/* ObjectWindows circular child-object list. */

#include "tdkpin_object_list.h"

enum {
    CONTAINER_CHILD_TAIL_OFFSET = 0x0a,
    CHILD_NEXT_OFFSET = 0x19,
    CHILD_WINDOW_HANDLE_OFFSET = 4,
    CHILD_CAN_CLOSE_SLOT = 0x3c,
    CHILD_BLOCKS_CLOSE_OFFSET = 0x0ec0,
    CHILD_GROUP_OFFSET = 0x17,
    CHILD_FLAGS_OFFSET = 0x16,
    CHILD_ACTIVATE_SLOT = 0x20,
    CHILD_TRANSFER_SLOT = 0x40,
    CHILD_TRANSFER_FLAG = 0x10,
    OBJECT_TRANSFER_POINTER_OFFSET = 0x0e,
};

static Win16FarPtr read_far(Win16FarPtr object, uint16_t offset)
{
    return win16_read_far_pointer(object, offset);
}

static void write_far(
    Win16FarPtr object, uint16_t offset, Win16FarPtr value)
{
    win16_write_u16(object, offset, win16_far_offset(value));
    win16_write_u16(
        object, (uint16_t)(offset + 2), win16_far_selector(value));
}

/*
 * 1018:069a — append one child to a circular singly linked ring.
 * The container stores the tail; tail->next is the oldest/head child.
 */
void object_windows_append_child(
    Win16FarPtr container, Win16FarPtr child)
{
    if (child == 0) {
        return;
    }
    Win16FarPtr tail = read_far(container, CONTAINER_CHILD_TAIL_OFFSET);
    if (tail == 0) {
        write_far(child, CHILD_NEXT_OFFSET, child);
    } else {
        write_far(child, CHILD_NEXT_OFFSET,
                  read_far(tail, CHILD_NEXT_OFFSET));
        write_far(tail, CHILD_NEXT_OFFSET, child);
    }
    write_far(container, CONTAINER_CHILD_TAIL_OFFSET, child);
}

/* 1018:071c — unlink one exact far child, maintaining the tail invariant. */
void object_windows_remove_child(
    Win16FarPtr container, Win16FarPtr child)
{
    Win16FarPtr tail = read_far(container, CONTAINER_CHILD_TAIL_OFFSET);
    if (tail == 0) {
        return;
    }

    Win16FarPtr previous = tail;
    while (true) {
        Win16FarPtr candidate = read_far(previous, CHILD_NEXT_OFFSET);
        if (candidate == child || candidate == tail) {
            if (candidate != child) {
                return;
            }
            if (candidate == previous) {
                write_far(container, CONTAINER_CHILD_TAIL_OFFSET, 0);
                return;
            }
            if (candidate == tail) {
                write_far(container, CONTAINER_CHILD_TAIL_OFFSET, previous);
            }
            write_far(previous, CHILD_NEXT_OFFSET,
                      read_far(candidate, CHILD_NEXT_OFFSET));
            return;
        }
        previous = candidate;
    }
}

/* 1018:080d — visit head-to-tail and return the first matching child. */
Win16FarPtr object_windows_find_child(
    Win16FarPtr container, Win16FarPtr predicate)
{
    Win16FarPtr tail = read_far(container, CONTAINER_CHILD_TAIL_OFFSET);
    if (tail == 0) {
        return 0;
    }
    Win16FarPtr child = read_far(tail, CHILD_NEXT_OFFSET);
    while (true) {
        if (win16_call_object_predicate(predicate, child)) {
            return child;
        }
        if (child == tail) {
            return 0;
        }
        child = read_far(child, CHILD_NEXT_OFFSET);
    }
}

/*
 * 1018:085a — visit every child head-to-tail. The next far pointer is read
 * before each callback so the callback may unlink or destroy the current node.
 */
void object_windows_for_each_child(
    Win16FarPtr container, Win16FarPtr action)
{
    Win16FarPtr tail = read_far(container, CONTAINER_CHILD_TAIL_OFFSET);
    if (tail == 0) {
        return;
    }
    Win16FarPtr child = read_far(tail, CHILD_NEXT_OFFSET);
    while (child != tail) {
        Win16FarPtr next = read_far(child, CHILD_NEXT_OFFSET);
        win16_call_object_action(action, child);
        child = next;
    }
    win16_call_object_action(action, tail);
}

/* 1018:08ac — inherited virtual default returning AX=0xffff. */
uint16_t object_windows_minus_one_default(Win16FarPtr object)
{
    (void)object;
    return 0xffff;
}

/* 1018:0ec0 — predicate: a windowed child whose CanClose returns false. */
bool object_windows_child_blocks_close(
    uint16_t ignored, Win16FarPtr child)
{
    (void)ignored;
    if (win16_read_u16(win16_far_add_offset(
            child, CHILD_WINDOW_HANDLE_OFFSET)) == 0) {
        return false;
    }
    uint16_t vmt = win16_read_u16(child);
    Win16FarPtr can_close =
        win16_read_far_pointer(win16_dgroup_pointer(vmt), CHILD_CAN_CLOSE_SLOT);
    return !win16_call_object_bool_method(can_close, child);
}

/* 1018:0ef4 — true exactly when no child blocks container shutdown. */
bool object_windows_all_children_can_close(Win16FarPtr container)
{
    Win16FarPtr blocker = object_windows_find_child(
        container,
        win16_relocated_code_pointer(4, CHILD_BLOCKS_CLOSE_OFFSET));
    return blocker == 0;
}

/* 1018:03e9 — nested ForEach callback: dispose the supplied child object. */
void object_windows_dispose_child_callback(
    uint16_t ignored, Win16FarPtr child)
{
    (void)ignored;
    borland_dispose_object(child);
}

/* 1018:0466 — nested predicate for signed group field +0x17. */
bool object_windows_child_group_matches(
    int16_t group, Win16FarPtr child)
{
    return group >= 0 &&
        win16_read_u16(win16_far_add_offset(child, CHILD_GROUP_OFFSET)) ==
            (uint16_t)group;
}

/*
 * 1018:049e — evaluate one child and preserve the minimized-window text
 * refresh side effect. The function returns true only for flag-4 children
 * whose VMT +0x20 method returns false.
 */
bool object_windows_try_child_activation(
    uint16_t ignored, Win16FarPtr child)
{
    (void)ignored;
    bool continue_processing = true;
    uint8_t flags = win16_read_u8(
        win16_far_add_offset(child, CHILD_FLAGS_OFFSET));
    if ((flags & 4) != 0) {
        uint16_t vmt = win16_read_u16(child);
        Win16FarPtr procedure = win16_read_far_pointer(
            win16_dgroup_pointer(vmt), CHILD_ACTIVATE_SLOT);
        if (!win16_call_object_bool_method(procedure, child)) {
            continue_processing = false;
        }
    }
    if (continue_processing) {
        HWND16 window = win16_read_u16(win16_far_add_offset(
            child, CHILD_WINDOW_HANDLE_OFFSET));
        if (IsIconic16(window) != 0) {
            char text[82];
            (void)GetWindowText16(window, text, 81);
            (void)SetWindowText16(window, text);
        }
    }
    return !continue_processing;
}

/* 1018:0524 — group-zero predicate gated by 1018:049e. */
bool object_windows_unindexed_child_matches(
    uint16_t ignored, Win16FarPtr child)
{
    return win16_read_u16(win16_far_add_offset(
               child, CHILD_GROUP_OFFSET)) == 0 &&
        object_windows_try_child_activation(ignored, child);
}

static Win16FarPtr find_child_in_group(
    Win16FarPtr container, int16_t group, bool require_activation)
{
    Win16FarPtr tail = read_far(container, CONTAINER_CHILD_TAIL_OFFSET);
    if (tail == 0) {
        return 0;
    }
    Win16FarPtr child = read_far(tail, CHILD_NEXT_OFFSET);
    while (true) {
        bool matches = object_windows_child_group_matches(group, child);
        if (matches &&
            (!require_activation ||
             object_windows_try_child_activation(0, child))) {
            return child;
        }
        if (child == tail) {
            return 0;
        }
        child = read_far(child, CHILD_NEXT_OFFSET);
    }
}

/*
 * 1018:055c — scan numbered groups starting at one. Each found child is passed
 * through 049e; after the first missing group, group zero is searched for a
 * child whose 049e result is true. The unusual final inversion is preserved.
 */
bool object_windows_validate_child_groups(Win16FarPtr container)
{
    int16_t group = 1;
    bool result = false;
    Win16FarPtr child;
    do {
        child = find_child_in_group(container, group, false);
        if (child != 0) {
            result = object_windows_try_child_activation(0, child);
        }
        group++;
    } while (!result && child != 0);
    if (!result) {
        return find_child_in_group(container, 0, true) == 0;
    }
    return true;
}

/* 1018:0d9b — validate child groups, store status -4, or call VMT +0x44(2). */
void object_windows_prepare_window(Win16FarPtr window)
{
    if (!object_windows_validate_child_groups(window)) {
        win16_write_u16(window, 2, 0xfffc);
        return;
    }
    uint16_t vmt = win16_read_u16(window);
    Win16FarPtr procedure =
        win16_read_far_pointer(win16_dgroup_pointer(vmt), 0x44);
    win16_call_object_u16_method(procedure, window, 2);
}

/*
 * 1018:0dcd — nested transfer callback. Flag 0x10 selects participants;
 * VMT +0x40 receives child, direction, and the current far cursor. AX advances
 * only the cursor offset with 16-bit wrap, preserving its selector.
 */
void object_windows_transfer_child_callback(
    ObjectWindowsTransferContext *context, Win16FarPtr child)
{
    uint8_t flags = win16_read_u8(
        win16_far_add_offset(child, CHILD_FLAGS_OFFSET));
    if ((flags & CHILD_TRANSFER_FLAG) == 0) {
        return;
    }
    uint16_t vmt = win16_read_u16(child);
    Win16FarPtr procedure = win16_read_far_pointer(
        win16_dgroup_pointer(vmt), CHILD_TRANSFER_SLOT);
    uint16_t consumed = win16_call_object_transfer_method(
        procedure, child, context->direction, context->cursor);
    context->cursor = win16_make_far_pointer(
        win16_far_selector(context->cursor),
        (uint16_t)(win16_far_offset(context->cursor) + consumed));
}

/* 1018:0e0a — transfer across the circular child list head-to-tail. */
void object_windows_transfer_child_data(
    Win16FarPtr object, uint16_t direction)
{
    Win16FarPtr cursor =
        read_far(object, OBJECT_TRANSFER_POINTER_OFFSET);
    if (cursor == 0) {
        return;
    }
    ObjectWindowsTransferContext context = {cursor, direction};
    Win16FarPtr tail = read_far(object, CONTAINER_CHILD_TAIL_OFFSET);
    if (tail == 0) {
        return;
    }
    Win16FarPtr child = read_far(tail, CHILD_NEXT_OFFSET);
    while (child != tail) {
        Win16FarPtr next = read_far(child, CHILD_NEXT_OFFSET);
        object_windows_transfer_child_callback(&context, child);
        child = next;
    }
    object_windows_transfer_child_callback(&context, tail);
}