/*
 *
 * File		:	config_parser.c
 *
 * Author	:	Zurcher Jeremy
 *
 * Date		:
 *
 * Purpose	:
 *
 */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include "config_parser.h"

#define COMMENT '#'
#define STREND '\0'
#define NEWLINE '\n'
#define TABULATION '\t'
#define SPACE ' '

enum { NOPE, UNFINISHED_LINE, UNFINISHED_COMMENT };

struct config_reader {
    int fd;
    int last;
    char *pos;
    char *end;
    int state;
    int current_line;
    char buffer[BUFFLEN];
};

static struct config_reader reader = { 0 };

#ifdef _DEBUG_
static void debug_buffer() {
    printf("\tBUFFER : ");
    int i;
    for (i=0; i<BUFFLEN; i++) {
        char ch = reader.buffer[i];
        if(ch==NEWLINE)printf("*");
        else if(ch==STREND)printf("@");
        else printf("%c",ch);
    }
    printf("\n\tpos : %c[%d]\n",*reader.pos,(reader.pos-reader.buffer));
    printf("\tend : %c[%d]\n",*reader.end,(reader.end-reader.buffer));
}
#endif /* _DEBUG_ */

static int feed_buffer(int fd, char *buffer, int len)
{
    int ret;
    if(reader.last) return 0;
    ret = read(fd,buffer,len);
    if(ret==-1) return -1;
    if(ret<len) reader.last = 1;
    buffer[ret] = STREND;
    reader.pos = buffer;
    reader.end = &buffer[ret];
    return ret;
}

static char* eat_comment(char *from)
{
    int ret;
    char *tmp;
    for(;;) {
        tmp = strchr(from, NEWLINE);
        if(tmp!=NULL) {
            reader.current_line++;
            return tmp;
        }
        ret = feed_buffer(reader.fd, reader.buffer, BUFFLEN-1);
        if(ret==-1) return (char*)-1;
        if(ret==0) return NULL;
        from = reader.pos;
    }
}

static char* clean_tail(char *str)
{
    char *tmp = strchr(str, COMMENT);
    if(tmp!=NULL) {
        *tmp=STREND;
        reader.state = UNFINISHED_COMMENT;
    } else {
        reader.state = UNFINISHED_LINE;
    }
    tmp = strchr(str, STREND);
    for(;;) {
        tmp--;
        if(*tmp!=SPACE && *tmp!=TABULATION) break;
    }
    tmp++;
    *tmp=STREND;
    return tmp;
}

static char* prepare_line()
{
    int len;
    int ret;
    char *cret;
    char *tmp;
    tmp = strchr(reader.pos, NEWLINE);
    if(tmp!=NULL) {
        *tmp=STREND;
        cret = reader.pos;
        reader.pos = tmp+1;
        clean_tail(cret);
        reader.state = NOPE;
        return cret;
    }
    len = (reader.end-reader.pos);
    memmove(reader.buffer,reader.pos,len);
    reader.pos = reader.buffer+len;
    ret = feed_buffer(reader.fd, reader.pos, reader.end-reader.pos);
    if(ret==-1) return (char*)-1;
    tmp = strchr(reader.pos, NEWLINE);
    if(tmp!=NULL) {
        *tmp=STREND;
        reader.pos = tmp+1;
        clean_tail(reader.buffer);
        reader.state = NOPE;
    }
    else {
        clean_tail(reader.pos);
    }
    return reader.buffer;
}

static char* find_next_token()
{
    int ret;
    char *end;
    char *tmp = reader.pos;
    if(reader.state==UNFINISHED_COMMENT){
        tmp=eat_comment(reader.pos);
        if(tmp==(char*)-1) return (char*)-1;
        if(tmp==NULL) return NULL;
        reader.state=NOPE;
    }
    else if (reader.state==UNFINISHED_LINE) {
        ret = feed_buffer(reader.fd, reader.buffer, BUFFLEN-1);
        if(ret==-1) return (char*)-1;
        if(ret==0) return NULL;
        reader.state=NOPE;
        return prepare_line();
    }
    end = reader.end;
    reader.current_line++;
    for(;;) {
        if(tmp==end) {
            int ret = feed_buffer(reader.fd, reader.buffer, BUFFLEN-1);
            if(ret==-1) return (char*)-1;
            if(ret==0) return NULL;
            tmp = reader.pos;
            end = reader.end;
        }
        if(*tmp==NEWLINE) {
            reader.current_line++;
        }
        else if(*tmp==COMMENT) {
            tmp = eat_comment(tmp);
            if(tmp==(char*)-1) return (char*)-1;
            if(tmp==NULL) return NULL;
            end = reader.end;
        }
        else if(*tmp!=SPACE || *tmp!=TABULATION) {
            reader.pos = tmp;
            return prepare_line();
        }
        tmp++;
    }
}

static int init(char *filename)
{
    if(reader.fd) close(reader.fd);
    reader.fd = open(filename,O_RDONLY);
    if(reader.fd==-1) return 1;
    reader.state = NOPE;
    reader.last = 0;
    reader.current_line = 0;
    reader.pos = reader.end = reader.buffer;
    return 0;
}

int read_config(char *filename, config_callback callback)
{
    int ret = EXIT_SUCCESS;
    char *token;
    if(init(filename)) return EXIT_FAILURE;
    for(;;) {
        token = find_next_token();
        if(token==NULL) break;
        if(token==(char*)-1) { ret=EXIT_FAILURE; break; }
        ret = callback(token,reader.state!=NOPE);
        if(ret) break;
    }
    close(reader.fd);
    reader.fd = -1;
    return ret;
}