/*
 * Copyright (c) 2020, the SerenityOS developers.
 * Copyright (c) 2022, Luke Wilde <lukew@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/DocumentType.h>
#include <LibWeb/DOM/Node.h>
#include <LibWeb/DOM/Range.h>
#include <LibWeb/DOM/Window.h>

namespace Web::DOM {

NonnullRefPtr<Range> Range::create(Window& window)
{
    return Range::create(window.associated_document());
}

NonnullRefPtr<Range> Range::create(Document& document)
{
    return adopt_ref(*new Range(document));
}

NonnullRefPtr<Range> Range::create(Node& start_container, u32 start_offset, Node& end_container, u32 end_offset)
{
    return adopt_ref(*new Range(start_container, start_offset, end_container, end_offset));
}

NonnullRefPtr<Range> Range::create_with_global_object(Bindings::WindowObject& window)
{
    return Range::create(window.impl());
}

Range::Range(Document& document)
    : Range(document, 0, document, 0)
{
}

Range::Range(Node& start_container, u32 start_offset, Node& end_container, u32 end_offset)
    : AbstractRange(start_container, start_offset, end_container, end_offset)
{
}

Range::~Range()
{
}

// https://dom.spec.whatwg.org/#concept-range-root
Node& Range::root()
{
    // The root of a live range is the root of its start node.
    return m_start_container->root();
}

Node const& Range::root() const
{
    return m_start_container->root();
}

enum class RelativeBoundaryPointPosition {
    Equal,
    Before,
    After,
};

// https://dom.spec.whatwg.org/#concept-range-bp-position
static RelativeBoundaryPointPosition position_of_boundary_point_relative_to_other_boundary_point(Node const& node_a, u32 offset_a, Node const& node_b, u32 offset_b)
{
    // 1. Assert: nodeA and nodeB have the same root.
    VERIFY(&node_a.root() == &node_b.root());

    // 2. If nodeA is nodeB, then return equal if offsetA is offsetB, before if offsetA is less than offsetB, and after if offsetA is greater than offsetB.
    if (&node_a == &node_b) {
        if (offset_a == offset_b)
            return RelativeBoundaryPointPosition::Equal;

        if (offset_a < offset_b)
            return RelativeBoundaryPointPosition::Before;

        return RelativeBoundaryPointPosition::After;
    }

    // 3. If nodeA is following nodeB, then if the position of (nodeB, offsetB) relative to (nodeA, offsetA) is before, return after, and if it is after, return before.
    if (node_a.is_following(node_b)) {
        auto relative_position = position_of_boundary_point_relative_to_other_boundary_point(node_b, offset_b, node_a, offset_a);

        if (relative_position == RelativeBoundaryPointPosition::Before)
            return RelativeBoundaryPointPosition::After;

        if (relative_position == RelativeBoundaryPointPosition::After)
            return RelativeBoundaryPointPosition::Before;
    }

    // 4. If nodeA is an ancestor of nodeB:
    if (node_a.is_ancestor_of(node_b)) {
        // 1. Let child be nodeB.
        NonnullRefPtr<Node> child = node_b;

        // 2. While child is not a child of nodeA, set child to its parent.
        while (!node_a.is_parent_of(child)) {
            auto* parent = child->parent();
            VERIFY(parent);
            child = *parent;
        }

        // 3. If child’s index is less than offsetA, then return after.
        if (child->index() < offset_a)
            return RelativeBoundaryPointPosition::After;
    }

    // 5. Return before.
    return RelativeBoundaryPointPosition::Before;
}

ExceptionOr<void> Range::set_start_or_end(Node& node, u32 offset, StartOrEnd start_or_end)
{
    // To set the start or end of a range to a boundary point (node, offset), run these steps:

    // 1. If node is a doctype, then throw an "InvalidNodeTypeError" DOMException.
    if (is<DocumentType>(node))
        return InvalidNodeTypeError::create("Node cannot be a DocumentType.");

    // 2. If offset is greater than node’s length, then throw an "IndexSizeError" DOMException.
    if (offset > node.length())
        return IndexSizeError::create(String::formatted("Node does not contain a child at offset {}", offset));

    // 3. Let bp be the boundary point (node, offset).

    if (start_or_end == StartOrEnd::Start) {
        // -> If these steps were invoked as "set the start"

        // 1. If range’s root is not equal to node’s root, or if bp is after the range’s end, set range’s end to bp.
        if (&root() != &node.root() || position_of_boundary_point_relative_to_other_boundary_point(node, offset, m_end_container, m_end_offset) == RelativeBoundaryPointPosition::After) {
            m_end_container = node;
            m_end_offset = offset;
        }

        // 2. Set range’s start to bp.
        m_start_container = node;
        m_start_offset = offset;
    } else {
        // -> If these steps were invoked as "set the end"
        VERIFY(start_or_end == StartOrEnd::End);

        // 1. If range’s root is not equal to node’s root, or if bp is before the range’s start, set range’s start to bp.
        if (&root() != &node.root() || position_of_boundary_point_relative_to_other_boundary_point(node, offset, m_start_container, m_start_offset) == RelativeBoundaryPointPosition::Before) {
            m_start_container = node;
            m_start_offset = offset;
        }

        // 2. Set range’s end to bp.
        m_end_container = node;
        m_end_offset = offset;
    }

    return {};
}

// https://dom.spec.whatwg.org/#concept-range-bp-set
ExceptionOr<void> Range::set_start(Node& node, u32 offset)
{
    // The setStart(node, offset) method steps are to set the start of this to boundary point (node, offset).
    return set_start_or_end(node, offset, StartOrEnd::Start);
}

ExceptionOr<void> Range::set_end(Node& node, u32 offset)
{
    // The setEnd(node, offset) method steps are to set the end of this to boundary point (node, offset).
    return set_start_or_end(node, offset, StartOrEnd::End);
}

NonnullRefPtr<Range> Range::clone_range() const
{
    return adopt_ref(*new Range(const_cast<Node&>(*m_start_container), m_start_offset, const_cast<Node&>(*m_end_container), m_end_offset));
}

NonnullRefPtr<Range> Range::inverted() const
{
    return adopt_ref(*new Range(const_cast<Node&>(*m_end_container), m_end_offset, const_cast<Node&>(*m_start_container), m_start_offset));
}

NonnullRefPtr<Range> Range::normalized() const
{
    if (m_start_container.ptr() == m_end_container.ptr()) {
        if (m_start_offset <= m_end_offset)
            return clone_range();

        return inverted();
    }

    if (m_start_container->is_before(m_end_container))
        return clone_range();

    return inverted();
}

// https://dom.spec.whatwg.org/#dom-range-commonancestorcontainer
NonnullRefPtr<Node> Range::common_ancestor_container() const
{
    // 1. Let container be start node.
    auto container = m_start_container;

    // 2. While container is not an inclusive ancestor of end node, let container be container’s parent.
    while (!container->is_inclusive_ancestor_of(m_end_container)) {
        VERIFY(container->parent());
        container = *container->parent();
    }

    // 3. Return container.
    return container;
}

}