uqa_sql/expr/binary/

comparison.rs

//
// Unified Query Algebra
//
// Copyright (c) 2023-2026 Cognica, Inc.
//

//! SQL NULL and row comparison rules share the native controlled value owners.

use super::super::enums::{EnumComparisonState, EnumLabelCatalog};
use super::{BinaryOp, Result, SQLError, Value};
use std::cmp::Ordering;
use uqa_core::memory::ProductionControl;

mod records;

#[cfg(test)]
pub(in crate::expr) fn eval_comparison_op(op: BinaryOp, l: &Value, r: &Value) -> Result<Value> {
    Ok(eval_comparison_truth(op, l, r)?
        .map(Value::Bool)
        .unwrap_or(Value::Null))
}

/// Compare two values without allocating an intermediate [`Value::Bool`]. `None` represents SQL UNKNOWN, including an undecided anonymous row comparison.
#[inline]
pub fn eval_comparison_truth(op: BinaryOp, l: &Value, r: &Value) -> Result<Option<bool>> {
    eval_comparison_truth_with_control(op, l, r, &ProductionControl::uncontrolled())
}

/// Evaluate the same three-valued comparison while admitting the native numeric, JSONB and array comparison workspace to the caller's allowance.
pub fn eval_comparison_truth_with_control(
    op: BinaryOp,
    l: &Value,
    r: &Value,
    control: &ProductionControl<'_>,
) -> Result<Option<bool>> {
    control.check()?;
    let out = match op {
        BinaryOp::Equal => values_equal_nullable_with_control(l, r, control)?,
        BinaryOp::NotEqual => values_equal_nullable_with_control(l, r, control)?.map(|v| !v),
        BinaryOp::Less => compare_nullable_with_control(l, r, control)?.map(|v| v.is_lt()),
        BinaryOp::LessEqual => compare_nullable_with_control(l, r, control)?.map(|v| v.is_le()),
        BinaryOp::Greater => compare_nullable_with_control(l, r, control)?.map(|v| v.is_gt()),
        BinaryOp::GreaterEqual => compare_nullable_with_control(l, r, control)?.map(|v| v.is_ge()),
        _ => {
            return Err(SQLError::Internal(format!(
                "non-comparison operator {op:?} reached comparison evaluation"
            )))
        }
    };
    Ok(out)
}

/// Borrow physical type metadata from scalar hooks even when the embedder provides no enum capability.
pub fn eval_comparison_truth_with_engine(
    op: BinaryOp,
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    engine: Option<&dyn crate::expr::EngineHook>,
    state: Option<&EnumComparisonState>,
) -> Result<Option<bool>> {
    eval_comparison_truth_with_deferred_state(op, left, right, control, engine, || state)
}

/// Primitive scalar comparisons need no catalog or private enum call state. Resolve that state only when the evaluated carriers require the general comparison path; operand evaluation and its SQL ordering remain the caller's responsibility.
#[inline]
pub fn eval_comparison_truth_with_deferred_state<'a>(
    op: BinaryOp,
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    engine: Option<&dyn crate::expr::EngineHook>,
    state: impl FnOnce() -> Option<&'a EnumComparisonState>,
) -> Result<Option<bool>> {
    control.check()?;
    let primitive = match (left, right) {
        (Value::Null, _) | (_, Value::Null) => Some(None),
        (Value::Int(_), Value::Int(_))
        | (Value::Float(_), Value::Float(_))
        | (Value::Bool(_), Value::Bool(_)) => Some(Some(left.cmp(right))),
        _ => None,
    };
    if let Some(order) = primitive {
        return match op {
            BinaryOp::Equal => Ok(order.map(Ordering::is_eq)),
            BinaryOp::NotEqual => Ok(order.map(|order| !order.is_eq())),
            BinaryOp::Less => Ok(order.map(Ordering::is_lt)),
            BinaryOp::LessEqual => Ok(order.map(Ordering::is_le)),
            BinaryOp::Greater => Ok(order.map(Ordering::is_gt)),
            BinaryOp::GreaterEqual => Ok(order.map(Ordering::is_ge)),
            _ => Err(SQLError::Internal(format!(
                "non-comparison operator {op:?} reached comparison evaluation"
            ))),
        };
    }
    let catalog = engine.map(crate::expr::value_catalog::EngineValueCatalog);
    eval_comparison_truth_with_enum_catalog(
        op,
        left,
        right,
        control,
        catalog
            .as_ref()
            .map(|catalog| catalog as &dyn crate::expr::SQLValueCatalog),
        state(),
    )
}

/// Observe scalar and nested enums through the caller's catalog, preserving private scalar/row call state, shared type support state and ordinary three-valued rules.
pub fn eval_comparison_truth_with_enum_catalog(
    op: BinaryOp,
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn super::super::enums::EnumLabelCatalog>,
    state: Option<&super::super::enums::EnumComparisonState>,
) -> Result<Option<bool>> {
    control.check()?;
    if matches!(op, BinaryOp::Equal | BinaryOp::NotEqual) {
        return values_equal_nullable_with_catalog(left, right, control, enums)
            .map(|equal| equal.map(|equal| if op == BinaryOp::Equal { equal } else { !equal }));
    }
    if !matches!(
        op,
        BinaryOp::Less | BinaryOp::LessEqual | BinaryOp::Greater | BinaryOp::GreaterEqual
    ) {
        return Err(SQLError::Internal(format!(
            "non-comparison operator {op:?} reached comparison evaluation"
        )));
    }
    let order = compare_nullable_with_catalog(left, right, control, enums, state)?;
    Ok(order.map(|order| match op {
        BinaryOp::Less => order.is_lt(),
        BinaryOp::LessEqual => order.is_le(),
        BinaryOp::Greater => order.is_gt(),
        BinaryOp::GreaterEqual => order.is_ge(),
        _ => unreachable!("only comparison operators reach comparison evaluation"),
    }))
}

/// Two-valued equality treats SQL UNKNOWN as no match for CASE, NULLIF and membership probes.
#[cfg(test)]
pub(in crate::expr) fn values_equal(a: &Value, b: &Value) -> Result<bool> {
    Ok(values_equal_nullable(a, b)? == Some(true))
}

pub fn values_equal_with_control(
    a: &Value,
    b: &Value,
    control: &ProductionControl<'_>,
) -> Result<bool> {
    Ok(values_equal_nullable_with_control(a, b, control)? == Some(true))
}

#[cfg(test)]
pub(in crate::expr) fn values_equal_nullable(a: &Value, b: &Value) -> Result<Option<bool>> {
    values_equal_nullable_with_control(a, b, &ProductionControl::uncontrolled())
}

pub fn values_equal_nullable_with_control(
    a: &Value,
    b: &Value,
    control: &ProductionControl<'_>,
) -> Result<Option<bool>> {
    values_equal_nullable_with_catalog(a, b, control, None)
}

fn values_equal_nullable_with_catalog(
    a: &Value,
    b: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn super::super::enums::EnumLabelCatalog>,
) -> Result<Option<bool>> {
    control.check()?;
    if let Some(value) = super::super::enums::eval_comparison(BinaryOp::Equal, a, b, enums, None)? {
        return match value {
            Value::Null => Ok(None),
            Value::Bool(value) => Ok(Some(value)),
            _ => unreachable!("equality returns boolean or NULL"),
        };
    }
    if let Some(order) = super::super::datums::compare_jsonb_with_control(a, b, control)? {
        return Ok(Some(order.is_eq()));
    }
    let equal = match (a, b) {
        (Value::Null, _) | (_, Value::Null) => None,
        (Value::Datum(datum), _) => {
            return values_equal_nullable_with_catalog(
                &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
                b,
                control,
                enums,
            )
        }
        (_, Value::Datum(datum)) => {
            return values_equal_nullable_with_catalog(
                a,
                &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
                control,
                enums,
            )
        }
        (Value::Temporal(x), Value::Str(y)) | (Value::Str(y), Value::Temporal(x)) => Some(
            x.parse_same_kind_in_order_with_control(
                y,
                crate::expr::transaction_timestamp_or_clock(),
                crate::expr::temporal_date_order(),
                control,
            )?
            .is_some_and(|parsed| x.cmp(&parsed).is_eq()),
        ),
        (Value::FixedChar(x), Value::Str(y)) | (Value::Str(y), Value::FixedChar(x)) => {
            Some(compare_fixed_text(x, y, control)?.is_eq())
        }
        // Anonymous rows use SQL three-valued equality: a definite mismatch wins over an earlier NULL field. Native arrays and stored records instead use total element equality through the value owner below.
        (Value::Row(xs), Value::Row(ys)) => {
            if xs.len() != ys.len() {
                return Ok(Some(false));
            }
            let mut unknown = false;
            for (x, y) in xs.iter().zip(ys) {
                let equal = if matches!((x, y), (Value::Row(_), Value::Row(_))) {
                    Some(equal_values(x, y, control, enums, false)?)
                } else {
                    values_equal_nullable_with_catalog(x, y, control, enums)?
                };
                match equal {
                    Some(false) => return Ok(Some(false)),
                    Some(true) => {}
                    None => unknown = true,
                }
            }
            if unknown {
                None
            } else {
                Some(true)
            }
        }
        _ => Some(equal_values(a, b, control, enums, false)?),
    };
    Ok(equal)
}

/// Compare with the existing two-valued selector convention that SQL UNKNOWN sorts as equal.
pub fn compare_with_control(
    a: &Value,
    b: &Value,
    control: &ProductionControl<'_>,
) -> Result<Ordering> {
    Ok(compare_nullable_with_control(a, b, control)?.unwrap_or(Ordering::Equal))
}

pub fn compare_nullable_with_control(
    a: &Value,
    b: &Value,
    control: &ProductionControl<'_>,
) -> Result<Option<Ordering>> {
    compare_nullable_with_catalog(a, b, control, None, None)
}

fn compare_nullable_with_catalog(
    a: &Value,
    b: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
    state: Option<&EnumComparisonState>,
) -> Result<Option<Ordering>> {
    control.check()?;
    if matches!(a, Value::Null) || matches!(b, Value::Null) {
        return Ok(None);
    }
    if let Some(order) = super::super::enums::comparison_order(a, b, enums, state, false)? {
        return Ok(Some(order));
    }
    if let Some(order) = super::super::datums::compare_jsonb_with_control(a, b, control)? {
        return Ok(Some(order));
    }
    match (a, b) {
        (Value::Null, _) | (_, Value::Null) => Ok(None),
        (Value::Datum(datum), _) => compare_nullable_with_catalog(
            &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
            b,
            control,
            enums,
            state,
        ),
        (_, Value::Datum(datum)) => compare_nullable_with_catalog(
            a,
            &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
            control,
            enums,
            state,
        ),
        (
            Value::Int(_) | Value::Float(_) | Value::Decimal(_),
            Value::Int(_) | Value::Float(_) | Value::Decimal(_),
        )
        | (Value::Bool(_), Value::Decimal(_))
        | (Value::Decimal(_), Value::Bool(_))
        | (Value::Str(_), Value::Str(_))
        | (Value::FixedChar(_), Value::FixedChar(_))
        | (Value::JsonB(_), Value::JsonB(_))
        | (Value::Temporal(_), Value::Temporal(_))
        | (Value::Bool(_), Value::Bool(_))
        | (Value::Array(_), Value::Array(_))
        | (Value::LegacyVector(_), Value::LegacyVector(_))
        | (Value::List(_), Value::List(_))
        | (Value::Record(_), Value::Record(_) | Value::Row(_))
        | (Value::Row(_), Value::Record(_))
        | (Value::Enum(_), Value::Enum(_)) => Ok(Some(compare_sql_values(a, b, control, enums)?)),
        (Value::FixedChar(x), Value::Str(y)) | (Value::Str(x), Value::FixedChar(y)) => {
            Ok(Some(compare_fixed_text(x, y, control)?))
        }
        (Value::Temporal(x), Value::Str(y)) => x
            .parse_same_kind_in_order_with_control(
                y,
                crate::expr::transaction_timestamp_or_clock(),
                crate::expr::temporal_date_order(),
                control,
            )?
            .map(|parsed| Some(x.cmp(&parsed)))
            .ok_or_else(|| SQLError::TypeMismatch(format!("cannot compare {a:?} with {b:?}"))),
        (Value::Str(x), Value::Temporal(y)) => y
            .parse_same_kind_in_order_with_control(
                x,
                crate::expr::transaction_timestamp_or_clock(),
                crate::expr::temporal_date_order(),
                control,
            )?
            .map(|parsed| Some(parsed.cmp(y)))
            .ok_or_else(|| SQLError::TypeMismatch(format!("cannot compare {a:?} with {b:?}"))),
        // Ordering is lexicographic; reaching NULL before a definite comparison leaves it unknown.
        (Value::Row(xs), Value::Row(ys)) => compare_anonymous_row(xs, ys, control, enums, state),
        (lhs, rhs) => Err(SQLError::TypeMismatch(format!(
            "cannot compare {lhs:?} with {rhs:?}"
        ))),
    }
}

fn compare_anonymous_row(
    left: &[Value],
    right: &[Value],
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
    state: Option<&EnumComparisonState>,
) -> Result<Option<Ordering>> {
    for (index, (left, right)) in left.iter().zip(right).enumerate() {
        let field =
            if matches!(left, Value::Enum(_) | Value::Datum(_)) && !matches!(right, Value::Null) {
                state.map(|state| state.field(index))
            } else {
                None
            };
        let order = if matches!((left, right), (Value::Row(_), Value::Row(_))) {
            Some(compare_typed_values_with_catalog(
                left, right, control, enums,
            )?)
        } else {
            compare_nullable_with_catalog(left, right, control, enums, field.as_deref())?
        };
        match order {
            Some(Ordering::Equal) => {}
            other => return Ok(other),
        }
    }
    Ok(Some(left.len().cmp(&right.len())))
}

fn compare_sql_values(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
) -> Result<Ordering> {
    // Primitive mixed float/integer and float/numeric operators select float8 inputs. Physical keys and already-bound container elements keep their exact carrier order.
    if matches!(
        (left, right),
        (Value::Float(_), Value::Int(_) | Value::Decimal(_))
            | (Value::Int(_) | Value::Decimal(_), Value::Float(_))
    ) {
        let left =
            super::super::cast_value_from_with_control(left, "double precision", None, control)?;
        let right =
            super::super::cast_value_from_with_control(right, "double precision", None, control)?;
        return Ok(left.cmp(&right));
    }
    compare_typed_values_with_catalog(left, right, control, enums)
}

/// Compare already-bound values, preserving type operator failures and total container NULL semantics. Callers supply top-level NULL placement and must apply operator-selected casts first.
pub fn compare_typed_values_with_control(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
) -> Result<Ordering> {
    compare_typed_values_with_catalog(left, right, control, None)
}

/// Compare one physical ordering key with its private scalar enum call state. Nested array/record fields use the catalog's shared type comparison state.
pub fn compare_typed_values_with_enum_catalog(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
    state: Option<&EnumComparisonState>,
) -> Result<Ordering> {
    control.check()?;
    if !matches!(left, Value::Null) && !matches!(right, Value::Null) {
        if let Some(order) =
            super::super::enums::comparison_order(left, right, enums, state, false)?
        {
            return Ok(order);
        }
    }
    compare_typed_values_with_catalog(left, right, control, enums)
}

/// Order internal equality groups by physical enum identity, including nested keys. This ordering is not exposed as SQL ORDER BY and never observes an enum label merely to eliminate duplicates.
pub fn compare_grouping_values_with_enum_catalog(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
) -> Result<Ordering> {
    compare_typed_values_for_purpose(left, right, control, enums, EnumKeyOrder::Identity)
}

#[derive(Clone, Copy)]
enum EnumKeyOrder {
    Declaration,
    Identity,
}

fn enum_key_order(
    left: &Value,
    right: &Value,
    enums: Option<&dyn EnumLabelCatalog>,
    order: EnumKeyOrder,
) -> Result<Option<Ordering>> {
    if matches!(order, EnumKeyOrder::Identity) {
        if let Some(enums) = enums {
            if let (Some(left), Some(right)) = (
                super::super::enums::comparison_identity(enums, left)?,
                super::super::enums::comparison_identity(enums, right)?,
            ) {
                return Ok(Some(left.cmp(&right)));
            }
        }
        return Ok(None);
    }
    super::super::enums::comparison_order(left, right, enums, None, true)
}

fn compare_typed_values_with_catalog(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
) -> Result<Ordering> {
    compare_typed_values_for_purpose(left, right, control, enums, EnumKeyOrder::Declaration)
}

fn compare_typed_values_for_purpose(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
    enum_order: EnumKeyOrder,
) -> Result<Ordering> {
    control.check()?;
    if let Some(order) = super::super::datums::compare_jsonb_with_control(left, right, control)? {
        return Ok(order);
    }
    match (left, right) {
        (Value::Null, Value::Null) => return Ok(Ordering::Equal),
        (Value::Null, _) => return Ok(Ordering::Greater),
        (_, Value::Null) => return Ok(Ordering::Less),
        _ => {}
    }
    if let Some(order) = enum_key_order(left, right, enums, enum_order)? {
        return Ok(order);
    }
    match (left, right) {
        (Value::Datum(datum), _) => {
            return compare_typed_values_for_purpose(
                &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
                right,
                control,
                enums,
                enum_order,
            )
        }
        (_, Value::Datum(datum)) => {
            return compare_typed_values_for_purpose(
                left,
                &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
                control,
                enums,
                enum_order,
            )
        }
        (Value::Array(left), Value::Array(right)) => {
            validate_array_element_types(left, right)?;
            return left.cmp_by_with_control(right, control, |left, right, control| {
                compare_typed_values_for_purpose(left, right, control, enums, enum_order)
            });
        }
        (Value::Record(_) | Value::Row(_), Value::Record(_) | Value::Row(_)) => {
            return records::compare(
                left,
                right,
                enums,
                control,
                Ordering::Equal,
                |left, right| {
                    let order =
                        compare_typed_values_for_purpose(left, right, control, enums, enum_order)?;
                    Ok((!order.is_eq()).then_some(order))
                },
            );
        }
        (Value::List(left), Value::List(right)) => {
            return compare_sequence(left.iter(), right.iter(), control, enums, enum_order);
        }
        // Enum operators are declared on one enum type; binding coerces every other operand to it.
        (Value::Enum(left), Value::Enum(right)) if left.type_oid() == right.type_oid() => {
            return Ok(left.key().cmp(right.key()));
        }
        (Value::Enum(_), _) | (_, Value::Enum(_)) => {
            return Err(SQLError::Internal(format!(
                "enum comparison reached operands of different types: {} and {}",
                comparison_operand_type(left),
                comparison_operand_type(right)
            )));
        }
        _ => {}
    }
    for value in [left, right] {
        if let Value::LegacyVector(vector) = value {
            validate_legacy_vector_comparison(vector)?;
        }
    }
    left.cmp_with_control(right, control).map_err(Into::into)
}

fn comparison_operand_type(value: &Value) -> String {
    match value {
        Value::Enum(label) => format!("enum type OID {}", label.type_oid()),
        other => super::super::diagnostics::value_type_name(other).to_owned(),
    }
}

/// Validate the layout required by the `oidvector` scalar equality, ordering and hashing operators. Array operators on `int2vector` permit dimensionless arrays.
pub fn validate_legacy_vector_comparison(vector: &uqa_core::LegacyVectorValue) -> Result<()> {
    if vector.kind() == uqa_core::LegacyVectorKind::Oid && !vector.has_vector_layout() {
        return Err(SQLError::Routine {
            sqlstate: "42804".into(),
            message: "array is not a valid oidvector".into(),
        });
    }
    Ok(())
}

/// Declared SQL keys whose runtime values may require a fallible comparison operator.
pub fn type_comparison_can_fail(ty: &crate::ast::ColumnType) -> bool {
    use crate::ast::ColumnType;
    match ty {
        ColumnType::OidVector
        | ColumnType::Record
        | ColumnType::Composite(_)
        | ColumnType::Array(_) => true,
        ColumnType::Domain { base: element, .. } => type_comparison_can_fail(element),
        _ => false,
    }
}

/// Whether an opaque value key can suppress a SQL operator failure. A single such input remains legal until an operator compares it.
pub fn value_comparison_can_fail(value: &Value) -> bool {
    match value {
        Value::Datum(_) => true,
        Value::LegacyVector(vector) => {
            vector.kind() == uqa_core::LegacyVectorKind::Oid && !vector.has_vector_layout()
        }
        Value::Array(array) => {
            array.element_type_oid().is_some()
                || array.elements().iter().any(value_comparison_can_fail)
        }
        Value::Row(values) => values.iter().any(value_comparison_can_fail),
        Value::List(values) => values.iter().any(value_comparison_can_fail),
        Value::Record(fields) => {
            fields.type_oid().is_some()
                || fields
                    .iter()
                    .any(|(_, value)| value_comparison_can_fail(value))
        }
        _ => false,
    }
}

/// Compare already-bound group/hash keys without enum output. Physical enum
/// identities use the same equality as `enum_eq`, including inside containers.
pub fn equal_typed_values_with_enum_catalog(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn super::super::enums::EnumLabelCatalog>,
) -> Result<bool> {
    equal_values(left, right, control, enums, true)
}

fn equal_values(
    left: &Value,
    right: &Value,
    control: &ProductionControl<'_>,
    enums: Option<&dyn super::super::enums::EnumLabelCatalog>,
    typed: bool,
) -> Result<bool> {
    control.check()?;
    if let Some(order) = super::super::datums::compare_jsonb_with_control(left, right, control)? {
        return Ok(order.is_eq());
    }
    if matches!(left, Value::Null) || matches!(right, Value::Null) {
        return Ok(matches!((left, right), (Value::Null, Value::Null)));
    }
    if let Some(enums) = enums {
        if let (Some(left), Some(right)) = (
            super::super::enums::comparison_identity(enums, left)?,
            super::super::enums::comparison_identity(enums, right)?,
        ) {
            return Ok(left == right);
        }
    }
    match (left, right) {
        (Value::Datum(datum), _) => equal_values(
            &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
            right,
            control,
            enums,
            typed,
        ),
        (_, Value::Datum(datum)) => equal_values(
            left,
            &*super::super::datums::read_with_value_catalog_and_control(datum, enums, control)?,
            control,
            enums,
            typed,
        ),
        (Value::Array(left), Value::Array(right)) => {
            validate_array_element_types(left, right)?;
            left.eq_by_with_control(right, control, |left, right, control| {
                equal_values(left, right, control, enums, typed)
            })
        }
        (Value::Record(_) | Value::Row(_), Value::Record(_) | Value::Row(_)) => {
            records::compare(left, right, enums, control, true, |left, right| {
                Ok((!equal_values(left, right, control, enums, typed)?).then_some(false))
            })
        }
        (Value::List(left), Value::List(right)) => {
            equal_sequence(left.iter(), right.iter(), control, enums, typed)
        }
        _ if typed => Ok(compare_typed_values_with_control(left, right, control)?.is_eq()),
        _ => Ok(compare_sql_values(left, right, control, enums)?.is_eq()),
    }
}

fn validate_array_element_types(
    left: &uqa_core::ArrayValue,
    right: &uqa_core::ArrayValue,
) -> Result<()> {
    if matches!((left.element_type_oid(), right.element_type_oid()), (Some(left), Some(right)) if left != right)
    {
        return Err(SQLError::Routine {
            sqlstate: "42804".into(),
            message: "cannot compare arrays of different element types".into(),
        });
    }
    Ok(())
}

fn equal_sequence<'a>(
    mut left: impl Iterator<Item = &'a Value>,
    mut right: impl Iterator<Item = &'a Value>,
    control: &ProductionControl<'_>,
    enums: Option<&dyn super::super::enums::EnumLabelCatalog>,
    typed: bool,
) -> Result<bool> {
    loop {
        control.check()?;
        match (left.next(), right.next()) {
            (Some(left), Some(right)) if equal_values(left, right, control, enums, typed)? => {}
            (None, None) => return Ok(true),
            _ => return Ok(false),
        }
    }
}

fn compare_sequence<'a>(
    mut left: impl Iterator<Item = &'a Value>,
    mut right: impl Iterator<Item = &'a Value>,
    control: &ProductionControl<'_>,
    enums: Option<&dyn EnumLabelCatalog>,
    enum_order: EnumKeyOrder,
) -> Result<Ordering> {
    loop {
        control.check()?;
        let ordering = match (left.next(), right.next()) {
            (Some(left), Some(right)) => {
                compare_typed_values_for_purpose(left, right, control, enums, enum_order)?
            }
            (Some(_), None) => Ordering::Greater,
            (None, Some(_)) => Ordering::Less,
            (None, None) => return Ok(Ordering::Equal),
        };
        if !ordering.is_eq() {
            return Ok(ordering);
        }
    }
}

fn compare_fixed_text(
    left: &str,
    right: &str,
    control: &ProductionControl<'_>,
) -> Result<Ordering> {
    fn trim<'a>(text: &'a str, control: &ProductionControl<'_>) -> Result<&'a [u8]> {
        let mut bytes = text.as_bytes();
        let mut checked = 0;
        while bytes.last() == Some(&b' ') {
            if checked % 4096 == 0 {
                control.check()?;
            }
            bytes = &bytes[..bytes.len() - 1];
            checked += 1;
        }
        Ok(bytes)
    }
    let left = trim(left, control)?;
    let right = trim(right, control)?;
    for (left, right) in left.chunks(4096).zip(right.chunks(4096)) {
        control.check()?;
        let ordering = left.cmp(right);
        if !ordering.is_eq() {
            return Ok(ordering);
        }
    }
    control.check()?;
    Ok(left.len().cmp(&right.len()))
}

#[cfg(test)]
mod tests;