//! Encode and display information in a QR code.
use crate::renderer::{self, Renderer};
use crate::widget::canvas;
use crate::Backend;

use iced_native::layout;
use iced_native::widget::Tree;
use iced_native::{
    Color, Element, Layout, Length, Point, Rectangle, Size, Vector, Widget,
};
use thiserror::Error;

const DEFAULT_CELL_SIZE: u16 = 4;
const QUIET_ZONE: usize = 2;

/// A type of matrix barcode consisting of squares arranged in a grid which
/// can be read by an imaging device, such as a camera.
#[derive(Debug)]
pub struct QRCode<'a> {
    state: &'a State,
    dark: Color,
    light: Color,
    cell_size: u16,
}

impl<'a> QRCode<'a> {
    /// Creates a new [`QRCode`] with the provided [`State`].
    pub fn new(state: &'a State) -> Self {
        Self {
            cell_size: DEFAULT_CELL_SIZE,
            dark: Color::BLACK,
            light: Color::WHITE,
            state,
        }
    }

    /// Sets both the dark and light [`Color`]s of the [`QRCode`].
    pub fn color(mut self, dark: Color, light: Color) -> Self {
        self.dark = dark;
        self.light = light;
        self
    }

    /// Sets the size of the squares of the grid cell of the [`QRCode`].
    pub fn cell_size(mut self, cell_size: u16) -> Self {
        self.cell_size = cell_size;
        self
    }
}

impl<'a, Message, B, T> Widget<Message, Renderer<B, T>> for QRCode<'a>
where
    B: Backend,
{
    fn width(&self) -> Length {
        Length::Shrink
    }

    fn height(&self) -> Length {
        Length::Shrink
    }

    fn layout(
        &self,
        _renderer: &Renderer<B, T>,
        _limits: &layout::Limits,
    ) -> layout::Node {
        let side_length = (self.state.width + 2 * QUIET_ZONE) as f32
            * f32::from(self.cell_size);

        layout::Node::new(Size::new(side_length, side_length))
    }

    fn draw(
        &self,
        _state: &Tree,
        renderer: &mut Renderer<B, T>,
        _theme: &T,
        _style: &renderer::Style,
        layout: Layout<'_>,
        _cursor_position: Point,
        _viewport: &Rectangle,
    ) {
        use iced_native::Renderer as _;

        let bounds = layout.bounds();
        let side_length = self.state.width + 2 * QUIET_ZONE;

        // Reuse cache if possible
        let geometry = self.state.cache.draw(bounds.size(), |frame| {
            // Scale units to cell size
            frame.scale(f32::from(self.cell_size));

            // Draw background
            frame.fill_rectangle(
                Point::ORIGIN,
                Size::new(side_length as f32, side_length as f32),
                self.light,
            );

            // Avoid drawing on the quiet zone
            frame.translate(Vector::new(QUIET_ZONE as f32, QUIET_ZONE as f32));

            // Draw contents
            self.state
                .contents
                .iter()
                .enumerate()
                .filter(|(_, value)| **value == qrcode::Color::Dark)
                .for_each(|(index, _)| {
                    let row = index / self.state.width;
                    let column = index % self.state.width;

                    frame.fill_rectangle(
                        Point::new(column as f32, row as f32),
                        Size::UNIT,
                        self.dark,
                    );
                });
        });

        let translation = Vector::new(bounds.x, bounds.y);

        renderer.with_translation(translation, |renderer| {
            renderer.draw_primitive(geometry.into_primitive());
        });
    }
}

impl<'a, Message, B, T> From<QRCode<'a>>
    for Element<'a, Message, Renderer<B, T>>
where
    B: Backend,
{
    fn from(qr_code: QRCode<'a>) -> Self {
        Self::new(qr_code)
    }
}

/// The state of a [`QRCode`].
///
/// It stores the data that will be displayed.
#[derive(Debug)]
pub struct State {
    contents: Vec<qrcode::Color>,
    width: usize,
    cache: canvas::Cache,
}

impl State {
    /// Creates a new [`State`] with the provided data.
    ///
    /// This method uses an [`ErrorCorrection::Medium`] and chooses the smallest
    /// size to display the data.
    pub fn new(data: impl AsRef<[u8]>) -> Result<Self, Error> {
        let encoded = qrcode::QrCode::new(data)?;

        Ok(Self::build(encoded))
    }

    /// Creates a new [`State`] with the provided [`ErrorCorrection`].
    pub fn with_error_correction(
        data: impl AsRef<[u8]>,
        error_correction: ErrorCorrection,
    ) -> Result<Self, Error> {
        let encoded = qrcode::QrCode::with_error_correction_level(
            data,
            error_correction.into(),
        )?;

        Ok(Self::build(encoded))
    }

    /// Creates a new [`State`] with the provided [`Version`] and
    /// [`ErrorCorrection`].
    pub fn with_version(
        data: impl AsRef<[u8]>,
        version: Version,
        error_correction: ErrorCorrection,
    ) -> Result<Self, Error> {
        let encoded = qrcode::QrCode::with_version(
            data,
            version.into(),
            error_correction.into(),
        )?;

        Ok(Self::build(encoded))
    }

    fn build(encoded: qrcode::QrCode) -> Self {
        let width = encoded.width();
        let contents = encoded.into_colors();

        Self {
            contents,
            width,
            cache: canvas::Cache::new(),
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
/// The size of a [`QRCode`].
///
/// The higher the version the larger the grid of cells, and therefore the more
/// information the [`QRCode`] can carry.
pub enum Version {
    /// A normal QR code version. It should be between 1 and 40.
    Normal(u8),

    /// A micro QR code version. It should be between 1 and 4.
    Micro(u8),
}

impl From<Version> for qrcode::Version {
    fn from(version: Version) -> Self {
        match version {
            Version::Normal(v) => qrcode::Version::Normal(i16::from(v)),
            Version::Micro(v) => qrcode::Version::Micro(i16::from(v)),
        }
    }
}

/// The error correction level.
///
/// It controls the amount of data that can be damaged while still being able
/// to recover the original information.
///
/// A higher error correction level allows for more corrupted data.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ErrorCorrection {
    /// Low error correction. 7% of the data can be restored.
    Low,
    /// Medium error correction. 15% of the data can be restored.
    Medium,
    /// Quartile error correction. 25% of the data can be restored.
    Quartile,
    /// High error correction. 30% of the data can be restored.
    High,
}

impl From<ErrorCorrection> for qrcode::EcLevel {
    fn from(ec_level: ErrorCorrection) -> Self {
        match ec_level {
            ErrorCorrection::Low => qrcode::EcLevel::L,
            ErrorCorrection::Medium => qrcode::EcLevel::M,
            ErrorCorrection::Quartile => qrcode::EcLevel::Q,
            ErrorCorrection::High => qrcode::EcLevel::H,
        }
    }
}

/// An error that occurred when building a [`State`] for a [`QRCode`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Error)]
pub enum Error {
    /// The data is too long to encode in a QR code for the chosen [`Version`].
    #[error(
        "The data is too long to encode in a QR code for the chosen version"
    )]
    DataTooLong,

    /// The chosen [`Version`] and [`ErrorCorrection`] combination is invalid.
    #[error(
        "The chosen version and error correction level combination is invalid."
    )]
    InvalidVersion,

    /// One or more characters in the provided data are not supported by the
    /// chosen [`Version`].
    #[error(
        "One or more characters in the provided data are not supported by the \
        chosen version"
    )]
    UnsupportedCharacterSet,

    /// The chosen ECI designator is invalid. A valid designator should be
    /// between 0 and 999999.
    #[error(
        "The chosen ECI designator is invalid. A valid designator should be \
        between 0 and 999999."
    )]
    InvalidEciDesignator,

    /// A character that does not belong to the character set was found.
    #[error("A character that does not belong to the character set was found")]
    InvalidCharacter,
}

impl From<qrcode::types::QrError> for Error {
    fn from(error: qrcode::types::QrError) -> Self {
        use qrcode::types::QrError;

        match error {
            QrError::DataTooLong => Error::DataTooLong,
            QrError::InvalidVersion => Error::InvalidVersion,
            QrError::UnsupportedCharacterSet => Error::UnsupportedCharacterSet,
            QrError::InvalidEciDesignator => Error::InvalidEciDesignator,
            QrError::InvalidCharacter => Error::InvalidCharacter,
        }
    }
}