/******* helpmake.c: Create the index file for a help database. *******
 Command-line parameters: the help database name (input file), and the
 help index file name (output file).  File formats described elsewhere.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXNAME 10            /* Maximum length of a help item name */
#define MAXDESCRIPTION 50     /* Maximum length of the short description */

void putstring(char *str, FILE *f);  /* Fn to write nul-terminated string */
int process_help_entry(FILE *helpdata, FILE *index);
    /* process_help_entry returns true if another entry follows this one. */
FILE * file_open(char name[], char access_mode[]);

main(int argc, char *argv[]) {
    FILE *helpdata, *index;
    int there_is_another_entry;
    /* Open files. */
    if (argc != 3) {
        fprintf(
            stderr,
            "You must supply a help database name and a name\n"
            "for the index file to be created.\n"
        );
        exit(EXIT_FAILURE);
    }
    helpdata = file_open(argv[1], "r");
    index = file_open(argv[2], "wb");

    /* Check format of help database */
    if (getc(helpdata) != ':' || getc(helpdata) != ':') {
        /* First two input characters are not "::", print error and stop. */
        fprintf(stderr, "Incorrect format to help database.\n");
        exit(EXIT_FAILURE);
    }

    /* Write index file header entry. */
    fputs("!!", index);      /* Note: OK to write chars to binary stream */
    putstring(argv[1], index);

    do {
        there_is_another_entry = process_help_entry(helpdata, index);
    } while (there_is_another_entry);

    fclose(helpdata); fclose(index);
    return 0;
}

/**** putstring: write a nul-terminated string ****
 On entry: str is a string, f is an open output file.
 On exit:  Characters in string, including terminating nul, are written
           to file, or an error message printed and program stopped.
*/
void putstring(char str[], FILE *f) { /* Fn to write nul-terminated string
*/
    int leng = strlen(str) + 1;      /* +1 for the nul */
    if (fwrite(str, 1, leng, f) != leng) {
        perror("Error writing index file"); exit(EXIT_FAILURE);
    }
}

/**** process_help_entry: reads a help entry, and writes info to index ****
 On entry: helpdata is the help database file, open for input, positioned
           just after the "::" starting an entry.
           index is the index file, open for output in binary.
 On exit:  Writes entry to the index file.  If another entry follows this
           in the database, positions helpdata input just past its "::",
           and returns 1, else returns 0.  Terminates program on error.
*/
int process_help_entry(FILE *helpdata, FILE *index) {
    char name[MAXNAME+1], description[MAXDESCRIPTION+1], flag[3];
    int status, entry_size, ch;
    fpos_t location;

    /* Read item name & description; write to index file. */
    if (fscanf(helpdata, "%10s %50[^\n]%*[^\n]", name, description) < 2) {
        perror("Missing items in help data"); exit(EXIT_FAILURE);
    }
    putstring(name, index);
    putstring(description, index);

    getc(helpdata);             /* Advance past end-of-line in input file */

    /* Find file location; write to index file. */
    if (fgetpos(helpdata, &location) != 0) {            /* error */
        perror("Can't find help file position"); exit(EXIT_FAILURE);
    }
    fwrite(&location, sizeof(fpos_t), 1, index);   /* error check shortly */

    /* Skip the rest of the help entry (until EOF or "\n::" is seen).
       Measure the size of the text as it is skipped.
       We are at the start of a line, skip a line at a time */

    entry_size = 0;                            /* Seen nothing yet */
    status = fscanf(helpdata, "%2[^\n]", flag);/* first two chars in line */

    while (status >= 0 && strcmp(flag,"::") != 0) { /*Skip a line per loop*/
        entry_size += strlen(flag);            /* Up to 2 chars already */
        while (ch = getc(helpdata), ch != EOF && ch != '\n') {
            entry_size++;                      /* Skip & count a char */
        }                                      /* until end of line */
        if (ch == '\n') entry_size++;          /* Count end of lines */
        status = fscanf(helpdata, "%2[^\n]",flag);/* 2 chars in next line */
    }

    /* Now write entry size to index file */
    if (fwrite(&entry_size, sizeof(int), 1, index) != 1) {
        perror("Error writing index file"); exit(EXIT_FAILURE);
    }

    if (status == EOF) {                /* If EOF encountered, return 0. */
        return 0;                       /* No more entries */
    }

    return 1;                           /* The "::" of another entry seen */
}

/* The following #ifdef includes the file_open function; if you have
   it in a personal function library, you may wish to delete these lines
   and link the two files separately.
*/
#ifdef __cplusplus
    #include "lst10-7.cpp"    /* or maybe "lst10-7.cxx" */
#else
    #include "lst10-7.c"
#endif