Markdown to ToC

mdtotoc.c

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

#define TOP 1
#define MAX 10

typedef struct {
    char *source_file;
    int top;
    int max;
    int count;
    char *level;
    char *header;
    char *start;
    char *anchor;
    char **seen;
    int seen_count;
} ToCWriter;

void initialize_ToCWriter(ToCWriter *writer, char *source_file, int top, int max) {
    writer->source_file = source_file;
    writer->top = top;
    writer->max = max;
    writer->count = 1;
    writer->level = malloc(256);
    writer->header = malloc(256);
    writer->start = malloc(256);
    writer->anchor = malloc(256);
    writer->seen = malloc(256 * sizeof(char*));
    writer->seen_count = 0;
}

void free_ToCWriter(ToCWriter *writer) {
    free(writer->level);
    free(writer->header);
    free(writer->start);
    free(writer->anchor);
    for (int i = 0; i < writer->seen_count; i++) {
        free(writer->seen[i]);
    }
    free(writer->seen);
}

int ignore_this_header(ToCWriter *writer) {
    return (strcmp(writer->header, "Table of contents") == 0) ||
           (strlen(writer->level) < writer->top) ||
           (strlen(writer->level) > writer->max);
}

void set_anchor(ToCWriter *writer) {
    strcpy(writer->anchor, writer->header);
    for (int i = 0; writer->anchor[i]; i++) {
        writer->anchor[i] = tolower(writer->anchor[i]);
        if (!isalnum(writer->anchor[i]) && writer->anchor[i] != '_' && writer->anchor[i] != '-' && writer->anchor[i] != ' ') {
            writer->anchor[i] = '\0';
        }
    }
    char *ptr = writer->anchor;
    while (*ptr) {
        if (*ptr == ' ') *ptr = '-';
        ptr++;
    }
}

void update_if_seen(ToCWriter *writer) {
    int inc = 2;
    int found;
    do {
        found = 0;
        for (int i = 0; i < writer->seen_count; i++) {
            if (strcmp(writer->seen[i], writer->anchor) == 0) {
                found = 1;
                break;
            }
        }
        if (found) {
            char suffix[10];
            sprintf(suffix, "-%d", inc++);
            strcat(writer->anchor, suffix);
        }
    } while (found);
    writer->seen[writer->seen_count] = strdup(writer->anchor);
    writer->seen_count++;
}

void set_start(ToCWriter *writer) {
    int len = strlen(writer->level);
    if (len == writer->top) {
        sprintf(writer->start, "%d.", writer->count++);
    } else {
        char bullet = len % 2 == 0 ? '-' : '*';
        memset(writer->start, ' ', 256);
        for (int i = 0; i < (len - writer->top) * 4; i++) {
            writer->start[i] = ' ';
        }
        writer->start[(len - writer->top) * 4] = bullet;
        writer->start[(len - writer->top) * 4 + 1] = '\0';
    }
}

void write_ToC(ToCWriter *writer) {
    printf("#### Table of contents\n\n");
    FILE *file = fopen(writer->source_file, "r");
    char line[256];
    int line_number = 0;
    while (fgets(line, sizeof(line), file)) {
        line_number++;
        if (line_number == 1) continue;
        if (line[0] != '#') continue;
        sscanf(line, "%s %[^\n]", writer->level, writer->header);
        if (ignore_this_header(writer)) continue;
        set_anchor(writer);
        update_if_seen(writer);
        set_start(writer);
        printf("%s [%s](#%s)\n", writer->start, writer->header, writer->anchor);
    }
    fclose(file);
}

int main() {
    // Define the filename directly
    char filename[] = "example.md";

    // Define the default TOP and MAX values
    int top = TOP;
    int max = MAX;

    ToCWriter writer;
    initialize_ToCWriter(&writer, filename, top, max);
    write_ToC(&writer);
    free_ToCWriter(&writer);
    return 0;
}