//! Helper functions and structures for the translation.
use crate::environ::{WasmError, WasmResult};
use core::u32;
use cranelift_codegen::entity::entity_impl;
use cranelift_codegen::ir;
use wasmparser;

/// Index type of a function (imported or defined) inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct FuncIndex(u32);
entity_impl!(FuncIndex);

/// Index type of a defined function inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct DefinedFuncIndex(u32);
entity_impl!(DefinedFuncIndex);

/// Index type of a defined table inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct DefinedTableIndex(u32);
entity_impl!(DefinedTableIndex);

/// Index type of a defined memory inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct DefinedMemoryIndex(u32);
entity_impl!(DefinedMemoryIndex);

/// Index type of a defined global inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct DefinedGlobalIndex(u32);
entity_impl!(DefinedGlobalIndex);

/// Index type of a table (imported or defined) inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct TableIndex(u32);
entity_impl!(TableIndex);

/// Index type of a global variable (imported or defined) inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct GlobalIndex(u32);
entity_impl!(GlobalIndex);

/// Index type of a linear memory (imported or defined) inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct MemoryIndex(u32);
entity_impl!(MemoryIndex);

/// Index type of a signature (imported or defined) inside the WebAssembly module.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
pub struct SignatureIndex(u32);
entity_impl!(SignatureIndex);

/// WebAssembly global.
#[derive(Debug, Clone, Copy)]
pub struct Global {
    /// The type of the value stored in the global.
    pub ty: ir::Type,
    /// A flag indicating whether the value may change at runtime.
    pub mutability: bool,
    /// The source of the initial value.
    pub initializer: GlobalInit,
}

/// Globals are initialized via the four `const` operators or by referring to another import.
#[derive(Debug, Clone, Copy)]
pub enum GlobalInit {
    /// An `i32.const`.
    I32Const(i32),
    /// An `i64.const`.
    I64Const(i64),
    /// An `f32.const`.
    F32Const(u32),
    /// An `f64.const`.
    F64Const(u64),
    /// A `get_global` of another global.
    GetGlobal(GlobalIndex),
    ///< The global is imported from, and thus initialized by, a different module.
    Import,
}

/// WebAssembly table.
#[derive(Debug, Clone, Copy)]
pub struct Table {
    /// The type of data stored in elements of the table.
    pub ty: TableElementType,
    /// The minimum number of elements in the table.
    pub minimum: u32,
    /// The maximum number of elements in the table.
    pub maximum: Option<u32>,
}

/// WebAssembly table element. Can be a function or a scalar type.
#[derive(Debug, Clone, Copy)]
pub enum TableElementType {
    /// A scalar type.
    Val(ir::Type),
    /// A function.
    Func,
}

/// WebAssembly linear memory.
#[derive(Debug, Clone, Copy)]
pub struct Memory {
    /// The minimum number of pages in the memory.
    pub minimum: u32,
    /// The maximum number of pages in the memory.
    pub maximum: Option<u32>,
    /// Whether the memory may be shared between multiple threads.
    pub shared: bool,
}

/// Helper function translating wasmparser types to Cranelift types when possible.
pub fn type_to_type(ty: wasmparser::Type) -> WasmResult<ir::Type> {
    Ok(match ty {
        wasmparser::Type::I32 => ir::types::I32,
        wasmparser::Type::I64 => ir::types::I64,
        wasmparser::Type::F32 => ir::types::F32,
        wasmparser::Type::F64 => ir::types::F64,
        _ => return Err(WasmError::Unsupported("unsupported wasm type")),
    })
}

/// Helper function translating wasmparser possible table types to Cranelift types when possible,
/// or None for Func tables.
pub fn tabletype_to_type(ty: wasmparser::Type) -> WasmResult<Option<ir::Type>> {
    Ok(match ty {
        wasmparser::Type::I32 => Some(ir::types::I32),
        wasmparser::Type::I64 => Some(ir::types::I64),
        wasmparser::Type::F32 => Some(ir::types::F32),
        wasmparser::Type::F64 => Some(ir::types::F64),
        wasmparser::Type::AnyFunc => None,
        _ => return Err(WasmError::Unsupported("unsupported table wasm type")),
    })
}

/// Helper function translating wasmparser block signatures to Cranelift types when possible.
pub fn blocktype_to_type(ty: wasmparser::TypeOrFuncType) -> WasmResult<ir::Type> {
    match ty {
        wasmparser::TypeOrFuncType::Type(ty) => type_to_type(ty),
        wasmparser::TypeOrFuncType::FuncType(_) => {
            Err(WasmError::Unsupported("multi-value block signatures"))
        }
    }
}

/// Turns a `wasmparser` `f32` into a `Cranelift` one.
pub fn f32_translation(x: wasmparser::Ieee32) -> ir::immediates::Ieee32 {
    ir::immediates::Ieee32::with_bits(x.bits())
}

/// Turns a `wasmparser` `f64` into a `Cranelift` one.
pub fn f64_translation(x: wasmparser::Ieee64) -> ir::immediates::Ieee64 {
    ir::immediates::Ieee64::with_bits(x.bits())
}

/// Translate a `wasmparser` type into its `Cranelift` equivalent, when possible
pub fn num_return_values(ty: wasmparser::TypeOrFuncType) -> WasmResult<usize> {
    match ty {
        wasmparser::TypeOrFuncType::Type(ty) => match ty {
            wasmparser::Type::EmptyBlockType => Ok(0),
            wasmparser::Type::I32
            | wasmparser::Type::F32
            | wasmparser::Type::I64
            | wasmparser::Type::F64 => Ok(1),
            _ => Err(WasmError::Unsupported("unsupported return value type")),
        },
        wasmparser::TypeOrFuncType::FuncType(_) => {
            Err(WasmError::Unsupported("multi-value block signatures"))
        }
    }
}

/// Special VMContext value label. It is tracked as 0xffff_fffe label.
pub fn get_vmctx_value_label() -> ir::ValueLabel {
    const VMCTX_LABEL: u32 = 0xffff_fffe;
    ir::ValueLabel::from_u32(VMCTX_LABEL)
}