#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>

#define MODULE_NAME "aoc2023d3p1"
MODULE_AUTHOR("logan2611");
MODULE_LICENSE("Dual MIT/GPL");
MODULE_DESCRIPTION("Advent of Code 2023 Day 3 Part 1 (The Linux Kernel Module)");
MODULE_VERSION("0.1");

const int length = 140; // Number of lines
//const int length = 10; // Number of lines
const int width = length + 1; // Width of lines (including newline, carriage return or null terminator)

// Parameter that specifies the input file
static char *path = "/tmp/input";
module_param(path, charp, S_IRUGO);
MODULE_PARM_DESC(path, "The path to the data input.");

static ssize_t read_input(struct file *file, loff_t pos, size_t n, char *buffer) {
    ssize_t bytes_read;

    bytes_read = kernel_read(file, buffer, n, &pos);
    if (bytes_read < 0) {
        pr_err("%s: Error reading file: %zd\n", MODULE_NAME, bytes_read);
    }

    return bytes_read;
}

// I cleaned this up in part 2, please don't look at this
static int find_numbers(char *top, char *middle, char *bottom) {
    int beginning = -1;
    int end = -1;
    int sum = 0;

    for(int i = 0; i < width; i++) {
        if(i < end+1) continue;
        if(middle[i] >= 48 && middle[i] <= 57) {
            beginning = i-1;
            end = i-1;
            //pr_info("%s: %d\n", MODULE_NAME, i);

            if(beginning < 0) {
                beginning = 0;
            }

            for(int j = 0; j <= 4; j++) {
                if(middle[i+j] < 48 || middle[i+j] > 57) {
                    end = i+j;

                    char numstr[8] = {0};
                    memcpy(numstr, middle + i, j);

                    int ret = 0;
                    int err = 0;
                    err = kstrtoint(numstr, 10, &ret);
                    if (ret < 0) {
                        pr_err("%s: Failed to convert string to number: \"%d\"\n", MODULE_NAME, err);
                        return 0;
                    }

                    //pr_info("%s: %d %d %d\n", MODULE_NAME, ret, i, end);
                    for(int k = 0; k <= end - beginning; k++) {
                        //pr_info("%s: Checking position %d\n", MODULE_NAME, beginning+k);

                        char topcheck = top[beginning+k];
                        char middlecheck = middle[beginning+k];
                        char bottomcheck = bottom[beginning+k];

                        if( (((topcheck >= 33 && topcheck <= 47) || (topcheck >= 58 && topcheck <= 64)) && topcheck != '.') ||
                            (((middlecheck >= 33 && middlecheck <= 47) || (middlecheck >= 58 && middlecheck <= 64)) && middlecheck != '.') ||
                            (((bottomcheck >= 33 && bottomcheck <= 47) || (bottomcheck >= 58 && bottomcheck <= 64)) && bottomcheck != '.'))
                        {
                            pr_info("%s: ADJACENT %d\n", MODULE_NAME, ret);
                            sum += ret;
                            break;
                        } else {
                            //pr_info("%s: %d, %d and %d are not symbols\n", MODULE_NAME, topcheck, middlecheck, bottomcheck);
                        };
                    } // End Check for symbols loop
                    break;
                } // End Check for numbers loop
            } // End find tail of number
        } // End If number is found
    } // End Find numbers loop
    return sum;
}



static int __init test_init(void) {
    struct file *f;

    pr_info("%s: Module loaded\n", MODULE_NAME);

    f = filp_open(path, O_RDONLY, 0);
    if(IS_ERR(f)) {
        pr_err("%s: Failed to open %s\n", MODULE_NAME, path);
        return PTR_ERR(f);
    }

    char buf[3][width+1];
    memset(buf, 0, sizeof(buf));

    read_input(f, 0, width, buf[2]);

    int sum = 0;

    for(int line = 1; line <= length; line++) {
        pr_info("%s: %s", MODULE_NAME, buf[2]);

        memcpy(buf[0], buf[1], sizeof(buf[0]));
        memcpy(buf[1], buf[2], sizeof(buf[1]));

        if(length - line > 0) {
            read_input(f, line*width, length, buf[2]);
        } else {
            memset(buf[2], 0, sizeof(buf[2]));
        }

        sum += find_numbers(buf[0], buf[1], buf[2]);
    }

    filp_close(f, NULL);

    pr_info("%s: %d\n", MODULE_NAME, sum);
    return 0;
}

static void __exit test_exit(void) {
    pr_info("%s: Module unloaded\n", MODULE_NAME);
}

module_init(test_init);
module_exit(test_exit);