/* TDKPIN's small ObjectWindows/MMTIMER system-timer class. */

#include "tdkpin_system_timer.h"

enum {
    SYSTEM_TIMER_VMT_OFFSET = 0,
    SYSTEM_TIMER_ID_OFFSET = 2,
    SYSTEM_TIMER_RECIPIENT_OFFSET = 4,
};

/*
 * 1008:295c — create the underlying MMTIMER timer.
 * MOV AL,[BP+0a] deliberately preserves AH returned by the stack checker, so
 * the imported word-valued one_shot argument is not merely zero or one.
 */
uint16_t tdkpin_system_timer_start(
    Win16FarPtr object,
    uint8_t one_shot,
    uint16_t resolution_ms,
    uint16_t delay_ms)
{
    uint16_t stack_result = borland_check_stack(2);
    uint16_t one_shot_word =
        (uint16_t)((stack_result & 0xff00u) | one_shot);
    HWND16 recipient =
        win16_read_u16(win16_far_add_offset(
            object, SYSTEM_TIMER_RECIPIENT_OFFSET));
    return SystemTimerMake16(
        recipient, delay_ms, resolution_ms, one_shot_word);
}

/* 1008:2932 — cancel a live multimedia timer, then clear its id. */
void tdkpin_system_timer_stop(Win16FarPtr object)
{
    (void)borland_check_stack(0);
    uint16_t timer_id =
        win16_read_u16(win16_far_add_offset(object, SYSTEM_TIMER_ID_OFFSET));
    if (timer_id != 0) {
        (void)TimeKillEvent16(timer_id);
    }
    win16_write_u16(object, SYSTEM_TIMER_ID_OFFSET, 0);
}

/*
 * 1008:28a3 — construct the six-byte timer object and start its timer.
 * A zero timer id invokes the Borland constructor-failure cleanup. That frees
 * newly allocated instances but leaves caller-owned instances in place because
 * 1020:03ef cleared their hidden VMT ownership argument.
 */
Win16FarPtr tdkpin_system_timer_construct(
    Win16FarPtr object,
    uint16_t vmt,
    uint8_t one_shot,
    uint16_t resolution_ms,
    uint16_t delay_ms,
    HWND16 recipient)
{
    (void)borland_check_stack(0);
    BorlandObjectCallFrame frame = {object, vmt};
    if (!borland_enter_object_constructor(
            &frame, SYSTEM_TIMER_VMT_OFFSET)) {
        return frame.object;
    }

    frame.object = borland_default_object_constructor(frame.object, 0);
    win16_write_u16(frame.object, SYSTEM_TIMER_ID_OFFSET, 0);
    win16_write_u16(frame.object, SYSTEM_TIMER_RECIPIENT_OFFSET, recipient);
    uint16_t timer_id = tdkpin_system_timer_start(
        frame.object, one_shot, resolution_ms, delay_ms);
    win16_write_u16(frame.object, SYSTEM_TIMER_ID_OFFSET, timer_id);
    if (timer_id == 0) {
        borland_finish_object_destructor(
            &frame, SYSTEM_TIMER_VMT_OFFSET);
    }
    return frame.object;
}

/* 1008:2906 — stop the timer, run the root destructor, and release if owned. */
void tdkpin_system_timer_destruct(Win16FarPtr object, uint16_t vmt)
{
    (void)borland_check_stack(0);
    BorlandObjectCallFrame frame = {object, vmt};
    tdkpin_system_timer_stop(frame.object);
    borland_default_object_destructor(frame.object, 0);
    borland_finish_object_destructor(&frame, SYSTEM_TIMER_VMT_OFFSET);
}