pVfs);
    sqlite3_snprintf(nByte, zErrMsg, "Loadable extensions are not supported");
    zErrMsg[nByte - 1] = '\0';
}

static void (*ecophoneDlSym(sqlite3_vfs *pVfs, void *pH, const char *z))(void)
{
    UNUSED(pVfs);
    UNUSED(pH);
    UNUSED(z);
    return 0;
}

static void ecophoneDlClose(sqlite3_vfs *pVfs, void *pHandle)
{
    UNUSED(pVfs);
    UNUSED(pHandle);
    return;
}

/*
 ** Parameter zByte points to a buffer nByte bytes in size. Populate this
 ** buffer with pseudo-random data.
 */
static int ecophoneRandomness(sqlite3_vfs *pVfs, int nByte, char *zByte)
{
    UNUSED(pVfs);
    UNUSED(nByte);
    UNUSED(zByte);
    return SQLITE_OK;
}

/*
 ** Sleep for at least nMicro microseconds. Return the (approximate) number
 ** of microseconds slept for.
 */
static int ecophoneSleep(sqlite3_vfs *pVfs, int nMicro)
{
    UNUSED(pVfs);

    const TickType_t xDelay = nMicro / 1000 / portTICK_PERIOD_MS;
    vTaskDelay(xDelay);

    return nMicro;
}

/*
 ** Set *pTime to the current UTC time expressed as a Julian day. Return
 ** SQLITE_OK if successful, or an error code otherwise.
 **
 **   http://en.wikipedia.org/wiki/Julian_day
 **
 ** This implementation is not very good. The current time is rounded to
 ** an integer number of seconds. Also, assuming time_t is a signed 32-bit
 ** value, it will stop working some time in the year 2038 AD (the so-called
 ** "year 2038" problem that afflicts systems that store time this way).
 */
static int ecophoneCurrentTime(sqlite3_vfs *pVfs, double *pTime)
{

    time_t t = time(0);
    *pTime   = t / 86400.0 + 2440587.5;
    return SQLITE_OK;
}

/*
 ** This function returns a pointer to the VFS implemented in this file.
 ** To make the VFS available to SQLite:
 **
 **   sqlite3_vfs_register(sqlite3_ecophonevfs(), 0);
 */
#pragma GCC diagnostic ignored "-Wmissing-field-initializers"

sqlite3_vfs *sqlite3_ecophonevfs(void)
{
    static sqlite3_vfs ecophonevfs = {
        1,                    /* iVersion */
        sizeof(EcophoneFile), /* szOsFile */
        MAXPATHNAME,          /* mxPathname */
        0,                    /* pNext */
        "ecophone",           /* zName */
        0,                    /* pAppData */
        ecophoneOpen,         /* xOpen */
        ecophoneDelete,       /* xDelete */
        ecophoneAccess,       /* xAccess */
        ecophoneFullPathname, /* xFullPathname */
        ecophoneDlOpen,       /* xDlOpen */
        ecophoneDlError,      /* xDlError */
        ecophoneDlSym,        /* xDlSym */
        ecophoneDlClose,      /* xDlClose */
        ecophoneRandomness,   /* xRandomness */
        ecophoneSleep,        /* xSleep */
        ecophoneCurrentTime,  /* xCurrentTime */
    };
    return &ecophonevfs;
}

#endif /* !defined(SQLITE_TEST) || SQLITE_OS_UNIX */