#include "piano_roll.hpp"
#include <FL/Fl.H>
#include <FL/fl_draw.H>
#include <FL/fl_ask.H>
#include <algorithm>
#include <cstdio>

namespace {
constexpr int key_width = 64, row_height = 16, scale = 96, header = 28;
}

/**
 * @brief Creates a piano-roll editor for a MIDI clip.
 *
 * The pre-edit guard, when non-NULL, is called before every project mutation
 * and can veto the edit by returning an error.
 *
 * @param left Left edge of the widget in the parent's coordinate system.
 * @param top Top edge of the widget in the parent's coordinate system.
 * @param project Borrowed project that must outlive the widget.
 * @param clip ID of the MIDI clip to edit.
 * @param before Optional pre-edit guard; NULL means no guard is used.
 * @param context Opaque pointer passed to @p before on every edit.
 */
PianoRollWidget::PianoRollWidget(int left, int top, xtc_project *project, uint64_t clip, BeforeEdit before,
                                 void *context)
    : Fl_Widget(left, top, 900, header + 128 * row_height), project_(project), clip_(clip), before_(before),
      context_(context)
{
    set_project(project, clip);
}

/**
 * @brief Points the editor at a different project or clip.
 *
 * Clears any in-progress drag when the project or clip changes and resizes the
 * widget to fit the clip's source length. The current selection is not changed.
 *
 * @param project Borrowed project that must outlive the widget.
 * @param clip ID of the MIDI clip to display.
 */
void PianoRollWidget::set_project(xtc_project *project, uint64_t clip)
{
    if (project != project_ || clip != clip_)
        mode_ = 0;
    project_ = project;
    clip_ = clip;
    xtc_clip_info c{};
    int width = xtc_project_find_clip(project_, clip_, &c) == XTC_OK
                    ? static_cast<int>(c.source_length_tick * scale / 960) + key_width + 20
                    : 900;
    size(std::max(900, width), header + 128 * row_height);
    redraw();
}

/**
 * @brief Converts a horizontal pixel position to a snapped tick.
 *
 * The position is measured in absolute window coordinates and snapped down to
 * the nearest sixteenth note (240 ticks).
 *
 * @param px Horizontal position in window coordinates.
 * @return Tick offset within the clip source, or 0 for positions on or left of
 *         the keyboard.
 */
uint64_t PianoRollWidget::tick(int px) const
{
    return static_cast<uint64_t>(std::max(0, px - x() - key_width)) * 960U / scale / 240U * 240U;
}

/**
 * @brief Reports an edit result and notifies listeners on success.
 *
 * On success the widget callback runs and the editor is redrawn; on failure an
 * alert shows the error and the project is left unchanged.
 *
 * @param result Result of the attempted project mutation.
 * @return The same result code.
 */
xtc_result PianoRollWidget::change(xtc_result result)
{
    if (result == XTC_OK) {
        do_callback();
        redraw();
    } else
        fl_alert("Note unchanged: %s", xtc_result_string(result));
    return result;
}

/**
 * @brief Adds a note to the current clip and selects the new note.
 *
 * Invokes the pre-edit guard, if any, before mutating the project.
 *
 * @param start Note start in clip source ticks.
 * @param length Note length in ticks.
 * @param pitch MIDI pitch from 0 to 127.
 * @param velocity MIDI velocity from 1 to 127.
 * @param channel MIDI channel from 0 to 15.
 * @return XTC_OK on success, the guard's error, or the project error.
 */
xtc_result PianoRollWidget::add_note(uint64_t start, uint64_t length, unsigned int pitch, unsigned int velocity,
                                     unsigned int channel)
{
    xtc_result r = before_ ? before_(context_) : XTC_OK;
    uint64_t id;
    if (r == XTC_OK)
        r = xtc_project_add_note(project_, clip_, start, length, pitch, velocity, channel, &id);
    if (r == XTC_OK)
        selected_ = id;
    return change(r);
}

/**
 * @brief Removes the selected note from the current clip.
 *
 * Invokes the pre-edit guard, if any, before mutating the project. The
 * selection is cleared only when the removal succeeds.
 *
 * @return XTC_OK on success, the guard's error, or the project error.
 */
xtc_result PianoRollWidget::delete_selected()
{
    xtc_result r = before_ ? before_(context_) : XTC_OK;
    if (r == XTC_OK)
        r = xtc_project_remove_note(project_, selected_);
    if (r == XTC_OK)
        selected_ = UINT64_MAX;
    return change(r);
}

/**
 * @brief Draws the keyboard, beat grid, and notes of the current clip.
 *
 * Paints only the background when the clip is missing or is not a MIDI clip.
 */
void PianoRollWidget::draw()
{
    fl_push_clip(x(), y(), w(), h());
    fl_color(fl_rgb_color(30, 33, 38));
    fl_rectf(x(), y(), w(), h());
    xtc_clip_info clip{};
    if (xtc_project_find_clip(project_, clip_, &clip) != XTC_OK || !clip.midi) {
        fl_pop_clip();
        return;
    }
    int cx, cy, cw, ch;
    fl_clip_box(x(), y(), w(), h(), cx, cy, cw, ch);
    fl_font(FL_HELVETICA, 11);
    for (int pitch = 0; pitch < 128; ++pitch) {
        int py = y() + header + (127 - pitch) * row_height;
        if (py + row_height < cy || py > cy + ch)
            continue;
        int pc = pitch % 12;
        bool black = pc == 1 || pc == 3 || pc == 6 || pc == 8 || pc == 10;
        fl_color(black ? fl_rgb_color(29, 31, 35) : fl_rgb_color(43, 46, 52));
        fl_rectf(cx, py, cw, row_height - 1);
        fl_color(black ? fl_rgb_color(60, 63, 70) : fl_rgb_color(130, 135, 140));
        fl_rectf(x(), py, key_width - 2, row_height - 1);
        if (!pc) {
            char text[20];
            std::snprintf(text, sizeof(text), "C%d", pitch / 12 - 1);
            fl_color(FL_WHITE);
            fl_draw(text, x() + 6, py + 12);
        }
    }
    int first = std::max(0, (cx - x() - key_width) / (scale / 4));
    int last = (cx + cw - x() - key_width) / (scale / 4) + 1;
    for (int step = first; step <= last; ++step) {
        int px = x() + key_width + step * (scale / 4);
        fl_color(step % 16 == 0 ? fl_rgb_color(95, 98, 105) : fl_rgb_color(52, 55, 62));
        fl_line(px, cy, px, cy + ch);
    }
    size_t count = 0;
    xtc_project_note_count(project_, &count);
    for (size_t i = 0; i < count; ++i) {
        xtc_note_info n{};
        xtc_project_get_note(project_, i, &n);
        if (n.clip_id != clip_)
            continue;
        int left = x() + key_width + static_cast<int>(n.start_tick * scale / 960);
        int right = left + std::max(3, static_cast<int>(n.length_tick * scale / 960));
        int py = y() + header + (127 - static_cast<int>(n.pitch)) * row_height;
        int a = std::max(cx, left), b = std::min(cx + cw, right);
        if (a >= b || py + row_height < cy || py > cy + ch)
            continue;
        fl_color(n.id == selected_ ? fl_rgb_color(230, 190, 80) : fl_rgb_color(90, 175, 130));
        fl_rectf(a, py + 1, b - a, row_height - 3);
    }
    fl_pop_clip();
}

/**
 * @brief Handles mouse, keyboard, and focus events for the editor.
 *
 * Left-click on empty space adds a note, clicking a note selects it, and
 * dragging moves or resizes it. Right-click and Delete remove the selected
 * note; Escape cancels an in-progress drag.
 *
 * @param event FLTK event code.
 * @return 1 when the event was handled, otherwise the result of the base
 *         class handler.
 */
int PianoRollWidget::handle(int event)
{
    if (event == FL_PUSH) {
        take_focus();
        mode_ = 0;
        size_t count = 0;
        xtc_project_note_count(project_, &count);
        selected_ = UINT64_MAX;
        for (size_t i = count; i > 0; --i) {
            xtc_note_info n{};
            xtc_project_get_note(project_, i - 1, &n);
            int left = x() + key_width + static_cast<int>(n.start_tick * scale / 960);
            int right = left + std::max(3, static_cast<int>(n.length_tick * scale / 960));
            int top = y() + header + (127 - static_cast<int>(n.pitch)) * row_height;
            if (n.clip_id == clip_ && Fl::event_x() >= left && Fl::event_x() < right && Fl::event_y() >= top &&
                Fl::event_y() < top + row_height) {
                selected_ = n.id;
                original_ = n;
                drag_x_ = Fl::event_x();
                drag_y_ = Fl::event_y();
                mode_ = right - Fl::event_x() <= 6 ? 2 : 1;
                break;
            }
        }
        if (selected_ != UINT64_MAX && Fl::event_button() == FL_RIGHT_MOUSE) {
            delete_selected();
            mode_ = 0;
        } else if (Fl::event_button() == FL_LEFT_MOUSE && selected_ == UINT64_MAX && Fl::event_x() >= x() + key_width &&
                   Fl::event_y() >= y() + header) {
            int pitch = 127 - (Fl::event_y() - y() - header) / row_height;
            xtc_clip_info c{};
            uint64_t start = tick(Fl::event_x());
            if (pitch >= 0 && pitch <= 127 && xtc_project_find_clip(project_, clip_, &c) == XTC_OK &&
                start < c.source_length_tick)
                add_note(start, std::min<uint64_t>(960, c.source_length_tick - start),
                         static_cast<unsigned int>(pitch));
        }
        redraw();
        return 1;
    }
    if (event == FL_DRAG)
        return mode_ != 0;
    if (event == FL_RELEASE && mode_) {
        int mode = mode_;
        mode_ = 0;
        int64_t delta = static_cast<int64_t>(Fl::event_x() - drag_x_) * 960 / scale / 240 * 240;
        xtc_clip_info c{};
        if (xtc_project_find_clip(project_, clip_, &c) != XTC_OK)
            return 1;
        int64_t start = static_cast<int64_t>(original_.start_tick),
                length = static_cast<int64_t>(original_.length_tick);
        unsigned int pitch = original_.pitch;
        if (mode == 1) {
            start = std::clamp<int64_t>(start + delta, 0, static_cast<int64_t>(c.source_length_tick) - length);
            pitch = static_cast<unsigned int>(
                std::clamp(static_cast<int>(pitch) - (Fl::event_y() - drag_y_) / row_height, 0, 127));
        } else {
            int64_t maximum = static_cast<int64_t>(c.source_length_tick) - start;
            length = std::clamp<int64_t>(length + delta, std::min<int64_t>(240, maximum), maximum);
        }
        xtc_result r = before_ ? before_(context_) : XTC_OK;
        if (r == XTC_OK)
            r = xtc_project_edit_note(project_, selected_, static_cast<uint64_t>(start), static_cast<uint64_t>(length),
                                      pitch, original_.velocity, original_.channel);
        change(r);
        return 1;
    }
    if (event == FL_KEYDOWN && Fl::event_key() == FL_Delete) {
        delete_selected();
        return 1;
    }
    if (event == FL_KEYDOWN && Fl::event_key() == FL_Escape) {
        mode_ = 0;
        return 1;
    }
    if (event == FL_FOCUS || event == FL_UNFOCUS)
        return 1;
    return Fl_Widget::handle(event);
}