//! Style type for representing available space as a sizing constraint
use crate::{
    prelude::{FromLength, TaffyMaxContent, TaffyMinContent, TaffyZero},
    sys::abs,
    Size,
};

/// The amount of space available to a node in a given axis
/// <https://www.w3.org/TR/css-sizing-3/#available>
#[derive(Copy, Clone, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Serialize))]
pub enum AvailableSpace {
    /// The amount of space available is the specified number of pixels
    Definite(f32),
    /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
    MinContent,
    /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
    MaxContent,
}
impl TaffyZero for AvailableSpace {
    const ZERO: Self = Self::Definite(0.0);
}
impl TaffyMaxContent for AvailableSpace {
    const MAX_CONTENT: Self = Self::MaxContent;
}
impl TaffyMinContent for AvailableSpace {
    const MIN_CONTENT: Self = Self::MinContent;
}
impl FromLength for AvailableSpace {
    fn from_length<Input: Into<f32> + Copy>(value: Input) -> Self {
        Self::Definite(value.into())
    }
}

impl AvailableSpace {
    /// Returns true for definite values, else false
    pub const fn is_definite(self) -> bool {
        matches!(self, AvailableSpace::Definite(_))
    }

    /// Convert to Option
    /// Definite values become Some(value). Constraints become None.
    pub const fn into_option(self) -> Option<f32> {
        match self {
            AvailableSpace::Definite(value) => Some(value),
            _ => None,
        }
    }

    /// Return the definite value or a default value
    pub fn unwrap_or(self, default: f32) -> f32 {
        self.into_option().unwrap_or(default)
    }

    /// Return the definite value. Panic is the value is not definite.
    #[track_caller]
    pub fn unwrap(self) -> f32 {
        self.into_option().unwrap()
    }

    /// Return self if definite or a default value
    pub fn or(self, default: AvailableSpace) -> AvailableSpace {
        match self {
            AvailableSpace::Definite(_) => self,
            _ => default,
        }
    }

    /// Return self if definite or a the result of the default value callback
    pub fn or_else(self, default_cb: impl FnOnce() -> AvailableSpace) -> AvailableSpace {
        match self {
            AvailableSpace::Definite(_) => self,
            _ => default_cb(),
        }
    }

    /// Return the definite value or the result of the default value callback
    pub fn unwrap_or_else(self, default_cb: impl FnOnce() -> f32) -> f32 {
        self.into_option().unwrap_or_else(default_cb)
    }

    /// If passed value is Some then return AvailableSpace::Definite containing that value, else return self
    pub fn maybe_set(self, value: Option<f32>) -> AvailableSpace {
        match value {
            Some(value) => AvailableSpace::Definite(value),
            None => self,
        }
    }

    /// If passed value is Some then return AvailableSpace::Definite containing that value, else return self
    pub fn map_definite_value(self, map_function: impl FnOnce(f32) -> f32) -> AvailableSpace {
        match self {
            AvailableSpace::Definite(value) => AvailableSpace::Definite(map_function(value)),
            _ => self,
        }
    }

    /// Compute free_space given the passed used_space
    pub fn compute_free_space(&self, used_space: f32) -> f32 {
        match self {
            AvailableSpace::MaxContent => f32::INFINITY,
            AvailableSpace::MinContent => 0.0,
            AvailableSpace::Definite(available_space) => available_space - used_space,
        }
    }

    /// Compare equality with another AvailableSpace, treating definite values
    /// that are within f32::EPSILON of each other as equal
    pub fn is_roughly_equal(self, other: AvailableSpace) -> bool {
        use AvailableSpace::*;
        match (self, other) {
            (Definite(a), Definite(b)) => abs(a - b) < f32::EPSILON,
            (MinContent, MinContent) => true,
            (MaxContent, MaxContent) => true,
            _ => false,
        }
    }
}

impl From<f32> for AvailableSpace {
    fn from(value: f32) -> Self {
        Self::Definite(value)
    }
}

impl From<Option<f32>> for AvailableSpace {
    fn from(option: Option<f32>) -> Self {
        match option {
            Some(value) => Self::Definite(value),
            None => Self::MaxContent,
        }
    }
}

impl Size<AvailableSpace> {
    /// Convert `Size<AvailableSpace>` into `Size<Option<f32>>`
    pub fn into_options(self) -> Size<Option<f32>> {
        Size { width: self.width.into_option(), height: self.height.into_option() }
    }

    /// If passed value is Some then return AvailableSpace::Definite containing that value, else return self
    pub fn maybe_set(self, value: Size<Option<f32>>) -> Size<AvailableSpace> {
        Size { width: self.width.maybe_set(value.width), height: self.height.maybe_set(value.height) }
    }
}