/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2014 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <sys/types.h>
#include <math.h>

#include "macro.h"
#include "util.h"
#include "utf8.h"
#include "json.h"

enum {
        STATE_NULL,
        STATE_VALUE,
        STATE_VALUE_POST,
};

static void inc_lines(unsigned *line, const char *s, size_t n) {
        const char *p = s;

        if (!line)
                return;

        for (;;) {
                const char *f;

                f = memchr(p, '\n', n);
                if (!f)
                        return;

                n -= (f - p) + 1;
                p = f + 1;
                (*line)++;
        }
}

static int unhex_ucs2(const char *c, uint16_t *ret) {
        int aa, bb, cc, dd;
        uint16_t x;

        assert(c);
        assert(ret);

        aa = unhexchar(c[0]);
        if (aa < 0)
                return -EINVAL;

        bb = unhexchar(c[1]);
        if (bb < 0)
                return -EINVAL;

        cc = unhexchar(c[2]);
        if (cc < 0)
                return -EINVAL;

        dd = unhexchar(c[3]);
        if (dd < 0)
                return -EINVAL;

        x =     ((uint16_t) aa << 12) |
                ((uint16_t) bb << 8) |
                ((uint16_t) cc << 4) |
                ((uint16_t) dd);

        if (x <= 0)
                return -EINVAL;

        *ret = x;

        return 0;
}

static int json_parse_string(const char **p, char **ret) {
        _cleanup_free_ char *s = NULL;
        size_t n = 0, allocated = 0;
        const char *c;

        assert(p);
        assert(*p);
        assert(ret);

        c = *p;

        if (*c != '"')
                return -EINVAL;

        c++;

        for (;;) {
                int len;

                /* Check for EOF */
                if (*c == 0)
                        return -EINVAL;

                /* Check for control characters 0x00..0x1f */
                if (*c > 0 && *c < ' ')
                        return -EINVAL;

                /* Check for control character 0x7f */
                if (*c == 0x7f)
                        return -EINVAL;

                if (*c == '"') {
                        if (!s) {
                                s = strdup("");
                                if (!s)
                                        return -ENOMEM;
                        } else
                                s[n] = 0;

                        *p = c + 1;

                        *ret = s;
                        s = NULL;
                        return JSON_STRING;
                }

                if (*c == '\\') {
                        char ch = 0;
                        c++;

                        if (*c == 0)
                                return -EINVAL;

                        if (IN_SET(*c, '"', '\\', '/'))
                                ch = *c;
                        else if (*c == 'b')
                                ch = '\b';
                        else if (*c == 'f')
                                ch = '\f';
                        else if (*c == 'n')
                                ch = '\n';
                        else if (*c == 'r')
                                ch = '\r';
                        else if (*c == 't')
                                ch = '\t';
                        else if (*c == 'u') {
                                uint16_t x;
                                int r;

                                r = unhex_ucs2(c + 1, &x);
                                if (r < 0)
                                        return r;

                                c += 5;

                                if (!GREEDY_REALLOC(s, allocated, n + 4))
                                        return -ENOMEM;

                                if (!utf16_is_surrogate(x))
                                        n += utf8_encode_unichar(s + n, x);
                                else if (utf16_is_trailing_surrogate(x))
                                        return -EINVAL;
                                else {
                                        uint16_t y;

                                        if (c[0] != '\\' || c[1] != 'u')
                                                return -EINVAL;

                                        r = unhex_ucs2(c + 2, &y);
                                        if (r < 0)
                                                return r;

                                        c += 6;

                                        if (!utf16_is_trailing_surrogate(y))
                                                return -EINVAL;

                                        n += utf8_encode_unichar(s + n, utf16_surrogate_pair_to_unichar(x, y));
                                }

                                continue;
                        } else
                                return -EINVAL;

                        if (!GREEDY_REALLOC(s, allocated, n + 2))
                                return -ENOMEM;

                        s[n++] = ch;
                        c ++;
                        continue;
                }

                len = utf8_encoded_valid_unichar(c);
                if (len < 0)
                        return len;

                if (!GREEDY_REALLOC(s, allocated, n + len + 1))
                        return -ENOMEM;

                memcpy(s + n, c, len);
                n += len;
                c += len;
        }
}

static int json_parse_number(const char **p, union json_value *ret) {
        bool negative = false, exponent_negative = false, is_double = false;
        double x = 0.0, y = 0.0, exponent = 0.0, shift = 1.0;
        intmax_t i = 0;
        const char *c;

        assert(p);
        assert(*p);
        assert(ret);

        c = *p;

        if (*c == '-') {
                negative = true;
                c++;
        }

        if (*c == '0')
                c++;
        else {
                if (!strchr("123456789", *c) || *c == 0)
                        return -EINVAL;

                do {
                        if (!is_double) {
                                int64_t t;

                                t = 10 * i + (*c - '0');
                                if (t < i) /* overflow */
                                        is_double = false;
                                else
                                        i = t;
                        }

                        x = 10.0 * x + (*c - '0');
                        c++;
                } while (strchr("0123456789", *c) && *c != 0);
        }

        if (*c == '.') {
                is_double = true;
                c++;

                if (!strchr("0123456789", *c) || *c == 0)
                        return -EINVAL;

                do {
                        y = 10.0 * y + (*c - '0');
                        shift = 10.0 * shift;
                        c++;
                } while (strchr("0123456789", *c) && *c != 0);
        }

        if (*c == 'e' || *c == 'E') {
                is_double = true;
                c++;

                if (*c == '-') {
                        exponent_negative = true;
                        c++;
                } else if (*c == '+')
                        c++;

                if (!strchr("0123456789", *c) || *c == 0)
                        return -EINVAL;

                do {
                        exponent = 10.0 * exponent + (*c - '0');
                        c++;
                } while (strchr("0123456789", *c) && *c != 0);
        }

        if (*c != 0)
                return -EINVAL;

        *p = c;

        if (is_double) {
                ret->real = ((negative ? -1.0 : 1.0) * (x + (y / shift))) * exp10((exponent_negative ? -1.0 : 1.0) * exponent);
                return JSON_REAL;
        } else {
                ret->integer = negative ? -i : i;
                return JSON_INTEGER;
        }
}

int json_tokenize(
                const char **p,
                char **ret_string,
                union json_value *ret_value,
                void **state,
                unsigned *line) {

        const char *c;
        int t;
        int r;

        assert(p);
        assert(*p);
        assert(ret_string);
        assert(ret_value);
        assert(state);

        t = PTR_TO_INT(*state);
        c = *p;

        if (t == STATE_NULL) {
                if (line)
                        *line = 1;
                t = STATE_VALUE;
        }

        for (;;) {
                const char *b;

                b = c + strspn(c, WHITESPACE);
                if (*b == 0)
                        return JSON_END;

                inc_lines(line, c, b - c);
                c = b;

                switch (t) {

                case STATE_VALUE:

                        if (*c == '{') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE);
                                return JSON_OBJECT_OPEN;

                        } else if (*c == '}') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_OBJECT_CLOSE;

                        } else if (*c == '[') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE);
                                return JSON_ARRAY_OPEN;

                        } else if (*c == ']') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_ARRAY_CLOSE;

                        } else if (*c == '"') {
                                r = json_parse_string(&c, ret_string);
                                if (r < 0)
                                        return r;

                                *ret_value = JSON_VALUE_NULL;
                                *p = c;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return r;

                        } else if (strchr("-0123456789", *c)) {
                                r = json_parse_number(&c, ret_value);
                                if (r < 0)
                                        return r;

                                *ret_string = NULL;
                                *p = c;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return r;

                        } else if (startswith(c, "true")) {
                                *ret_string = NULL;
                                ret_value->boolean = true;
                                *p = c + 4;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_BOOLEAN;

                        } else if (startswith(c, "false")) {
                                *ret_string = NULL;
                                ret_value->boolean = false;
                                *p = c + 5;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_BOOLEAN;

                        } else if (startswith(c, "null")) {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 4;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_NULL;

                        } else
                                return -EINVAL;

                case STATE_VALUE_POST:

                        if (*c == ':') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE);
                                return JSON_COLON;
                        } else if (*c == ',') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE);
                                return JSON_COMMA;
                        } else if (*c == '}') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_OBJECT_CLOSE;
                        } else if (*c == ']') {
                                *ret_string = NULL;
                                *ret_value = JSON_VALUE_NULL;
                                *p = c + 1;
                                *state = INT_TO_PTR(STATE_VALUE_POST);
                                return JSON_ARRAY_CLOSE;
                        } else
                                return -EINVAL;
                }

        }
}