#pragma once

#include <string>
#include <vector>

struct GLFWwindow;

// One row for the extensible right-hand stats list (oil temp, coolant
// temp, etc.) — push more entries onto EngineStats::extra_stats as the
// sim grows, no Gui changes needed.
struct StatEntry {
    std::string label;
    double value;
    std::string unit;
};

// Plain data the GUI reads each frame. The GUI knows nothing about
// Engine/Transmission/Vehicle — main.cpp fills this in from Simulation.
struct EngineStats {
    double rpm = 0.0;
    double redline_rpm = 6500.0;  // tach gauge: start of red zone
    double max_rpm = 8000.0;      // tach gauge: full scale

    double fuel_consumption_lph = 0.0;
    double crank_power_kw = 0.0;
    double output_heat_j = 0.0;

    std::vector<StatEntry> extra_stats;
};

// Which parasitic-load accessories are toggled on, via checkboxes drawn
// in the left column by render(). Placeholders (Alternator, A/C, Power
// Steering) until there's an actual load model behind them.
struct AccessoryState {
    bool alternator = false;
    bool ac = false;
    bool power_steering = false;
};

class Gui {
public:
    bool init();                     // create window + ImGui context
    bool begin_frame();               // returns false when the window should close
    void render(const EngineStats& stats);
    void end_frame();                 // swap buffers
    void shutdown();

    // Reflects the throttle lever as of the most recent render() call.
    // Spring-loaded: holds whatever value the drag left it at only
    // while the mouse is down, and snaps back to 0 the instant it's
    // released. Read it any time after render() this frame, or before
    // render() next frame, to feed it into the engine.
    double throttle() const { return static_cast<double>(m_throttle_lever); }

    // Reflects the checkbox state as of the most recent render() call —
    // read it any time after render() this frame, or before render()
    // next frame, to feed accessory load into the engine.
    const AccessoryState& accessories() const { return m_accessories; }

private:
    GLFWwindow* m_window = nullptr;
    float m_throttle_lever = 0.0f;
    AccessoryState m_accessories;
};