/*
** 2007 May 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: icu.c,v 1.7 2007/12/13 21:54:11 drh Exp $
**
** This file implements an integration between the ICU library
** ("International Components for Unicode", an open-source library
** for handling unicode data) and SQLite. The integration uses
** ICU to provide the following to SQLite:
**
**   * An implementation of the SQL regexp() function (and hence REGEXP
**     operator) using the ICU uregex_XX() APIs.
**
**   * Implementations of the SQL scalar upper() and lower() functions
**     for case mapping.
**
**   * Integration of ICU and SQLite collation sequences.
**
**   * An implementation of the LIKE operator that uses ICU to
**     provide case-independent matching.
*/

#include "pch.h"
#include "framework.h"

#if !defined(SQLITE_CORE)                  \
 || defined(SQLITE_ENABLE_ICU)             \
 || defined(SQLITE_ENABLE_ICU_COLLATIONS)

/* Include ICU headers */
#include <icu.h>

#include <assert.h>

#ifndef SQLITE_CORE
#include "./sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#else
#include "sqlite3.h"
#endif


URegexpFlag regexFlags = (URegexpFlag)0;

/*
** This function is called when an ICU function called from within
** the implementation of an SQL scalar function returns an error.
**
** The scalar function context passed as the first argument is
** loaded with an error message based on the following two args.
*/
static void icuFunctionError(
    sqlite3_context* pCtx,       /* SQLite scalar function context */
    const char* zName,           /* Name of ICU function that failed */
    UErrorCode e                 /* Error code returned by ICU function */
) {
    char zBuf[128];
    sqlite3_snprintf(128, zBuf, "ICU error: %s(): %s", zName, u_errorName(e));
    zBuf[127] = '\0';
    sqlite3_result_error(pCtx, zBuf, -1);
}

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU)

/*
** Maximum length (in bytes) of the pattern in a LIKE or GLOB
** operator.
*/
#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
#endif

/*
** Version of sqlite3_free() that is always a function, never a macro.
*/
static void xFree(void* p) {
    sqlite3_free(p);
}

/*
** This lookup table is used to help decode the first byte of
** a multi-byte UTF8 character. It is copied here from SQLite source
** code file utf8.c.
*/
static const unsigned char icuUtf8Trans1[] = {
  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
};

#define SQLITE_ICU_READ_UTF8(zIn, c)                       \
  c = *(zIn++);                                            \
  if( c>=0xc0 ){                                           \
    c = icuUtf8Trans1[c-0xc0];                             \
    while( (*zIn & 0xc0)==0x80 ){                          \
      c = (c<<6) + (0x3f & *(zIn++));                      \
    }                                                      \
  }

#define SQLITE_ICU_SKIP_UTF8(zIn)                          \
  assert( *zIn );                                          \
  if( *(zIn++)>=0xc0 ){                                    \
    while( (*zIn & 0xc0)==0x80 ){zIn++;}                   \
  }


/*
** Compare two UTF-8 strings for equality where the first string is
** a "LIKE" expression. Return true (1) if they are the same and
** false (0) if they are different.
*/
static int icuLikeCompare(
    const uint8_t* zPattern,   /* LIKE pattern */
    const uint8_t* zString,    /* The UTF-8 string to compare against */
    const UChar32 uEsc         /* The escape character */
) {
    static const uint32_t MATCH_ONE = (uint32_t)'_';
    static const uint32_t MATCH_ALL = (uint32_t)'%';

    int prevEscape = 0;     /* True if the previous character was uEsc */

    while (1) {

        /* Read (and consume) the next character from the input pattern. */
        uint32_t uPattern;
        SQLITE_ICU_READ_UTF8(zPattern, uPattern);
        if (uPattern == 0) break;

        /* There are now 4 possibilities:
        **
        **     1. uPattern is an unescaped match-all character "%",
        **     2. uPattern is an unescaped match-one character "_",
        **     3. uPattern is an unescaped escape character, or
        **     4. uPattern is to be handled as an ordinary character
        */
        if (uPattern == MATCH_ALL && !prevEscape && uPattern != (uint32_t)uEsc) {
            /* Case 1. */
            uint8_t c;

            /* Skip any MATCH_ALL or MATCH_ONE characters that follow a
            ** MATCH_ALL. For each MATCH_ONE, skip one character in the
            ** test string.
            */
            while ((c = *zPattern) == MATCH_ALL || c == MATCH_ONE) {
                if (c == MATCH_ONE) {
                    if (*zString == 0) return 0;
                    SQLITE_ICU_SKIP_UTF8(zString);
                }
                zPattern++;
            }

            if (*zPattern == 0) return 1;

            while (*zString) {
                if (icuLikeCompare(zPattern, zString, uEsc)) {
                    return 1;
                }
                SQLITE_ICU_SKIP_UTF8(zString);
            }
            return 0;

        }
        else if (uPattern == MATCH_ONE && !prevEscape && uPattern != (uint32_t)uEsc) {
            /* Case 2. */
            if (*zString == 0) return 0;
            SQLITE_ICU_SKIP_UTF8(zString);

        }
        else if (uPattern == (uint32_t)uEsc && !prevEscape) {
            /* Case 3. */
            prevEscape = 1;

        }
        else {
            /* Case 4. */
            uint32_t uString;
            SQLITE_ICU_READ_UTF8(zString, uString);
            uString = (uint32_t)u_foldCase((UChar32)uString, U_FOLD_CASE_DEFAULT);
            uPattern = (uint32_t)u_foldCase((UChar32)uPattern, U_FOLD_CASE_DEFAULT);
            if (uString != uPattern) {
                return 0;
            }
            prevEscape = 0;
        }
    }

    return *zString == 0;
}

/*
** Implementation of the like() SQL function.  This function implements
** the build-in LIKE operator.  The first argument to the function is the
** pattern and the second argument is the string.  So, the SQL statements:
**
**       A LIKE B
**
** is implemented as like(B, A). If there is an escape character E,
**
**       A LIKE B ESCAPE E
**
** is mapped to like(B, A, E).
*/
static void icuLikeFunc(
    sqlite3_context* context,
    int argc,
    sqlite3_value** argv
) {
    const unsigned char* zA = sqlite3_value_text(argv[0]);
    const unsigned char* zB = sqlite3_value_text(argv[1]);
    UChar32 uEsc = 0;

    /* Limit the length of the LIKE or GLOB pattern to avoid problems
    ** of deep recursion and N*N behavior in patternCompare().
    */
    if (sqlite3_value_bytes(argv[0]) > SQLITE_MAX_LIKE_PATTERN_LENGTH) {
        sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
        return;
    }


    if (argc == 3) {
        /* The escape character string must consist of a single UTF-8 character.
        ** Otherwise, return an error.
        */
        int nE = sqlite3_value_bytes(argv[2]);
        const unsigned char* zE = sqlite3_value_text(argv[2]);
        int i = 0;
        if (zE == 0) return;
        U8_NEXT(zE, i, nE, uEsc);
        if (i != nE) {
            sqlite3_result_error(context,
                "ESCAPE expression must be a single character", -1);
            return;
        }
    }

    if (zA && zB) {
        sqlite3_result_int(context, icuLikeCompare(zA, zB, uEsc));
    }
}

/*
** Function to delete compiled regexp objects. Registered as
** a destructor function with sqlite3_set_auxdata().
*/
static void icuRegexpDelete(void* p) {
    URegularExpression* pExpr = (URegularExpression*)p;
    uregex_close(pExpr);
}

/*
** Implementation of SQLite REGEXP operator. This scalar function takes
** two arguments. The first is a regular expression pattern to compile
** the second is a string to match against that pattern. If either
** argument is an SQL NULL, then NULL Is returned. Otherwise, the result
** is 1 if the string matches the pattern, or 0 otherwise.
**
** SQLite maps the regexp() function to the regexp() operator such
** that the following two are equivalent:
**
**     zString REGEXP zPattern
**     regexp(zPattern, zString)
**
** Uses the following ICU regexp APIs:
**
**     uregex_open()
**     uregex_matches()
**     uregex_close()
*/
static void icuRegexpFunc(sqlite3_context* p, int nArg, sqlite3_value** apArg) {
    UErrorCode status = U_ZERO_ERROR;
    URegularExpression* pExpr;
    UBool res;
    const UChar* zString = (UChar*)sqlite3_value_text16(apArg[1]);

    (void)nArg;  /* Unused parameter */

    /* If the left hand side of the regexp operator is NULL,
    ** then the result is also NULL.
    */
    if (!zString) {
        return;
    }

    pExpr = (URegularExpression*)sqlite3_get_auxdata(p, 0);
    if (!pExpr) {
        const UChar* zPattern = (UChar*)sqlite3_value_text16(apArg[0]);
        if (!zPattern) {
            return;
        }
        pExpr = uregex_open(zPattern, -1, regexFlags, 0, &status);

        if (U_SUCCESS(status)) {
            sqlite3_set_auxdata(p, 0, pExpr, icuRegexpDelete);
        }
        else {
            assert(!pExpr);
            icuFunctionError(p, "uregex_open", status);
            return;
        }
    }

    /* Configure the text that the regular expression operates on. */
    uregex_setText(pExpr, zString, -1, &status);
    if (!U_SUCCESS(status)) {
        icuFunctionError(p, "uregex_setText", status);
        return;
    }

    /* Attempt the match */
    res = uregex_find(pExpr, 0, &status);
    if (!U_SUCCESS(status)) {
        icuFunctionError(p, "uregex_matches", status);
        return;
    }

    /* Set the text that the regular expression operates on to a NULL
    ** pointer. This is not really necessary, but it is tidier than
    ** leaving the regular expression object configured with an invalid
    ** pointer after this function returns.
    */
    uregex_setText(pExpr, 0, 0, &status);

    /* Return 1 or 0. */
    sqlite3_result_int(p, res ? 1 : 0);
}

/*
** Implementations of scalar functions for case mapping - upper() and
** lower(). Function upper() converts its input to upper-case (ABC).
** Function lower() converts to lower-case (abc).
**
** ICU provides two types of case mapping, "general" case mapping and
** "language specific". Refer to ICU documentation for the differences
** between the two.
**
** To utilise "general" case mapping, the upper() or lower() scalar
** functions are invoked with one argument:
**
**     upper('ABC') -> 'abc'
**     lower('abc') -> 'ABC'
**
** To access ICU "language specific" case mapping, upper() or lower()
** should be invoked with two arguments. The second argument is the name
** of the locale to use. Passing an empty string ("") or SQL NULL value
** as the second argument is the same as invoking the 1 argument version
** of upper() or lower().
**
**     lower('I', 'en_us') -> 'i'
**     lower('I', 'tr_tr') -> '\u131' (small dotless i)
**
** http://www.icu-project.org/userguide/posix.html#case_mappings
*/
static void icuCaseFunc16(sqlite3_context* p, int nArg, sqlite3_value** apArg) {
    const UChar* zInput;            /* Pointer to input string */
    UChar* zOutput = 0;             /* Pointer to output buffer */
    int nInput;                     /* Size of utf-16 input string in bytes */
    int nOut;                       /* Size of output buffer in bytes */
    int cnt;
    int bToUpper;                   /* True for toupper(), false for tolower() */
    UErrorCode status;
    const char* zLocale = 0;

    assert(nArg == 1 || nArg == 2);
    bToUpper = (sqlite3_user_data(p) != 0);
    if (nArg == 2) {
        zLocale = (const char*)sqlite3_value_text(apArg[1]);
    }

    zInput = (UChar*)sqlite3_value_text16(apArg[0]);
    if (!zInput) {
        return;
    }
    nOut = nInput = sqlite3_value_bytes16(apArg[0]);
    if (nOut == 0) {
        sqlite3_result_text16(p, "", 0, SQLITE_STATIC);
        return;
    }

    for (cnt = 0; cnt < 2; cnt++) {
        UChar* zNew = (UChar*)sqlite3_realloc(zOutput, nOut);
        if (zNew == 0) {
            sqlite3_free(zOutput);
            sqlite3_result_error_nomem(p);
            return;
        }
        zOutput = zNew;
        status = U_ZERO_ERROR;
        if (bToUpper) {
            nOut = 2 * u_strToUpper(zOutput, nOut / 2, zInput, nInput / 2, zLocale, &status);
        }
        else {
            nOut = 2 * u_strToLower(zOutput, nOut / 2, zInput, nInput / 2, zLocale, &status);
        }

        if (U_SUCCESS(status)) {
            sqlite3_result_text16(p, zOutput, nOut, xFree);
        }
        else if (status == U_BUFFER_OVERFLOW_ERROR) {
            assert(cnt == 0);
            continue;
        }
        else {
            icuFunctionError(p, bToUpper ? "u_strToUpper" : "u_strToLower", status);
        }
        return;
    }
    assert(0);     /* Unreachable */
}

#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU) */

/*
** Collation sequence destructor function. The pCtx argument points to
** a UCollator structure previously allocated using ucol_open().
*/
static void icuCollationDel(void* pCtx) {
    UCollator* p = (UCollator*)pCtx;
    ucol_close(p);
}

/*
** Collation sequence comparison function. The pCtx argument points to
** a UCollator structure previously allocated using ucol_open().
*/
static int icuCollationColl(
    void* pCtx,
    int nLeft,
    const void* zLeft,
    int nRight,
    const void* zRight
) {
    UCollationResult res;
    UCollator* p = (UCollator*)pCtx;
    res = ucol_strcoll(p, (UChar*)zLeft, nLeft / 2, (UChar*)zRight, nRight / 2);
    switch (res) {
    case UCOL_LESS:    return -1;
    case UCOL_GREATER: return +1;
    case UCOL_EQUAL:   return 0;
    }
    assert(!"Unexpected return value from ucol_strcoll()");
    return 0;
}

/*
** Implementation of the scalar function icu_load_collation().
**
** This scalar function is used to add ICU collation based collation
** types to an SQLite database connection. It is intended to be called
** as follows:
**
**     SELECT icu_load_collation(<locale>, <collation-name>);
**
** Where <locale> is a string containing an ICU locale identifier (i.e.
** "en_AU", "tr_TR" etc.) and <collation-name> is the name of the
** collation sequence to create.
*/
static void icuLoadCollation(
    sqlite3_context* p,
    int nArg,
    sqlite3_value** apArg
) {
    sqlite3* db = (sqlite3*)sqlite3_user_data(p);
    UErrorCode status = U_ZERO_ERROR;
    const char* zLocale;      /* Locale identifier - (eg. "jp_JP") */
    const char* zName;        /* SQL Collation sequence name (eg. "japanese") */
    UCollator* pUCollator;    /* ICU library collation object */
    int rc;                   /* Return code from sqlite3_create_collation_x() */

    assert(nArg == 2);
    (void)nArg; /* Unused parameter */
    zLocale = (const char*)sqlite3_value_text(apArg[0]);
    zName = (const char*)sqlite3_value_text(apArg[1]);

    if (!zLocale || !zName) {
        return;
    }

    pUCollator = ucol_open(zLocale, &status);
    if (!U_SUCCESS(status)) {
        icuFunctionError(p, "ucol_open", status);
        return;
    }
    assert(p);

    rc = sqlite3_create_collation_v2(db, zName, SQLITE_UTF16, (void*)pUCollator,
        icuCollationColl, icuCollationDel
    );
    if (rc != SQLITE_OK) {
        ucol_close(pUCollator);
        sqlite3_result_error(p, "Error registering collation function", -1);
    }
}

/*
** Register the ICU extension functions with database db.
*/
int brogden(sqlite3* db) {
# define SQLITEICU_EXTRAFLAGS (SQLITE_DETERMINISTIC|SQLITE_INNOCUOUS)
    static const struct IcuScalar {
        const char* zName;                        /* Function name */
        unsigned char nArg;                       /* Number of arguments */
        unsigned int enc;                         /* Optimal text encoding */
        unsigned char iContext;                   /* sqlite3_user_data() context */
        void (*xFunc)(sqlite3_context*, int, sqlite3_value**);
    } scalars[] = {
      {"icu_load_collation",2,SQLITE_UTF8 | SQLITE_DIRECTONLY,1, icuLoadCollation},
  #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU)
      {"regexp", 2, SQLITE_ANY | SQLITEICU_EXTRAFLAGS,         0, icuRegexpFunc},
      {"lower",  1, SQLITE_UTF16 | SQLITEICU_EXTRAFLAGS,       0, icuCaseFunc16},
      {"lower",  2, SQLITE_UTF16 | SQLITEICU_EXTRAFLAGS,       0, icuCaseFunc16},
      {"upper",  1, SQLITE_UTF16 | SQLITEICU_EXTRAFLAGS,       1, icuCaseFunc16},
      {"upper",  2, SQLITE_UTF16 | SQLITEICU_EXTRAFLAGS,       1, icuCaseFunc16},
      {"lower",  1, SQLITE_UTF8 | SQLITEICU_EXTRAFLAGS,        0, icuCaseFunc16},
      {"lower",  2, SQLITE_UTF8 | SQLITEICU_EXTRAFLAGS,        0, icuCaseFunc16},
      {"upper",  1, SQLITE_UTF8 | SQLITEICU_EXTRAFLAGS,        1, icuCaseFunc16},
      {"upper",  2, SQLITE_UTF8 | SQLITEICU_EXTRAFLAGS,        1, icuCaseFunc16},
      {"like",   2, SQLITE_UTF8 | SQLITEICU_EXTRAFLAGS,        0, icuLikeFunc},
      {"like",   3, SQLITE_UTF8 | SQLITEICU_EXTRAFLAGS,        0, icuLikeFunc},
  #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU) */
    };
    int rc = SQLITE_OK;
    int i;

    for (i = 0; rc == SQLITE_OK && i < (int)(sizeof(scalars) / sizeof(scalars[0])); i++) {
        const struct IcuScalar* p = &scalars[i];
        rc = sqlite3_create_function(
            db, p->zName, p->nArg, p->enc,
            p->iContext ? (void*)db : (void*)0,
            p->xFunc, 0, 0
        );
    }

    return rc;
}


extern "C"
{
    int __declspec(dllexport) sqlite3_icu_init(
        sqlite3* db,
        char** pzErrMsg,
        const sqlite3_api_routines* pApi
    ) {
        SQLITE_EXTENSION_INIT2(pApi)

            return brogden(db);
    }

    void __declspec(dllexport) sqlite3_icu_regex_flags(int flags)
    {
        regexFlags = (URegexpFlag)flags;
    }
}


#endif