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use std::fmt;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
/// The kind of geographic boundary set to fetch from GeoFRED / Maps (the
/// `shape` parameter of `geofred/shapes/file`) — which regions' polygons the
/// returned [`ShapeFile`](crate::ShapeFile) covers.
///
/// Carried on the wire as a lowercase token (e.g. `"bea"`). Tokens this version
/// does not name round-trip verbatim through [`ShapeType::Other`] rather than
/// failing (ADR-0005), and the enum is `#[non_exhaustive]` so new variants can
/// be promoted out of `Other` later without breaking callers' `match` arms.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum ShapeType {
/// U.S. state boundaries.
State,
/// U.S. county boundaries.
County,
/// Metropolitan Statistical Area boundaries.
Msa,
/// Country boundaries.
Country,
/// Bureau of Economic Analysis region boundaries.
Bea,
/// A shape type FRED accepts that this version does not name; holds the raw
/// token verbatim.
Other(String),
}
impl ShapeType {
/// Map a GeoFRED shape token to a [`ShapeType`].
fn from_token(token: &str) -> Self {
match token {
"state" => Self::State,
"county" => Self::County,
"msa" => Self::Msa,
"country" => Self::Country,
"bea" => Self::Bea,
other => Self::Other(other.to_owned()),
}
}
/// The GeoFRED query token for this shape (the `shape` parameter): `state`,
/// `county`, `msa`, `country`, `bea`. For [`ShapeType::Other`] this returns
/// the raw token.
pub fn query_code(&self) -> &str {
match self {
Self::State => "state",
Self::County => "county",
Self::Msa => "msa",
Self::Country => "country",
Self::Bea => "bea",
Self::Other(token) => token,
}
}
}
impl fmt::Display for ShapeType {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(self.query_code())
}
}
impl<'de> Deserialize<'de> for ShapeType {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
let token = String::deserialize(deserializer)?;
Ok(Self::from_token(&token))
}
}
impl Serialize for ShapeType {
/// Serializes as the GeoFRED token — symmetric with [`Deserialize`].
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
serializer.serialize_str(self.query_code())
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn known_token_maps_to_variant() {
assert_eq!(
serde_json::from_str::<ShapeType>("\"bea\"").unwrap(),
ShapeType::Bea
);
}
#[test]
fn unknown_token_is_preserved_verbatim() {
assert_eq!(
serde_json::from_str::<ShapeType>("\"necta\"").unwrap(),
ShapeType::Other("necta".to_owned())
);
}
#[test]
fn query_codes_match_fred() {
assert_eq!(ShapeType::Bea.query_code(), "bea");
assert_eq!(ShapeType::State.query_code(), "state");
assert_eq!(ShapeType::Other("necta".to_owned()).query_code(), "necta");
}
/// Every named (non-`Other`) [`ShapeType`], hand-maintained. The crate
/// declines a `strum`/`EnumIter` dependency (ADR-0030), so this list is the
/// drift anchor; [`known_list_is_exhaustive`] keeps it complete.
const KNOWN: &[ShapeType] = &[
ShapeType::State,
ShapeType::County,
ShapeType::Msa,
ShapeType::Country,
ShapeType::Bea,
];
#[test]
fn every_known_variant_round_trips_through_serde() {
for variant in KNOWN {
let json = serde_json::to_string(variant).unwrap();
let back: ShapeType = serde_json::from_str(&json).unwrap();
assert_eq!(
&back, variant,
"{variant:?} serialized to {json} but deserialized back to {back:?} — a \
named variant whose token is not wired into `from_token` is silently \
swallowed by `Other`, the exact bug ADR-0030 pins"
);
}
}
#[test]
fn known_list_is_exhaustive() {
// Compile-time drift tripwire: adding a variant makes this match
// non-exhaustive and the crate stops compiling. The fix is to add the new
// variant to `KNOWN` above, which pulls it into the round-trip test.
fn account_for_every_variant(shape_type: &ShapeType) {
match shape_type {
ShapeType::State
| ShapeType::County
| ShapeType::Msa
| ShapeType::Country
| ShapeType::Bea
| ShapeType::Other(_) => {}
}
}
account_for_every_variant(&ShapeType::State);
assert!(
KNOWN.iter().all(|v| !matches!(v, ShapeType::Other(_))),
"`KNOWN` must list only named variants, never `Other`"
);
}
}