/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Dmitry Volyntsev
 * Copyright (C) NGINX, Inc.
 */


#include <njs_main.h>

#ifdef NJS_HAVE_PCRE2

#define PCRE2_CODE_UNIT_WIDTH 8
#include <pcre2.h>


static const u_char* njs_regex_pcre2_error(int errcode, u_char buffer[128]);

#else

#include <pcre.h>


static void *njs_pcre_malloc(size_t size);
static void njs_pcre_free(void *p);


static njs_regex_generic_ctx_t  *regex_context;

#endif


njs_regex_generic_ctx_t *
njs_regex_generic_ctx_create(njs_pcre_malloc_t private_malloc,
    njs_pcre_free_t private_free, void *memory_data)
{
#ifdef NJS_HAVE_PCRE2

    return pcre2_general_context_create(private_malloc, private_free,
                                        memory_data);
#else

    njs_regex_generic_ctx_t  *ctx;

    ctx = private_malloc(sizeof(njs_regex_generic_ctx_t), memory_data);

    if (njs_fast_path(ctx != NULL)) {
        ctx->private_malloc = private_malloc;
        ctx->private_free = private_free;
        ctx->memory_data = memory_data;
    }

    return ctx;

#endif
}


njs_regex_compile_ctx_t *
njs_regex_compile_ctx_create(njs_regex_generic_ctx_t *ctx)
{
#ifdef NJS_HAVE_PCRE2
    pcre2_compile_context  *cc;

    cc = pcre2_compile_context_create(ctx);

#ifdef PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES
    if (njs_fast_path(cc != NULL)) {
        /* Workaround for surrogate pairs in regular expressions
         *
         * This option is needed because njs, unlike the standard ECMAScript,
         * stores and processes strings in UTF-8 encoding.
         * PCRE2 does not support surrogate pairs by default when it
         * is compiled for UTF-8 only strings. But many polyfills
         * and transpilers use such surrogate pairs expressions.
         */
        pcre2_set_compile_extra_options(cc,
                                        PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES);
    }
#endif

    return cc;

#else

    return ctx;

#endif
}



njs_int_t
njs_regex_escape(njs_mp_t *mp, njs_str_t *text)
{
#ifdef NJS_HAVE_PCRE2
    size_t  anychars, nomatches;
    u_char  *p, *dst, *start, *end;

    /*
     * 1) [^] is a valid regexp expression in JavaScript, but PCRE2
     * rejects it as invalid, replacing it with equivalent PCRE2 [\s\S]
     * expression.
     * 2) [] is a valid regexp expression in JavaScript, but PCRE2
     * rejects it as invalid, replacing it with equivalent PCRE2 (?!)
     * expression which matches nothing.
     */

    start = text->start;
    end = text->start + text->length;

    anychars = 0;
    nomatches = 0;

    for (p = start; p < end; p++) {
        switch (*p) {
        case '[':
            if (p + 1 < end && p[1] == ']') {
                p += 1;
                nomatches += 1;

            } else if (p + 2 < end && p[1] == '^' && p[2] == ']') {
                p += 2;
                anychars += 1;
            }

            break;
        }
    }

    if (!anychars && !nomatches) {
        return NJS_OK;
    }

    text->length = text->length
                   + anychars * (njs_length("\\s\\S") - njs_length("^"))
                   + nomatches * (njs_length("?!"));

    text->start = njs_mp_alloc(mp, text->length);
    if (njs_slow_path(text->start == NULL)) {
        return NJS_ERROR;
    }

    dst = text->start;

    for (p = start; p < end; p++) {

        switch (*p) {
        case '[':
            if (p + 1 < end && p[1] == ']') {
                p += 1;
                dst = njs_cpymem(dst, "(?!)", 4);
                continue;

            } else if (p + 2 < end && p[1] == '^' && p[2] == ']') {
                p += 2;
                dst = njs_cpymem(dst, "[\\s\\S]", 6);
                continue;
            }
        }

        *dst++ = *p;
    }

    return NJS_OK;

#else

    /*
     * 1) PCRE with PCRE_JAVASCRIPT_COMPAT flag rejects regexps with
     * lone closing square brackets as invalid.  Whereas according
     * to ES6: 11.8.5 it is a valid regexp expression.
     *
     * 2) escaping zero byte characters as "\u0000".
     *
     * Escaping it here as a workaround.
     */

    size_t      brackets, zeros;
    u_char      *p, *dst, *start, *end;
    njs_bool_t  in;

    start = text->start;
    end = text->start + text->length;

    in = 0;
    zeros = 0;
    brackets = 0;

    for (p = start; p < end; p++) {

        switch (*p) {
        case '[':
            in = 1;
            break;

        case ']':
            if (!in) {
                brackets++;
            }

            in = 0;
            break;

        case '\\':
            p++;

            if (p == end || *p != '\0') {
                break;
            }

            /* Fall through. */

        case '\0':
            zeros++;
            break;
        }
    }

    if (!brackets && !zeros) {
        return NJS_OK;
    }

    text->length = text->length + brackets + zeros * njs_length("\\u0000");

    text->start = njs_mp_alloc(mp, text->length);
    if (njs_slow_path(text->start == NULL)) {
        return NJS_ERROR;
    }

    in = 0;
    dst = text->start;

    for (p = start; p < end; p++) {

        switch (*p) {
        case '[':
            in = 1;
            break;

        case ']':
            if (!in) {
                *dst++ = '\\';
            }

            in = 0;
            break;

        case '\\':
            *dst++ = *p++;

            if (p == end) {
                goto done;
            }

            if (*p != '\0') {
                break;
            }

            /* Fall through. */

        case '\0':
            dst = njs_cpymem(dst, "\\u0000", 6);
            continue;
        }

        *dst++ = *p;
    }

done:

    text->length = dst - text->start;

    return NJS_OK;

#endif
}


njs_int_t
njs_regex_compile(njs_regex_t *regex, u_char *source, size_t len,
    njs_regex_flags_t flags, njs_regex_compile_ctx_t *cctx, njs_trace_t *trace)
{
#ifdef NJS_HAVE_PCRE2

    int         ret;
    u_char      *error;
    size_t      erroff;
    njs_uint_t  options;
    u_char      errstr[128];

    options = PCRE2_ALT_BSUX | PCRE2_MATCH_UNSET_BACKREF;

    if ((flags & NJS_REGEX_IGNORE_CASE)) {
         options |= PCRE2_CASELESS;
    }

    if ((flags & NJS_REGEX_MULTILINE)) {
         options |= PCRE2_MULTILINE;
    }

    if ((flags & NJS_REGEX_STICKY)) {
         options |= PCRE2_ANCHORED;
    }

    if ((flags & NJS_REGEX_UTF8)) {
         options |= PCRE2_UTF;
    }

    regex->code = pcre2_compile(source, len, options, &ret, &erroff, cctx);

    if (njs_slow_path(regex->code == NULL)) {
        error = &source[erroff];

        njs_alert(trace, NJS_LEVEL_ERROR,
                  "pcre_compile2(\"%s\") failed: %s at \"%s\"",
                  source, njs_regex_pcre2_error(ret, errstr), error);

        return NJS_DECLINED;
    }

    ret = pcre2_pattern_info(regex->code, PCRE2_INFO_CAPTURECOUNT,
                             &regex->ncaptures);

    if (njs_slow_path(ret < 0)) {
        njs_alert(trace, NJS_LEVEL_ERROR,
               "pcre2_pattern_info(\"%s\", PCRE2_INFO_CAPTURECOUNT) failed: %s",
               source, njs_regex_pcre2_error(ret, errstr));

        return NJS_ERROR;
    }

    ret = pcre2_pattern_info(regex->code, PCRE2_INFO_BACKREFMAX,
                             &regex->backrefmax);

    if (njs_slow_path(ret < 0)) {
        njs_alert(trace, NJS_LEVEL_ERROR,
                 "pcre2_pattern_info(\"%s\", PCRE2_INFO_BACKREFMAX) failed: %s",
                 source, njs_regex_pcre2_error(ret, errstr));

        return NJS_ERROR;
    }

    /* Reserve additional elements for the first "$0" capture. */
    regex->ncaptures++;

    if (regex->ncaptures > 1) {
        ret = pcre2_pattern_info(regex->code, PCRE2_INFO_NAMECOUNT,
                                 &regex->nentries);

        if (njs_slow_path(ret < 0)) {
            njs_alert(trace, NJS_LEVEL_ERROR,
                  "pcre2_pattern_info(\"%s\", PCRE2_INFO_NAMECOUNT) failed: %s",
                   source, njs_regex_pcre2_error(ret, errstr));

            return NJS_ERROR;
        }

        if (regex->nentries != 0) {
            ret = pcre2_pattern_info(regex->code, PCRE2_INFO_NAMEENTRYSIZE,
                                     &regex->entry_size);

            if (njs_slow_path(ret < 0)) {
                njs_alert(trace, NJS_LEVEL_ERROR,
                          "pcre2_pattern_info(\"%s\", PCRE2_INFO_NAMEENTRYSIZE)"
                          " failed: %s", source,
                          njs_regex_pcre2_error(ret, errstr));

                return NJS_ERROR;
            }

            ret = pcre2_pattern_info(regex->code, PCRE2_INFO_NAMETABLE,
                                     &regex->entries);

            if (njs_slow_path(ret < 0)) {
                njs_alert(trace, NJS_LEVEL_ERROR,
                          "pcre2_pattern_info(\"%s\", PCRE2_INFO_NAMETABLE) "
                          "failed: %s", source,
                          njs_regex_pcre2_error(ret, errstr));

                return NJS_ERROR;
            }
        }
    }

    return NJS_OK;

#else

    int                      ret, err, erroff;
    char                     *pattern, *error;
    void                     *(*saved_malloc)(size_t size);
    void                     (*saved_free)(void *p);
    njs_uint_t               options;
    const char               *errstr;
    njs_regex_generic_ctx_t  *ctx;

    ctx = cctx;

    ret = NJS_ERROR;

    saved_malloc = pcre_malloc;
    pcre_malloc = njs_pcre_malloc;
    saved_free = pcre_free;
    pcre_free = njs_pcre_free;
    regex_context = ctx;

#ifdef PCRE_JAVASCRIPT_COMPAT
    /* JavaScript compatibility has been introduced in PCRE-7.7. */
    options = PCRE_JAVASCRIPT_COMPAT;
#else
    options = 0;
#endif

    if ((flags & NJS_REGEX_IGNORE_CASE)) {
         options |= PCRE_CASELESS;
    }

    if ((flags & NJS_REGEX_MULTILINE)) {
         options |= PCRE_MULTILINE;
    }

    if ((flags & NJS_REGEX_STICKY)) {
         options |= PCRE_ANCHORED;
    }

    if ((flags & NJS_REGEX_UTF8)) {
         options |= PCRE_UTF8;
    }

    pattern = (char *) source;

    regex->code = pcre_compile(pattern, options, &errstr, &erroff, NULL);

    if (njs_slow_path(regex->code == NULL)) {
        error = pattern + erroff;

        if (*error != '\0') {
            njs_alert(trace, NJS_LEVEL_ERROR,
                      "pcre_compile(\"%s\") failed: %s at \"%s\"",
                      pattern, errstr, error);

        } else {
            njs_alert(trace, NJS_LEVEL_ERROR,
                      "pcre_compile(\"%s\") failed: %s", pattern, errstr);
        }

        ret = NJS_DECLINED;

        goto done;
    }

    regex->extra = pcre_study(regex->code, 0, &errstr);

    if (njs_slow_path(errstr != NULL)) {
        njs_alert(trace, NJS_LEVEL_WARN,
                  "pcre_study(\"%s\") failed: %s", pattern, errstr);
    }

    err = pcre_fullinfo(regex->code, NULL, PCRE_INFO_CAPTURECOUNT,
                        &regex->ncaptures);

    if (njs_slow_path(err < 0)) {
        njs_alert(trace, NJS_LEVEL_ERROR,
                  "pcre_fullinfo(\"%s\", PCRE_INFO_CAPTURECOUNT) failed: %d",
                  pattern, err);

        goto done;
    }

    err = pcre_fullinfo(regex->code, NULL, PCRE_INFO_BACKREFMAX,
                        &regex->backrefmax);

    if (njs_slow_path(err < 0)) {
        njs_alert(trace, NJS_LEVEL_ERROR,
                  "pcre_fullinfo(\"%s\", PCRE_INFO_BACKREFMAX) failed: %d",
                  pattern, err);

        goto done;
    }

    /* Reserve additional elements for the first "$0" capture. */
    regex->ncaptures++;

    if (regex->ncaptures > 1) {
        err = pcre_fullinfo(regex->code, NULL, PCRE_INFO_NAMECOUNT,
                            &regex->nentries);

        if (njs_slow_path(err < 0)) {
            njs_alert(trace, NJS_LEVEL_ERROR,
                      "pcre_fullinfo(\"%s\", PCRE_INFO_NAMECOUNT) failed: %d",
                      pattern, err);

            goto done;
        }

        if (regex->nentries != 0) {
            err = pcre_fullinfo(regex->code, NULL, PCRE_INFO_NAMEENTRYSIZE,
                                &regex->entry_size);

            if (njs_slow_path(err < 0)) {
                njs_alert(trace, NJS_LEVEL_ERROR, "pcre_fullinfo(\"%s\", "
                          "PCRE_INFO_NAMEENTRYSIZE) failed: %d", pattern, err);

                goto done;
            }

            err = pcre_fullinfo(regex->code, NULL, PCRE_INFO_NAMETABLE,
                                &regex->entries);

            if (njs_slow_path(err < 0)) {
                njs_alert(trace, NJS_LEVEL_ERROR, "pcre_fullinfo(\"%s\", "
                          "PCRE_INFO_NAMETABLE) failed: %d", pattern, err);

                goto done;
            }
        }
    }

    ret = NJS_OK;

done:

    pcre_malloc = saved_malloc;
    pcre_free = saved_free;
    regex_context = NULL;

    return ret;

#endif
}


njs_bool_t
njs_regex_is_valid(njs_regex_t *regex)
{
    return (regex->code != NULL);
}


njs_int_t
njs_regex_named_captures(njs_regex_t *regex, njs_str_t *name, int n)
{
    char  *entry;

    if (name == NULL) {
        return regex->nentries;
    }

    if (n >= regex->nentries) {
        return NJS_ERROR;
    }

    entry = regex->entries + regex->entry_size * n;

    name->start = (u_char *) entry + 2;
    name->length = njs_strlen(name->start);

    return (entry[0] << 8) + entry[1];
}


njs_regex_match_data_t *
njs_regex_match_data(njs_regex_t *regex, njs_regex_generic_ctx_t *ctx)
{
#ifdef NJS_HAVE_PCRE2

    if (regex != NULL) {
        return pcre2_match_data_create_from_pattern(regex->code, ctx);
    }

    return pcre2_match_data_create(0, ctx);

#else

    size_t                  size;
    njs_uint_t              ncaptures;
    njs_regex_match_data_t  *match_data;

    if (regex != NULL) {
        ncaptures = regex->ncaptures - 1;

    } else {
        ncaptures = 0;
    }

    /* Each capture is stored in 3 "int" vector elements. */
    ncaptures *= 3;
    size = sizeof(njs_regex_match_data_t) + ncaptures * sizeof(int);

    match_data = ctx->private_malloc(size, ctx->memory_data);

    if (njs_fast_path(match_data != NULL)) {
        match_data->ncaptures = ncaptures + 3;
    }

    return match_data;

#endif
}


void
njs_regex_match_data_free(njs_regex_match_data_t *match_data,
    njs_regex_generic_ctx_t *ctx)
{
#ifdef NJS_HAVE_PCRE2

    pcre2_match_data_free(match_data);

#else

    ctx->private_free(match_data, ctx->memory_data);

#endif
}


njs_int_t
njs_regex_match(njs_regex_t *regex, const u_char *subject, size_t off,
    size_t len, njs_regex_match_data_t *match_data, njs_trace_t *trace)
{
#ifdef NJS_HAVE_PCRE2

    int     ret;
    u_char  errstr[128];

    ret = pcre2_match(regex->code, subject, len, off, 0, match_data, NULL);

    if (ret < 0) {
        if (ret == PCRE2_ERROR_NOMATCH) {
            return NJS_DECLINED;
        }

        njs_alert(trace, NJS_LEVEL_ERROR, "pcre2_match() failed: %s",
                  njs_regex_pcre2_error(ret, errstr));
        return NJS_ERROR;
    }

    return ret;

#else

    int  ret;

    ret = pcre_exec(regex->code, regex->extra, (const char *) subject, len,
                    off, 0, match_data->captures, match_data->ncaptures);

    if (ret <= PCRE_ERROR_NOMATCH) {
        if (ret == PCRE_ERROR_NOMATCH) {
            return NJS_DECLINED;
        }

        njs_alert(trace, NJS_LEVEL_ERROR, "pcre_exec() failed: %d", ret);
        return NJS_ERROR;
    }

    return ret;

#endif
}


size_t
njs_regex_capture(njs_regex_match_data_t *match_data, njs_uint_t n)
{
#ifdef NJS_HAVE_PCRE2

    size_t  c;

    c = pcre2_get_ovector_pointer(match_data)[n];

    if (c == PCRE2_UNSET) {
        return NJS_REGEX_UNSET;
    }

    return c;

#else

    return match_data->captures[n];

#endif
}

#ifdef NJS_HAVE_PCRE2

static const u_char *
njs_regex_pcre2_error(int errcode, u_char buffer[128])
{
    pcre2_get_error_message(errcode, buffer, 128);

    return buffer;
}

#else

static void *
njs_pcre_malloc(size_t size)
{
    return regex_context->private_malloc(size, regex_context->memory_data);
}


static void
njs_pcre_free(void *p)
{
    regex_context->private_free(p, regex_context->memory_data);
}

#endif