/* This file is part of Ground Control.

Ground Control is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

Ground Control is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
Ground Control. If not, see <https://www.gnu.org/licenses/>. */
#include "wren.h"
#include "bencode.h"

const char* read_int(const char* buf, int* out) {
    int result = 0;
    while (*buf != 'e') {
        int digit = *buf - '0';
        result *= 10;
        result += digit;
        buf++;
    }
    buf++;
    *out = result;
    return buf;
}

static const char* bdecode_partial(WrenVM* vm, const char* buf) {
    wrenEnsureSlots(vm, 1);
    switch (*buf) {
        case 't':
        case 'f': {
            wrenSetSlotBool(vm, 0, *buf=='t');
            buf++;
            break;
        }
        case 'n': {
            wrenSetSlotNull(vm, 0);
            buf++;
            break;
        }
        case 'i': {
            int value;
            buf++;
            buf = read_int(buf, &value);
            wrenSetSlotDouble(vm, 0, (double)value);
            break;
        }
        case 's': {
            int len;
            buf++;
            buf = read_int(buf, &len);
            wrenSetSlotBytes(vm, 0, buf, len);
            buf += len;
            break;
        }
        case 'l': {
            WrenHandle* list;
            buf++;
            wrenEnsureSlots(vm, 2);
            wrenSetSlotNewList(vm, 0);
            list = wrenGetSlotHandle(vm, 0);
            while (*buf != 'e') {
                buf = bdecode_partial(vm, buf);
                wrenSetSlotHandle(vm, 1, list);
                wrenInsertInList(vm, 1, -1, 0);
            }
            wrenSetSlotHandle(vm, 0, list);
            wrenReleaseHandle(vm, list);
            buf++;
            break;
        }
        case 'd': {
            WrenHandle* map;
            WrenHandle* key;
            buf++;
            wrenEnsureSlots(vm, 3);
            wrenSetSlotNewMap(vm, 0);
            map = wrenGetSlotHandle(vm, 0);
            while (*buf != 'e') {
                buf = bdecode_partial(vm, buf);
                key = wrenGetSlotHandle(vm, 0);
                buf = bdecode_partial(vm, buf);
                /* value is in slot 0 */
                wrenSetSlotHandle(vm, 1, key); /* key is in slot 1 */
                wrenReleaseHandle(vm, key);
                wrenSetSlotHandle(vm, 2, map); /* map is in slot 2 */
                wrenSetMapValue(vm, 2, 1, 0);
            }
            wrenSetSlotHandle(vm, 0, map);
            wrenReleaseHandle(vm, map);
            buf++;
            break;
        }
    }
    return buf;
}

void bdecode(WrenVM* vm) {
    const char* buf = wrenGetSlotString(vm, 1);
    bdecode_partial(vm, buf);
}