const std = @import("std");

const ig = @import("cimgui_docking");
const sokol = @import("sokol");
const slog = sokol.log;
const sg = sokol.gfx;
const sapp = sokol.app;
const sglue = sokol.glue;
const sfetch = sokol.fetch;
const simgui = sokol.imgui;

const stbi = @cImport({
    @cInclude("stb_image.h");
});

const shd = @import("shd/quad.glsl.zig");

const state = struct {
    const MaxSprites = 100;
    const MaxLights = 100;

    var pass_action: sg.PassAction = .{};
    var bind: sg.Bindings = .{};
    var pip: sg.Pipeline = .{};

    var pip_shadow: sg.Pipeline = .{};
    
    var bind_light: sg.Bindings = .{};
    var pip_light: sg.Pipeline = .{}; 

    var img_buf: [1024 * 1024]u8 = undefined;

    var cam = [2]f32{ -300, -300 };

    var sprites_buf: [MaxSprites]Sprite = undefined;
    var sprites = std.ArrayListUnmanaged(Sprite).initBuffer(&state.sprites_buf);
    var lights_buf: [MaxLights]Light = undefined;
    var lights = std.ArrayListUnmanaged(Light).initBuffer(&state.lights_buf);
};

const Sprite = struct {
    texid: usize = shd.IMG_tex,
    pos: [2]f32 = [_]f32{ 0, 0 },
    size: [2]i32 = [_]i32{ 300, 300 },
};

const Light = struct {
    pos: [2]f32 = [_]f32{ 0, 0 },
};

export fn init() void {
    // initialize sokol-gfx
    sg.setup(.{
        .buffer_pool_size = 8,
        .image_pool_size = 4,
        .shader_pool_size = 8,
        .pipeline_pool_size = 8,
        .attachments_pool_size = 1,
        .environment = sglue.environment(),
        .logger = .{ .func = slog.func },
    });
    sfetch.setup(.{
        .max_requests = 2,
        .num_channels = 2,
        .num_lanes = 1,
        .logger = .{ .func = slog.func },
    });

    // initialize sokol-imgui
    simgui.setup(.{
        .logger = .{ .func = slog.func },
    });
    ig.igGetIO().*.ConfigFlags |= ig.ImGuiConfigFlags_DockingEnable;

    // initial clear color
    state.pass_action.colors[0] = .{
        .load_action = .CLEAR,
        .clear_value = .{ .r = 0.0, .g = 0.5, .b = 1.0, .a = 1.0 },
    };

    // default pass
    state.bind.images[shd.IMG_tex] = sg.allocImage();

    state.bind.samplers[shd.SMP_smp] = sg.makeSampler(.{
        .min_filter = sg.Filter.NEAREST,
        .mag_filter = sg.Filter.NEAREST,
    });

    // dynamic vertex buffer for instancing data
    state.bind.vertex_buffers[0] = sg.makeBuffer(.{
        .usage = .{ .stream_update = true },
        .size = state.MaxSprites * @sizeOf(Sprite),
    });

    // a shader and pipeline state object
    state.pip = sg.makePipeline(.{
        .shader = sg.makeShader(shd.quadShaderDesc(sg.queryBackend())),
        .layout = init: {
            var l = sg.VertexLayoutState{};
            l.buffers[0].step_func = .PER_INSTANCE;
            l.attrs[shd.ATTR_quad_inst_pos] = .{ .format = .FLOAT2, .offset = @offsetOf(Sprite, "pos") };
            l.attrs[shd.ATTR_quad_inst_size] = .{ .format = .INT2, .offset = @offsetOf(Sprite, "size") };
            l.buffers[0].stride = @sizeOf(Sprite);
            break :init l;
        },
    });

    // shadow pass
    state.pip_shadow = sg.makePipeline(.{
        .shader = sg.makeShader(shd.shadowShaderDesc(sg.queryBackend())),
        .layout = init: {
            var l = sg.VertexLayoutState{};
            l.buffers[0].step_func = .PER_INSTANCE;
            l.attrs[shd.ATTR_shadow_inst_pos] = .{ .format = .FLOAT2, .offset = @offsetOf(Sprite, "pos") };
            l.attrs[shd.ATTR_shadow_inst_size] = .{ .format = .INT2, .offset = @offsetOf(Sprite, "size") };
            l.buffers[0].stride = @sizeOf(Sprite);
            break :init l;
        },
    });

    // light pass
    state.bind_light.vertex_buffers[0] = sg.makeBuffer(.{
        .usage = .{ .stream_update = true },
        .size = state.MaxLights * @sizeOf(Light),
    });

    state.pip_light = sg.makePipeline(.{
        .shader = sg.makeShader(shd.lightShaderDesc(sg.queryBackend())),
        .layout = init: {
            var l = sg.VertexLayoutState{};
            l.buffers[0].step_func = .PER_INSTANCE;
            l.attrs[shd.ATTR_light_light_pos] = .{ .format = .FLOAT2, .offset = @offsetOf(Light, "pos") };
            l.buffers[0].stride = @sizeOf(Light);
            break :init l;
        },
    });

    // fetch resources
    const FileCb = struct {
        fn img(res: [*c]const sfetch.Response) callconv(.c) void {
            if (res.*.finished) {
                var w: c_int = 0;
                var h: c_int = 0;
                var n: c_int = 0;
                const pixels = stbi.stbi_load_from_memory(@ptrCast(res.*.data.ptr.?), @intCast(res.*.data.size), &w, &h, &n, 4);
                if (pixels != null) {
                    sg.initImage(state.bind.images[shd.IMG_tex], .{
                        .width = w,
                        .height = h,
                        .pixel_format = sg.PixelFormat.RGBA8,
                        .data = init: {
                            var i = sg.ImageData{};
                            i.subimage[0][0] = .{
                                .ptr = pixels,
                                .size = @intCast(w * h * 4),
                            };
                            break :init i;
                        },
                    });
                }
            }
        }
    };
    _ = sfetch.send(.{
        .path = "img/test.png",
        .callback = FileCb.img,
        .buffer = .{ .ptr = &state.img_buf, .size = state.img_buf.len },
    });

    state.sprites.appendAssumeCapacity(.{});
    state.lights.appendAssumeCapacity(.{ .pos = [_]f32{ 150, -300 } });
}

fn ui() void {
    if (ig.igBegin("Hello Dear ImGui!", null, ig.ImGuiWindowFlags_None)) {
        _ = ig.igColorEdit3("Background", &state.pass_action.colors[0].clear_value.r, ig.ImGuiColorEditFlags_None);
        _ = ig.igDragFloat2("cam", &state.cam);

        {
            ig.igPushIDPtr(state.sprites.items.ptr);
            if (ig.igButton("+")) {
                _ = state.sprites.appendAssumeCapacity(.{});
            }

            var i: u16 = 0;
            while (i < state.sprites.items.len) {
                var sprite = &state.sprites.items[i];
                i += 1;
                ig.igPushIDInt(i);
                ig.igPushItemWidth(100);
                _ = ig.igDragFloat2("pos", &sprite.pos);
                ig.igSameLine();
                _ = ig.igDragInt2("size", &sprite.size);
                ig.igSameLine();
                if (ig.igButton("-")) {
                    i -= 1;
                    _ = state.sprites.swapRemove(i);
                }
                ig.igPopID();
            }
            ig.igPopID();
        }

        {
            ig.igPushIDPtr(state.lights.items.ptr);
            if (ig.igButton("+")) {
                _ = state.lights.appendAssumeCapacity(.{});
            }

            var i: u16 = 0;
            while (i < state.lights.items.len) {
                var light = &state.lights.items[i];
                i += 1;
                ig.igPushIDInt(i);
                ig.igPushItemWidth(100);
                _ = ig.igDragFloat2("pos", &light.pos);
                ig.igSameLine();
                if (ig.igButton("-")) {
                    i -= 1;
                    _ = state.lights.swapRemove(i);
                }
                ig.igPopID();
            }
            ig.igPopID();
        }

        ig.igEnd();
    }
}

export fn frame() void {
    sfetch.dowork();

    const width = sapp.width();
    const height = sapp.height();
    const widthf = sapp.widthf();
    const heightf = sapp.heightf();

    // call simgui.newFrame() before any ImGui calls
    simgui.newFrame(.{
        .width = width,
        .height = height,
        .delta_time = sapp.frameDuration(),
        .dpi_scale = sapp.dpiScale(),
    });
    ui();

    // update instance vertex buffer
    sg.updateBuffer(state.bind.vertex_buffers[0], sg.asRange(state.sprites.items));
    sg.updateBuffer(state.bind_light.vertex_buffers[0], sg.asRange(state.lights.items));

    sg.beginPass(.{ .action = state.pass_action, .swapchain = sglue.swapchain() });

    // shadow pass
    sg.applyPipeline(state.pip_shadow);
    sg.applyBindings(state.bind);

    sg.applyUniforms(shd.UB_Game, sg.asRange(&shd.Game{
        .screen = [_]f32{ widthf, heightf },
        .cam = state.cam,
    }));

    for (state.lights.items) |light| {
        sg.applyUniforms(shd.UB_Light, sg.asRange(&shd.Light{
            .light_pos = light.pos,
        }));

        sg.draw(0, 6, @truncate(state.sprites.items.len));
    }

    // default pass
    sg.applyPipeline(state.pip);
    sg.applyBindings(state.bind);

    sg.applyUniforms(shd.UB_Game, sg.asRange(&shd.Game{
        .screen = [_]f32{ widthf, heightf },
        .cam = state.cam,
    }));

    sg.draw(0, 6, @truncate(state.sprites.items.len));

    // light pass
    sg.applyPipeline(state.pip_light);
    sg.applyBindings(state.bind_light);

    sg.applyUniforms(shd.UB_Game, sg.asRange(&shd.Game{
        .screen = [_]f32{ widthf, heightf },
        .cam = state.cam,
    }));

    sg.draw(0, 6, @truncate(state.lights.items.len));

    simgui.render();
    sg.endPass();
    sg.commit();
}

export fn cleanup() void {
    simgui.shutdown();
    sfetch.shutdown();
    sg.shutdown();
}

export fn event(ev: [*c]const sapp.Event) void {
    // forward input events to sokol-imgui
    _ = simgui.handleEvent(ev.*);
}

pub fn main() void {
    sapp.run(.{
        .init_cb = init,
        .frame_cb = frame,
        .cleanup_cb = cleanup,
        .event_cb = event,
        .window_title = "sokol-zig + Dear Imgui",
        .width = 800,
        .height = 600,
        .icon = .{ .sokol_default = true },
        .logger = .{ .func = slog.func },
    });
}