parse-rust-core 0.1.0

//! The `ParseValue` model: every JSON value a client can send or receive in an object body.
//!
//! Two decisions here are load-bearing, and both look like mistakes until the reason is stated.
//!
//! **`ParseMap` preserves key order.** Several upstream behaviors iterate object keys, and the
//! resulting order is observable in golden-file comparison even where it is not semantically
//! meaningful. A `HashMap` destroys it on every round trip and makes snapshot testing impossible.
//!
//! **Nothing here derives `PartialEq`.** A derived one would compile, read as correct, and get
//! both float edge cases backwards at the one call site that decides which keys a client is told
//! about. Use [`deep_strict_eq`], which implements Node's `util.isDeepStrictEqual` semantics.

use indexmap::IndexMap;

use crate::date::ParseDate;
use crate::js_number;

/// An order-preserving string-keyed map. See the module note.
pub type ParseMap = IndexMap<String, ParseValue>;

/// A Parse value.
///
/// The data plane stays dynamic on purpose. There is no compile-time struct per application
/// class, because the schema does not exist at compile time. `Object` and `Array` contents are
/// deliberately opaque.
///
/// Deliberately no `PartialEq`. See the module note.
///
/// **Deliberately not `#[non_exhaustive]`, either**, and that is the opposite of the usual
/// advice. `non_exhaustive` lets a downstream crate keep compiling when a variant is added, by
/// forcing it to carry a wildcard arm. For this type that is precisely the wrong trade: every
/// consumer is a *total* function over the value space, an encoder, a decoder, a storage
/// transform, an equality predicate, and a wildcard arm in any of them is a silent data-loss bug
/// waiting for the next variant. The whole premise of writing this in Rust is that forgetting a
/// case is a compile error; `non_exhaustive` on this enum would make that false across exactly
/// the crate boundary that matters.
///
/// Adding a variant here is a breaking change on purpose. `ErrorCode` keeps `non_exhaustive`,
/// because nobody exhaustively matches sixty error codes and a new one genuinely is additive.
#[derive(Debug, Clone)]
pub enum ParseValue {
    Null,
    Bool(bool),
    /// JavaScript has exactly one number type. Matching its lossiness above 2^53 is the goal,
    /// not avoiding it.
    Number(f64),
    String(String),
    Array(Vec<ParseValue>),
    Object(ParseMap),
    /// `{"__type":"Date","iso":"..."}`, or a bare ISO string at `createdAt`/`updatedAt`.
    Date(ParseDate),
    /// `{"__type":"Pointer","className":"...","objectId":"..."}`
    Pointer {
        class_name: String,
        object_id: String,
    },
    /// `{"__type":"GeoPoint","latitude":n,"longitude":n}`
    GeoPoint {
        latitude: f64,
        longitude: f64,
    },
    /// `{"__type":"Bytes","base64":"..."}`. Held decoded, because Mongo stores BSON Binary and
    /// re-encoding from a canonical byte slice is what keeps the two backends agreeing.
    Bytes(Vec<u8>),
    /// `{"__type":"File","name":"...","url":"..."}`. `url` is absent on a file pointer that has
    /// not been through `expandFilesInObject`, so it is optional rather than defaulted.
    File {
        name: String,
        url: Option<String>,
    },
    /// `{"__type":"Polygon","coordinates":[[lat,lng],...]}`
    ///
    /// Note the axis order: Parse's wire form is **latitude first**, the reverse of GeoJSON.
    /// `PolygonCoder.databaseToJSON` swaps on the way out (`MongoTransform.js:1362-1372`), so
    /// holding it in wire order keeps that swap confined to the Mongo boundary.
    Polygon(Vec<(f64, f64)>),
    /// `{"__type":"Relation","className":"..."}`
    Relation {
        class_name: String,
    },
}

impl ParseValue {
    /// Serialize to the exact bytes Parse Server would emit.
    ///
    /// Numbers go through [`js_number::to_ecma_string`] rather than any Rust float formatter,
    /// for the reasons in that module. Non-finite numbers become `null`, which is what
    /// `JSON.stringify` does; `to_ecma_string` alone would emit `NaN`, which is not valid JSON.
    pub fn to_json(&self) -> String {
        let mut s = String::new();
        self.write_json(&mut s);
        s
    }

    fn write_json(&self, out: &mut String) {
        match self {
            ParseValue::Null => out.push_str("null"),
            ParseValue::Bool(true) => out.push_str("true"),
            ParseValue::Bool(false) => out.push_str("false"),
            ParseValue::Number(n) => {
                if n.is_finite() {
                    out.push_str(&js_number::to_ecma_string(*n));
                } else {
                    // JSON.stringify(NaN) === "null", same for both infinities.
                    out.push_str("null");
                }
            }
            ParseValue::String(s) => write_json_string(s, out),
            ParseValue::Array(items) => {
                out.push('[');
                for (i, v) in items.iter().enumerate() {
                    if i > 0 {
                        out.push(',');
                    }
                    v.write_json(out);
                }
                out.push(']');
            }
            ParseValue::Object(map) => {
                out.push('{');
                for (i, (k, v)) in map.iter().enumerate() {
                    if i > 0 {
                        out.push(',');
                    }
                    write_json_string(k, out);
                    out.push(':');
                    v.write_json(out);
                }
                out.push('}');
            }
            ParseValue::Date(d) => {
                out.push_str(r#"{"__type":"Date","iso":"#);
                write_json_string(&d.to_iso(), out);
                out.push('}');
            }
            ParseValue::Pointer {
                class_name,
                object_id,
            } => {
                out.push_str(r#"{"__type":"Pointer","className":"#);
                write_json_string(class_name, out);
                out.push_str(r#","objectId":"#);
                write_json_string(object_id, out);
                out.push('}');
            }
            ParseValue::GeoPoint {
                latitude,
                longitude,
            } => {
                out.push_str(r#"{"__type":"GeoPoint","latitude":"#);
                out.push_str(&js_number::to_ecma_string(*latitude));
                out.push_str(r#","longitude":"#);
                out.push_str(&js_number::to_ecma_string(*longitude));
                out.push('}');
            }
            ParseValue::Bytes(raw) => {
                out.push_str(r#"{"__type":"Bytes","base64":"#);
                write_json_string(&base64_encode(raw), out);
                out.push('}');
            }
            ParseValue::File { name, url } => {
                out.push_str(r#"{"__type":"File","name":"#);
                write_json_string(name, out);
                if let Some(u) = url {
                    out.push_str(r#","url":"#);
                    write_json_string(u, out);
                }
                out.push('}');
            }
            ParseValue::Polygon(coords) => {
                out.push_str(r#"{"__type":"Polygon","coordinates":["#);
                for (i, (lat, lng)) in coords.iter().enumerate() {
                    if i > 0 {
                        out.push(',');
                    }
                    out.push('[');
                    out.push_str(&js_number::to_ecma_string(*lat));
                    out.push(',');
                    out.push_str(&js_number::to_ecma_string(*lng));
                    out.push(']');
                }
                out.push_str("]}");
            }
            ParseValue::Relation { class_name } => {
                out.push_str(r#"{"__type":"Relation","className":"#);
                write_json_string(class_name, out);
                out.push('}');
            }
        }
    }
}

/// Standard base64 with padding, matching what `BytesCoder` accepts
/// (`MongoTransform.js:1306`). Hand-rolled to keep `parse-rust-core` dependency-light; it is 20 lines
/// and the alphabet is fixed by the wire format.
pub(crate) fn base64_encode(data: &[u8]) -> String {
    const T: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    let mut out = String::with_capacity(data.len().div_ceil(3) * 4);
    for chunk in data.chunks(3) {
        let b = [
            chunk[0],
            *chunk.get(1).unwrap_or(&0),
            *chunk.get(2).unwrap_or(&0),
        ];
        let n = ((b[0] as u32) << 16) | ((b[1] as u32) << 8) | b[2] as u32;
        out.push(T[(n >> 18) as usize & 63] as char);
        out.push(T[(n >> 12) as usize & 63] as char);
        out.push(if chunk.len() > 1 {
            T[(n >> 6) as usize & 63] as char
        } else {
            '='
        });
        out.push(if chunk.len() > 2 {
            T[n as usize & 63] as char
        } else {
            '='
        });
    }
    out
}

/// The inverse. Rejects any character outside the alphabet rather than skipping it, because a
/// lenient decoder would silently accept a corrupted payload from an untrusted client.
pub(crate) fn base64_decode(s: &str) -> Option<Vec<u8>> {
    let mut acc: u32 = 0;
    let mut bits = 0u32;
    let mut out = Vec::with_capacity(s.len() / 4 * 3);
    for c in s.bytes() {
        let v = match c {
            b'A'..=b'Z' => c - b'A',
            b'a'..=b'z' => c - b'a' + 26,
            b'0'..=b'9' => c - b'0' + 52,
            b'+' => 62,
            b'/' => 63,
            b'=' => break,
            _ => return None,
        } as u32;
        acc = (acc << 6) | v;
        bits += 6;
        if bits >= 8 {
            bits -= 8;
            out.push((acc >> bits) as u8);
        }
    }
    Some(out)
}

/// JSON string escaping, matching `JSON.stringify`: the two mandatory escapes, the five
/// short forms, and `\u00XX` for the rest of the C0 range. Characters above 0x1F are emitted
/// as-is, including non-ASCII, which is what Node does.
pub(crate) fn write_json_string(s: &str, out: &mut String) {
    out.push('"');
    for c in s.chars() {
        match c {
            '"' => out.push_str("\\\""),
            '\\' => out.push_str("\\\\"),
            '\n' => out.push_str("\\n"),
            '\r' => out.push_str("\\r"),
            '\t' => out.push_str("\\t"),
            '\u{08}' => out.push_str("\\b"),
            '\u{0c}' => out.push_str("\\f"),
            c if (c as u32) < 0x20 => {
                out.push_str(&format!("\\u{:04x}", c as u32));
            }
            c => out.push(c),
        }
    }
    out.push('"');
}

/// Deep equality with Node's `util.isDeepStrictEqual` semantics.
///
/// Two float cases differ from what a derived `PartialEq` would do, and both are reachable:
/// Node compares primitives with `Object.is`, so **`NaN` equals `NaN`** and **`+0.0` does not
/// equal `-0.0`**. `JSON.parse("-0")` yields `-0`, and a stored BSON double can be `-0`, so this
/// is not theoretical.
///
/// Note the deliberate tension with the encoder: `-0.0` and `0.0` compare as distinct here and
/// serialize identically (both as `0`). Both are correct, and both must hold at once.
pub fn deep_strict_eq(a: &ParseValue, b: &ParseValue) -> bool {
    use ParseValue::*;
    match (a, b) {
        (Null, Null) => true,
        (Bool(x), Bool(y)) => x == y,
        (Number(x), Number(y)) => js_object_is(*x, *y),
        (String(x), String(y)) => x == y,
        (Array(x), Array(y)) => {
            x.len() == y.len() && x.iter().zip(y).all(|(i, j)| deep_strict_eq(i, j))
        }
        (Object(x), Object(y)) => {
            // Key *order* is preserved by ParseMap but is not part of equality, matching Node,
            // where two objects with the same keys in different orders are deep-strict-equal.
            x.len() == y.len()
                && x.iter()
                    .all(|(k, v)| y.get(k).is_some_and(|w| deep_strict_eq(v, w)))
        }
        (Date(x), Date(y)) => x == y,
        (
            Pointer {
                class_name: c1,
                object_id: o1,
            },
            Pointer {
                class_name: c2,
                object_id: o2,
            },
        ) => c1 == c2 && o1 == o2,
        (
            GeoPoint {
                latitude: la1,
                longitude: lo1,
            },
            GeoPoint {
                latitude: la2,
                longitude: lo2,
            },
        ) => js_object_is(*la1, *la2) && js_object_is(*lo1, *lo2),
        (Bytes(x), Bytes(y)) => x == y,
        (File { name: n1, url: u1 }, File { name: n2, url: u2 }) => n1 == n2 && u1 == u2,
        (Polygon(x), Polygon(y)) => {
            x.len() == y.len()
                && x.iter()
                    .zip(y)
                    .all(|(a, b)| js_object_is(a.0, b.0) && js_object_is(a.1, b.1))
        }
        (Relation { class_name: c1 }, Relation { class_name: c2 }) => c1 == c2,
        _ => false,
    }
}

/// `Object.is` for f64: NaN equals NaN, and zeros differ by sign.
fn js_object_is(x: f64, y: f64) -> bool {
    if x.is_nan() && y.is_nan() {
        return true;
    }
    x == y && x.is_sign_negative() == y.is_sign_negative()
}

#[cfg(test)]
mod tests {
    use super::*;

    fn n(v: f64) -> ParseValue {
        ParseValue::Number(v)
    }
    fn s(v: &str) -> ParseValue {
        ParseValue::String(v.to_string())
    }

    #[test]
    fn numbers_serialize_through_the_ecmascript_formatter() {
        assert_eq!(n(100.0).to_json(), "100");
        assert_eq!(n(1e20).to_json(), "100000000000000000000");
        assert_eq!(n(1e-6).to_json(), "0.000001");
        assert_eq!(n(-0.0).to_json(), "0");
    }

    #[test]
    fn non_finite_numbers_become_null_not_nan() {
        assert_eq!(n(f64::NAN).to_json(), "null");
        assert_eq!(n(f64::INFINITY).to_json(), "null");
        assert_eq!(n(f64::NEG_INFINITY).to_json(), "null");
    }

    #[test]
    fn object_key_order_survives_serialization() {
        let mut m = ParseMap::new();
        m.insert("zebra".into(), n(1.0));
        m.insert("apple".into(), n(2.0));
        m.insert("mango".into(), n(3.0));
        assert_eq!(
            ParseValue::Object(m).to_json(),
            r#"{"zebra":1,"apple":2,"mango":3}"#,
            "insertion order must be preserved, not sorted"
        );
    }

    #[test]
    fn tagged_types_have_the_upstream_key_order() {
        let d = ParseDate::parse_iso("2026-08-14T13:34:33.581Z").unwrap();
        assert_eq!(
            ParseValue::Date(d).to_json(),
            r#"{"__type":"Date","iso":"2026-08-14T13:34:33.581Z"}"#
        );
        assert_eq!(
            ParseValue::Pointer {
                class_name: "_User".into(),
                object_id: "abc123".into()
            }
            .to_json(),
            r#"{"__type":"Pointer","className":"_User","objectId":"abc123"}"#
        );
        assert_eq!(
            ParseValue::GeoPoint {
                latitude: 40.0,
                longitude: -75.5
            }
            .to_json(),
            r#"{"__type":"GeoPoint","latitude":40,"longitude":-75.5}"#
        );
    }

    #[test]
    fn string_escaping_matches_json_stringify() {
        assert_eq!(s(r#"a"b"#).to_json(), r#""a\"b""#);
        assert_eq!(s("a\\b").to_json(), r#""a\\b""#);
        assert_eq!(s("a\nb").to_json(), r#""a\nb""#);
        // C0 controls take the \u00xx form, lowercase hex. Verified against Node:
        //   JSON.stringify("a" + String.fromCharCode(1) + "b")  ->  "a\\u0001b"
        assert_eq!(s("a\u{1}b").to_json(), "\"a\\u0001b\"");
        assert_eq!(s("a\u{1f}b").to_json(), "\"a\\u001fb\"");
        // Non-ASCII is emitted raw, as Node does.
        assert_eq!(s("héllo").to_json(), "\"héllo\"");
    }

    #[test]
    fn deep_strict_eq_follows_object_is_on_floats() {
        // The two cases a derived PartialEq gets backwards.
        assert!(
            deep_strict_eq(&n(f64::NAN), &n(f64::NAN)),
            "NaN must equal NaN"
        );
        assert!(!deep_strict_eq(&n(0.0), &n(-0.0)), "+0 must not equal -0");
        assert!(deep_strict_eq(&n(0.0), &n(0.0)));
        assert!(deep_strict_eq(&n(-0.0), &n(-0.0)));
    }

    #[test]
    fn minus_zero_compares_distinct_but_serializes_identically() {
        // Both properties are required at once. This test exists to stop someone "fixing" one.
        assert!(!deep_strict_eq(&n(0.0), &n(-0.0)));
        assert_eq!(n(0.0).to_json(), n(-0.0).to_json());
    }

    #[test]
    fn deep_strict_eq_ignores_key_order_but_not_content() {
        let mut a = ParseMap::new();
        a.insert("x".into(), n(1.0));
        a.insert("y".into(), n(2.0));
        let mut b = ParseMap::new();
        b.insert("y".into(), n(2.0));
        b.insert("x".into(), n(1.0));
        assert!(deep_strict_eq(
            &ParseValue::Object(a.clone()),
            &ParseValue::Object(b)
        ));

        let mut c = ParseMap::new();
        c.insert("x".into(), n(1.0));
        assert!(!deep_strict_eq(
            &ParseValue::Object(a),
            &ParseValue::Object(c)
        ));
    }

    #[test]
    fn deep_strict_eq_is_recursive_and_type_strict() {
        let nested = |v: ParseValue| ParseValue::Array(vec![ParseValue::Array(vec![v])]);
        assert!(deep_strict_eq(&nested(n(1.0)), &nested(n(1.0))));
        assert!(!deep_strict_eq(&nested(n(1.0)), &nested(n(2.0))));
        // No cross-type coercion: 1 is not "1" and not true.
        assert!(!deep_strict_eq(&n(1.0), &s("1")));
        assert!(!deep_strict_eq(&n(1.0), &ParseValue::Bool(true)));
        assert!(!deep_strict_eq(&ParseValue::Null, &ParseValue::Bool(false)));
    }
}