topodb-json 0.0.1

//! JSON ↔ engine-type conversions shared by TopoDB's JSON-speaking front ends
//! (currently `topodb-mcp`; `topodb-cli` is next).
//!
//! Every function here is pure (no I/O, no `Db` access) and returns `Result<_,
//! String>` — callers are responsible for mapping the `String` into their own
//! error type (`topodb-mcp`'s `server.rs` maps it to an `rmcp::ErrorData`:
//! `invalid_params` for bad input, `internal_error` otherwise). Nothing here
//! ever panics: an unrepresentable value is always an `Err`, never an
//! `unwrap`/`expect`.

use serde_json::{Map, Value};
use std::str::FromStr;
use topodb::{
    EdgeRecord, IndexSpec, NodeRecord, PropIndex, PropValue, Props, Scope, ScopeId, ScopeSet,
    Subgraph,
};

/// Label/prop name constants for the two built-in write shapes
/// (`create_memory`/`create-memory`, `create_entity`/`create-entity`). Single
/// source of truth shared by every front end (`topodb-mcp`'s default
/// [`IndexSpec`](topodb::IndexSpec) and write tools, `topodb-cli`'s
/// `create-entity`/`create-memory` subcommands) so writes land on exactly the
/// `(label, prop)` pairs the default spec indexes — search and lookup work
/// out of the box regardless of which front end wrote the data.
pub const ENTITY_LABEL: &str = "Entity";
pub const ENTITY_NAME_PROP: &str = "name";
pub const MEMORY_LABEL: &str = "Memory";
pub const MEMORY_CONTENT_PROP: &str = "content";

/// The ONE canonical default [`IndexSpec`] for TopoDB's built-in write shapes,
/// shared by every front end (`topodb-mcp` when `--spec` is omitted;
/// `topodb-cli` when it creates a brand-new db file). Declares equality on
/// `(Entity, name)` and text on `(Memory, content)`, using the shared
/// [`ENTITY_LABEL`]/[`ENTITY_NAME_PROP`]/[`MEMORY_LABEL`]/[`MEMORY_CONTENT_PROP`]
/// constants.
///
/// Single-sourcing this is load-bearing: because a CLI-created db and an
/// MCP-created db are opened with a *byte-identical* persisted `index_spec`,
/// either front end can later serve a db the other created via `open_stored`
/// without triggering an FTS reindex or mis-declaring the equality index — and
/// both `find` (equality on `Entity`/`name`) and `search` (text on
/// `Memory`/`content`) work out of the box on a fresh db regardless of which
/// tool wrote it.
pub fn default_spec() -> IndexSpec {
    IndexSpec {
        equality: vec![PropIndex {
            label: ENTITY_LABEL.into(),
            prop: ENTITY_NAME_PROP.into(),
        }],
        text: vec![PropIndex {
            label: MEMORY_LABEL.into(),
            prop: MEMORY_CONTENT_PROP.into(),
        }],
    }
}

/// Human/JSON-facing rendering of a [`Scope`]: `"shared"` or the ULID string.
/// Reused by every front end's `info`/`db_info`-style output and scope
/// round-tripping. (Distinct from [`scope_to_json`], which wraps the same
/// rendering in a `serde_json::Value` for a JSON response body; this returns
/// a bare `String` for contexts — like a struct field — that want the label
/// without a `Value` wrapper.)
pub fn scope_label(scope: &Scope) -> String {
    match scope {
        Scope::Shared => "shared".to_string(),
        Scope::Id(id) => id.to_string(),
    }
}

/// Error string for both directions of an unrepresentable [`PropValue`]:
/// `Bytes` and `DateTime` have no JSON counterpart over MCP v0, and any JSON
/// shape that isn't a string/number/bool (array, object, null) has no
/// [`PropValue`] counterpart either.
pub const UNSUPPORTED: &str = "unsupported over MCP v0";

/// `PropValue` → `serde_json::Value`. `Str`/`Int`/`Bool` map directly; `Float`
/// maps to a JSON number (`Err` only for a non-finite float, which JSON has no
/// representation for). `Bytes`/`DateTime` are [`UNSUPPORTED`].
pub fn prop_value_to_json(v: &PropValue) -> Result<Value, String> {
    match v {
        PropValue::Str(s) => Ok(Value::String(s.clone())),
        PropValue::Int(i) => Ok(Value::Number((*i).into())),
        PropValue::Float(f) => serde_json::Number::from_f64(*f)
            .map(Value::Number)
            .ok_or_else(|| format!("{UNSUPPORTED}: non-finite float")),
        PropValue::Bool(b) => Ok(Value::Bool(*b)),
        PropValue::Bytes(_) | PropValue::DateTime(_) => Err(UNSUPPORTED.to_string()),
    }
}

/// `serde_json::Value` → `PropValue`. Strings/bools map directly. A JSON
/// integer maps to `Int` when it fits `i64`, and is an error when it doesn't
/// (`(i64::MAX, u64::MAX]` — silently downgrading it to a lossy `Float` would
/// corrupt the value); only a genuine non-integer number maps to `Float`.
/// This is the inverse of `prop_value_to_json`'s `Int`/`Float` handling.
/// Every other JSON shape (array, object, null — and, structurally, anything
/// that would have needed to round-trip through `Bytes`/`DateTime`) is
/// [`UNSUPPORTED`].
pub fn json_to_prop_value(v: &Value) -> Result<PropValue, String> {
    match v {
        Value::String(s) => Ok(PropValue::Str(s.clone())),
        Value::Bool(b) => Ok(PropValue::Bool(*b)),
        Value::Number(n) => {
            if let Some(i) = n.as_i64() {
                Ok(PropValue::Int(i))
            } else if n.is_u64() {
                // An integer above i64::MAX: representable in JSON but not in
                // PropValue::Int, and f64 can't hold it losslessly either.
                Err(format!("integer out of supported range (max {})", i64::MAX))
            } else if let Some(f) = n.as_f64() {
                Ok(PropValue::Float(f))
            } else {
                Err(format!("{UNSUPPORTED}: number out of range"))
            }
        }
        Value::Array(_) | Value::Object(_) | Value::Null => Err(UNSUPPORTED.to_string()),
    }
}

/// `Props` (a `BTreeMap<String, PropValue>`) → a JSON object, propagating the
/// first unrepresentable value as `Err`.
pub fn props_to_json(props: &Props) -> Result<Value, String> {
    let mut map = Map::with_capacity(props.len());
    for (k, v) in props {
        map.insert(k.clone(), prop_value_to_json(v)?);
    }
    Ok(Value::Object(map))
}

/// A JSON object → `Props`, propagating the first unrepresentable value as
/// `Err`. `Err` if `v` isn't a JSON object at all.
///
/// The inverse of `props_to_json`; `topodb-mcp`'s write tools (`create_entity`
/// / `create_memory` / `link`) call this on the caller-supplied `props`
/// object.
///
/// **v0 limitation:** a JSON integer literal below `i64::MIN` (e.g.
/// `-99999999999999999999`) is *already* an `f64` by the time it reaches
/// [`json_to_prop_value`] — `serde_json`'s parser itself has no `i64`-sized
/// negative bucket wide enough to hold it, so it falls back to a lossy float
/// at parse time, upstream of anything this module can inspect or reject
/// (unlike the positive out-of-range case above `i64::MAX`, which parses to
/// `u64` and so is still catchable). Undetectable and unfixable at this
/// layer without `serde_json`'s `arbitrary_precision` feature; documented
/// here as a known v0 gap rather than silently accepted as correct.
pub fn json_to_props(v: &Value) -> Result<Props, String> {
    let obj = v
        .as_object()
        .ok_or_else(|| "expected a JSON object for props".to_string())?;
    let mut props = Props::new();
    for (k, val) in obj {
        props.insert(k.clone(), json_to_prop_value(val)?);
    }
    Ok(props)
}

/// Builds the `Props` map for a write tool that has one required, caller-named
/// field (`create_memory`'s `content`, `create_entity`'s `name`) plus an
/// optional JSON `props` object of additional metadata. `key`/`value` are the
/// required field, already converted to a `PropValue`; `extra` is the tool
/// call's optional `props` param, converted via `json_to_props`.
///
/// `Err` if `extra` (once converted) already contains `key` — a collision
/// with the required field is a caller error to be corrected, never silently
/// overwritten. `Err` also propagates straight through from `json_to_props`
/// (non-object `extra`, or an unrepresentable value inside it).
pub fn merge_required_prop(
    key: &str,
    value: PropValue,
    extra: Option<&Value>,
) -> Result<Props, String> {
    let mut props = match extra {
        Some(v) => json_to_props(v)?,
        None => Props::new(),
    };
    if props.contains_key(key) {
        return Err(format!(
            "props must not include {key:?}: it is already set from the tool's own parameter"
        ));
    }
    props.insert(key.to_string(), value);
    Ok(props)
}

/// A `Scope` → its JSON rendering: `"shared"` or the scope's ULID string.
/// Mirrors the `shared`/ULID label convention used across TopoDB's JSON-facing
/// front ends (e.g. `topodb-mcp`'s `db_info` tool).
pub fn scope_to_json(scope: Scope) -> Value {
    Value::String(match scope {
        Scope::Shared => "shared".to_string(),
        Scope::Id(id) => id.to_string(),
    })
}

/// A `NodeRecord` → JSON: `id`/`label` as strings (ULID via `Display` for
/// `id`), `scope` per [`scope_to_json`], and `props` per [`props_to_json`].
/// Deliberately omits the `embedding` field — no MCP v0 tool surfaces vector
/// data (that's a later concern via dedicated embedding tools).
pub fn node_to_json(n: &NodeRecord) -> Result<Value, String> {
    let mut map = Map::new();
    map.insert("id".into(), Value::String(n.id.to_string()));
    map.insert("scope".into(), scope_to_json(n.scope));
    map.insert("label".into(), Value::String(n.label.to_string()));
    map.insert("props".into(), props_to_json(&n.props)?);
    Ok(Value::Object(map))
}

/// An `EdgeRecord` → JSON: `id`/`from`/`to` as ULID strings, `type` for `ty`
/// (JSON-friendlier than the Rust keyword-adjacent field name), `scope` per
/// [`scope_to_json`], `props` per [`props_to_json`], and the temporal bounds
/// `valid_from`/`valid_to` (`valid_to` is `null` while the edge is open).
pub fn edge_to_json(e: &EdgeRecord) -> Result<Value, String> {
    let mut map = Map::new();
    map.insert("id".into(), Value::String(e.id.to_string()));
    map.insert("scope".into(), scope_to_json(e.scope));
    map.insert("type".into(), Value::String(e.ty.to_string()));
    map.insert("from".into(), Value::String(e.from.to_string()));
    map.insert("to".into(), Value::String(e.to.to_string()));
    map.insert("props".into(), props_to_json(&e.props)?);
    map.insert("valid_from".into(), Value::Number(e.valid_from.into()));
    map.insert(
        "valid_to".into(),
        match e.valid_to {
            Some(t) => Value::Number(t.into()),
            None => Value::Null,
        },
    );
    Ok(Value::Object(map))
}

/// A `Subgraph` → `{"nodes": [...], "edges": [...]}`, each element per
/// [`node_to_json`]/[`edge_to_json`].
pub fn subgraph_to_json(sg: &Subgraph) -> Result<Value, String> {
    let nodes: Vec<Value> = sg
        .nodes
        .iter()
        .map(node_to_json)
        .collect::<Result<_, _>>()?;
    let edges: Vec<Value> = sg
        .edges
        .iter()
        .map(edge_to_json)
        .collect::<Result<_, _>>()?;
    Ok(serde_json::json!({ "nodes": nodes, "edges": edges }))
}

/// Resolves a tool's optional `scope` string param to a `Scope`: `None` →
/// `default` (the server's configured default scope); `Some("shared")`
/// (case-insensitive) → `Scope::Shared`; `Some(<ulid>)` → `Scope::Id`; any
/// other string → a clear `Err`. Mirrors `topodb-mcp`'s `config::parse_scope`
/// "shared" / ULID contract, generalized to the `Option` (tool-call) case.
pub fn resolve_scope(scope: Option<&str>, default: Scope) -> Result<Scope, String> {
    match scope {
        None => Ok(default),
        Some(s) if s.eq_ignore_ascii_case("shared") => Ok(Scope::Shared),
        Some(s) => ScopeId::from_str(s)
            .map(Scope::Id)
            .map_err(|e| format!("invalid scope {s:?} (expected \"shared\" or a ULID): {e}")),
    }
}

/// A resolved `Scope` → the singleton `ScopeSet` a read call needs: `Shared`
/// admits only the shared scope, `Id(id)` admits only that one scope id.
pub fn scope_to_scope_set(scope: Scope) -> ScopeSet {
    match scope {
        Scope::Shared => ScopeSet::default().with_shared(),
        Scope::Id(id) => ScopeSet::of(&[id]),
    }
}

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

    fn props(pairs: &[(&str, PropValue)]) -> Props {
        pairs
            .iter()
            .cloned()
            .map(|(k, v)| (k.to_string(), v))
            .collect()
    }

    // --- PropValue <-> Value: Str/Int/Bool both ways ---

    #[test]
    fn str_round_trips() {
        let v = PropValue::Str("hello".into());
        let j = prop_value_to_json(&v).unwrap();
        assert_eq!(j, Value::String("hello".into()));
        assert_eq!(json_to_prop_value(&j).unwrap(), v);
    }

    #[test]
    fn int_round_trips() {
        let v = PropValue::Int(-42);
        let j = prop_value_to_json(&v).unwrap();
        assert_eq!(j, serde_json::json!(-42));
        assert_eq!(json_to_prop_value(&j).unwrap(), v);
    }

    #[test]
    fn bool_round_trips() {
        for b in [true, false] {
            let v = PropValue::Bool(b);
            let j = prop_value_to_json(&v).unwrap();
            assert_eq!(j, Value::Bool(b));
            assert_eq!(json_to_prop_value(&j).unwrap(), v);
        }
    }

    // --- Float <-> JSON number: JSON int -> Int, JSON float -> Float ---

    #[test]
    fn float_to_json_is_a_json_number() {
        let v = PropValue::Float(3.5);
        let j = prop_value_to_json(&v).unwrap();
        assert_eq!(j, serde_json::json!(3.5));
    }

    #[test]
    fn json_integer_literal_decodes_to_int_not_float() {
        let j = serde_json::json!(7);
        assert_eq!(json_to_prop_value(&j).unwrap(), PropValue::Int(7));
    }

    #[test]
    fn json_float_literal_decodes_to_float() {
        let j = serde_json::json!(7.5);
        assert_eq!(json_to_prop_value(&j).unwrap(), PropValue::Float(7.5));
    }

    #[test]
    fn i64_max_round_trips_as_int() {
        let v = PropValue::Int(i64::MAX);
        let j = prop_value_to_json(&v).unwrap();
        assert_eq!(j, serde_json::json!(i64::MAX));
        assert_eq!(json_to_prop_value(&j).unwrap(), v);
    }

    #[test]
    fn json_integer_above_i64_max_is_an_error_not_a_lossy_float() {
        let j = serde_json::json!(u64::MAX);
        let err = json_to_prop_value(&j).unwrap_err();
        assert!(
            err.contains("integer out of supported range"),
            "expected a clear out-of-range error, got: {err}"
        );
        // And just past the i64 boundary too, not only at the extreme.
        let j = serde_json::json!(i64::MAX as u64 + 1);
        assert!(json_to_prop_value(&j).is_err());
    }

    #[test]
    fn non_finite_float_to_json_is_an_error() {
        assert!(prop_value_to_json(&PropValue::Float(f64::NAN)).is_err());
        assert!(prop_value_to_json(&PropValue::Float(f64::INFINITY)).is_err());
    }

    // --- Bytes/DateTime unsupported, both directions ---

    #[test]
    fn bytes_to_json_is_unsupported() {
        let err = prop_value_to_json(&PropValue::Bytes(vec![1, 2, 3])).unwrap_err();
        assert_eq!(err, UNSUPPORTED);
    }

    #[test]
    fn datetime_to_json_is_unsupported() {
        let err = prop_value_to_json(&PropValue::DateTime(123)).unwrap_err();
        assert_eq!(err, UNSUPPORTED);
    }

    #[test]
    fn json_array_to_propvalue_is_unsupported() {
        let err = json_to_prop_value(&serde_json::json!([1, 2])).unwrap_err();
        assert_eq!(err, UNSUPPORTED);
    }

    #[test]
    fn json_object_to_propvalue_is_unsupported() {
        let err = json_to_prop_value(&serde_json::json!({"a": 1})).unwrap_err();
        assert_eq!(err, UNSUPPORTED);
    }

    #[test]
    fn json_null_to_propvalue_is_unsupported() {
        let err = json_to_prop_value(&Value::Null).unwrap_err();
        assert_eq!(err, UNSUPPORTED);
    }

    // --- Props <-> JSON object ---

    #[test]
    fn props_round_trip() {
        let p = props(&[
            ("name", PropValue::Str("ada".into())),
            ("age", PropValue::Int(30)),
            ("active", PropValue::Bool(true)),
            ("score", PropValue::Float(1.5)),
        ]);
        let j = props_to_json(&p).unwrap();
        assert!(j.is_object());
        let back = json_to_props(&j).unwrap();
        assert_eq!(back, p);
    }

    #[test]
    fn props_to_json_propagates_unsupported_value() {
        let p = props(&[("blob", PropValue::Bytes(vec![9]))]);
        assert!(props_to_json(&p).is_err());
    }

    #[test]
    fn json_to_props_rejects_non_object() {
        assert!(json_to_props(&serde_json::json!([1, 2])).is_err());
    }

    #[test]
    fn json_to_props_propagates_unsupported_field() {
        let j = serde_json::json!({"bad": [1, 2]});
        assert!(json_to_props(&j).is_err());
    }

    // --- merge_required_prop: the create_memory/create_entity collision rule ---

    #[test]
    fn merge_required_prop_with_no_extra_just_sets_the_key() {
        let props = merge_required_prop("content", PropValue::Str("hi".into()), None).unwrap();
        assert_eq!(props.len(), 1);
        assert_eq!(props["content"], PropValue::Str("hi".into()));
    }

    #[test]
    fn merge_required_prop_merges_additional_fields() {
        let extra = serde_json::json!({"source": "chat", "confidence": 3});
        let props =
            merge_required_prop("content", PropValue::Str("hi".into()), Some(&extra)).unwrap();
        assert_eq!(props.len(), 3);
        assert_eq!(props["content"], PropValue::Str("hi".into()));
        assert_eq!(props["source"], PropValue::Str("chat".into()));
        assert_eq!(props["confidence"], PropValue::Int(3));
    }

    #[test]
    fn merge_required_prop_rejects_collision_with_required_key() {
        let extra = serde_json::json!({"content": "sneaky overwrite"});
        let err =
            merge_required_prop("content", PropValue::Str("hi".into()), Some(&extra)).unwrap_err();
        assert!(
            err.contains("content"),
            "error should name the colliding key: {err}"
        );
        // And the same for `name` (create_entity's required key), to confirm
        // this isn't hardcoded to "content".
        let extra = serde_json::json!({"name": "sneaky"});
        assert!(merge_required_prop("name", PropValue::Str("ada".into()), Some(&extra)).is_err());
    }

    #[test]
    fn merge_required_prop_does_not_overwrite_on_collision() {
        // The collision must be rejected outright, not silently resolved by
        // either value winning — assert no props map is returned at all.
        let extra = serde_json::json!({"content": "other"});
        let result = merge_required_prop("content", PropValue::Str("mine".into()), Some(&extra));
        assert!(result.is_err());
    }

    #[test]
    fn merge_required_prop_propagates_non_object_extra() {
        let extra = serde_json::json!([1, 2]);
        assert!(merge_required_prop("content", PropValue::Str("hi".into()), Some(&extra)).is_err());
    }

    // --- node/edge/subgraph -> JSON ---

    fn sample_node(scope: Scope) -> NodeRecord {
        NodeRecord {
            id: NodeId::new(),
            scope,
            label: "Entity".into(),
            props: props(&[("name", PropValue::Str("ada".into()))]),
            embedding: None,
        }
    }

    fn sample_edge(scope: Scope, from: NodeId, to: NodeId) -> EdgeRecord {
        EdgeRecord {
            id: topodb::EdgeId::new(),
            scope,
            ty: "ABOUT".into(),
            from,
            to,
            props: Props::new(),
            valid_from: 1_000,
            valid_to: None,
        }
    }

    #[test]
    fn node_to_json_has_ulid_id_and_declared_fields() {
        let scope = Scope::Id(ScopeId::new());
        let n = sample_node(scope);
        let j = node_to_json(&n).unwrap();
        assert_eq!(j["id"], Value::String(n.id.to_string()));
        assert_eq!(j["label"], Value::String("Entity".into()));
        assert_eq!(j["scope"], scope_to_json(scope));
        assert_eq!(j["props"]["name"], Value::String("ada".into()));
        // `id` round-trips through NodeId's ULID Display/FromStr.
        let parsed: NodeId = j["id"].as_str().unwrap().parse().unwrap();
        assert_eq!(parsed, n.id);
    }

    #[test]
    fn node_to_json_propagates_unsupported_prop() {
        let mut n = sample_node(Scope::Shared);
        n.props.insert("blob".into(), PropValue::Bytes(vec![1]));
        assert!(node_to_json(&n).is_err());
    }

    #[test]
    fn edge_to_json_has_ulid_ids_and_temporal_bounds() {
        let scope = Scope::Shared;
        let a = NodeId::new();
        let b = NodeId::new();
        let e = sample_edge(scope, a, b);
        let j = edge_to_json(&e).unwrap();
        assert_eq!(j["id"], Value::String(e.id.to_string()));
        assert_eq!(j["from"], Value::String(a.to_string()));
        assert_eq!(j["to"], Value::String(b.to_string()));
        assert_eq!(j["type"], Value::String("ABOUT".into()));
        assert_eq!(j["valid_from"], serde_json::json!(1_000));
        assert_eq!(j["valid_to"], Value::Null);
    }

    #[test]
    fn edge_to_json_closed_edge_has_numeric_valid_to() {
        let mut e = sample_edge(Scope::Shared, NodeId::new(), NodeId::new());
        e.valid_to = Some(2_000);
        let j = edge_to_json(&e).unwrap();
        assert_eq!(j["valid_to"], serde_json::json!(2_000));
    }

    #[test]
    fn subgraph_to_json_nests_nodes_and_edges() {
        let scope = Scope::Shared;
        let a = sample_node(scope);
        let b = sample_node(scope);
        let e = sample_edge(scope, a.id, b.id);
        let sg = Subgraph {
            nodes: vec![a.clone(), b.clone()],
            edges: vec![e.clone()],
        };
        let j = subgraph_to_json(&sg).unwrap();
        assert_eq!(j["nodes"].as_array().unwrap().len(), 2);
        assert_eq!(j["edges"].as_array().unwrap().len(), 1);
        assert_eq!(j["edges"][0]["id"], Value::String(e.id.to_string()));
    }

    // --- scope resolution ---

    #[test]
    fn resolve_scope_none_uses_default() {
        let id = ScopeId::new();
        assert_eq!(resolve_scope(None, Scope::Shared).unwrap(), Scope::Shared);
        assert_eq!(resolve_scope(None, Scope::Id(id)).unwrap(), Scope::Id(id));
    }

    #[test]
    fn resolve_scope_shared_is_case_insensitive() {
        assert_eq!(
            resolve_scope(Some("shared"), Scope::Id(ScopeId::new())).unwrap(),
            Scope::Shared
        );
        assert_eq!(
            resolve_scope(Some("SHARED"), Scope::Id(ScopeId::new())).unwrap(),
            Scope::Shared
        );
    }

    #[test]
    fn resolve_scope_ulid_parses_to_id() {
        let id = ScopeId::new();
        let s = id.to_string();
        assert_eq!(
            resolve_scope(Some(&s), Scope::Shared).unwrap(),
            Scope::Id(id)
        );
    }

    #[test]
    fn resolve_scope_garbage_is_a_clear_error() {
        let err = resolve_scope(Some("not-a-ulid"), Scope::Shared).unwrap_err();
        assert!(err.contains("not-a-ulid"));
    }

    #[test]
    fn scope_to_scope_set_shared_admits_only_shared() {
        let set = scope_to_scope_set(Scope::Shared);
        assert!(set.contains(Scope::Shared));
        assert!(!set.contains(Scope::Id(ScopeId::new())));
    }

    #[test]
    fn scope_to_scope_set_id_admits_only_that_id() {
        let id = ScopeId::new();
        let set = scope_to_scope_set(Scope::Id(id));
        assert!(set.contains(Scope::Id(id)));
        assert!(!set.contains(Scope::Shared));
        assert!(!set.contains(Scope::Id(ScopeId::new())));
    }
}