#include "libconf.h"

/* 字符串预处理，设置转义字符 */
static void string_pretreatment(char *str, int *len)
{
    char *lf, *p, *ori_strs[] = { "\\r", "\\n", "\\b", "\\v", "\\f", "\\t", "\\a", "\\b", "\\0" }, to_chrs[] = { '\r', '\n', '\b', '\v', '\f', '\t', '\a', '\b', '\0' };
    int i;

    while ((lf = strchr(str, '\n')) != NULL) {
        for (p = lf + 1; *p == ' ' || *p == '\t' || *p == '\n' || *p == '\r'; p++)
            *len -= 1;
        strcpy(lf, p);
        *len -= 1;
    }
    for (i = 0; i < sizeof(to_chrs); i++) {
        for (p = strstr(str, ori_strs[i]); p; p = strstr(p, ori_strs[i])) {
            //支持\\r
            *(p - 1) == '\\' ? (*p--) : (*p = to_chrs[i]);
            memmove(p + 1, p + 2, strlen(p + 2));
            (*len)--;
        }
    }
}

/* 在content中，设置变量(var)的首地址，值(val)的位置首地址和末地址，返回下一行指针 */
static char *set_var_val_lineEnd(char *content, char **var, char **val_begin, char **val_end)
{

    char *p, *pn, *lineEnd;
    ;
    int val_len;

    while (1)
    {
        if (content == NULL)
            return NULL;

        for (;*content == ' ' || *content == '\t' || *content == '\r' || *content == '\n'; content++);
        if (*content == '\0')
            return NULL;
        *var = content;
        pn = strchr(content, '\n');
        p = strchr(content, '=');
        if (p == NULL)
        {
            if (pn)
            {
                content = pn + 1;
                continue;
            }
            else
                return NULL;
        }
        content = p;
        //将变量以\0结束
        for (p--; *p == ' ' || *p == '\t'; p--);
        *(p+1) = '\0';
        //值的首地址
        for (content++; *content == ' ' || *content == '\t'; content++);
        if (*content == '\0')
            return NULL;
        //双引号引起来的值支持换行
        if (*content == '"')
        {
            *val_begin = content + 1;
            *val_end = strstr(*val_begin, "\";");
            if (*val_end != NULL)
                break;
        }
        else
            *val_begin = content;
        *val_end = strchr(content, ';');
        if (pn && *val_end > pn)
        {
            content = pn + 1;
            continue;
        }
        break;
    }

    if (*val_end)
    {
        **val_end = '\0';
        val_len = *val_end - *val_begin;
        lineEnd = *val_end;
    }
    else
    {
        val_len = strlen(*val_begin);
        *val_end = lineEnd = *val_begin + val_len;
    }
    string_pretreatment(*val_begin, &val_len);
    *val_end = *val_begin + val_len;
    //printf("var[%s]\nbegin[%s]\n\n", *var, *val_begin);
    return lineEnd;
}

static char *parse_global_module(char *content, char *key)
{
    char *var, *val_begin, *val_end, *lineEnd;
    
    while ((lineEnd = set_var_val_lineEnd(content, &var, &val_begin, &val_end)) != NULL)
    {
        if (strcasecmp(var, key) == 0) {
            //printf("%s\n", val_begin);
            return val_begin;
        }
        content = strchr(lineEnd+1, '\n');
    }
    return NULL;
}

/* 在buff中读取模块(global http https httpdns httpudp)内容 */
static char *read_module(char *buff, const char *module_name)
{
    int len;
    char *p, *p0;

    len = strlen(module_name);
    p = buff;
    while (1)
    {
        while (*p == ' ' || *p == '\t' || *p == '\r' || *p == '\n')
            p++;
        if (strncasecmp(p, module_name, len) == 0)
        {
            p += len;
            while (*p == ' ' || *p == '\t' || *p == '\r' || *p == '\n')
                p++;
            if (*p == '{')
                break;
        }
        if ((p = strchr(p, '\n')) == NULL)
            return NULL;
    }
    
    if ((p0 = strchr(++p, '}')) == NULL)
        return NULL;
    return strndup(p, p0 - p);
}

char *read_conf(char *filename, char *module, char *key)
{
    char *buff, *global_content;
    FILE *file;
    long file_size;

    file = fopen(filename, "r");
    if (file == NULL)
        perror("cannot open config file.");
    fseek(file, 0, SEEK_END);
    file_size = ftell(file);
    buff = (char *)alloca(file_size + 1);
    if (buff == NULL)
        perror("out of memory.");
    rewind(file);
    fread(buff, file_size, 1, file);
    fclose(file);
    buff[file_size] = '\0';

    if ((global_content = read_module(buff, module)) == NULL) {
        perror("read module error");
    }
    return parse_global_module(global_content, key);
    free(global_content);
}