#![deny(clippy::all, clippy::pedantic)]

use std::collections::BTreeMap;
use std::time::{Duration, Instant};

use glfw::window::KeyState;
use glfw::{Window, WindowBuilder};

use crate::camera::Camera;
use crate::lighting::LightSource;
use crate::object::{Id as ObjectId, Object};
use crate::renderer::Renderer;
use crate::vector::Vec2;

mod opengl;
mod projection;
mod renderer;
mod shader_preprocessor;
mod transform;

pub mod camera;
pub mod data_types;
pub mod lighting;
pub mod material;
pub mod math;
pub mod mesh;
pub mod object;
pub mod shader;
pub mod texture;
pub mod vertex;

pub use glfw::window::Key;
pub use glfw::WindowSize;

pub(crate) use crate::data_types::matrix;
pub use crate::data_types::{color, vector};

#[derive(Debug)]
pub struct Engine<CameraT>
{
    /// Objects have to be dropped before window. Otherwise, UB.
    objects: BTreeMap<ObjectId, Object>,
    light_source: Option<LightSource>,
    renderer: Renderer<CameraT>,
    window: Window,
    delta_time: Duration,
}

impl<CameraT> Engine<CameraT>
where
    CameraT: Camera,
{
    /// Creates and initializes a new engine.
    ///
    /// # Errors
    /// Will return `Err` if window creation or window configuration fails.
    pub fn new(window_settings: &WindowSettings, camera: CameraT) -> Result<Self, Error>
    {
        let window_builder = WindowBuilder::new();

        #[cfg(feature = "debug")]
        let window_builder =
            window_builder.hint(glfw::window::Hint::OpenGLDebugContext, 1);

        let window = window_builder
            .create(&window_settings.size, &window_settings.title)
            .map_err(Error::CreateWindowFailed)?;

        window
            .make_context_current()
            .map_err(Error::ConfigureWindowFailed)?;

        window.set_framebuffer_size_callback(move |new_window_size| {
            Renderer::<CameraT>::set_viewport(&Vec2::ZERO, &new_window_size);
        });

        Self::set_window_input_modes(&window, window_settings)?;

        window
            .set_cursor_mode(window_settings.cursor_mode)
            .map_err(|err| Error::SetWindowCursorModeFailed {
                source: err,
                cursor_mode: window_settings.cursor_mode,
            })?;

        let renderer =
            Renderer::new(&window, camera).map_err(Error::InitializeRendererFailed)?;

        Ok(Self {
            window,
            renderer,
            objects: BTreeMap::new(),
            light_source: None,
            delta_time: Duration::ZERO,
        })
    }

    pub fn add_object(&mut self, object: Object)
    {
        self.objects.insert(object.id(), object);
    }

    pub fn set_objecs(&mut self, objects: impl IntoIterator<Item = Object>)
    {
        self.objects
            .extend(objects.into_iter().map(|object| (object.id(), object)));
    }

    pub fn set_light_source(&mut self, light_source: LightSource)
    {
        self.light_source = Some(light_source);
    }

    #[must_use]
    pub fn light_source(&self) -> Option<&LightSource>
    {
        self.light_source.as_ref()
    }

    #[must_use]
    pub fn light_source_mut(&mut self) -> Option<&mut LightSource>
    {
        self.light_source.as_mut()
    }

    #[must_use]
    pub fn get_object_by_id(&self, id: ObjectId) -> Option<&Object>
    {
        self.objects.get(&id)
    }

    #[must_use]
    pub fn get_object_by_id_mut(&mut self, id: ObjectId) -> Option<&mut Object>
    {
        self.objects.get_mut(&id)
    }

    /// Starts the engine.
    ///
    /// # Errors
    /// Will return `Err` if updating the window fails.
    pub fn start(&mut self, mut func: impl FnMut(&mut Self)) -> Result<(), Error>
    {
        self.renderer
            .create_shader_programs(self.objects.values().map(Object::shader))
            .map_err(Error::ShaderCreationFailed)?;

        let mut prev_frame_start: Option<Instant> = None;

        while !self.window.should_close() {
            self.update_delta_time(&mut prev_frame_start);

            func(self);

            let window_size = self.window.size().map_err(Error::GetWindowSizeFailed)?;

            self.renderer
                .render(
                    self.objects.values(),
                    self.light_source.as_ref(),
                    &window_size,
                )
                .map_err(Error::RenderingFailed)?;

            self.window
                .swap_buffers()
                .map_err(Error::UpdateWindowFailed)?;

            self.window
                .poll_events()
                .map_err(Error::UpdateWindowFailed)?;
        }

        Ok(())
    }

    #[must_use]
    pub fn camera(&self) -> &CameraT
    {
        self.renderer.camera()
    }

    pub fn camera_mut(&mut self) -> &mut CameraT
    {
        self.renderer.camera_mut()
    }

    /// Returns the current delta time. Will be 0 if not called from the function
    /// passed to [`start`].
    #[must_use]
    pub fn delta_time(&self) -> &Duration
    {
        &self.delta_time
    }

    /// Returns whether or not a keyboard key is currently pressed.
    ///
    /// # Errors
    /// Will return `Err` if getting the key state fails.
    pub fn is_key_pressed(&self, key: Key) -> Result<bool, Error>
    {
        self.window
            .get_key(key)
            .map(|key_state| matches!(key_state, KeyState::Pressed))
            .map_err(Error::GetKeyStateFailed)
    }

    /// Returns the cursor position.
    ///
    /// # Errors
    /// Will return `Err` if unable to get the cursor position from GLFW.
    pub fn get_cursor_pos(&self) -> Result<Vec2<f64>, Error>
    {
        let pos = self
            .window
            .get_cursor_position()
            .map_err(Error::GetCursorPosFailed)?;

        Ok(Vec2 { x: pos.x, y: pos.y })
    }

    fn update_delta_time(&mut self, prev_frame_start: &mut Option<Instant>)
    {
        let frame_start_time = Instant::now();

        if let Some(last_frame_start) = prev_frame_start {
            self.delta_time = frame_start_time.duration_since(*last_frame_start);
        }

        *prev_frame_start = Some(frame_start_time);
    }

    fn set_window_input_modes(
        window: &Window,
        window_settings: &WindowSettings,
    ) -> Result<(), Error>
    {
        for (input_mode, enabled) in &window_settings.input_modes {
            window
                .set_input_mode(*input_mode, *enabled)
                .map_err(|err| Error::SetWindowInputModeFailed {
                    source: err,
                    input_mode: *input_mode,
                    enabled: *enabled,
                })?;
        }

        Ok(())
    }
}

/// Engine Error
#[derive(Debug, thiserror::Error)]
pub enum Error
{
    #[error("Failed to create window")]
    CreateWindowFailed(#[source] glfw::Error),

    #[error("Failed to configure window")]
    ConfigureWindowFailed(#[source] glfw::Error),

    #[error("Failed to initialize renderer")]
    InitializeRendererFailed(#[source] renderer::Error),

    #[error("Failed to update window")]
    UpdateWindowFailed(#[source] glfw::Error),

    #[error("Failed to get window size")]
    GetWindowSizeFailed(#[source] glfw::Error),

    #[error("Failed to set window input mode {input_mode:?} to {enabled}")]
    SetWindowInputModeFailed
    {
        #[source]
        source: glfw::Error,
        input_mode: InputMode,
        enabled: bool,
    },

    #[error("Failed to set window cursor mode to {cursor_mode:?}")]
    SetWindowCursorModeFailed
    {
        #[source]
        source: glfw::Error,
        cursor_mode: CursorMode,
    },

    #[error("Failed to get key state")]
    GetKeyStateFailed(#[source] glfw::Error),

    #[error("Failed to get cursor position")]
    GetCursorPosFailed(#[source] glfw::Error),

    #[error("Rendering failed")]
    RenderingFailed(#[source] renderer::Error),

    #[error("Failed to create shaders")]
    ShaderCreationFailed(#[source] renderer::Error),
}

#[derive(Debug)]
pub struct WindowSettings
{
    size: WindowSize,
    title: Box<str>,
    input_modes: BTreeMap<InputMode, bool>,
    cursor_mode: CursorMode,
}

#[derive(Debug)]
pub struct WindowSettingsBuilder
{
    input_modes: BTreeMap<InputMode, bool>,
    cursor_mode: CursorMode,
}

impl WindowSettingsBuilder
{
    #[must_use]
    pub fn new() -> Self
    {
        Self::default()
    }

    #[must_use]
    pub fn input_mode(mut self, input_mode: InputMode, enabled: bool) -> Self
    {
        self.input_modes.insert(input_mode, enabled);

        self
    }

    #[must_use]
    pub fn input_modes(
        mut self,
        input_modes: impl IntoIterator<Item = (InputMode, bool)>,
    ) -> Self
    {
        self.input_modes.extend(input_modes);

        self
    }

    #[must_use]
    pub fn cursor_mode(mut self, cursor_mode: CursorMode) -> Self
    {
        self.cursor_mode = cursor_mode;

        self
    }

    pub fn build(&self, size: WindowSize, title: impl Into<Box<str>>) -> WindowSettings
    {
        WindowSettings {
            size,
            title: title.into(),
            input_modes: self.input_modes.clone(),
            cursor_mode: self.cursor_mode,
        }
    }
}

impl Default for WindowSettingsBuilder
{
    fn default() -> Self
    {
        Self {
            input_modes: BTreeMap::new(),
            cursor_mode: CursorMode::Normal,
        }
    }
}

pub use glfw::window::{CursorMode, InputMode};