#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_LINE 2048

// Parse one CSV field, advancing the pointer
char* get_field(char** line) {
    static char field[256];
    char* start = *line;
    char* p = field;
    
    if (!*start) {
        field[0] = '\0';
        return field;
    }
    
    while (*start) {
        if (*start == ',') {
            start++;
            break;
        }
        *p++ = *start++;
    }
    *p = '\0';
    *line = start;
    return field;
}

int main(int argc, char* argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s input.csv\n", argv[0]);
        return 1;
    }

    FILE* in = fopen(argv[1], "r");
    if (!in) {
        perror("Cannot open input file");
        return 1;
    }

    FILE* out = fopen("vsx.dat", "w");
    if (!out) {
        perror("Cannot open output file");
        fclose(in);
        return 1;
    }

    char line[MAX_LINE];
    int first = 1;

    while (fgets(line, sizeof(line), in)) {
        if (first) {  // Skip header
            first = 0;
            continue;
        }

        char* ptr = line;
        char* field;
        char outbuf[300] = "";

        // OID (7 chars)
        field = get_field(&ptr);
        sprintf(outbuf, "%-7s ", field ? field : "");

        // Name (30 chars)
        field = get_field(&ptr);
        strcat(outbuf, field ? field : "");
        int pad = 30 - strlen(field ? field : "");
        for (int i = 0; i < pad; i++) strcat(outbuf, " ");
        strcat(outbuf, " ");

        // VarFlag (1 char + 2 spaces)
        field = get_field(&ptr);
        sprintf(outbuf + strlen(outbuf), "%s   ", field ? field : "");

        // RAdeg (9 chars)
        field = get_field(&ptr);
        sprintf(outbuf + strlen(outbuf), "%9.5f  ", field && *field ? atof(field) : 0.0);

        // DEdeg (9 chars)
        field = get_field(&ptr);
        sprintf(outbuf + strlen(outbuf), "%9.5f ", field && *field ? atof(field) : 0.0);

        // Type (30 chars)
        field = get_field(&ptr);
        strcat(outbuf, field ? field : "");
        pad = 30 - strlen(field ? field : "");
        for (int i = 0; i < pad; i++) strcat(outbuf, " ");
        strcat(outbuf, " ");

        // LimitFlagOnMax (1 char)
        field = get_field(&ptr);
        strcat(outbuf, field && *field ? field : " ");
        strcat(outbuf, "  ");

        // MagMax (7 chars)
        field = get_field(&ptr);
        if (field && *field) {
            sprintf(outbuf + strlen(outbuf), "%7.3f", atof(field));
        } else {
            strcat(outbuf, "       ");
        }
        strcat(outbuf, "   ");

        // MaxUncertaintyFlag (skipped)
        field = get_field(&ptr);

        // MaxPassband (7 chars)
        field = get_field(&ptr);
        sprintf(outbuf + strlen(outbuf), "%-7s  ", field && *field ? field : "");

        // MinIsAmplitude (1 char)
        field = get_field(&ptr);
        sprintf(outbuf + strlen(outbuf), "%-1s     ", field && *field ? field : "");

        // LimitFlagOnMin (skipped)
        field = get_field(&ptr);

        // MagMin (7 chars)
        field = get_field(&ptr);
        if (field && *field) {
            sprintf(outbuf + strlen(outbuf), "%7.3f", atof(field));
        } else {
            strcat(outbuf, "       ");
        }
        strcat(outbuf, "   ");

        // MinUncertaintyFlag (skipped)
        field = get_field(&ptr);

        // MinPassband (8 chars)
        field = get_field(&ptr);
        sprintf(outbuf + strlen(outbuf), "%-8s  ", field && *field ? field : "");

        // Epoch (14 chars)
        field = get_field(&ptr);
        if (field && *field) {
            sprintf(outbuf + strlen(outbuf), "%14.5f", atof(field));
        } else {
            strcat(outbuf, "              ");
        }
        strcat(outbuf, "  ");

        // EpochUncertaintyFlag (skipped)
        field = get_field(&ptr);

        // LimitFlagOnPeriod (1 char)
        field = get_field(&ptr);
        strcat(outbuf, field && *field ? field : " ");
        strcat(outbuf, "  ");

        // Period (19 chars)
        field = get_field(&ptr);
        if (field && *field) {
            sprintf(outbuf + strlen(outbuf), "%19.12f", atof(field));
        } else {
            strcat(outbuf, "                   ");
        }
        strcat(outbuf, "  ");

        // PeriodUncertaintyFlag (1 char)
        field = get_field(&ptr);
        strcat(outbuf, field && *field ? field : " ");
        strcat(outbuf, "  ");

        // SpectralType (remaining)
        field = get_field(&ptr);
        strcat(outbuf, field && *field ? field : "");
        //strcat(outbuf, "\n");

        fputs(outbuf, out);
    }

    fclose(in);
    fclose(out);
    return 0;
}