#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

int max(int a, int b) {
    if (a < b) {
        return b;
    }
    return a;
}

int fill_buffer(int fd, char* buffer, int size) {
    int result = read(fd, buffer, size);
    int total_read = 0;
    if (result > 0) {
        total_read += result;
        while (total_read != size && result != 0) {
            result = read(fd, buffer + total_read, size - total_read);
            if (result < 0) {
                return result;
            }
            total_read += result;
        }
        return total_read;
    }
    return result;
}

struct FileContent read_file(int fd) {
    int SIZE = 4096;
    char buffer[SIZE];

    int result = fill_buffer(fd, buffer, SIZE);
    if (result == -1) {
        struct FileContent error;
        error.size = -1;
        error.data = NULL;
        return error;
    }

    struct FileContent content;
    content.size = 0;
    size_t capacity = result + 1;
    content.data = malloc(capacity * sizeof(*content.data));
    if (content.data == NULL) {
        content.size = -1;
        return content;
    }

    while (result > 0) {
        if (result + content.size > capacity) {
            int new_capacity = content.size + max(SIZE, capacity * 2);
            char* tmp = realloc(content.data, new_capacity);
            if (!tmp) {
                free(content.data);
                content.data = NULL;
                content.size = -1;
                return content;
            }
            content.data = tmp;
            capacity = new_capacity;
        }
        memcpy(content.data + content.size, buffer, result);
        content.size += result;
        result = fill_buffer(fd, buffer, SIZE);
        if (result == -1) {
            free(content.data);
            content.data = NULL;
            content.size = -1;
            return content;
        }
    }

    if (content.size >= capacity) {
        int new_capacity = content.size + 1;
        char* tmp = realloc(content.data, new_capacity);
        if (!tmp) {
            free(content.data);
            content.data = NULL;
            content.size = -1;
            return content;
        }
        content.data = tmp;
        capacity = new_capacity;
    }

    content.data[content.size] = '\0';
    return content;
}