kyyn-core 0.1.13

//! Backend-neutral analytical query plans and the typed builder schemas use
//! to produce them. The builder closure runs once against typed field proxies;
//! only the resulting serde AST crosses the schema/engine boundary.

use std::marker::PhantomData;

use chrono::NaiveDate;
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct QueryDecl {
    pub name: String,
    #[serde(default, skip_serializing_if = "String::is_empty")]
    pub doc: String,
    pub bindings: Vec<BindingDecl>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub filter: Option<BoolExpr>,
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub group_by: Vec<ScalarExpr>,
    pub columns: Vec<OutputColumn>,
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub order_by: Vec<QueryOrder>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub limit: Option<usize>,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct BindingDecl {
    pub id: u32,
    pub kind: String,
    pub source: BindingSource,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum BindingSource {
    Root,
    Follow {
        from: u32,
        field: String,
        direction: EdgeDirection,
        #[serde(default = "yes")]
        required: bool,
    },
}

fn yes() -> bool {
    true
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum EdgeDirection {
    Out,
    In,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct FieldRef {
    pub binding: u32,
    pub field: String,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum ScalarExpr {
    Field(FieldRef),
    Literal(TypedLiteral),
    Aggregate {
        op: AggregateOp,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        expr: Option<Box<ScalarExpr>>,
    },
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum TypedLiteral {
    String(String),
    Int(i64),
    Decimal(String),
    Date(NaiveDate),
    Bool(bool),
    Enum { type_name: String, variant: String },
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum AggregateOp {
    Count,
    CountDistinct,
    Sum,
    Min,
    Max,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum BoolExpr {
    And(Vec<BoolExpr>),
    Or(Vec<BoolExpr>),
    Not(Box<BoolExpr>),
    Compare {
        left: ScalarExpr,
        op: CompareOp,
        right: ScalarExpr,
    },
}

impl BoolExpr {
    pub fn and(self, other: BoolExpr) -> BoolExpr {
        match self {
            BoolExpr::And(mut xs) => {
                xs.push(other);
                BoolExpr::And(xs)
            }
            one => BoolExpr::And(vec![one, other]),
        }
    }

    pub fn or(self, other: BoolExpr) -> BoolExpr {
        match self {
            BoolExpr::Or(mut xs) => {
                xs.push(other);
                BoolExpr::Or(xs)
            }
            one => BoolExpr::Or(vec![one, other]),
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum CompareOp {
    Eq,
    Ne,
    Gt,
    Gte,
    Lt,
    Lte,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct OutputColumn {
    pub name: String,
    pub expr: ScalarExpr,
    /// Display-only formatting; the underlying value stays exact and sorting
    /// uses the raw value, never the rendered text.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub format: Option<ColumnFormat>,
}

/// Declarative column formatting — serializable AST data the gate can check
/// and every face renders identically. Thousands grouping uses a SPACE
/// (29 669 069.38): the KB-wide convention.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct ColumnFormat {
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub prefix: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub suffix: Option<String>,
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub thousands: bool,
    /// Display rounding/padding only.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub decimals: Option<u8>,
}

impl ColumnFormat {
    /// The money shape: prefix + space-grouped thousands + 2 decimals.
    pub fn money(prefix: impl Into<String>) -> ColumnFormat {
        ColumnFormat {
            prefix: Some(prefix.into()),
            suffix: None,
            thousands: true,
            decimals: Some(2),
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct QueryOrder {
    pub expr: ScalarExpr,
    pub direction: SortDirection,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum SortDirection {
    Asc,
    Desc,
}

/// A schema model that can produce a typed proxy for one query binding.
/// Implementations are normally generated alongside the registry declaration.
pub trait QueryModel: Sized {
    type Fields;
    const KIND: &'static str;
    fn fields(binding: u32) -> Self::Fields;
}

/// A typed reference to one field. `T` makes incompatible comparisons fail in
/// Rust before a plan can be emitted; serde sees only the contained FieldRef.
#[derive(Debug)]
pub struct FieldExpr<T> {
    field: FieldRef,
    marker: PhantomData<fn() -> T>,
}

impl<T> Clone for FieldExpr<T> {
    fn clone(&self) -> Self {
        Self {
            field: self.field.clone(),
            marker: PhantomData,
        }
    }
}

impl<T> FieldExpr<T> {
    pub fn new(binding: u32, field: impl Into<String>) -> Self {
        Self {
            field: FieldRef {
                binding,
                field: field.into(),
            },
            marker: PhantomData,
        }
    }

    pub fn expr(&self) -> ScalarExpr {
        ScalarExpr::Field(self.field.clone())
    }

    fn compare(&self, op: CompareOp, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        BoolExpr::Compare {
            left: self.expr(),
            op,
            right: ScalarExpr::Literal(value.into_query_literal()),
        }
    }

    pub fn eq(&self, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        self.compare(CompareOp::Eq, value)
    }

    pub fn ne(&self, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        self.compare(CompareOp::Ne, value)
    }

    pub fn gt(&self, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        self.compare(CompareOp::Gt, value)
    }

    pub fn gte(&self, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        self.compare(CompareOp::Gte, value)
    }

    pub fn lt(&self, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        self.compare(CompareOp::Lt, value)
    }

    pub fn lte(&self, value: T) -> BoolExpr
    where
        T: QueryLiteral,
    {
        self.compare(CompareOp::Lte, value)
    }

    /// The binding this field belongs to — what join builders anchor on
    /// until slice 3's typed EdgeExpr replaces the string field name.
    pub fn binding(&self) -> u32 {
        self.field.binding
    }
}

pub trait QueryLiteral {
    fn into_query_literal(self) -> TypedLiteral;
}

impl QueryLiteral for String {
    fn into_query_literal(self) -> TypedLiteral {
        TypedLiteral::String(self)
    }
}
impl QueryLiteral for &str {
    fn into_query_literal(self) -> TypedLiteral {
        TypedLiteral::String(self.to_string())
    }
}
impl QueryLiteral for i64 {
    fn into_query_literal(self) -> TypedLiteral {
        TypedLiteral::Int(self)
    }
}
impl QueryLiteral for bool {
    fn into_query_literal(self) -> TypedLiteral {
        TypedLiteral::Bool(self)
    }
}
impl QueryLiteral for NaiveDate {
    fn into_query_literal(self) -> TypedLiteral {
        TypedLiteral::Date(self)
    }
}

/// Builder used inside a schema crate. It is deliberately stateful: the
/// closure describes one plan, then `finish()` returns plain serializable data.
pub struct QueryBuilder {
    query: QueryDecl,
    next_binding: u32,
}

impl QueryBuilder {
    pub fn new(name: impl Into<String>, doc: impl Into<String>) -> Self {
        Self {
            query: QueryDecl {
                name: name.into(),
                doc: doc.into(),
                bindings: vec![],
                filter: None,
                group_by: vec![],
                columns: vec![],
                order_by: vec![],
                limit: None,
            },
            next_binding: 0,
        }
    }

    pub fn from<M: QueryModel>(&mut self) -> M::Fields {
        let id = self.next_binding;
        self.next_binding += 1;
        self.query.bindings.push(BindingDecl {
            id,
            kind: M::KIND.into(),
            source: BindingSource::Root,
        });
        M::fields(id)
    }

    pub fn filter(&mut self, expr: BoolExpr) {
        self.query.filter = Some(expr);
    }

    pub fn group_by<T>(&mut self, field: &FieldExpr<T>) {
        self.query.group_by.push(field.expr());
    }

    pub fn field<T>(&mut self, name: impl Into<String>, field: &FieldExpr<T>) -> ColumnHandle<'_> {
        self.push_column(name, field.expr())
    }

    fn push_column(&mut self, name: impl Into<String>, expr: ScalarExpr) -> ColumnHandle<'_> {
        self.query.columns.push(OutputColumn {
            name: name.into(),
            expr,
            format: None,
        });
        ColumnHandle {
            column: self.query.columns.last_mut().expect("just pushed"),
        }
    }

    pub fn count(&mut self, name: impl Into<String>) -> ColumnHandle<'_> {
        self.push_column(
            name,
            ScalarExpr::Aggregate {
                op: AggregateOp::Count,
                expr: None,
            },
        )
    }

    /// Count rows where the expression is non-null — the SQL COUNT(col)
    /// semantics; with a LEFT join this is how "0 related" stays 0.
    pub fn count_of<T>(
        &mut self,
        name: impl Into<String>,
        field: &FieldExpr<T>,
    ) -> ColumnHandle<'_> {
        self.aggregate(name, AggregateOp::Count, field)
    }

    pub fn count_distinct<T>(
        &mut self,
        name: impl Into<String>,
        field: &FieldExpr<T>,
    ) -> ColumnHandle<'_> {
        self.aggregate(name, AggregateOp::CountDistinct, field)
    }

    pub fn sum<T>(&mut self, name: impl Into<String>, field: &FieldExpr<T>) -> ColumnHandle<'_> {
        self.aggregate(name, AggregateOp::Sum, field)
    }

    pub fn min<T>(&mut self, name: impl Into<String>, field: &FieldExpr<T>) -> ColumnHandle<'_> {
        self.aggregate(name, AggregateOp::Min, field)
    }

    pub fn max<T>(&mut self, name: impl Into<String>, field: &FieldExpr<T>) -> ColumnHandle<'_> {
        self.aggregate(name, AggregateOp::Max, field)
    }

    fn aggregate<T>(
        &mut self,
        name: impl Into<String>,
        op: AggregateOp,
        field: &FieldExpr<T>,
    ) -> ColumnHandle<'_> {
        self.push_column(
            name,
            ScalarExpr::Aggregate {
                op,
                expr: Some(Box::new(field.expr())),
            },
        )
    }

    /// JOIN: bind records of `M` whose OWN link field `field` points at the
    /// `anchor` binding's record (SQL: FROM anchor JOIN M ON M.field = anchor).
    /// `required: false` is a LEFT join — anchor rows without a match keep one
    /// row with the M binding absent. The field name is a string until slice
    /// 3's typed EdgeExpr; the registry gate validates it at emission.
    pub fn follow_in<M: QueryModel>(
        &mut self,
        anchor: u32,
        field: impl Into<String>,
        required: bool,
    ) -> M::Fields {
        self.follow::<M>(anchor, field, EdgeDirection::In, required)
    }

    /// JOIN along a link field ON THE ANCHOR pointing out at records of `M`.
    pub fn follow_out<M: QueryModel>(
        &mut self,
        anchor: u32,
        field: impl Into<String>,
        required: bool,
    ) -> M::Fields {
        self.follow::<M>(anchor, field, EdgeDirection::Out, required)
    }

    fn follow<M: QueryModel>(
        &mut self,
        anchor: u32,
        field: impl Into<String>,
        direction: EdgeDirection,
        required: bool,
    ) -> M::Fields {
        let id = self.next_binding;
        self.next_binding += 1;
        self.query.bindings.push(BindingDecl {
            id,
            kind: M::KIND.into(),
            source: BindingSource::Follow {
                from: anchor,
                field: field.into(),
                direction,
                required,
            },
        });
        M::fields(id)
    }

    pub fn order_by<T>(&mut self, field: &FieldExpr<T>, direction: SortDirection) {
        self.query.order_by.push(QueryOrder {
            expr: field.expr(),
            direction,
        });
    }

    /// Order by an output column's expression (aggregates included).
    pub fn order_by_column(&mut self, name: &str, direction: SortDirection) {
        if let Some(col) = self.query.columns.iter().find(|c| c.name == name) {
            self.query.order_by.push(QueryOrder {
                expr: col.expr.clone(),
                direction,
            });
        }
    }

    pub fn limit(&mut self, limit: usize) {
        self.query.limit = Some(limit);
    }

    pub fn finish(self) -> QueryDecl {
        self.query
    }
}

/// Fluent formatting on the just-declared column:
/// `q.sum("total budget", &f).money("R ")`.
pub struct ColumnHandle<'a> {
    column: &'a mut OutputColumn,
}

impl ColumnHandle<'_> {
    pub fn format(self, format: ColumnFormat) -> Self {
        self.column.format = Some(format);
        self
    }

    pub fn money(self, prefix: impl Into<String>) -> Self {
        self.format(ColumnFormat::money(prefix))
    }
}

pub fn query(
    name: impl Into<String>,
    doc: impl Into<String>,
    build: impl FnOnce(&mut QueryBuilder),
) -> QueryDecl {
    let mut q = QueryBuilder::new(name, doc);
    build(&mut q);
    q.finish()
}