const std = @import("std");
const GeneralPurposeAllocator = std.heap.GeneralPurposeAllocator(.{});

const core = @import("mach").core;
const Renderer = @import("./renderer.zig");

pub const App = @This();

gpa: GeneralPurposeAllocator,
allocator: std.mem.Allocator,
random: std.rand.Random,

renderer: *Renderer,

app_timer: core.Timer,
title_timer: core.Timer,

pub fn init(app: *App) !void {
    try core.init(.{
        // Request high performance = prefer dedicated GPU when available.
        .power_preference = .high_performance,
    });

    // Set up a "general purpose allocator" that will handle allocations for
    // the lifetime of the application, for which a more specific allocation
    // strategy is not necessary.
    //
    // Here, `gpa` is an instance of this allocator, which handles the
    // allocation logic, while `allocator` is the interface through which
    // functions such as `alloc` and `free` are called.
    app.gpa = GeneralPurposeAllocator{};
    app.allocator = app.gpa.allocator();

    // Create a pseudo-random number generator, but initialize it with
    // a constant seed so we always get the same result when launching.
    var prng = std.rand.DefaultPrng.init(0);
    app.random = prng.random();

    app.renderer = try Renderer.init(app);

    app.app_timer = try core.Timer.start();
    app.title_timer = try core.Timer.start();
}

pub fn deinit(app: *App) void {
    // Using `defer` here, so we can specify them
    // in the order they were created in `init`.
    defer core.deinit();
    defer _ = app.gpa.deinit(); // TODO: Check for memory leaks?
    defer app.renderer.deinit();
}

pub fn update(app: *App) !bool {
    // Read events from the OS such as input.
    var iter = core.pollEvents();
    while (iter.next()) |event| {
        switch (event) {
            // Allow the renderer to act on the window being resized.
            // This is required so we can resize necessary buffers.
            .framebuffer_resize => |_| app.renderer.resize(),

            // Close the window when requested, such as when
            // pressing the X button in the window title bar.
            .close => return true,

            else => {},
        }
    }

    app.renderer.update();

    // Update the window title to show FPS and input frequency.
    if (app.title_timer.read() >= 1.0) {
        app.title_timer.reset();
        try core.printTitle("Triangle [ {d}fps ] [ Input {d}hz ]", .{ core.frameRate(), core.inputRate() });
    }

    return false;
}