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//! Conversion from values into other types.
use std::ops::Deref;
use fontdock::{FontStretch, FontStyle, FontWeight};
use super::{Value, ValueDict, ValueFunc};
use crate::diag::Diag;
use crate::geom::Linear;
use crate::layout::{Dir, SpecAlign};
use crate::paper::Paper;
use crate::syntax::{Ident, SpanWith, Spanned, SynTree};
/// Types that values can be converted into.
pub trait Convert: Sized {
/// Convert a value into `Self`.
///
/// If the conversion works out, this should return `Ok(...)` with an
/// instance of `Self`. If it doesn't, it should return `Err(...)` giving
/// back the original value.
///
/// In addition to the result, the method can return an optional diagnostic
/// to warn even when the conversion suceeded or to explain the problem when
/// the conversion failed.
///
/// The function takes a `Spanned<Value>` instead of just a `Value` so that
/// this trait can be blanket implemented for `Spanned<T>` where `T:
/// Convert`.
fn convert(value: Spanned<Value>) -> (Result<Self, Value>, Option<Diag>);
}
impl<T: Convert> Convert for Spanned<T> {
fn convert(value: Spanned<Value>) -> (Result<Self, Value>, Option<Diag>) {
let span = value.span;
let (result, diag) = T::convert(value);
(result.map(|v| v.span_with(span)), diag)
}
}
/// A value type that matches [length] values.
///
/// [length]: enum.Value.html#variant.Length
pub struct Absolute(pub f64);
impl From<Absolute> for f64 {
fn from(abs: Absolute) -> f64 {
abs.0
}
}
/// A value type that matches [relative] values.
///
/// [relative]: enum.Value.html#variant.Relative
pub struct Relative(pub f64);
impl From<Relative> for f64 {
fn from(rel: Relative) -> f64 {
rel.0
}
}
/// A value type that matches [identifier] and [string] values.
///
/// [identifier]: enum.Value.html#variant.Ident
/// [string]: enum.Value.html#variant.Str
pub struct StringLike(pub String);
impl From<StringLike> for String {
fn from(like: StringLike) -> String {
like.0
}
}
impl Deref for StringLike {
type Target = str;
fn deref(&self) -> &str {
self.0.as_str()
}
}
macro_rules! impl_match {
($type:ty, $name:expr, $($p:pat => $r:expr),* $(,)?) => {
impl Convert for $type {
fn convert(value: Spanned<Value>) -> (Result<Self, Value>, Option<Diag>) {
#[allow(unreachable_patterns)]
match value.v {
$($p => (Ok($r), None)),*,
v => {
let err = error!("expected {}, found {}", $name, v.ty());
(Err(v), Some(err))
},
}
}
}
};
}
impl_match!(Value, "value", v => v);
impl_match!(Ident, "identifier", Value::Ident(v) => v);
impl_match!(bool, "bool", Value::Bool(v) => v);
impl_match!(i64, "integer", Value::Int(v) => v);
impl_match!(f64, "float",
Value::Int(v) => v as f64,
Value::Float(v) => v,
);
impl_match!(Absolute, "length", Value::Length(v) => Absolute(v));
impl_match!(Relative, "relative", Value::Relative(v) => Relative(v));
impl_match!(Linear, "linear",
Value::Linear(v) => v,
Value::Length(v) => Linear::abs(v),
Value::Relative(v) => Linear::rel(v),
);
impl_match!(String, "string", Value::Str(v) => v);
impl_match!(SynTree, "tree", Value::Content(v) => v);
impl_match!(ValueDict, "dictionary", Value::Dict(v) => v);
impl_match!(ValueFunc, "function", Value::Func(v) => v);
impl_match!(StringLike, "identifier or string",
Value::Ident(Ident(v)) => StringLike(v),
Value::Str(v) => StringLike(v),
);
macro_rules! impl_ident {
($type:ty, $name:expr, $parse:expr) => {
impl Convert for $type {
fn convert(value: Spanned<Value>) -> (Result<Self, Value>, Option<Diag>) {
match value.v {
Value::Ident(id) => {
if let Some(thing) = $parse(&id) {
(Ok(thing), None)
} else {
(Err(Value::Ident(id)), Some(error!("invalid {}", $name)))
}
}
v => {
let err = error!("expected {}, found {}", $name, v.ty());
(Err(v), Some(err))
}
}
}
}
};
}
impl_ident!(Dir, "direction", |v| match v {
"ltr" => Some(Self::LTR),
"rtl" => Some(Self::RTL),
"ttb" => Some(Self::TTB),
"btt" => Some(Self::BTT),
_ => None,
});
impl_ident!(SpecAlign, "alignment", |v| match v {
"left" => Some(Self::Left),
"right" => Some(Self::Right),
"top" => Some(Self::Top),
"bottom" => Some(Self::Bottom),
"center" => Some(Self::Center),
_ => None,
});
impl_ident!(FontStyle, "font style", Self::from_str);
impl_ident!(FontStretch, "font stretch", Self::from_str);
impl_ident!(Paper, "paper", Self::from_name);
impl Convert for FontWeight {
fn convert(value: Spanned<Value>) -> (Result<Self, Value>, Option<Diag>) {
match value.v {
Value::Int(number) => {
let [min, max] = [100, 900];
let warning = if number < min {
Some(warning!("the minimum font weight is {}", min))
} else if number > max {
Some(warning!("the maximum font weight is {}", max))
} else {
None
};
let weight = Self::from_number(number.min(max).max(min) as u16);
(Ok(weight), warning)
}
Value::Ident(id) => {
if let Some(thing) = FontWeight::from_str(&id) {
(Ok(thing), None)
} else {
(Err(Value::Ident(id)), Some(error!("invalid font weight")))
}
}
v => {
let err =
error!("expected font weight (name or number), found {}", v.ty());
(Err(v), Some(err))
}
}
}
}
|
