#include "../include/quickmedia/XpathTokenizer.h"
#include <stdlib.h>
#include <string.h>

void quickmedia_xpath_tokenizer_init(QuickMediaXpathTokenizer *self, const char *xpath) {
    self->code = xpath;
    self->identifier.data = NULL;
    self->identifier.size = 0;
}

static int is_alpha(char c) {
    return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
}

static int is_num(char c) {
    return c >= '0' && c <= '9';
}

static int c_to_num(char c) {
    return c - '0';
}

static int is_alphanum(char c) {
    return is_alpha(c) || is_num(c);
}

static const char* find_end_of_string(const char *str, char escape_symbol) {
    int escape = 0;
    while(*str != '\0') {
        char c = *str;
        if(c == '\\') {
            escape = !escape;
        } else if(c == escape_symbol) {
            if(!escape)
                return str;
        } else {
            escape = 0;
        }
        ++str;
    }
    return str;
}

QuickMediaXpathToken quickmedia_xpath_tokenizer_next(QuickMediaXpathTokenizer *self) {
    char c = *self->code;
    if(c == '/') {
        ++self->code;
        c = *self->code;
        if(c == '/') {
            ++self->code;
            return QUICKMEDIA_XPATH_TOKEN_CHILD_RECURSIVE;
        }
        return QUICKMEDIA_XPATH_TOKEN_CHILD;
    } else if(is_alpha(c)) {
        self->identifier.data = self->code;
        ++self->code;
        while(is_alphanum(*self->code) || *self->code == '_' || *self->code == '-') {
            ++self->code;
        }
        self->identifier.size = self->code - self->identifier.data;
        return QUICKMEDIA_XPATH_TOKEN_IDENTIFIER;
    } else if(is_num(c)) {
        int number = c_to_num(c);
        ++self->code;
        while(is_num(*self->code)) {
            number = number * 10 + c_to_num(*self->code);
            ++self->code;
        }
        self->number = number;
        return QUICKMEDIA_XPATH_TOKEN_NUMBER;
    } else if(c == '[') {
        ++self->code;
        return QUICKMEDIA_XPATH_TOKEN_OPEN_BRACKET;
    } else if(c == ']') {
        ++self->code;
        return QUICKMEDIA_XPATH_TOKEN_CLOSING_BRACKET;
    } else if(c == '=') {
        ++self->code;
        return QUICKMEDIA_XPATH_TOKEN_EQUAL;
    } else if(c == '"' || c == '\'') {
        char escape_symbol = c;
        ++self->code;
        self->string.data = self->code;
        self->code = find_end_of_string(self->string.data, escape_symbol);
        if(*self->code == '\0') {
            /* Reached end of xpath before end of string */
            return QUICKMEDIA_XPATH_TOKEN_INVALID;
        }
        self->string.size = self->code - self->string.data;
        ++self->code;
        return QUICKMEDIA_XPATH_TOKEN_STRING;
    } else if(c == '\0') {
        return QUICKMEDIA_XPATH_TOKEN_END_OF_FILE;
    } else {
        /* Invalid symbol @c */
        return QUICKMEDIA_XPATH_TOKEN_INVALID;
    }
}

int quickmedia_xpath_tokenizer_next_if(QuickMediaXpathTokenizer *self, QuickMediaXpathToken token) {
    const char *restore_point = self->code;
    if(quickmedia_xpath_tokenizer_next(self) == token)
        return 0;
    self->code = restore_point;
    return -1;
}