use super::{HandleMap, HandleSet, ModuleMap};
use crate::arena::{Arena, Handle};

pub struct ExpressionTracer<'tracer> {
    pub constants: &'tracer Arena<crate::Constant>,
    pub overrides: &'tracer Arena<crate::Override>,

    /// The arena in which we are currently tracing expressions.
    pub expressions: &'tracer Arena<crate::Expression>,

    /// The used map for `types`.
    pub types_used: &'tracer mut HandleSet<crate::Type>,

    /// The used map for `constants`.
    pub constants_used: &'tracer mut HandleSet<crate::Constant>,

    /// The used map for `overrides`.
    pub overrides_used: &'tracer mut HandleSet<crate::Override>,

    /// The used set for `arena`.
    ///
    /// This points to whatever arena holds the expressions we are
    /// currently tracing: either a function's expression arena, or
    /// the module's constant expression arena.
    pub expressions_used: &'tracer mut HandleSet<crate::Expression>,

    /// The used set for the module's `global_expressions` arena.
    ///
    /// If `None`, we are already tracing the constant expressions,
    /// and `expressions_used` already refers to their handle set.
    pub global_expressions_used: Option<&'tracer mut HandleSet<crate::Expression>>,
}

impl ExpressionTracer<'_> {
    /// Propagate usage through `self.expressions`, starting with `self.expressions_used`.
    ///
    /// Treat `self.expressions_used` as the initial set of "known
    /// live" expressions, and follow through to identify all
    /// transitively used expressions.
    ///
    /// Mark types, constants, and constant expressions used directly
    /// by `self.expressions` as used. Items used indirectly are not
    /// marked.
    ///
    /// [fe]: crate::Function::expressions
    /// [ce]: crate::Module::global_expressions
    pub fn trace_expressions(&mut self) {
        log::trace!(
            "entering trace_expression of {}",
            if self.global_expressions_used.is_some() {
                "function expressions"
            } else {
                "const expressions"
            }
        );

        // We don't need recursion or a work list. Because an
        // expression may only refer to other expressions that precede
        // it in the arena, it suffices to make a single pass over the
        // arena from back to front, marking the referents of used
        // expressions as used themselves.
        for (handle, expr) in self.expressions.iter().rev() {
            // If this expression isn't used, it doesn't matter what it uses.
            if !self.expressions_used.contains(handle) {
                continue;
            }

            log::trace!("tracing new expression {:?}", expr);
            self.trace_expression(expr);
        }
    }

    pub fn trace_expression(&mut self, expr: &crate::Expression) {
        use crate::Expression as Ex;
        match *expr {
            // Expressions that do not contain handles that need to be traced.
            Ex::Literal(_)
            | Ex::FunctionArgument(_)
            | Ex::GlobalVariable(_)
            | Ex::LocalVariable(_)
            | Ex::CallResult(_)
            | Ex::SubgroupBallotResult
            | Ex::RayQueryProceedResult => {}

            // Expressions can refer to constants and overrides, which can refer
            // in turn to expressions, which complicates our nice one-pass
            // algorithm. But since constants and overrides don't refer to each
            // other directly, only via expressions, we can get around this by
            // looking *through* each constant/override and marking its
            // initializer expression as used immediately. Since `expr` refers
            // to the constant/override, which then refers to the initializer,
            // the initializer must precede `expr` in the arena, so we know we
            // have yet to visit the initializer, so it's not too late to mark
            // it.
            Ex::Constant(handle) => {
                self.constants_used.insert(handle);
                let constant = &self.constants[handle];
                self.types_used.insert(constant.ty);
                match self.global_expressions_used {
                    Some(ref mut used) => used.insert(constant.init),
                    None => self.expressions_used.insert(constant.init),
                };
            }
            Ex::Override(handle) => {
                self.overrides_used.insert(handle);
                let r#override = &self.overrides[handle];
                self.types_used.insert(r#override.ty);
                if let Some(init) = r#override.init {
                    match self.global_expressions_used {
                        Some(ref mut used) => used.insert(init),
                        None => self.expressions_used.insert(init),
                    };
                }
            }
            Ex::ZeroValue(ty) => {
                self.types_used.insert(ty);
            }
            Ex::Compose { ty, ref components } => {
                self.types_used.insert(ty);
                self.expressions_used
                    .insert_iter(components.iter().cloned());
            }
            Ex::Access { base, index } => self.expressions_used.insert_iter([base, index]),
            Ex::AccessIndex { base, index: _ } => {
                self.expressions_used.insert(base);
            }
            Ex::Splat { size: _, value } => {
                self.expressions_used.insert(value);
            }
            Ex::Swizzle {
                size: _,
                vector,
                pattern: _,
            } => {
                self.expressions_used.insert(vector);
            }
            Ex::Load { pointer } => {
                self.expressions_used.insert(pointer);
            }
            Ex::ImageSample {
                image,
                sampler,
                gather: _,
                coordinate,
                array_index,
                offset,
                ref level,
                depth_ref,
            } => {
                self.expressions_used
                    .insert_iter([image, sampler, coordinate]);
                self.expressions_used.insert_iter(array_index);
                self.expressions_used.insert_iter(offset);
                use crate::SampleLevel as Sl;
                match *level {
                    Sl::Auto | Sl::Zero => {}
                    Sl::Exact(expr) | Sl::Bias(expr) => {
                        self.expressions_used.insert(expr);
                    }
                    Sl::Gradient { x, y } => self.expressions_used.insert_iter([x, y]),
                }
                self.expressions_used.insert_iter(depth_ref);
            }
            Ex::ImageLoad {
                image,
                coordinate,
                array_index,
                sample,
                level,
            } => {
                self.expressions_used.insert(image);
                self.expressions_used.insert(coordinate);
                self.expressions_used.insert_iter(array_index);
                self.expressions_used.insert_iter(sample);
                self.expressions_used.insert_iter(level);
            }
            Ex::ImageQuery { image, ref query } => {
                self.expressions_used.insert(image);
                use crate::ImageQuery as Iq;
                match *query {
                    Iq::Size { level } => self.expressions_used.insert_iter(level),
                    Iq::NumLevels | Iq::NumLayers | Iq::NumSamples => {}
                }
            }
            Ex::RayQueryVertexPositions {
                query,
                committed: _,
            } => {
                self.expressions_used.insert(query);
            }
            Ex::Unary { op: _, expr } => {
                self.expressions_used.insert(expr);
            }
            Ex::Binary { op: _, left, right } => {
                self.expressions_used.insert_iter([left, right]);
            }
            Ex::Select {
                condition,
                accept,
                reject,
            } => self
                .expressions_used
                .insert_iter([condition, accept, reject]),
            Ex::Derivative {
                axis: _,
                ctrl: _,
                expr,
            } => {
                self.expressions_used.insert(expr);
            }
            Ex::Relational { fun: _, argument } => {
                self.expressions_used.insert(argument);
            }
            Ex::Math {
                fun: _,
                arg,
                arg1,
                arg2,
                arg3,
            } => {
                self.expressions_used.insert(arg);
                self.expressions_used.insert_iter(arg1);
                self.expressions_used.insert_iter(arg2);
                self.expressions_used.insert_iter(arg3);
            }
            Ex::As {
                expr,
                kind: _,
                convert: _,
            } => {
                self.expressions_used.insert(expr);
            }
            Ex::ArrayLength(expr) => {
                self.expressions_used.insert(expr);
            }
            Ex::AtomicResult { ty, comparison: _ }
            | Ex::WorkGroupUniformLoadResult { ty }
            | Ex::SubgroupOperationResult { ty } => {
                self.types_used.insert(ty);
            }
            Ex::RayQueryGetIntersection {
                query,
                committed: _,
            } => {
                self.expressions_used.insert(query);
            }
        }
    }
}

impl ModuleMap {
    /// Fix up all handles in `expr`.
    ///
    /// Use the expression handle remappings in `operand_map`, and all
    /// other mappings from `self`.
    pub fn adjust_expression(
        &self,
        expr: &mut crate::Expression,
        operand_map: &HandleMap<crate::Expression>,
    ) {
        let adjust = |expr: &mut Handle<crate::Expression>| {
            operand_map.adjust(expr);
        };

        use crate::Expression as Ex;
        match *expr {
            // Expressions that do not contain handles that need to be adjusted.
            Ex::Literal(_)
            | Ex::FunctionArgument(_)
            | Ex::GlobalVariable(_)
            | Ex::LocalVariable(_)
            | Ex::CallResult(_)
            | Ex::SubgroupBallotResult
            | Ex::RayQueryProceedResult => {}

            // Expressions that contain handles that need to be adjusted.
            Ex::Constant(ref mut constant) => self.constants.adjust(constant),
            Ex::Override(ref mut r#override) => self.overrides.adjust(r#override),
            Ex::ZeroValue(ref mut ty) => self.types.adjust(ty),
            Ex::Compose {
                ref mut ty,
                ref mut components,
            } => {
                self.types.adjust(ty);
                for component in components {
                    adjust(component);
                }
            }
            Ex::Access {
                ref mut base,
                ref mut index,
            } => {
                adjust(base);
                adjust(index);
            }
            Ex::AccessIndex {
                ref mut base,
                index: _,
            } => adjust(base),
            Ex::Splat {
                size: _,
                ref mut value,
            } => adjust(value),
            Ex::Swizzle {
                size: _,
                ref mut vector,
                pattern: _,
            } => adjust(vector),
            Ex::Load { ref mut pointer } => adjust(pointer),
            Ex::ImageSample {
                ref mut image,
                ref mut sampler,
                gather: _,
                ref mut coordinate,
                ref mut array_index,
                ref mut offset,
                ref mut level,
                ref mut depth_ref,
            } => {
                adjust(image);
                adjust(sampler);
                adjust(coordinate);
                operand_map.adjust_option(array_index);
                operand_map.adjust_option(offset);
                self.adjust_sample_level(level, operand_map);
                operand_map.adjust_option(depth_ref);
            }
            Ex::ImageLoad {
                ref mut image,
                ref mut coordinate,
                ref mut array_index,
                ref mut sample,
                ref mut level,
            } => {
                adjust(image);
                adjust(coordinate);
                operand_map.adjust_option(array_index);
                operand_map.adjust_option(sample);
                operand_map.adjust_option(level);
            }
            Ex::ImageQuery {
                ref mut image,
                ref mut query,
            } => {
                adjust(image);
                self.adjust_image_query(query, operand_map);
            }
            Ex::Unary {
                op: _,
                ref mut expr,
            } => adjust(expr),
            Ex::Binary {
                op: _,
                ref mut left,
                ref mut right,
            } => {
                adjust(left);
                adjust(right);
            }
            Ex::Select {
                ref mut condition,
                ref mut accept,
                ref mut reject,
            } => {
                adjust(condition);
                adjust(accept);
                adjust(reject);
            }
            Ex::Derivative {
                axis: _,
                ctrl: _,
                ref mut expr,
            } => adjust(expr),
            Ex::Relational {
                fun: _,
                ref mut argument,
            } => adjust(argument),
            Ex::Math {
                fun: _,
                ref mut arg,
                ref mut arg1,
                ref mut arg2,
                ref mut arg3,
            } => {
                adjust(arg);
                operand_map.adjust_option(arg1);
                operand_map.adjust_option(arg2);
                operand_map.adjust_option(arg3);
            }
            Ex::As {
                ref mut expr,
                kind: _,
                convert: _,
            } => adjust(expr),
            Ex::AtomicResult {
                ref mut ty,
                comparison: _,
            } => self.types.adjust(ty),
            Ex::WorkGroupUniformLoadResult { ref mut ty } => self.types.adjust(ty),
            Ex::SubgroupOperationResult { ref mut ty } => self.types.adjust(ty),
            Ex::ArrayLength(ref mut expr) => adjust(expr),
            Ex::RayQueryGetIntersection {
                ref mut query,
                committed: _,
            } => adjust(query),
            Ex::RayQueryVertexPositions {
                ref mut query,
                committed: _,
            } => adjust(query),
        }
    }

    fn adjust_sample_level(
        &self,
        level: &mut crate::SampleLevel,
        operand_map: &HandleMap<crate::Expression>,
    ) {
        let adjust = |expr: &mut Handle<crate::Expression>| operand_map.adjust(expr);

        use crate::SampleLevel as Sl;
        match *level {
            Sl::Auto | Sl::Zero => {}
            Sl::Exact(ref mut expr) => adjust(expr),
            Sl::Bias(ref mut expr) => adjust(expr),
            Sl::Gradient {
                ref mut x,
                ref mut y,
            } => {
                adjust(x);
                adjust(y);
            }
        }
    }

    fn adjust_image_query(
        &self,
        query: &mut crate::ImageQuery,
        operand_map: &HandleMap<crate::Expression>,
    ) {
        use crate::ImageQuery as Iq;

        match *query {
            Iq::Size { ref mut level } => operand_map.adjust_option(level),
            Iq::NumLevels | Iq::NumLayers | Iq::NumSamples => {}
        }
    }
}
