/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/Badge.h>
#include <AK/StringBuilder.h>
#include <AK/Utf8View.h>
#include <LibCore/Timer.h>
#include <LibGUI/TextDocument.h>
#include <LibGUI/TextEditor.h>
#include <ctype.h>

namespace GUI {

NonnullRefPtr<TextDocument> TextDocument::create(Client* client)
{
    return adopt(*new TextDocument(client));
}

TextDocument::TextDocument(Client* client)
{
    if (client)
        m_clients.set(client);
    append_line(make<TextDocumentLine>(*this));

    // TODO: Instead of a repating timer, this we should call a delayed 2 sec timer when the user types.
    m_undo_timer = Core::Timer::construct(
        2000, [this] {
            update_undo_timer();
        });
}

TextDocument::~TextDocument()
{
}

void TextDocument::set_text(const StringView& text)
{
    m_client_notifications_enabled = false;
    m_spans.clear();
    remove_all_lines();

    size_t start_of_current_line = 0;

    auto add_line = [&](size_t current_position) {
        size_t line_length = current_position - start_of_current_line;
        auto line = make<TextDocumentLine>(*this);
        if (line_length)
            line->set_text(*this, text.substring_view(start_of_current_line, current_position - start_of_current_line));
        append_line(move(line));
        start_of_current_line = current_position + 1;
    };
    size_t i = 0;
    for (i = 0; i < text.length(); ++i) {
        if (text[i] == '\n')
            add_line(i);
    }
    add_line(i);
    m_client_notifications_enabled = true;

    for (auto* client : m_clients)
        client->document_did_set_text();
}

size_t TextDocumentLine::first_non_whitespace_column() const
{
    for (size_t i = 0; i < length(); ++i) {
        auto code_point = code_points()[i];
        if (!isspace(code_point))
            return i;
    }
    return length();
}

Optional<size_t> TextDocumentLine::last_non_whitespace_column() const
{
    for (ssize_t i = length() - 1; i >= 0; --i) {
        auto code_point = code_points()[i];
        if (!isspace(code_point))
            return i;
    }
    return {};
}

bool TextDocumentLine::ends_in_whitespace() const
{
    if (!length())
        return false;
    return isspace(code_points()[length() - 1]);
}

String TextDocumentLine::to_utf8() const
{
    StringBuilder builder;
    builder.append(view());
    return builder.to_string();
}

TextDocumentLine::TextDocumentLine(TextDocument& document)
{
    clear(document);
}

TextDocumentLine::TextDocumentLine(TextDocument& document, const StringView& text)
{
    set_text(document, text);
}

void TextDocumentLine::clear(TextDocument& document)
{
    m_text.clear();
    document.update_views({});
}

void TextDocumentLine::set_text(TextDocument& document, const Vector<u32> text)
{
    m_text = move(text);
    document.update_views({});
}

void TextDocumentLine::set_text(TextDocument& document, const StringView& text)
{
    if (text.is_empty()) {
        clear(document);
        return;
    }
    m_text.clear();
    Utf8View utf8_view(text);
    for (auto code_point : utf8_view)
        m_text.append(code_point);
    document.update_views({});
}

void TextDocumentLine::append(TextDocument& document, const u32* code_points, size_t length)
{
    if (length == 0)
        return;
    m_text.append(code_points, length);
    document.update_views({});
}

void TextDocumentLine::append(TextDocument& document, u32 code_point)
{
    insert(document, length(), code_point);
}

void TextDocumentLine::prepend(TextDocument& document, u32 code_point)
{
    insert(document, 0, code_point);
}

void TextDocumentLine::insert(TextDocument& document, size_t index, u32 code_point)
{
    if (index == length()) {
        m_text.append(code_point);
    } else {
        m_text.insert(index, code_point);
    }
    document.update_views({});
}

void TextDocumentLine::remove(TextDocument& document, size_t index)
{
    if (index == length()) {
        m_text.take_last();
    } else {
        m_text.remove(index);
    }
    document.update_views({});
}

void TextDocumentLine::remove_range(TextDocument& document, size_t start, size_t length)
{
    ASSERT(length <= m_text.size());

    Vector<u32> new_data;
    new_data.ensure_capacity(m_text.size() - length);
    for (size_t i = 0; i < start; ++i)
        new_data.append(m_text[i]);
    for (size_t i = (start + length); i < m_text.size(); ++i)
        new_data.append(m_text[i]);
    m_text = move(new_data);
    document.update_views({});
}

void TextDocumentLine::truncate(TextDocument& document, size_t length)
{
    m_text.resize(length);
    document.update_views({});
}

void TextDocument::append_line(NonnullOwnPtr<TextDocumentLine> line)
{
    lines().append(move(line));
    if (m_client_notifications_enabled) {
        for (auto* client : m_clients)
            client->document_did_append_line();
    }
}

void TextDocument::insert_line(size_t line_index, NonnullOwnPtr<TextDocumentLine> line)
{
    lines().insert((int)line_index, move(line));
    if (m_client_notifications_enabled) {
        for (auto* client : m_clients)
            client->document_did_insert_line(line_index);
    }
}

void TextDocument::remove_line(size_t line_index)
{
    lines().remove((int)line_index);
    if (m_client_notifications_enabled) {
        for (auto* client : m_clients)
            client->document_did_remove_line(line_index);
    }
}

void TextDocument::remove_all_lines()
{
    lines().clear();
    if (m_client_notifications_enabled) {
        for (auto* client : m_clients)
            client->document_did_remove_all_lines();
    }
}

TextDocument::Client::~Client()
{
}

void TextDocument::register_client(Client& client)
{
    m_clients.set(&client);
}

void TextDocument::unregister_client(Client& client)
{
    m_clients.remove(&client);
}

void TextDocument::update_views(Badge<TextDocumentLine>)
{
    notify_did_change();
}

void TextDocument::notify_did_change()
{
    if (m_client_notifications_enabled) {
        for (auto* client : m_clients)
            client->document_did_change();
    }
}

void TextDocument::set_all_cursors(const TextPosition& position)
{
    if (m_client_notifications_enabled) {
        for (auto* client : m_clients)
            client->document_did_set_cursor(position);
    }
}

String TextDocument::text_in_range(const TextRange& a_range) const
{
    auto range = a_range.normalized();

    StringBuilder builder;
    for (size_t i = range.start().line(); i <= range.end().line(); ++i) {
        auto& line = this->line(i);
        size_t selection_start_column_on_line = range.start().line() == i ? range.start().column() : 0;
        size_t selection_end_column_on_line = range.end().line() == i ? range.end().column() : line.length();
        builder.append(Utf32View(line.code_points() + selection_start_column_on_line, selection_end_column_on_line - selection_start_column_on_line));
        if (i != range.end().line())
            builder.append('\n');
    }

    return builder.to_string();
}

u32 TextDocument::code_point_at(const TextPosition& position) const
{
    ASSERT(position.line() < line_count());
    auto& line = this->line(position.line());
    if (position.column() == line.length())
        return '\n';
    return line.code_points()[position.column()];
}

TextPosition TextDocument::next_position_after(const TextPosition& position, SearchShouldWrap should_wrap) const
{
    auto& line = this->line(position.line());
    if (position.column() == line.length()) {
        if (position.line() == line_count() - 1) {
            if (should_wrap == SearchShouldWrap::Yes)
                return { 0, 0 };
            return {};
        }
        return { position.line() + 1, 0 };
    }
    return { position.line(), position.column() + 1 };
}

TextPosition TextDocument::previous_position_before(const TextPosition& position, SearchShouldWrap should_wrap) const
{
    if (position.column() == 0) {
        if (position.line() == 0) {
            if (should_wrap == SearchShouldWrap::Yes) {
                auto& last_line = this->line(line_count() - 1);
                return { line_count() - 1, last_line.length() };
            }
            return {};
        }
        auto& prev_line = this->line(position.line() - 1);
        return { position.line() - 1, prev_line.length() };
    }
    return { position.line(), position.column() - 1 };
}

TextRange TextDocument::find_next(const StringView& needle, const TextPosition& start, SearchShouldWrap should_wrap) const
{
    if (needle.is_empty())
        return {};

    TextPosition position = start.is_valid() ? start : TextPosition(0, 0);
    TextPosition original_position = position;

    TextPosition start_of_potential_match;
    size_t needle_index = 0;

    do {
        auto ch = code_point_at(position);
        // FIXME: This is not the right way to use a Unicode needle!
        if (ch == (u32)needle[needle_index]) {
            if (needle_index == 0)
                start_of_potential_match = position;
            ++needle_index;
            if (needle_index >= needle.length())
                return { start_of_potential_match, next_position_after(position, should_wrap) };
        } else {
            if (needle_index > 0)
                position = start_of_potential_match;
            needle_index = 0;
        }
        position = next_position_after(position, should_wrap);
    } while (position.is_valid() && position != original_position);

    return {};
}

TextRange TextDocument::find_previous(const StringView& needle, const TextPosition& start, SearchShouldWrap should_wrap) const
{
    if (needle.is_empty())
        return {};

    TextPosition position = start.is_valid() ? start : TextPosition(0, 0);
    position = previous_position_before(position, should_wrap);
    TextPosition original_position = position;

    TextPosition end_of_potential_match;
    size_t needle_index = needle.length() - 1;

    do {
        auto ch = code_point_at(position);
        // FIXME: This is not the right way to use a Unicode needle!
        if (ch == (u32)needle[needle_index]) {
            if (needle_index == needle.length() - 1)
                end_of_potential_match = position;
            if (needle_index == 0)
                return { position, next_position_after(end_of_potential_match, should_wrap) };
            --needle_index;
        } else {
            if (needle_index < needle.length() - 1)
                position = end_of_potential_match;
            needle_index = needle.length() - 1;
        }
        position = previous_position_before(position, should_wrap);
    } while (position.is_valid() && position != original_position);

    return {};
}

Vector<TextRange> TextDocument::find_all(const StringView& needle) const
{
    Vector<TextRange> ranges;

    TextPosition position;
    for (;;) {
        auto range = find_next(needle, position, SearchShouldWrap::No);
        if (!range.is_valid())
            break;
        ranges.append(range);
        position = range.end();
    }
    return ranges;
}

Optional<TextDocumentSpan> TextDocument::first_non_skippable_span_before(const TextPosition& position) const
{
    for (int i = m_spans.size() - 1; i >= 0; --i) {
        if (!m_spans[i].range.contains(position))
            continue;
        while ((i - 1) >= 0 && m_spans[i - 1].is_skippable)
            --i;
        if (i <= 0)
            return {};
        return m_spans[i - 1];
    }
    return {};
}

Optional<TextDocumentSpan> TextDocument::first_non_skippable_span_after(const TextPosition& position) const
{
    for (size_t i = 0; i < m_spans.size(); ++i) {
        if (!m_spans[i].range.contains(position))
            continue;
        while ((i + 1) < m_spans.size() && m_spans[i + 1].is_skippable)
            ++i;
        if (i >= (m_spans.size() - 1))
            return {};
        return m_spans[i + 1];
    }
    return {};
}

TextPosition TextDocument::first_word_break_before(const TextPosition& position, bool start_at_column_before) const
{
    if (position.column() == 0) {
        if (position.line() == 0) {
            return TextPosition(0, 0);
        }
        auto previous_line = this->line(position.line() - 1);
        return TextPosition(position.line() - 1, previous_line.length());
    }

    auto target = position;
    auto line = this->line(target.line());
    auto is_start_alphanumeric = isalnum(line.code_points()[target.column() - (start_at_column_before ? 1 : 0)]);

    while (target.column() > 0) {
        auto prev_code_point = line.code_points()[target.column() - 1];
        if ((is_start_alphanumeric && !isalnum(prev_code_point)) || (!is_start_alphanumeric && isalnum(prev_code_point)))
            break;
        target.set_column(target.column() - 1);
    }

    return target;
}

TextPosition TextDocument::first_word_break_after(const TextPosition& position) const
{
    auto target = position;
    auto line = this->line(target.line());

    if (position.column() >= line.length()) {
        if (position.line() >= this->line_count() - 1) {
            return position;
        }
        return TextPosition(position.line() + 1, 0);
    }

    auto is_start_alphanumeric = isalnum(line.code_points()[target.column()]);

    while (target.column() < line.length()) {
        auto next_code_point = line.code_points()[target.column()];
        if ((is_start_alphanumeric && !isalnum(next_code_point)) || (!is_start_alphanumeric && isalnum(next_code_point)))
            break;
        target.set_column(target.column() + 1);
    }

    return target;
}

void TextDocument::undo()
{
    if (!can_undo())
        return;
    m_undo_stack.undo();
    notify_did_change();
}

void TextDocument::redo()
{
    if (!can_redo())
        return;
    m_undo_stack.redo();
    notify_did_change();
}

void TextDocument::add_to_undo_stack(NonnullOwnPtr<TextDocumentUndoCommand> undo_command)
{
    m_undo_stack.push(move(undo_command));
}

TextDocumentUndoCommand::TextDocumentUndoCommand(TextDocument& document)
    : m_document(document)
{
}

TextDocumentUndoCommand::~TextDocumentUndoCommand()
{
}

InsertTextCommand::InsertTextCommand(TextDocument& document, const String& text, const TextPosition& position)
    : TextDocumentUndoCommand(document)
    , m_text(text)
    , m_range({ position, position })
{
}

void InsertTextCommand::redo()
{
    auto new_cursor = m_document.insert_at(m_range.start(), m_text, m_client);
    // NOTE: We don't know where the range ends until after doing redo().
    //       This is okay since we always do redo() after adding this to the undo stack.
    m_range.set_end(new_cursor);
    m_document.set_all_cursors(new_cursor);
}

void InsertTextCommand::undo()
{
    m_document.remove(m_range);
    m_document.set_all_cursors(m_range.start());
}

RemoveTextCommand::RemoveTextCommand(TextDocument& document, const String& text, const TextRange& range)
    : TextDocumentUndoCommand(document)
    , m_text(text)
    , m_range(range)
{
}

void RemoveTextCommand::redo()
{
    m_document.remove(m_range);
    m_document.set_all_cursors(m_range.start());
}

void RemoveTextCommand::undo()
{
    auto new_cursor = m_document.insert_at(m_range.start(), m_text);
    m_document.set_all_cursors(new_cursor);
}

void TextDocument::update_undo_timer()
{
    m_undo_stack.finalize_current_combo();
}

TextPosition TextDocument::insert_at(const TextPosition& position, const StringView& text, const Client* client)
{
    TextPosition cursor = position;
    Utf8View utf8_view(text);
    for (auto code_point : utf8_view)
        cursor = insert_at(cursor, code_point, client);
    return cursor;
}

TextPosition TextDocument::insert_at(const TextPosition& position, u32 code_point, const Client* client)
{
    bool automatic_indentation_enabled = client ? client->is_automatic_indentation_enabled() : false;
    size_t m_soft_tab_width = client ? client->soft_tab_width() : 4;

    bool at_head = position.column() == 0;
    bool at_tail = position.column() == line(position.line()).length();
    if (code_point == '\n') {
        if (at_tail || at_head) {
            String new_line_contents;
            if (automatic_indentation_enabled && at_tail) {
                size_t leading_spaces = 0;
                auto& old_line = lines()[position.line()];
                for (size_t i = 0; i < old_line.length(); ++i) {
                    if (old_line.code_points()[i] == ' ')
                        ++leading_spaces;
                    else
                        break;
                }
                if (leading_spaces)
                    new_line_contents = String::repeated(' ', leading_spaces);
            }

            size_t row = position.line();
            Vector<u32> line_content;
            for (size_t i = position.column(); i < line(row).length(); i++)
                line_content.append(line(row).code_points()[i]);
            insert_line(position.line() + (at_tail ? 1 : 0), make<TextDocumentLine>(*this, new_line_contents));
            notify_did_change();
            return { position.line() + 1, line(position.line() + 1).length() };
        }
        auto new_line = make<TextDocumentLine>(*this);
        new_line->append(*this, line(position.line()).code_points() + position.column(), line(position.line()).length() - position.column());

        Vector<u32> line_content;
        for (size_t i = 0; i < new_line->length(); i++)
            line_content.append(new_line->code_points()[i]);
        line(position.line()).truncate(*this, position.column());
        insert_line(position.line() + 1, move(new_line));
        notify_did_change();
        return { position.line() + 1, 0 };
    }
    if (code_point == '\t') {
        size_t next_soft_tab_stop = ((position.column() + m_soft_tab_width) / m_soft_tab_width) * m_soft_tab_width;
        size_t spaces_to_insert = next_soft_tab_stop - position.column();
        for (size_t i = 0; i < spaces_to_insert; ++i) {
            line(position.line()).insert(*this, position.column(), ' ');
        }
        notify_did_change();
        return { position.line(), next_soft_tab_stop };
    }
    line(position.line()).insert(*this, position.column(), code_point);
    notify_did_change();
    return { position.line(), position.column() + 1 };
}

void TextDocument::remove(const TextRange& unnormalized_range)
{
    if (!unnormalized_range.is_valid())
        return;

    auto range = unnormalized_range.normalized();

    // First delete all the lines in between the first and last one.
    for (size_t i = range.start().line() + 1; i < range.end().line();) {
        remove_line(i);
        range.end().set_line(range.end().line() - 1);
    }

    if (range.start().line() == range.end().line()) {
        // Delete within same line.
        auto& line = this->line(range.start().line());
        bool whole_line_is_selected = range.start().column() == 0 && range.end().column() == line.length();

        if (whole_line_is_selected) {
            line.clear(*this);
        } else {
            line.remove_range(*this, range.start().column(), range.end().column() - range.start().column());
        }
    } else {
        // Delete across a newline, merging lines.
        ASSERT(range.start().line() == range.end().line() - 1);
        auto& first_line = line(range.start().line());
        auto& second_line = line(range.end().line());
        Vector<u32> code_points;
        code_points.append(first_line.code_points(), range.start().column());
        code_points.append(second_line.code_points() + range.end().column(), second_line.length() - range.end().column());
        first_line.set_text(*this, move(code_points));
        remove_line(range.end().line());
    }

    if (lines().is_empty()) {
        append_line(make<TextDocumentLine>(*this));
    }

    notify_did_change();
}

bool TextDocument::is_empty() const
{
    return line_count() == 1 && line(0).is_empty();
}

TextRange TextDocument::range_for_entire_line(size_t line_index) const
{
    if (line_index >= line_count())
        return {};
    return { { line_index, 0 }, { line_index, line(line_index).length() } };
}

}