/* aoc-c.c: Advent of Code 2022, day 13
 *
 * Copyright (C) 2022 Bruno Raoult ("br")
 * Licensed under the GNU General Public License v3.0 or later.
 * Some rights reserved. See COPYING.
 *
 * You should have received a copy of the GNU General Public License along with this
 * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
 *
 * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
 */

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

#include "br.h"
#include "list.h"
#include "pool.h"

#include "aoc.h"

typedef enum {
    NIL,
    LIST,
    INT
} type_t;

#define CAR 0                                     /* always NUM or SUBLIST */
#define CDR 1                                     /* always LIST */

typedef struct node {
    type_t car_t;
    union {
        struct list_head sub;
        int value;
    } car;
    struct list_head cdr;
} node_t;

typedef struct nodes {
    struct list_head node;
    struct list_head list;
} nodes_t;
LIST_HEAD(nodes);

/* dummy nodes for integer vs list */
static struct list_head dummy_list;               /* tentative definition */
static node_t dummy = {
    .car_t = INT, .car.value = 0, .cdr = LIST_HEAD_INIT(dummy_list)
};
static struct list_head dummy_list = LIST_HEAD_INIT(dummy.cdr);

pool_t *pool_node, *pool_nodes;

static node_t *getnode()
{
    node_t *node = pool_get(pool_node);
    node->car_t = NIL;
    INIT_LIST_HEAD(&node->cdr);
    return node;
}

static int compare_tree(struct list_head *h1, struct list_head *h2)
{
    struct list_head *cur1, *cur2;
    node_t *n1, *n2;
    int res;

    /* get lists first entries */
    cur1 = h1->next;
    cur2 = h2->next;

     while (cur1 != h1 && cur2 != h2) {
        n1 = container_of(cur1, node_t, cdr);
        n2 = container_of(cur2, node_t, cdr);

        if (n1->car_t == n2->car_t) {
            if (n1->car_t == INT) {
                if (n1->car.value < n2->car.value) {
                    return 1;
                } else if (n1->car.value > n2->car.value) {
                    return -1;
                }
            } else {                              /* both sublists */
                res = compare_tree(&n1->car.sub, &n2->car.sub);
                if (res)
                    return res;
            }
        } else {                                  /* one number, one list */
            if (n1->car_t == INT) {
                dummy.car.value = n1->car.value;
                res = compare_tree(&dummy_list, &n2->car.sub);
            } else {
                dummy.car.value = n2->car.value;
                res = compare_tree(&n1->car.sub, &dummy_list);
            }
            if (res)
                return res;
        }
        cur1 = cur1->next;
        cur2 = cur2->next;
    }
    /* at least one list came to end */
     if (cur1 == h1 && cur2 == h2) {              /* both are ending */
        return 0;
     } else if (cur1 == h1) {                         /* first list did end */
        return 1;
    } else {
        return -1;
    }
}

static int add_node(nodes_t *h)
{
    nodes_t *first, *iter;
    struct list_head *node_next = &nodes;
    int num = 1;

    if (list_empty(&nodes))
        goto ins_node;
    first = iter = list_first_entry(&nodes, nodes_t, list);
    do {
        if (compare_tree(&h->node, &iter->node) > 0) {
            node_next = &iter->list;
            break;
        }
        iter = list_entry(iter->list.next, nodes_t, list);
        num++;
    } while (iter != first);
ins_node:
    list_add_tail(&h->list, node_next);
    return num;
}


static struct list_head *create_tree(char *s, int *consumed, int level, struct list_head *head)
{
    node_t *node = NULL;
    LIST_HEAD(sub);
    int num = 0, val, depth = 0, subconsumed;

    *consumed = 1;
    INIT_LIST_HEAD(head);
    for (; *s; s++, (*consumed)++) {
        val = 0;
        switch (*s) {
            case '[':
                switch (++depth) {
                    case 1:                       /* first level */
                        break;
                    case 2:                       /* second level (nested list) */
                        node = getnode();
                        node->car_t = LIST;
                        INIT_LIST_HEAD(&node->car.sub);
                        create_tree(s, &subconsumed, level + 1, &node->car.sub);
                        s += subconsumed - 1;
                        *consumed += subconsumed - 1;
                        list_add_tail(&node->cdr, head);
                        depth--;
                        num++;
                        break;
                    default:                      /* should not happen */
                        printf("error 1\n");
                        exit(0);
                        break;                    /* not reached */
                }
                break;
            case ',':
                break;
            case ']':
                if (!--depth)
                    goto end;
                break;
            default:                              /* number */
                sscanf(s, "%d%n", &val, &subconsumed);
                *consumed += subconsumed - 1;
                s += subconsumed - 1;
                node = getnode();
                node->car_t = INT;
                node->car.value = val;
                list_add_tail(&node->cdr, head);
                num++;
                break;
        }
    }
end:
    return head;
}

static int parse()
{
    size_t alloc = 0;
    ssize_t buflen;
    char *buf = NULL;
    int i = 0;
    nodes_t *head[2];
    int dummy, group = 1, res = 0;

    while (1) {
        buflen = getline(&buf, &alloc, stdin);
        if (--buflen > 0) {
            head[ i % 2] = pool_get(pool_nodes);
            create_tree(buf, &dummy, 0, &head[i % 2]->node);
            add_node(head[i %2]);
        }
        if (buflen != 0) {
            if (i % 2) {
                if (compare_tree(&head[0]->node, &head[1]->node) == 1)
                    res += group;
                group++;
            }
            i++;

        }
        if (buflen < 0)
            break;
    }
    return res;
}

static int part1()
{
    return parse();
}

static int part2()
{
    int dummy, res;
    struct nodes *h;
    parse();
    h = pool_get(pool_nodes);
    create_tree("[2]", &dummy, 0, &h->node);
    res = add_node(h);
    h = pool_get(pool_nodes);
    create_tree("[6]", &dummy, 0, &h->node);
    res *= add_node(h);
    return res;
}

int main(int ac, char **av)
{
    int part = parseargs(ac, av);
    pool_node =  pool_create("node", 512, sizeof(node_t));
    pool_nodes =  pool_create("nodes", 512, sizeof(nodes_t));

    printf("%s: res=%d\n", *av, part == 1? part1(): part2());
    pool_destroy(pool_node);
    pool_destroy(pool_nodes);
    exit(0);
}