// Controller input in the launcher: focus, back, the trackpad pointer and its click,
// checked through real ImGui frames.
#include "Launcher/gamepad_input.h"

#include <imgui.h>
#include <imgui_internal.h>

#include <iostream>
#include <optional>
#include <string>

using dingosdk::launcher_gui::PadFeed;
using dingosdk::launcher_gui::PadState;

namespace {

int failures = 0;

void check(bool condition, const char* what) {
    if (condition) return;
    std::cerr << "FAIL: " << what << '\n';
    ++failures;
}

constexpr std::uint16_t dpad_up = 0x0001, dpad_left = 0x0004;
constexpr std::uint16_t dpad_down = 0x0002, dpad_right = 0x0008, right_thumb = 0x0080, button_a = 0x1000, button_b = 0x2000;

struct Seen {
    std::string pressed;   // the button that reported a press this frame
    bool escape{};
    bool menu_open{};
    float list_scroll{};
};

// One launcher frame: the pad goes in before NewFrame, as gui.cpp does it.
// Two buttons stacked at the top left, and a menu popup opened on request.
Seen frame(PadFeed& feed, const PadState& pad, bool open_menu = false, bool panels = false, bool list = false) {
    auto& io = ImGui::GetIO();
    io.DisplaySize = ImVec2(800, 600);
    io.DeltaTime = 1.0f / 60.0f;
    feed.update(io, pad, 1.0f);
    ImGui::NewFrame();
    feed.after_new_frame();
    Seen seen;
    ImGui::SetNextWindowPos(ImVec2(0, 0));
    ImGui::SetNextWindowSize(ImVec2(800, 600));
    ImGui::Begin("##root", nullptr, ImGuiWindowFlags_NoDecoration);
    ImGui::SetCursorScreenPos(ImVec2(100, 100));
    if (ImGui::InvisibleButton("first", ImVec2(200, 50), ImGuiButtonFlags_EnableNav)) seen.pressed = "first";
    ImGui::SetCursorScreenPos(ImVec2(100, 200));
    if (ImGui::InvisibleButton("second", ImVec2(200, 50), ImGuiButtonFlags_EnableNav)) seen.pressed = "second";
    if (panels) {
        // A page's rail and content, side by side, as Settings and Mods lay them out.
        ImGui::SetCursorScreenPos(ImVec2(400, 200));
        ImGui::BeginChild("##rail", ImVec2(150, 200), ImGuiChildFlags_NavFlattened);
        if (ImGui::Button("tab", ImVec2(120, 40))) seen.pressed = "tab";
        ImGui::EndChild();
        ImGui::SetCursorScreenPos(ImVec2(580, 200));
        ImGui::BeginChild("##content", ImVec2(200, 200), ImGuiChildFlags_NavFlattened);
        if (ImGui::Button("option", ImVec2(120, 40))) seen.pressed = "option";
        ImGui::EndChild();
    }
    if (list) {
        // A long list in a panel, like GET MODS.
        ImGui::SetCursorScreenPos(ImVec2(400, 100));
        ImGui::BeginChild("##list", ImVec2(300, 200), ImGuiChildFlags_NavFlattened);
        for (int row = 0; row < 30; ++row) {
            ImGui::PushID(row);
            if (ImGui::Selectable("##row", false, 0, ImVec2(280, 40))) seen.pressed = "row " + std::to_string(row);
            ImGui::PopID();
        }
        seen.list_scroll = ImGui::GetScrollY();
        ImGui::EndChild();
    }
    if (open_menu) ImGui::OpenPopup("##menu");
    if (ImGui::BeginPopup("##menu")) {
        seen.menu_open = true;
        ImGui::MenuItem("Details");
        ImGui::EndPopup();
    }
    seen.escape = ImGui::IsKeyPressed(ImGuiKey_Escape, false);
    ImGui::End();
    ImGui::Render();
    return seen;
}

PadState pad(std::uint16_t buttons = 0, std::int16_t right_x = 0, std::int16_t right_y = 0, std::int16_t left_y = 0) {
    PadState state;
    state.left_y = left_y;
    state.connected = true;
    state.buttons = buttons;
    state.right_x = right_x;
    state.right_y = right_y;
    return state;
}

// Presses and lets go, returning what the frames saw.
std::string press(PadFeed& feed, std::uint16_t button) {
    std::string pressed = frame(feed, pad(button)).pressed;
    const auto released = frame(feed, pad()).pressed;
    return pressed.empty() ? released : pressed;
}

// The Mod manager's layout: a rail of tabs beside a list whose rows carry
// buttons, the rail's tiles level with the gaps between rows.
std::string mods_page(PadFeed& feed, const PadState& state) {
    auto& io = ImGui::GetIO();
    io.DisplaySize = ImVec2(900, 700);
    io.DeltaTime = 1.0f / 60.0f;
    feed.update(io, state, 1.0f);
    ImGui::NewFrame();
    feed.after_new_frame();
    std::string pressed;
    ImGui::SetNextWindowPos(ImVec2(0, 0));
    ImGui::SetNextWindowSize(ImVec2(900, 700));
    ImGui::Begin("##page", nullptr, ImGuiWindowFlags_NoDecoration);
    ImGui::SetCursorPos(ImVec2(20, 100));
    ImGui::BeginChild("##rail", ImVec2(200, 400), ImGuiChildFlags_NavFlattened);
    if (ImGui::Button("MY MODS", ImVec2(150, 40))) pressed = "MY MODS";
    dingosdk::launcher_gui::default_focus();
    if (ImGui::Button("GET MODS", ImVec2(150, 40))) pressed = "GET MODS";
    ImGui::EndChild();
    ImGui::SetCursorPos(ImVec2(260, 100));
    ImGui::BeginChild("##content", ImVec2(600, 500), ImGuiChildFlags_NavFlattened);
    for (int row = 0; row < 12; ++row) {
        ImGui::PushID(row);
        dingosdk::launcher_gui::begin_row();
        const ImVec2 start = ImGui::GetCursorScreenPos();
        if (ImGui::Selectable("##row", false, ImGuiSelectableFlags_AllowOverlap, ImVec2(560, 60)))
            pressed = "row " + std::to_string(row);
        const ImVec2 next = ImGui::GetCursorScreenPos();
        dingosdk::launcher_gui::row_buttons();
        ImGui::SetCursorScreenPos(ImVec2(start.x + 380, start.y + 14));
        if (ImGui::Button("INSTALL", ImVec2(100, 32))) pressed = "install " + std::to_string(row);
        dingosdk::launcher_gui::end_row();
        ImGui::SetCursorScreenPos(next);
        ImGui::PopID();
    }
    ImGui::EndChild();
    ImGui::End();
    ImGui::Render();
    return pressed;
}

// Taps a D-pad direction on the Mod manager, then A: what A pressed is where the focus went.
std::string mods_tap(PadFeed& feed, std::uint16_t button) {
    mods_page(feed, pad(button));
    for (int i = 0; i < 3; ++i) mods_page(feed, pad());
    std::string pressed = mods_page(feed, pad(button_a));
    pressed += mods_page(feed, pad());
    return pressed;
}

void fresh() {
    if (ImGui::GetCurrentContext()) ImGui::DestroyContext();
    ImGui::CreateContext();
    auto& io = ImGui::GetIO();
    io.IniFilename = nullptr;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
    io.Fonts->AddFontDefault();
    io.Fonts->Build();
}

} // namespace

int main() {
    // ------------------------------------------------ focus
    {
        fresh();
        PadFeed feed;
        frame(feed, pad());
        frame(feed, pad());
        press(feed, dpad_down);
        check(ImGui::GetIO().NavVisible, "The D-pad shows the focus");
        // The first move lands on the first item; the next one goes down.
        press(feed, dpad_down);
        check(press(feed, button_a) == "second", "A presses the item the D-pad moved to");
        check(!feed.pointing() && !ImGui::GetIO().MouseDrawCursor, "No pointer is drawn while the focus is used");
    }
    {
        fresh();
        PadFeed feed;
        frame(feed, pad());
        frame(feed, pad(button_a));
        check(ImGui::IsKeyDown(ImGuiKey_GamepadFaceDown), "A (Cross) is the gamepad's activate button");
        PadState gone;   // unplugged with A held
        frame(feed, gone);
        frame(feed, gone);
        check(!ImGui::IsKeyDown(ImGuiKey_GamepadFaceDown), "An unplugged pad lets go of A");
        check(!(ImGui::GetIO().BackendFlags & ImGuiBackendFlags_HasGamepad), "An unplugged pad is no gamepad");
    }

    // ------------------------------------------------ the Mod manager
    {
        fresh();
        PadFeed feed;
        mods_page(feed, pad());
        mods_page(feed, pad());
        check(GImGui->NavCursorVisible && mods_tap(feed, 0) == "MY MODS",
              "With a pad connected the page opens with the focus on its tab");
        check(mods_tap(feed, dpad_down) == "GET MODS", "Down goes to the next tab");
        const auto row = mods_tap(feed, dpad_right);
        check(row.rfind("row ", 0) == 0, "Right goes from a tab level with a gap between rows into the list");
        check(mods_tap(feed, dpad_left) == "GET MODS", "Left goes from the list back to the tabs");
        mods_tap(feed, dpad_right);
        const int first = std::stoi(mods_tap(feed, dpad_down).substr(4));
        check(mods_tap(feed, dpad_down) == "row " + std::to_string(first + 1), "Down goes to the next row in one press");
        check(mods_tap(feed, dpad_up) == "row " + std::to_string(first), "Up goes to the row above in one press");
        check(mods_tap(feed, dpad_right) == "install " + std::to_string(first), "Right goes to the row's own button");
        check(mods_tap(feed, dpad_up) == "row " + std::to_string(first - 1), "Up from a row's button goes to the row above");
    }
    {
        fresh();
        PadFeed feed;
        mods_page(feed, PadState{});
        mods_page(feed, PadState{});
        check(!GImGui->NavCursorVisible, "Without a pad nothing shows a focus");
    }

    // ------------------------------------------------ back
    {
        fresh();
        PadFeed feed;
        frame(feed, pad());
        frame(feed, pad());
        frame(feed, pad(button_b));
        check(ImGui::IsKeyPressed(ImGuiKey_Escape, false), "B is Escape with nothing open");
        frame(feed, pad());
        check(!ImGui::IsKeyDown(ImGuiKey_Escape), "Letting go of B lets go of Escape");
    }
    {
        fresh();
        PadFeed feed;
        frame(feed, pad());
        check(frame(feed, pad(), true).menu_open, "The menu opens");
        frame(feed, pad());
        const auto with_b = frame(feed, pad(button_b));
        const auto after = frame(feed, pad());
        check(!after.menu_open, "B closes an open menu");
        check(!with_b.escape && !after.escape, "Closing the menu is not also Escape, which would leave the page");
    }
    {
        fresh();
        PadFeed feed;
        frame(feed, pad());
        ImGui::GetIO().AddKeyEvent(ImGuiKey_Escape, true);   // the keyboard's Escape, held
        frame(feed, pad());
        frame(feed, pad());
        check(ImGui::IsKeyDown(ImGuiKey_Escape), "An idle pad does not let go of the keyboard's Escape");
    }

    {
        fresh();
        PadFeed feed;
        for (int i = 0; i < 2; ++i) frame(feed, pad(), false, true);
        const auto tap = [&](std::uint16_t button) { frame(feed, pad(button), false, true); frame(feed, pad(), false, true); };
        tap(dpad_down);   // onto "first"
        tap(dpad_down);   // "second", level with the panels
        tap(dpad_right);  // the rail
        tap(dpad_right);  // the content
        std::string pressed = frame(feed, pad(button_a), false, true).pressed;
        const auto released = frame(feed, pad(), false, true).pressed;
        check((pressed.empty() ? released : pressed) == "option",
              "The D-pad crosses from a page's rail into its content");
    }

    // ------------------------------------------------ scrolling
    {
        fresh();
        PadFeed feed;
        const auto tap = [&](std::uint16_t button) { frame(feed, pad(button), false, false, true); frame(feed, pad(), false, false, true); };
        for (int i = 0; i < 2; ++i) frame(feed, pad(), false, false, true);
        tap(dpad_right);   // from nothing onto the list's first row
        tap(dpad_right);
        float scroll{};
        for (int i = 0; i < 30; ++i) scroll = frame(feed, pad(0, 0, 0, -32767), false, false, true).list_scroll;
        scroll = frame(feed, pad(), false, false, true).list_scroll;
        check(scroll > 100, "The left stick scrolls the panel holding the focus");
        check(!feed.pointing() && GImGui->NavCursorVisible && GImGui->NavHighlightItemUnderNav,
              "Scrolling stays with the focus, not the mouse");
        for (int i = 0; i < 60; ++i) frame(feed, pad(0, 0, 0, 32767), false, false, true);
        check(frame(feed, pad(), false, false, true).list_scroll == 0, "Pushing up scrolls back to the top");
    }
    {
        fresh();
        PadFeed feed;
        ImGui::GetIO().AddMousePosEvent(500, 200);   // over the list
        for (int i = 0; i < 2; ++i) frame(feed, pad(), false, false, true);
        frame(feed, pad(0, 0, 0, 0), false, false, true);
        frame(feed, pad(right_thumb), false, false, true);   // the pointer shows, without a click
        frame(feed, pad(), false, false, true);
        float scroll{};
        for (int i = 0; i < 30; ++i) scroll = frame(feed, pad(0, 0, 0, -32767), false, false, true).list_scroll;
        scroll = frame(feed, pad(), false, false, true).list_scroll;
        check(scroll > 100, "The left stick scrolls the panel under the pointer");
        check(feed.pointing(), "Scrolling keeps the pointer");
    }
    {
        fresh();
        PadFeed feed;
        ImGui::GetIO().AddMousePosEvent(500, 200);   // the mouse resting over the list
        for (int i = 0; i < 2; ++i) frame(feed, pad(), false, false, true);
        float scroll{};
        for (int i = 0; i < 30; ++i) scroll = frame(feed, pad(0, 0, 0, -32767), false, false, true).list_scroll;
        scroll = frame(feed, pad(), false, false, true).list_scroll;
        check(scroll > 100, "The left stick scrolls the panel under the mouse");
    }

    // ------------------------------------------------ the Steam Deck's trackpad
    {
        fresh();
        PadFeed stick;
        PadFeed trackpad(true);
        ImGui::GetIO().AddMousePosEvent(400, 300);
        frame(trackpad, pad());
        for (int i = 0; i < 10; ++i) frame(trackpad, pad(0, 3300, 0));   // a slow swipe
        frame(trackpad, pad());
        check(ImGui::GetIO().MousePos.x > 405, "A slow swipe on the trackpad moves the pointer");
        fresh();
        ImGui::GetIO().AddMousePosEvent(400, 300);
        frame(stick, pad());
        for (int i = 0; i < 10; ++i) frame(stick, pad(0, 3300, 0));
        frame(stick, pad());
        check(!stick.pointing() && ImGui::GetIO().MousePos.x == 400, "The same small tilt of a thumbstick does not");

        fresh();
        PadFeed glide(true);
        ImGui::GetIO().AddMousePosEvent(100, 300);
        frame(glide, pad());
        for (int i = 0; i < 5; ++i) frame(glide, pad(0, 20000, 0));   // the swipe
        float tilt = 20000;
        float stopped = 0;
        for (int i = 0; i < 30; ++i) {   // the thumb lifted: the tilt only fades
            tilt *= 0.9f;
            frame(glide, pad(0, static_cast<std::int16_t>(tilt), 0));
            if (i == 6) stopped = ImGui::GetIO().MousePos.x;
        }
        frame(glide, pad());
        check(stopped > 100 && ImGui::GetIO().MousePos.x == stopped, "The trackpad's glide after the thumb lifts does not carry the pointer on");
    }

    // ------------------------------------------------ trackpad pointer
    {
        fresh();
        PadFeed feed;
        auto& io = ImGui::GetIO();
        io.AddMousePosEvent(400, 300);
        feed.mouse_moved(ImVec2(400, 300));
        frame(feed, pad());
        frame(feed, pad(0, 3000, 0));
        check(!feed.pointing() && io.MousePos.x == 400, "A thumb resting near the middle does not move the pointer");

        frame(feed, pad(0, 16000, 0));
        frame(feed, pad());
        check(feed.pointing() && io.MouseDrawCursor, "Tilting takes the pointer and draws it");
        check(io.MousePos.x > 400 && io.MousePos.y == 300, "Tilting right moves the pointer right, from the mouse's place");
        for (int i = 0; i < 120; ++i) frame(feed, pad(0, 32767, 32767));
        frame(feed, pad());
        check(io.MousePos.x == 799 && io.MousePos.y == 0, "The pointer stays inside the window");

        // The system cursor stays where the mouse left it, and is reported every frame.
        io.AddMousePosEvent(400, 300);
        frame(feed, pad());
        frame(feed, pad());
        check(io.MousePos.x == 799, "The system cursor's old place does not take the pointer back");
        feed.mouse_moved(ImVec2(400, 300));   // the same place, repeated by Windows
        check(feed.pointing(), "A mouse move repeated in the same place keeps the pointer");

        feed.mouse_moved(ImVec2(50, 60));     // the mouse, or a finger on the screen
        io.AddMousePosEvent(50, 60);
        frame(feed, pad());
        frame(feed, pad());
        check(!feed.pointing() && !io.MouseDrawCursor, "The mouse takes the pointer back");
        check(io.MousePos.x == 50, "The mouse's place wins once it moved");
    }
    {
        fresh();
        PadFeed feed;
        ImGui::GetIO().AddMousePosEvent(150, 225);   // over "second"
        frame(feed, pad());
        frame(feed, pad());
        std::string pressed = frame(feed, pad(right_thumb)).pressed;
        pressed += frame(feed, pad()).pressed;
        check(feed.pointing() && pressed.empty() && !ImGui::GetIO().MouseDown[0],
              "The first trackpad click (R3) only shows the pointer");
        pressed = frame(feed, pad(right_thumb)).pressed;
        check(ImGui::GetIO().MouseDown[0], "The next click holds the left button");
        pressed += frame(feed, pad()).pressed;
        check(pressed == "second", "The trackpad's click presses what the pointer is over");
        check(!ImGui::GetIO().MouseDown[0], "Letting go of R3 lets go of the left button");

        press(feed, dpad_down);
        check(!feed.pointing() && ImGui::GetIO().NavVisible, "The D-pad hands the screen back to the focus");
    }

    ImGui::DestroyContext();
    if (failures) {
        std::cerr << failures << " gamepad input check(s) failed\n";
        return 1;
    }
    std::cout << "Gamepad input checks passed.\n";
    return 0;
}