use image::{self, GenericImage};
use sdl2::pixels;
use sdl2::surface;
use sdl2::{self, Sdl};

use std::fmt;
use std::io::Read;

use audio;
use conf;
use event;
use filesystem::Filesystem;
use graphics;
use input;
use mouse;
use timer;
use GameError;
use GameResult;

/// A `Context` is an object that holds on to global resources.
/// It basically tracks hardware state such as the screen, audio
/// system, timers, and so on.  Generally this type is **not** thread-
/// safe and only one `Context` can exist at a time.  Trying to create
/// another one will fail.
///
/// Most functions that interact with the hardware, for instance
/// drawing things, playing sounds, or loading resources (which then
/// need to be transformed into a format the hardware likes) will need
/// to access the `Context`.
pub struct Context {
    /// The Conf object the Context was created with
    pub conf: conf::Conf,
    /// SDL context
    pub sdl_context: Sdl,
    /// Filesystem state
    pub filesystem: Filesystem,
    /// Graphics state
    pub(crate) gfx_context: graphics::GraphicsContext,
    /// Event context
    pub event_context: sdl2::EventSubsystem,
    /// Timer state
    pub timer_context: timer::TimeContext,
    /// Audio context
    pub audio_context: audio::AudioContext,
    /// Gamepad context
    pub gamepad_context: input::GamepadContext,
    /// Mouse context
    pub mouse_context: mouse::MouseContext,
    /// Default font
    pub default_font: graphics::Font,

    /// Context-specific unique ID.
    /// Compiles to nothing in release mode, and so
    /// vanishes; meanwhile we get dead-code warnings.
    #[allow(dead_code)]
    debug_id: DebugId,
}

impl fmt::Debug for Context {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "<Context: {:p}>", self)
    }
}

/// Sets the window icon from the Conf `window_icon` field.
/// An empty string in the conf's `window_icon`
/// means to do nothing.
fn set_window_icon(context: &mut Context) -> GameResult<()> {
    // This clone is a little annoying, but, borrowing is inconvenient.
    let icon = &context.conf.window_setup.icon.clone();
    if !icon.is_empty() {
        let mut f = context.filesystem.open(icon)?;
        let mut buf = Vec::new();
        f.read_to_end(&mut buf)?;
        let image = image::load_from_memory(&buf)?;
        let image_data = &mut image.to_rgba();
        // The "pitch" parameter here is not the count
        // between pixels, but the count between rows.
        // For some retarded reason.
        // Also SDL seems to have strange ideas of what
        // "RGBA" means.
        let surface = surface::Surface::from_data(
            image_data,
            image.width(),
            image.height(),
            image.width() * 4,
            pixels::PixelFormatEnum::ABGR8888,
        )?;
        let window = graphics::get_window_mut(context);
        window.set_icon(surface);
    };
    Ok(())
}

impl Context {
    /// Tries to create a new Context using settings from the given config file.
    /// Usually called by `Context::load_from_conf()`.
    fn from_conf(conf: conf::Conf, fs: Filesystem, sdl_context: Sdl) -> GameResult<Context> {
        let debug_id = DebugId::new();
        let video = sdl_context.video()?;
        let audio_context = audio::AudioContext::new()?;
        let event_context = sdl_context.event()?;
        let timer_context = timer::TimeContext::new();
        let font = graphics::Font::default_font()?;
        let backend_spec = graphics::GlBackendSpec::from(conf.backend);
        let graphics_context = graphics::GraphicsContext::new(
            &video,
            &conf.window_setup,
            conf.window_mode,
            backend_spec,
            debug_id,
        )?;
        let gamepad_context = input::GamepadContext::new(&sdl_context)?;
        let mouse_context = mouse::MouseContext::new();

        let mut ctx = Context {
            conf,
            sdl_context,
            filesystem: fs,
            gfx_context: graphics_context,
            event_context,
            timer_context,
            audio_context,
            gamepad_context,
            mouse_context,

            default_font: font,
            debug_id,
        };

        set_window_icon(&mut ctx)?;

        Ok(ctx)
    }

    /// Tries to create a new Context by loading a config
    /// file from its default path, using the given `Conf`
    /// object as a default if none is found.
    ///
    /// The `game_id` and `author` are game-specific strings that
    /// are used to locate the default storage locations for the
    /// platform it looks in, as documented in the `filesystem`
    /// module.  You can also always debug-print the
    /// `Context::filesystem` field to see what paths it is
    /// searching.
    pub fn load_from_conf(
        game_id: &'static str,
        author: &'static str,
        default_config: conf::Conf,
    ) -> GameResult<Context> {
        let sdl_context = sdl2::init()?;
        let mut fs = Filesystem::new(game_id, author)?;

        let config = match fs.read_config() {
            Ok(config) => {
                info!("Loading conf.toml");
                config
            }
            Err(e) => {
                info!("Could not load conf.toml, using default: {:?}", e);
                default_config
            }
        };

        Context::from_conf(config, fs, sdl_context)
    }

    /// Prints out information on the resources subsystem.
    pub fn print_resource_stats(&mut self) {
        // TODO: consider using logging macros.
        // ACTUALLY TODO: Deprecate this in favor of filesystem.log_all()
        self.filesystem.print_all();
    }

    /// Triggers a Quit event.
    pub fn quit(&mut self) -> GameResult<()> {
        let now_dur = timer::get_time_since_start(self);
        let now = timer::duration_to_f64(now_dur);
        let e = sdl2::event::Event::Quit {
            timestamp: now as u32,
        };
        // println!("Pushing event {:?}", e);
        self.event_context.push_event(e).map_err(GameError::from)
    }

    /// Feeds an `Event` into the `Context` so it can update any internal
    /// state it needs to, such as detecting window resizes.  If you are
    /// rolling your own event loop, you should call this on the events
    /// you receive before processing them yourself.
    pub fn process_event(&mut self, event: &event::Event) {
        match *event {
            event::Event::MouseMotion { x, y, .. } => {
                // Keeping the mouse state info in the Context is a bit of a hack, see issue #283.
                // Seems the best workaround though.
                use graphics::Point2;
                self.mouse_context
                    .set_last_position(Point2::new(x as f32, y as f32));
            }
            event::Event::Window {
                win_event: sdl2::event::WindowEvent::Resized(_, _),
                ..
            } => {
                self.gfx_context.resize_viewport();
            }
            _ => {}
        }
    }
}

use std::path;

/// A builder object for creating a context.
///
/// Can do everything the `Context::load_from_conf()` method does, plus you can
/// also specify new paths to add to the resource path list at build time instead
/// of using `filesystem::mount()`.
#[derive(Debug)]
pub struct ContextBuilder {
    game_id: &'static str,
    author: &'static str,
    conf: conf::Conf,
    paths: Vec<path::PathBuf>,
    load_conf_file: bool,
}

impl ContextBuilder {
    /// Create a new ContextBuilder
    pub fn new(game_id: &'static str, author: &'static str) -> Self {
        Self {
            game_id,
            author,
            conf: conf::Conf::default(),
            paths: vec![],
            load_conf_file: true,
        }
    }

    /// Sets the window setup settings
    pub fn window_setup(mut self, setup: conf::WindowSetup) -> Self {
        self.conf.window_setup = setup;
        self
    }

    /// Sets the window mode settings
    pub fn window_mode(mut self, mode: conf::WindowMode) -> Self {
        self.conf.window_mode = mode;
        self
    }

    /// Sets the graphics backend
    pub fn backend(mut self, backend: conf::Backend) -> Self {
        self.conf.backend = backend;
        self
    }

    /// Add a new read-only filesystem path to the places to search
    /// for resources.
    pub fn add_resource_path<T>(mut self, path: T) -> Self
    where
        T: Into<path::PathBuf>,
    {
        self.paths.push(path.into());
        self
    }

    /// Specifies whether or not to load the `conf.toml` file if it
    /// exists and use its settings to override the provided values.
    /// Defaults to `true` which is usually what you want, but being
    /// able to fiddle with it is sometimes useful for debugging.
    pub fn with_conf_file(mut self, load_conf_file: bool) -> Self {
        self.load_conf_file = load_conf_file;
        self
    }

    /// Build the Context.
    pub fn build(self) -> GameResult<Context> {
        let sdl_context = sdl2::init()?;
        let mut fs = Filesystem::new(self.game_id, self.author)?;

        let config = if self.load_conf_file {
            fs.read_config().unwrap_or(self.conf)
        } else {
            self.conf
        };

        for path in &self.paths {
            fs.mount(path, true);
        }

        Context::from_conf(config, fs, sdl_context)
    }
}

#[cfg(debug_assertions)]
use std::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
#[cfg(debug_assertions)]
static DEBUG_ID_COUNTER: AtomicUsize = ATOMIC_USIZE_INIT;

/// This is a type that contains a unique ID for each Context and
/// is contained in each thing created from the Context which contains
/// data that becomes invalid when the Context goes away (ie, texture
/// handles).  When compiling without assertions (ie in release mode) it
/// is replaced with a zero-size type, compiles down to nothing,
/// and should disappear entirely with a puff of optimization logic.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[cfg(debug_assertions)]
pub(crate) struct DebugId(u32);
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[cfg(not(debug_assertions))]
pub(crate) struct DebugId;

#[cfg(debug_assertions)]
impl DebugId {
    pub fn new() -> Self {
        let id = DEBUG_ID_COUNTER.fetch_add(1, Ordering::SeqCst) as u32;
        // fetch_add() wraps on overflow so we check for overflow explicitly.
        // JUST IN CASE YOU TRY TO CREATE 2^32 CONTEXTS IN ONE PROGRAM!
        assert!(DEBUG_ID_COUNTER.load(Ordering::SeqCst) as u32 > id);
        DebugId(id)
    }

    pub fn get(ctx: &Context) -> Self {
        DebugId(ctx.debug_id.0)
    }

    pub fn assert(&self, ctx: &Context) {
        if *self != ctx.debug_id {
            panic!("Tried to use a resource with a Context that did not create it; this should never happen!");
        }
    }
}

#[cfg(not(debug_assertions))]
impl DebugId {
    pub fn new() -> Self {
        DebugId
    }

    pub fn get(_ctx: &Context) -> Self {
        DebugId
    }

    pub fn assert(&self, _ctx: &Context) {
        // Do nothing.
    }
}