/*
 * Copyright (C) 2023 Kyle Reed
 *
 * This file is part of PortaPack.
 *
 * This program 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 2, or (at your option)
 * any later version.
 *
 * This program 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 this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#include "ui_fileman.hpp"
#include "ui_text_editor.hpp"
#include "string_format.hpp"

using namespace portapack;
namespace fs = std::filesystem;

namespace {
template <typename T>
T mid(const T& val1, const T& val2, const T& val3) {
    return std::max(val1, std::min(val2, val3));
}
}  // namespace

namespace ui {

TextEditorView::TextEditorView(NavigationView& nav)
    : nav_{nav} {
    add_children(
        {&button_open,
         &text_position});
    set_focusable(true);

    // log_.append("LOGS/NOTEPAD.TXT");

    button_open.on_select = [this](Button&) {
        auto open_view = nav_.push<FileLoadView>(".TXT");
        open_view->on_changed = [this](std::filesystem::path path) {
            open_file(path);
        };
    };
}

void TextEditorView::on_focus() {
    refresh_ui();
}

void TextEditorView::paint(Painter& painter) {
    auto first_line = paint_state_.first_line;
    auto first_col = paint_state_.first_col;

    if (!paint_state_.has_file)
        return;

    if (cursor_.line < first_line)
        first_line = cursor_.line;
    else if (cursor_.line >= first_line + max_line)
        first_line = cursor_.line - max_line + 1;

    if (cursor_.col < first_col)
        first_col = cursor_.col;
    if (cursor_.col >= first_col + max_col)
        first_col = cursor_.col - max_col + 1;

    if (first_line != paint_state_.first_line ||
        first_col != paint_state_.first_col) {
        paint_state_.first_line = first_line;
        paint_state_.first_col = first_col;
        paint_state_.redraw_text = true;
    }

    if (paint_state_.redraw_text) {
        paint_text(painter, first_line, first_col);
        paint_state_.redraw_text = false;
    }

    paint_cursor(painter);
}

bool TextEditorView::on_key(const KeyEvent key) {
    int16_t delta_col = 0;
    int16_t delta_line = 0;

    if (key == KeyEvent::Left)
        delta_col = -1;
    else if (key == KeyEvent::Right)
        delta_col = 1;
    else if (key == KeyEvent::Up)
        delta_line = -1;
    else if (key == KeyEvent::Down)
        delta_line = 1;
    /*	else if (key == KeyEvent::Select)
            ; // TODO: Edit/Menu */

    // Always allow cursor direction to be updated.
    cursor_.dir = delta_col != 0 ? ScrollDirection::Horizontal : ScrollDirection::Vertical;
    auto updated = apply_scrolling_constraints(delta_line, delta_col);

    if (updated)
        refresh_ui();
    return updated;
}

bool TextEditorView::on_encoder(EncoderEvent delta) {
    bool updated = false;

    if (cursor_.dir == ScrollDirection::Horizontal)
        updated = apply_scrolling_constraints(0, delta);
    else
        updated = apply_scrolling_constraints(delta, 0);

    if (updated)
        refresh_ui();

    return updated;
}

bool TextEditorView::apply_scrolling_constraints(int16_t delta_line, int16_t delta_col) {
    int32_t new_line = cursor_.line + delta_line;
    int32_t new_col = cursor_.col + delta_col;

    auto new_line_length = info_.line_length(new_line);

    if (new_col < 0)
        --new_line;
    else if (new_col > new_line_length && delta_line == 0) {
        // Only want to wrap if moving horizontally.
        new_col = 0;
        ++new_line;
    }

    if (new_line < 0 || (uint32_t)new_line >= info_.line_count())
        return false;

    new_line_length = info_.line_length(new_line);

    // TODO: don't wrap with encoder?
    // Wrap or clamp column.
    if (new_line_length == 0)
        new_col = 0;
    else if (new_col > new_line_length || new_col < 0)
        new_col = new_line_length;

    cursor_.line = new_line;
    cursor_.col = new_col;

    return true;
}

void TextEditorView::refresh_ui() {
    if (paint_state_.has_file) {
        text_position.set(
            to_string_dec_uint(cursor_.col + 1) + ":" +
            to_string_dec_uint(cursor_.line + 1) + "/" +
            to_string_dec_uint(info_.line_count()) +
            (info_.truncated ? "*" : "") +
            " Size: " +
            to_string_file_size(info_.size));
        focus();
    } else {
        button_open.focus();
    }

    set_dirty();
}

void TextEditorView::refresh_file_info() {
    constexpr size_t buffer_size = 128;
    char buffer[buffer_size];
    uint32_t base_offset = 0;

    file_.seek(0);
    info_.newlines.clear();
    info_.line_ending = LineEnding::LF;
    info_.size = file_.size();
    info_.truncated = false;

    while (true) {
        auto result = file_.read(buffer, buffer_size);
        if (result.is_error())
            break;  // TODO: report error?

        // TODO: CRLF state machine for cross block.
        for (uint32_t i = 0; i < result.value(); ++i) {
            switch (buffer[i]) {
                case '\n':
                    info_.newlines.push_back(base_offset + i);
            }
        }

        base_offset += result.value();

        // Fake a newline at the end for consistency.
        // Could check if there already is a trailing newline, but it doesn't hurt.
        if (result.value() < buffer_size) {
            info_.newlines.push_back(base_offset);
            break;
        }

        // HACK HACK: only show first 1000 lines for now.
        if (info_.newlines.size() >= 1000) {
            info_.truncated = true;
            break;
        }
    }

    refresh_ui();
}

void TextEditorView::open_file(const fs::path& path) {
    // TODO: need a temp backing file for edits.

    auto result = file_.open(path);
    paint_state_.has_file = !result.is_valid(); /* Has an error. */

    if (paint_state_.has_file) {
        refresh_file_info();
        paint_state_.first_line = 0;
        paint_state_.first_col = 0;
        cursor_.line = 0;
        cursor_.col = 0;
    } else {
        nav_.display_modal("Read Error", "Cannot open file:\n" + result.value().what());
        paint_state_.has_file = false;
    }

    paint_state_.redraw_text = true;
    refresh_ui();
}

std::string TextEditorView::read(uint32_t offset, uint32_t length) {
    if (offset >= info_.size)
        return {"[BAD OFFSET]"};

    std::string buffer(length + 1, '\0');
    file_.seek(offset);

    auto result = file_.read(&buffer[0], length);
    if (result.is_ok())
        /* resize? */;
    else
        return result.error().what();

    return buffer;
}

void TextEditorView::paint_text(Painter& painter, uint32_t line, uint16_t col) {
    // TODO: A line cache would use more memory but save a lot of IO.
    // Only the new lines/characters would need to be refetched.

    auto r = screen_rect();
    auto& lines = info_.newlines;
    auto line_start = info_.line_start(line);

    // Draw the lines from the file
    for (uint32_t i = 0; i < max_line && i < lines.size(); ++i) {
        auto line_end = lines[line + i];
        int32_t read_length = max_col;

        // Don't read past end of the line.
        if (line_start + col + (uint32_t)read_length > line_end)
            read_length = line_end - col - line_start;

        if (read_length > 0)
            painter.draw_string(
                {0, r.location().y() + (int)i * char_height},
                style_default, read(line_start + col, read_length));

        // Erase empty line sectons.
        if (read_length >= 0) {
            int32_t clear_width = max_col - read_length;
            if (clear_width > 0)
                painter.fill_rectangle(
                    {(max_col - clear_width) * char_width,
                     r.location().y() + (int)i * char_height,
                     clear_width * char_width, char_height},
                    style_default.background);
        }

        line_start = lines[line + i] + 1 /* newline */;
    }
}

void TextEditorView::paint_cursor(Painter& painter) {
    auto draw_cursor = [this, &painter](uint32_t line, uint16_t col, Color c) {
        auto r = screen_rect();
        line = line - paint_state_.first_line;
        col = col - paint_state_.first_col;

        painter.draw_rectangle(
            {(int)col * char_width - 1,
             r.location().y() + (int)line * char_height,
             char_width + 1, char_height},
            c);
    };

    // TOOD: bug where cursor doesn't clear at EOF.
    // TODO: XOR cursor?

    // Clear old cursor.
    draw_cursor(paint_state_.line, paint_state_.col, style_default.background);
    draw_cursor(cursor_.line, cursor_.col, style_default.foreground);
    paint_state_.line = cursor_.line;
    paint_state_.col = cursor_.col;
}

uint16_t TextEditorView::line_length() const {
    return info_.line_length(cursor_.line);
}

}  // namespace ui