ucp-schema 1.3.0

//! Core types for UCP schema resolution.

use serde::{Deserialize, Serialize};
use serde_json::Value;

/// Schema transition: from/to are visibility values (omit, optional, required).
/// During the transition period the field is always the `from` visibility.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct SchemaTransitionInfo {
    pub from: String,
    pub to: String,
    pub description: String,
}

/// Valid UCP operations for annotation object form.
pub const VALID_OPERATIONS: &[&str] = &["create", "update", "complete", "read"];

/// UCP annotation keys.
pub const UCP_ANNOTATIONS: &[&str] = &["ucp_request", "ucp_response"];

/// Returns the JSON type name for error messages.
pub fn json_type_name(value: &Value) -> &'static str {
    match value {
        Value::Null => "null",
        Value::Bool(_) => "boolean",
        Value::Number(_) => "number",
        Value::String(_) => "string",
        Value::Array(_) => "array",
        Value::Object(_) => "object",
    }
}

/// Direction of the schema transformation.
///
/// Determines whether to use `ucp_request` or `ucp_response` annotations.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum Direction {
    Request,
    Response,
}

impl Direction {
    /// Returns the annotation key for this direction.
    pub fn annotation_key(&self) -> &'static str {
        match self {
            Direction::Request => "ucp_request",
            Direction::Response => "ucp_response",
        }
    }

    /// Returns the bare direction string ("request" / "response").
    ///
    /// Used to build container operation-shape keys (`{op}_{direction}`,
    /// e.g. `search_response`) when selecting the validation target for
    /// container-shaped capabilities.
    pub fn dir_str(&self) -> &'static str {
        match self {
            Direction::Request => "request",
            Direction::Response => "response",
        }
    }

    /// Create direction from a request flag (true = Request, false = Response).
    pub fn from_request_flag(is_request: bool) -> Self {
        if is_request {
            Direction::Request
        } else {
            Direction::Response
        }
    }
}

/// Visibility of a field after resolution.
///
/// Determines how a field is transformed in the output schema.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
pub enum Visibility {
    /// No transformation - keep field as-is with original required status.
    #[default]
    Include,
    /// Remove field from properties and required array.
    Omit,
    /// Keep field and ensure it's in the required array.
    Required,
    /// Keep field but remove from required array.
    Optional,
}

impl Visibility {
    /// Parse a visibility value from a string.
    ///
    /// Returns `None` for unknown values (caller should error).
    pub fn parse(s: &str) -> Option<Self> {
        match s {
            "omit" => Some(Visibility::Omit),
            "required" => Some(Visibility::Required),
            "optional" => Some(Visibility::Optional),
            _ => None,
        }
    }
}

/// Returns true if (from, to) is a valid schema transition: both are visibility
/// values (omit, optional, required) and from != to.
pub fn is_valid_schema_transition(from: &str, to: &str) -> bool {
    from != to && Visibility::parse(from).is_some() && Visibility::parse(to).is_some()
}

// ---------------------------------------------------------------------------
// Version constraints (`requires` on extension schemas)
// ---------------------------------------------------------------------------

/// Check if a string is a valid UCP version (YYYY-MM-DD with valid month/day).
pub fn is_valid_version(s: &str) -> bool {
    if s.len() != 10 || s.as_bytes()[4] != b'-' || s.as_bytes()[7] != b'-' {
        return false;
    }
    if !s.bytes().enumerate().all(|(i, b)| {
        if i == 4 || i == 7 {
            b == b'-'
        } else {
            b.is_ascii_digit()
        }
    }) {
        return false;
    }
    let month: u8 = s[5..7].parse().unwrap_or(0);
    let day: u8 = s[8..10].parse().unwrap_or(0);
    (1..=12).contains(&month) && (1..=31).contains(&day)
}

/// Version range: minimum (required) and optional maximum, both inclusive.
///
/// Date-based versions (YYYY-MM-DD) are lexicographically orderable,
/// so constraint checking is simple string comparison.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct VersionConstraint {
    pub min: String,
    pub max: Option<String>,
}

impl VersionConstraint {
    /// Check if a version satisfies this constraint.
    pub fn satisfied_by(&self, version: &str) -> bool {
        if version < self.min.as_str() {
            return false;
        }
        if let Some(ref max) = self.max {
            if version > max.as_str() {
                return false;
            }
        }
        true
    }

    /// Parse from a JSON value: `{ "min": "...", "max": "..." }`.
    pub fn parse(value: &Value) -> Result<Self, String> {
        let obj = value.as_object().ok_or("expected object")?;

        let min = obj
            .get("min")
            .and_then(|v| v.as_str())
            .ok_or("missing required field \"min\"")?;

        if !is_valid_version(min) {
            return Err(format!(
                "invalid version format for \"min\": \"{}\" (expected YYYY-MM-DD)",
                min
            ));
        }

        let max = match obj.get("max") {
            Some(v) => {
                let s = v.as_str().ok_or("\"max\" must be a string")?;
                if !is_valid_version(s) {
                    return Err(format!(
                        "invalid version format for \"max\": \"{}\" (expected YYYY-MM-DD)",
                        s
                    ));
                }
                Some(s.to_string())
            }
            None => None,
        };

        Ok(Self {
            min: min.to_string(),
            max,
        })
    }
}

/// Extension schema version requirements (`requires` field).
///
/// Declares minimum (and optionally maximum) protocol and capability
/// versions needed for correct operation.
#[derive(Debug, Clone, PartialEq, Eq, Default)]
pub struct Requires {
    pub protocol: Option<VersionConstraint>,
    pub capabilities: Vec<(String, VersionConstraint)>,
}

impl Requires {
    /// Parse from a JSON value: the top-level `requires` object.
    pub fn parse(value: &Value) -> Result<Self, Vec<String>> {
        let obj = value
            .as_object()
            .ok_or_else(|| vec!["\"requires\" must be an object".to_string()])?;
        let mut errors = Vec::new();

        let protocol = match obj.get("protocol") {
            Some(v) => match VersionConstraint::parse(v) {
                Ok(vc) => Some(vc),
                Err(e) => {
                    errors.push(format!("requires.protocol: {}", e));
                    None
                }
            },
            None => None,
        };

        let mut capabilities = Vec::new();
        if let Some(caps_val) = obj.get("capabilities") {
            match caps_val.as_object() {
                Some(caps) => {
                    for (key, val) in caps {
                        match VersionConstraint::parse(val) {
                            Ok(vc) => capabilities.push((key.clone(), vc)),
                            Err(e) => errors.push(format!("requires.capabilities.{}: {}", key, e)),
                        }
                    }
                }
                None => errors.push("requires.capabilities must be an object".to_string()),
            }
        }

        if errors.is_empty() {
            Ok(Self {
                protocol,
                capabilities,
            })
        } else {
            Err(errors)
        }
    }
}

/// Options for schema resolution.
#[derive(Debug, Clone)]
pub struct ResolveOptions {
    /// Whether resolving for request or response.
    pub direction: Direction,
    /// The operation to resolve for (e.g., "create", "update").
    /// Will be normalized to lowercase.
    pub operation: String,
    /// When true, sets `additionalProperties: false` on all object schemas
    /// to reject unknown fields. Defaults to false to respect schema extensibility.
    pub strict: bool,
    /// When true, includes fields with `omit` visibility that have a transition
    /// targeting a non-omit value (i.e., planned additions). These fields appear
    /// in the resolved output with `x-ucp-schema-transition` metadata but are NOT
    /// added to `required`. Completes the lifecycle symmetry: deprecations (to=omit)
    /// are always surfaced; this flag surfaces planned additions (from=omit) too.
    pub include_future: bool,
    /// Explicit `$defs` entry to select as the validation/output target,
    /// overriding the `{op}_{direction}` derivation used for container
    /// capabilities. Names non-derivable shapes that aren't an operation +
    /// direction — transport message types (`error_response`), host views
    /// (`business_schema`), and sub-types of single-object schemas
    /// (`cart` → `checkout`). When set, selection ignores the container check
    /// so it works on schemas that also have a root body.
    pub def_name: Option<String>,
}

impl ResolveOptions {
    /// Create new resolve options with strict mode disabled (default).
    ///
    /// Operation is normalized to lowercase for case-insensitive matching.
    /// Strict mode is off by default to respect UCP's extensibility model:
    /// schemas validate known fields but allow additional properties.
    pub fn new(direction: Direction, operation: impl Into<String>) -> Self {
        Self {
            direction,
            operation: operation.into().to_lowercase(),
            strict: false,
            include_future: false,
            def_name: None,
        }
    }

    /// Set strict mode (additionalProperties: false on all objects).
    pub fn strict(mut self, strict: bool) -> Self {
        self.strict = strict;
        self
    }

    /// Include future fields (omit-visibility with non-omit transition target).
    pub fn include_future(mut self, include_future: bool) -> Self {
        self.include_future = include_future;
        self
    }

    /// Select an explicit `$defs` entry, overriding `{op}_{direction}`
    /// derivation (see [`Self::def_name`]).
    pub fn def_name(mut self, def_name: Option<String>) -> Self {
        self.def_name = def_name;
        self
    }
}

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

    #[test]
    fn direction_annotation_key() {
        assert_eq!(Direction::Request.annotation_key(), "ucp_request");
        assert_eq!(Direction::Response.annotation_key(), "ucp_response");
    }

    #[test]
    fn visibility_parse_valid() {
        assert_eq!(Visibility::parse("omit"), Some(Visibility::Omit));
        assert_eq!(Visibility::parse("required"), Some(Visibility::Required));
        assert_eq!(Visibility::parse("optional"), Some(Visibility::Optional));
    }

    #[test]
    fn visibility_parse_invalid() {
        assert_eq!(Visibility::parse("include"), None);
        assert_eq!(Visibility::parse("readonly"), None);
        assert_eq!(Visibility::parse(""), None);
    }

    #[test]
    fn valid_schema_transitions() {
        // Any distinct pair of visibility values is valid
        for (from, to) in [
            ("required", "optional"),
            ("required", "omit"),
            ("optional", "omit"),
            ("optional", "required"),
            ("omit", "required"),
            ("omit", "optional"),
        ] {
            assert!(super::is_valid_schema_transition(from, to));
        }
        // Disbarred: same value for both
        assert!(!super::is_valid_schema_transition("required", "required"));
        assert!(!super::is_valid_schema_transition("omit", "omit"));
        assert!(!super::is_valid_schema_transition("optional", "optional"));
        // Disbarred: invalid visibility value
        assert!(!super::is_valid_schema_transition("readonly", "omit"));
        assert!(!super::is_valid_schema_transition("required", "invalid"));
    }

    #[test]
    fn is_valid_version_format() {
        assert!(is_valid_version("2026-01-23"));
        assert!(is_valid_version("2025-12-31"));
        assert!(!is_valid_version("2026-1-23"));
        assert!(!is_valid_version("not-a-date"));
        assert!(!is_valid_version("20260123"));
        assert!(!is_valid_version(""));
        // Reject nonsense dates
        assert!(!is_valid_version("2026-13-32"));
        assert!(!is_valid_version("2026-00-15"));
        assert!(!is_valid_version("2026-06-00"));
        assert!(!is_valid_version("9999-99-99"));
    }

    #[test]
    fn version_constraint_satisfied_by() {
        let min_only = VersionConstraint {
            min: "2026-01-23".into(),
            max: None,
        };
        assert!(!min_only.satisfied_by("2026-01-22"));
        assert!(min_only.satisfied_by("2026-01-23")); // inclusive
        assert!(min_only.satisfied_by("2026-06-01"));
        assert!(min_only.satisfied_by("2099-12-31"));

        let range = VersionConstraint {
            min: "2026-01-23".into(),
            max: Some("2026-09-01".into()),
        };
        assert!(!range.satisfied_by("2026-01-22"));
        assert!(range.satisfied_by("2026-01-23")); // min inclusive
        assert!(range.satisfied_by("2026-06-01"));
        assert!(range.satisfied_by("2026-09-01")); // max inclusive
        assert!(!range.satisfied_by("2026-09-02"));

        // Exact pin: min == max
        let exact = VersionConstraint {
            min: "2026-06-01".into(),
            max: Some("2026-06-01".into()),
        };
        assert!(!exact.satisfied_by("2026-05-31"));
        assert!(exact.satisfied_by("2026-06-01"));
        assert!(!exact.satisfied_by("2026-06-02"));
    }

    #[test]
    fn version_constraint_parse_valid() {
        use serde_json::json;
        let vc = VersionConstraint::parse(&json!({"min": "2026-01-23"})).unwrap();
        assert_eq!(vc.min, "2026-01-23");
        assert_eq!(vc.max, None);

        let vc =
            VersionConstraint::parse(&json!({"min": "2026-01-23", "max": "2026-09-01"})).unwrap();
        assert_eq!(vc.min, "2026-01-23");
        assert_eq!(vc.max, Some("2026-09-01".into()));
    }

    #[test]
    fn version_constraint_parse_invalid() {
        use serde_json::json;
        assert!(VersionConstraint::parse(&json!({"max": "2026-01-23"})).is_err()); // missing min
        assert!(VersionConstraint::parse(&json!({"min": "bad"})).is_err()); // bad format
        assert!(VersionConstraint::parse(&json!("string")).is_err()); // not object
    }

    #[test]
    fn requires_parse_valid() {
        use serde_json::json;
        let req = Requires::parse(&json!({
            "protocol": { "min": "2026-01-23" },
            "capabilities": {
                "dev.ucp.shopping.checkout": { "min": "2026-06-01" }
            }
        }))
        .unwrap();
        assert!(req.protocol.is_some());
        assert_eq!(req.capabilities.len(), 1);
        assert_eq!(req.capabilities[0].0, "dev.ucp.shopping.checkout");
    }

    #[test]
    fn requires_parse_protocol_only() {
        use serde_json::json;
        let req = Requires::parse(&json!({
            "protocol": { "min": "2026-01-23" }
        }))
        .unwrap();
        assert!(req.protocol.is_some());
        assert!(req.capabilities.is_empty());
    }

    #[test]
    fn requires_parse_empty_object() {
        use serde_json::json;
        let req = Requires::parse(&json!({})).unwrap();
        assert!(req.protocol.is_none());
        assert!(req.capabilities.is_empty());
    }

    #[test]
    fn requires_parse_invalid() {
        use serde_json::json;
        // Not an object
        assert!(Requires::parse(&json!("string")).is_err());
        // Bad protocol constraint
        assert!(Requires::parse(&json!({"protocol": {"min": "bad"}})).is_err());
        // Bad capability constraint
        assert!(Requires::parse(&json!({
            "capabilities": { "x.y.z": "not-object" }
        }))
        .is_err());
    }

    #[test]
    fn resolve_options_normalizes_operation() {
        let opts = ResolveOptions::new(Direction::Request, "Create");
        assert_eq!(opts.operation, "create");

        let opts = ResolveOptions::new(Direction::Request, "UPDATE");
        assert_eq!(opts.operation, "update");
    }
}