icydb_model/node/

index.rs

use crate::prelude::*;
use icydb_schema::{SchemaContractError, SourceCheckExpr};
use std::{
    fmt::{self, Display},
    ops::Not,
};

use crate::node::{Schema, SourceExpressionResolver};

///
/// IndexExpression
///
/// Canonical deterministic expression key metadata for expression indexes.
/// This enum is semantic authority across schema/runtime/planner boundaries.
///
#[derive(Clone, Copy, Debug, Eq, PartialEq, Serialize)]
pub enum IndexExpression {
    Lower(&'static str),
    Upper(&'static str),
    Trim(&'static str),
    LowerTrim(&'static str),
    Date(&'static str),
    Year(&'static str),
    Month(&'static str),
    Day(&'static str),
}

impl IndexExpression {
    /// Borrow the referenced field for this expression key item.
    #[must_use]
    pub const fn field(&self) -> &'static str {
        match self {
            Self::Lower(field)
            | Self::Upper(field)
            | Self::Trim(field)
            | Self::LowerTrim(field)
            | Self::Date(field)
            | Self::Year(field)
            | Self::Month(field)
            | Self::Day(field) => field,
        }
    }
}

impl Display for IndexExpression {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Lower(field) => write!(f, "LOWER({field})"),
            Self::Upper(field) => write!(f, "UPPER({field})"),
            Self::Trim(field) => write!(f, "TRIM({field})"),
            Self::LowerTrim(field) => write!(f, "LOWER(TRIM({field}))"),
            Self::Date(field) => write!(f, "DATE({field})"),
            Self::Year(field) => write!(f, "YEAR({field})"),
            Self::Month(field) => write!(f, "MONTH({field})"),
            Self::Day(field) => write!(f, "DAY({field})"),
        }
    }
}

///
/// IndexKeyItem
///
/// Canonical index key-item metadata.
/// `Field` preserves field-key behavior.
/// `Expression` reserves deterministic expression-key identity metadata.
///
#[derive(Clone, Copy, Debug, Eq, PartialEq, Serialize)]
pub enum IndexKeyItem {
    Field(&'static str),
    Expression(IndexExpression),
}

impl IndexKeyItem {
    /// Borrow this key-item's referenced field.
    #[must_use]
    pub const fn field(&self) -> &'static str {
        match self {
            Self::Field(field) => field,
            Self::Expression(expression) => expression.field(),
        }
    }

    /// Render one deterministic canonical text form for diagnostics/display.
    #[must_use]
    pub fn canonical_text(&self) -> String {
        match self {
            Self::Field(field) => (*field).to_string(),
            Self::Expression(expression) => expression.to_string(),
        }
    }
}

///
/// IndexKeyItemsRef
///
/// Borrowed view over index key-item metadata.
/// Field-only indexes use `Fields`; mixed/explicit key metadata uses `Items`.
///
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum IndexKeyItemsRef {
    Fields(&'static [&'static str]),
    Items(&'static [IndexKeyItem]),
}

///
/// Index
///

#[derive(Clone, Debug, Serialize)]
pub struct Index {
    source_key: &'static str,
    name: &'static str,
    fields: &'static [&'static str],

    #[serde(skip_serializing_if = "Option::is_none")]
    key_items: Option<&'static [IndexKeyItem]>,

    #[serde(skip_serializing_if = "Not::not")]
    unique: bool,

    // Raw predicate SQL remains input metadata until lowered into canonical
    // predicate semantics at runtime schema boundary.
    #[serde(skip_serializing_if = "Option::is_none")]
    predicate: Option<&'static str>,

    #[serde(skip)]
    predicate_expression: Option<SourceExpressionResolver>,
}

impl Index {
    /// Build one index declaration from field-list and uniqueness metadata.
    #[must_use]
    pub const fn new(
        source_key: &'static str,
        name: &'static str,
        fields: &'static [&'static str],
        unique: bool,
    ) -> Self {
        Self::new_with_key_items_and_predicate(source_key, name, fields, None, unique, None, None)
    }

    /// Build one index declaration with optional conditional predicate metadata.
    #[must_use]
    pub const fn new_with_predicate(
        source_key: &'static str,
        name: &'static str,
        fields: &'static [&'static str],
        unique: bool,
        predicate: Option<&'static str>,
        predicate_expression: Option<SourceExpressionResolver>,
    ) -> Self {
        Self::new_with_key_items_and_predicate(
            source_key,
            name,
            fields,
            None,
            unique,
            predicate,
            predicate_expression,
        )
    }

    /// Build one index declaration with explicit canonical key-item metadata.
    #[must_use]
    pub const fn new_with_key_items(
        source_key: &'static str,
        name: &'static str,
        fields: &'static [&'static str],
        key_items: &'static [IndexKeyItem],
        unique: bool,
    ) -> Self {
        Self::new_with_key_items_and_predicate(
            source_key,
            name,
            fields,
            Some(key_items),
            unique,
            None,
            None,
        )
    }

    /// Build one index declaration with explicit key items + predicate metadata.
    #[must_use]
    pub const fn new_with_key_items_and_predicate(
        source_key: &'static str,
        name: &'static str,
        fields: &'static [&'static str],
        key_items: Option<&'static [IndexKeyItem]>,
        unique: bool,
        predicate: Option<&'static str>,
        predicate_expression: Option<SourceExpressionResolver>,
    ) -> Self {
        Self {
            source_key,
            name,
            fields,
            key_items,
            unique,
            predicate,
            predicate_expression,
        }
    }

    /// Borrow the immutable index source key.
    #[must_use]
    pub const fn source_key(&self) -> &'static str {
        self.source_key
    }

    /// Borrow the editable index name.
    #[must_use]
    pub const fn name(&self) -> &'static str {
        self.name
    }

    /// Borrow index field sequence.
    #[must_use]
    pub const fn fields(&self) -> &'static [&'static str] {
        self.fields
    }

    /// Borrow canonical key-item metadata for this index.
    #[must_use]
    pub const fn key_items(&self) -> IndexKeyItemsRef {
        if let Some(items) = self.key_items {
            IndexKeyItemsRef::Items(items)
        } else {
            IndexKeyItemsRef::Fields(self.fields)
        }
    }

    /// Return whether this index includes expression key items.
    #[must_use]
    pub const fn has_expression_key_items(&self) -> bool {
        let Some(items) = self.key_items else {
            return false;
        };

        let mut index = 0usize;
        while index < items.len() {
            if matches!(items[index], IndexKeyItem::Expression(_)) {
                return true;
            }
            index = index.saturating_add(1);
        }

        false
    }

    /// Return whether the index enforces uniqueness.
    #[must_use]
    pub const fn is_unique(&self) -> bool {
        self.unique
    }

    /// Return optional conditional-index predicate SQL metadata.
    ///
    /// This text is input-only; runtime/planner semantics must consume the
    /// canonical lowered predicate form.
    #[must_use]
    pub const fn predicate(&self) -> Option<&'static str> {
        self.predicate
    }

    /// Lower the optional compiler-validated predicate into the public source
    /// AST.
    ///
    /// # Errors
    ///
    /// Returns a typed proposal error when an enum literal no longer resolves
    /// through the sealed graph or the expression violates public bounds.
    pub fn source_predicate(
        &self,
        schema: &Schema,
    ) -> Result<Option<SourceCheckExpr>, SchemaContractError> {
        match (self.predicate, self.predicate_expression) {
            (None, None) => Ok(None),
            (Some(_), Some(resolve)) => resolve(schema).map(Some),
            (None, Some(_)) | (Some(_), None) => Err(SchemaContractError::InvalidExpression),
        }
    }

    #[must_use]
    pub fn is_prefix_of(&self, other: &Self) -> bool {
        self.fields().len() < other.fields().len() && other.fields().starts_with(self.fields())
    }

    fn joined_key_items(&self) -> String {
        match self.key_items() {
            IndexKeyItemsRef::Fields(fields) => fields.join(", "),
            IndexKeyItemsRef::Items(items) => {
                let mut joined = String::new();

                for item in items {
                    if !joined.is_empty() {
                        joined.push_str(", ");
                    }
                    joined.push_str(item.canonical_text().as_str());
                }

                joined
            }
        }
    }
}

impl Display for Index {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let fields = self.joined_key_items();

        if self.is_unique() {
            if let Some(predicate) = self.predicate() {
                write!(f, "UNIQUE ({fields}) WHERE {predicate}")
            } else {
                write!(f, "UNIQUE ({fields})")
            }
        } else if let Some(predicate) = self.predicate() {
            write!(f, "({fields}) WHERE {predicate}")
        } else {
            write!(f, "({fields})")
        }
    }
}

impl MacroNode for Index {
    fn as_any(&self) -> &dyn std::any::Any {
        self
    }
}

impl ValidateNode for Index {
    fn validate(&self) -> Result<(), ErrorTree> {
        let mut errs = ErrorTree::new();
        validate_source_key(
            &mut errs,
            "index",
            self.source_key(),
            icydb_schema::IndexSourceKey::try_new,
        );
        errs.result()
    }
}

impl VisitableNode for Index {
    fn route_key(&self) -> String {
        self.joined_key_items()
    }
}

///
/// TESTS
///

#[cfg(test)]
mod tests {
    use crate::node::index::{Index, IndexExpression, IndexKeyItem, IndexKeyItemsRef};

    #[test]
    fn index_with_predicate_reports_conditional_shape() {
        let index = Index::new_with_predicate(
            "email_active",
            "idx_user__email",
            &["email"],
            false,
            Some("active = true"),
            None,
        );

        assert_eq!(index.predicate(), Some("active = true"));
        assert_eq!(index.to_string(), "(email) WHERE active = true");
    }

    #[test]
    fn index_without_predicate_preserves_unconditional_shape() {
        let index = Index::new("email", "uidx_user__email", &["email"], true);

        assert_eq!(index.predicate(), None);
        assert_eq!(index.to_string(), "UNIQUE (email)");
    }

    #[test]
    fn index_with_explicit_key_items_exposes_expression_items() {
        static KEY_ITEMS: [IndexKeyItem; 2] = [
            IndexKeyItem::Field("tenant_id"),
            IndexKeyItem::Expression(IndexExpression::Lower("email")),
        ];
        let index = Index::new_with_key_items(
            "tenant_lower_email",
            "idx_user__tenant_id__lower_email",
            &["tenant_id"],
            &KEY_ITEMS,
            false,
        );

        assert!(index.has_expression_key_items());
        assert_eq!(index.to_string(), "(tenant_id, LOWER(email))");
        std::assert_matches!(
            index.key_items(),
            IndexKeyItemsRef::Items(items)
                if items == KEY_ITEMS.as_slice()
        );
    }
}