#include "bom.h"

#define BOMSIZE 3
unsigned char bom[] = { 0xEF, 0xBB, 0xBF };

int checkBOM(char *filePath) {
	FILE *inputFile = fopen(filePath, "r");
	if (inputFile == NULL) return ERROR;

    unsigned char check[BOMSIZE];
    if (BOMSIZE != fread(check, BOMSIZE, 1, inputFile)) {
        if (feof(inputFile)) return NOBOM;
        if (ferror(inputFile)) return ERROR;
    }
	if (fclose(inputFile)) return ERROR;

    if (!memcmp(&bom, check, BOMSIZE)) return HASBOM;
	return NOBOM;
}

char *tempFileName = "tempFile";

int removeBOM(char *filePath) {
    if (NOBOM == checkBOM(filePath)) return SUCCESS;

	FILE *inputFile = fopen(filePath, "r");
    if (inputFile == NULL) return ERROR;

	if (fseek(inputFile, BOMSIZE, SEEK_SET)) return ERROR;

	FILE *tempFile = fopen(tempFileName, "w");
    if (tempFile== NULL) return ERROR;

	int c = fgetc(inputFile);
	while (c != EOF) {
		if (EOF == fputc(c, tempFile)) return ERROR;
		c = fgetc(inputFile);
	}
    if (fclose(tempFile)) return ERROR;
    if (fclose(inputFile)) return ERROR;

    if (remove(filePath)) return ERROR;
    if (rename(tempFileName, filePath)) return ERROR;

    return SUCCESS;
}

int addBOM(char *filePath) {
    if (HASBOM == checkBOM(filePath)) return SUCCESS;

    FILE *inputFile = fopen(filePath, "r");
    if (inputFile == NULL) return ERROR;

    FILE *tempFile = fopen(tempFileName, "w");
    if (tempFile== NULL) return ERROR;

    for (int i = 0; i < BOMSIZE; i++)
        if (EOF == fputc(bom[i], tempFile)) return ERROR;

    int c = fgetc(inputFile);
    while (c != EOF) {
        if (EOF == fputc(c, tempFile)) return ERROR;
        c = fgetc(inputFile);
    }
    if (fclose(tempFile)) return ERROR;
    if (fclose(inputFile)) return ERROR;

    if (remove(filePath)) return ERROR;
    if (rename(tempFileName, filePath)) return ERROR;

    return SUCCESS;
}