/*
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 1997-2021. All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * %CopyrightEnd%
 */

/*
 * Purpose: Interface to the registry API.
 */

#include <windows.h>
#include "erl_driver.h"
#include "sys.h"

/*
 * Commands recognised by this driver.
 */

#define CMD_GET_CURRENT		0
#define CMD_OPEN_KEY		1
#define CMD_CREATE_KEY 		2
#define CMD_GET_ALL_SUBKEYS	3
#define CMD_GET_VALUE		4
#define CMD_GET_ALL_VALUES	5
#define CMD_SET_VALUE		6
#define CMD_DELETE_KEY		7
#define CMD_DELETE_VALUE	8

/*
 * Microsoft-specific function to map a WIN32 error code to a Posix errno.
 */

extern void _dosmaperr(DWORD);

/*
 * Information kept for a registry port (since there is no controlling
 * Erlang process, all state must be kept here).
 */

typedef struct {
    ErlDrvPort port;		/* Port handle. */
    REGSAM sam;			/* Access for handles. */
    HKEY hkey;			/* Handle to open key. */
    HKEY hkey_root;		/* Root handle for current key. */
    char* key;			/* Name of key. */
    DWORD key_size;		/* Size of key. */
    LPSTR name_buf;		/* Buffer for names. */
    DWORD name_buf_size;	/* Size of name buffer. */
    LPSTR value_buf;		/* Buffer for values. */
    DWORD value_buf_size;	/* Size of value buffer. */
} RegPort;


/*
 * Local functions.
 */

static void reply(RegPort* rp, LONG result);
static BOOL fix_value_result(RegPort* rp, LONG result, DWORD type,
			     LPSTR name, DWORD nameSize, LPSTR value,
			     DWORD valueSize);
static int key_reply(RegPort* rp, LPSTR name, DWORD nameSize);
static int value_reply(RegPort* rp, DWORD type, LPSTR name, DWORD nameSize,
		       LPSTR value, DWORD valueSize);
static int state_reply(RegPort* rp, HKEY root, LPSTR name, DWORD nameSize);
static int maperror(DWORD error);
/*
 * Local variables.
 */

static int reg_init(void);
static ErlDrvData reg_start(ErlDrvPort, char*);
static void reg_stop(ErlDrvData);
static void reg_from_erlang(ErlDrvData, char*, ErlDrvSizeT);

struct erl_drv_entry registry_driver_entry = {
    reg_init,
    reg_start,
    reg_stop,
    reg_from_erlang,
    NULL,
    NULL,
    "registry__drv__",
    NULL,
    NULL, /* handle */
    NULL, /* control */
    NULL, /* timeout */
    NULL, /* outputv */
    NULL, /* ready_async */
    NULL, /* flush */
    NULL, /* call */
    NULL, /* event */
    ERL_DRV_EXTENDED_MARKER,
    ERL_DRV_EXTENDED_MAJOR_VERSION,
    ERL_DRV_EXTENDED_MINOR_VERSION,
    0,
    NULL,
    NULL,
    NULL,
};

static int
reg_init(void)
{
    DEBUGF(("reg_init()\n"));
    return 0;
}

static ErlDrvData
reg_start(ErlDrvPort port, char* buf)
{
    RegPort* rp;
    char* s;
    REGSAM sam = KEY_READ;

    if ((s = strchr(buf, ' ')) != NULL) {
	while (isspace(*s))
	    s++;
	while (*s != '\0') {
	    if (*s == 'r') {
		sam |= KEY_READ;
	    } else if (*s == 'w') {
		sam |= KEY_WRITE;
	    }
	    s++;
	}
    }
  
    rp = driver_alloc(sizeof(RegPort));
    if (rp == NULL) {
	return ERL_DRV_ERROR_GENERAL;
    }
    rp->port = port;
    rp->hkey = rp->hkey_root = HKEY_CLASSES_ROOT;
    rp->sam = sam;
    rp->key = driver_alloc(1);
    rp->key_size = 0;
    rp->name_buf_size = 64;
    rp->name_buf = driver_alloc(rp->name_buf_size);
    rp->value_buf_size = 64;
    rp->value_buf = driver_alloc(rp->value_buf_size);
    return (ErlDrvData) rp;
}

static void
reg_stop(ErlDrvData clientData)
{
    RegPort* rp = (RegPort *) clientData;

    (void) RegCloseKey(rp->hkey);
    driver_free(rp->name_buf);
    driver_free(rp->value_buf);
    driver_free(rp->key);
    driver_free(rp);
    /* return 1; */
}

static void
reg_from_erlang(ErlDrvData clientData, char* buf, ErlDrvSizeT count)
{
    RegPort* rp = (RegPort *) clientData;
    int cmd;
    HKEY hkey;
    LONG result;
    DWORD nameSize;
    DWORD type;			/* Type of data in buffer. */
    DWORD valueSize;		/* Size of value buffer. */

    cmd = buf[0];
    buf++, count--;
    switch (cmd) {
    case CMD_GET_CURRENT:
	state_reply(rp, rp->hkey_root, rp->key, rp->key_size);
	break;
    case CMD_OPEN_KEY:
	{
	    char* key;
	    HKEY newKey;

	    /*
	     * [HKEY(DWORD), KeyString(string)]
	     */

	    hkey = (HKEY)(SWord) get_int32(buf+0);
	    rp->hkey_root = hkey;
	    key = buf+4;
	    result = RegOpenKeyEx(hkey, key, 0, rp->sam, &newKey);
	    if (result == ERROR_SUCCESS) {
		RegCloseKey(rp->hkey);
		rp->hkey = newKey;
		driver_free(rp->key);
		rp->key_size = strlen(key);
		rp->key = driver_alloc(rp->key_size+1);
		strcpy(rp->key, key);
	    }
	    reply(rp, result);
	    return;
	}
	break;
    case CMD_CREATE_KEY:
	{
	    char* key;
	    HKEY newKey;
	    DWORD disposition;

	    hkey = (HKEY)(SWord) get_int32(buf+0);
	    rp->hkey_root = hkey;
	    key = buf+4;
	    result = RegCreateKeyEx(hkey, key, 0, "", 0, rp->sam, NULL,
				    &newKey, &disposition);
	    if (result == ERROR_SUCCESS) {
		RegCloseKey(rp->hkey);
		rp->hkey = newKey;
		driver_free(rp->key);
		rp->key_size = strlen(key);
		rp->key = driver_alloc(rp->key_size+1);
		strcpy(rp->key, key);
	    }
	    reply(rp, result);
	    return;
	}
	break;
    case CMD_GET_ALL_SUBKEYS:
	{
	    int i;
      
	    i = 0;
	    for (;;) {
		nameSize = rp->name_buf_size;
		result = RegEnumKeyEx(rp->hkey, i, rp->name_buf, &nameSize,
				      NULL, NULL, NULL, NULL);
		if (result == ERROR_MORE_DATA) {
		    rp->name_buf_size *= 2;
		    rp->name_buf = driver_realloc(rp->name_buf,
						  rp->name_buf_size);
		    continue;
		} else if (result == ERROR_NO_MORE_ITEMS) {
		    reply(rp, ERROR_SUCCESS);
		    return;
		} else if (result != ERROR_SUCCESS) {
		    reply(rp, result);
		    return;
		}
		key_reply(rp, rp->name_buf, nameSize);
		i++;
	    }
	}
	break;
    case CMD_GET_VALUE:
	do {
	    valueSize = rp->value_buf_size;
	    result = RegQueryValueEx(rp->hkey, buf, NULL, &type,
				     rp->value_buf, &valueSize);
	} while (!fix_value_result(rp, result, type, buf, strlen(buf),
				   rp->value_buf, valueSize));
	break;
    case CMD_GET_ALL_VALUES:
	{
	    int i;

	    i = 0;
	    for (;;) {
		nameSize = rp->name_buf_size;
		valueSize = rp->value_buf_size;
		result = RegEnumValue(rp->hkey, i, rp->name_buf, &nameSize,
				      NULL, &type, rp->value_buf, &valueSize);
		if (result == ERROR_NO_MORE_ITEMS) {
		    reply(rp, ERROR_SUCCESS);
		    return;
		}
		if (fix_value_result(rp, result, type, rp->name_buf, nameSize,
				     rp->value_buf, valueSize)) {
		    i++;
		}
	    }
	}
	break;
    case CMD_SET_VALUE:
	{
	    LPSTR name;
	    DWORD dword;

	    /*
	     * [Type(DWORD), Name(string), Value(bytes)]
	     */

	    type = get_int32(buf);
	    buf += 4;
	    count -= 4;
	    name = buf;
	    nameSize = strlen(buf) + 1;
	    buf += nameSize;
	    count -= nameSize;
	    if (type == REG_DWORD) {
		/*
		 * Must pass a pointer to a DWORD in host byte order.
		 */
		dword = get_int32(buf);
		buf = (char *) &dword;
		ASSERT(count == 4);
	    }
	    result = RegSetValueEx(rp->hkey, name, 0, type, buf, (DWORD)count);
	    reply(rp, result);
	}
	break;
    case CMD_DELETE_KEY:
	{
	    char* key = buf;

	    result = RegDeleteKey(rp->hkey, key);
	    reply(rp, result);
	}
	break;
    case CMD_DELETE_VALUE:
	result = RegDeleteValue(rp->hkey, buf);
	reply(rp, result);
	break;
    }
    /* return 1; */
}

static BOOL
fix_value_result(RegPort* rp, LONG result, DWORD type,
		 LPSTR name, DWORD nameSize, LPSTR value, DWORD valueSize)
{
    if (result == ERROR_MORE_DATA) {
	DWORD max_name1;
	DWORD max_name2;
	DWORD max_value;
	int ok;

	ok = RegQueryInfoKey(rp->hkey, NULL, NULL, NULL,
			     NULL, &max_name1, NULL, NULL, &max_name2,
			     &max_value, NULL, NULL);
#ifdef DEBUG
	if (ok != ERROR_SUCCESS) {
	    char buff[256];
	    erts_snprintf(buff, sizeof(buff), "Failure in registry_drv line %d, error = %d",
		    __LINE__, GetLastError());
	    MessageBox(NULL, buff, "Internal error", MB_OK);
	    ASSERT(ok == ERROR_SUCCESS);
	}
#endif
	rp->name_buf_size = (max_name1 > max_name2 ? max_name1 : max_name2) 
	    + 1;
	rp->value_buf_size = max_value + 1;
	rp->name_buf = driver_realloc(rp->name_buf, rp->name_buf_size);
	rp->value_buf = driver_realloc(rp->value_buf, rp->value_buf_size);
	return FALSE;
    } else if (result != ERROR_SUCCESS) {
	reply(rp, result);
	return TRUE;
    }
  
    /*
     * Do some data conversion which is easier to do here
     * than in Erlang.
     */

    switch (type) {
    case REG_SZ:
    case REG_EXPAND_SZ:
	valueSize--;		/* No reason to send the '\0' to Erlang. */
	break;
    case REG_DWORD_LITTLE_ENDIAN:
    case REG_DWORD_BIG_ENDIAN:
	/*
	 * The value is a DWORD stored in host byte order.
	 * We must retrieve it and store it in network byte order.
	 */
	{
	    DWORD dword = * ((DWORD *) value);
	    put_int32(dword, value);
	    type = REG_DWORD;	/* Simplify life for Erlang code. */
	    break;
	}
    }

    return value_reply(rp, type, name, nameSize, value, valueSize);
}

/*
 * Sends one of the following replies back to Erlang,
 * depending on result:
 *
 * [$e|Posix error(string)]			Error
 * [$o]						Ok
 */

static void
reply(RegPort* rp, LONG result)
{
    char sbuf[256];

    if (result == ERROR_SUCCESS) {
	sbuf[0] = 'o';
	driver_output(rp->port, sbuf, 1);
    } else {
	char* s;
	char* t;
	int err;

	sbuf[0] = 'e';
	err = maperror(result);
	for (s = erl_errno_id(err), t = sbuf+1; *s; s++, t++) {
	    *t = tolower(*s);
	}
	driver_output(rp->port, sbuf, t-sbuf);
    }
    /* return 1; */
}

/*
 * Sends a key to Erlang:
 *
 * [$k, Keyname(string)]
 */

static int
key_reply(RegPort* rp,		/* Pointer to port structure. */
	  LPSTR name,		/* Pointer to name. */
	  DWORD nameSize)	/* Length of name. */
{
    char sbuf[512];
    char* s = sbuf;
    int needed = 1+nameSize;

    if (sizeof sbuf < needed) {
	s = driver_alloc(needed);
    }

    s[0] = 'k';
    memcpy(s+1, name, nameSize);
    driver_output(rp->port, s, needed);

    if (s != sbuf) {
	driver_free(s);
    }
    return 1;
}

/*
 * Sends a value to Erlang:
 *
 * [$v, Type(DWORD), Valuename(string), 0, Value(bytes)]
 */

static int
value_reply(RegPort* rp,	/* Pointer to port structure. */
	    DWORD type,		/* Type of value */
	    LPSTR name,		/* Pointer to name. */
	    DWORD nameSize,	/* Length of name. */
	    LPSTR value,	/* Pointer to value. */
	    DWORD valueSize)	/* Size of value. */
{
    char sbuf[512];
    char* s = sbuf;
    int needed = 1+4+nameSize+1+valueSize;
    int i;

    if (sizeof sbuf < needed) {
	s = driver_alloc(needed);
    }

    s[0] = 'v';
    i = 1;
    put_int32(type, s+i);
    i += 4;
    memcpy(s+i, name, nameSize);
    i += nameSize;
    s[i++] = '\0';
    memcpy(s+i, value, valueSize);
    ASSERT(i+valueSize == needed);
    driver_output(rp->port, s, needed);

    if (s != sbuf) {
	driver_free(s);
    }
    return 1;
}

/*
 * Sends a key to Erlang:
 *
 * [$s, HKEY(DWORD), Keyname(string)]	State
 */

static int
state_reply(RegPort* rp,	/* Pointer to port structure. */
	    HKEY root,		/* Handle to root key for this key. */
	    LPSTR name,		/* Pointer to name. */
	    DWORD nameSize)	/* Length of name. */
{
    char sbuf[512];
    char* s = sbuf;
    int needed = 1+4+nameSize;
    int i;

    if (sizeof sbuf < needed) {
	s = driver_alloc(needed);
    }

    s[0] = 's';
    i = 1;
    put_int32((DWORD)(SWord) root, s+i);
    i += 4;
    memcpy(s+i, name, nameSize);
    ASSERT(i+nameSize == needed);
    driver_output(rp->port, s, needed);

    if (s != sbuf) {
	driver_free(s);
    }
    return 1;
}

static int
maperror(DWORD error)
{
    DEBUGF(("Mapping %d\n", error));
    switch (error) {
    case ERROR_BADDB:
    case ERROR_BADKEY:
    case ERROR_CANTOPEN:
    case ERROR_CANTWRITE:
    case ERROR_REGISTRY_RECOVERED:
    case ERROR_REGISTRY_CORRUPT:
    case ERROR_REGISTRY_IO_FAILED:
    case ERROR_NOT_REGISTRY_FILE:
	return EIO;
    case ERROR_KEY_DELETED:
	return EINVAL;
    default:
	_dosmaperr(error);
	return errno;
    }
}