/*
 * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package ssa

import (
	"go/token"
	"go/types"
	"log"
	"unsafe"

	"github.com/goplus/llgo/ssa/abi"
	"github.com/goplus/llvm"
)

// -----------------------------------------------------------------------------

// abiBasic returns the abi type of the specified basic kind.
func (b Builder) abiBasic(t *types.Basic) Expr {
	/*
		TODO(xsw):
		name := abi.BasicName(t)
		g := b.Pkg.NewVarFrom(name, b.Prog.AbiTypePtrPtr())
		return b.Load(g.Expr)
	*/
	kind := int(abi.BasicKind(t))
	return b.InlineCall(b.Pkg.rtFunc("Basic"), b.Prog.Val(kind))
}

// abiStruct returns the abi type of the specified struct type.
func (b Builder) abiStruct(t *types.Struct) Expr {
	pkg := b.Pkg
	name, private := pkg.abi.StructName(t)
	g := pkg.VarOf(name)
	if g == nil {
		prog := b.Prog
		g = pkg.doNewVar(name, prog.AbiTypePtrPtr())
		g.Init(prog.Null(g.Type))
		pub := !private
		if pub {
			g.impl.SetLinkage(llvm.LinkOnceAnyLinkage)
		}
		pkg.abiini = append(pkg.abiini, func(param unsafe.Pointer) {
			b := Builder(param)
			expr := g.Expr
			var blks []BasicBlock
			if pub {
				eq := b.BinOp(token.EQL, b.Load(expr), b.Prog.Null(expr.Type))
				blks = b.Func.MakeBlocks(2)
				b.If(eq, blks[0], blks[1])
				b.SetBlockEx(blks[0], AtEnd, false)
			}
			tabi := b.structOf(t)
			b.Store(expr, tabi)
			if pub {
				b.Jump(blks[1])
				b.SetBlockEx(blks[1], AtEnd, false)
				b.blk.last = blks[1].last
			}
		})
	}
	return b.Load(g.Expr)
}

// func Struct(size uintptr, pkgPath string, fields []abi.StructField) *abi.Type
func (b Builder) structOf(t *types.Struct) Expr {
	pkg := b.Pkg
	prog := b.Prog
	n := t.NumFields()
	flds := make([]Expr, n)
	strucAbi := pkg.rtFunc("Struct")
	sfAbi := pkg.rtFunc("StructField")
	typ := prog.rawType(t)
	for i := 0; i < n; i++ {
		f := t.Field(i)
		off := uintptr(prog.OffsetOf(typ, i))
		flds[i] = b.structField(sfAbi, prog, f, off, t.Tag(i))
	}
	pkgPath := b.Str(pkg.abi.Pkg)
	params := strucAbi.raw.Type.(*types.Signature).Params()
	tSlice := prog.rawType(params.At(params.Len() - 1).Type().(*types.Slice))
	fldSlice := b.SliceLit(tSlice, flds...)
	return b.Call(strucAbi, pkgPath, fldSlice)
}

// func StructField(name string, typ *abi.Type, off uintptr, tag string, exported, embedded bool) abi.StructField
func (b Builder) structField(sfAbi Expr, prog Program, f *types.Var, offset uintptr, tag string) Expr {
	name := b.Str(f.Name())
	typ := b.abiType(f.Type())
	exported := prog.Val(f.Exported())
	embedded := prog.Val(f.Embedded())
	return b.Call(sfAbi, name, typ, prog.Val(offset), b.Str(tag), exported, embedded)
}

// abiType returns the abi type of the specified type.
func (b Builder) abiType(raw types.Type) Expr {
	switch tx := raw.(type) {
	case *types.Basic:
		return b.abiBasic(tx)
	case *types.Struct:
		return b.abiStruct(tx)
	}
	panic("todo")
}

// unsafeEface(t *abi.Type, data unsafe.Pointer) Eface
func (b Builder) unsafeEface(t, data llvm.Value) llvm.Value {
	return aggregateValue(b.impl, b.Prog.rtEface(), t, data)
}

// -----------------------------------------------------------------------------

// MakeInterface constructs an instance of an interface type from a
// value of a concrete type.
//
// Use Program.MethodSets.MethodSet(X.Type()) to find the method-set
// of X, and Program.MethodValue(m) to find the implementation of a method.
//
// To construct the zero value of an interface type T, use:
//
//	NewConst(constant.MakeNil(), T, pos)
//
// Example printed form:
//
//	t1 = make interface{} <- int (42:int)
//	t2 = make Stringer <- t0
func (b Builder) MakeInterface(tinter Type, x Expr) (ret Expr) {
	rawIntf := tinter.raw.Type.Underlying().(*types.Interface)
	if debugInstr {
		log.Printf("MakeInterface %v, %v\n", rawIntf, x.impl)
	}
	prog := b.Prog
	typ := x.Type
	tabi := b.abiType(typ.raw.Type)
	kind, _, lvl := abi.KindOf(typ.raw.Type, 0, prog.is32Bits)
	switch kind {
	case abi.Indirect:
		vptr := b.AllocU(typ)
		b.Store(vptr, x)
		return Expr{b.unsafeEface(tabi.impl, vptr.impl), tinter}
	}
	ximpl := x.impl
	if lvl > 0 {
		ximpl = extractVal(b.impl, ximpl, lvl)
	}
	var u llvm.Value
	switch kind {
	case abi.Pointer:
		return Expr{b.unsafeEface(tabi.impl, ximpl), tinter}
	case abi.Integer:
		tu := prog.Uintptr()
		u = llvm.CreateIntCast(b.impl, ximpl, tu.ll)
	case abi.BitCast:
		tu := prog.Uintptr()
		u = llvm.CreateBitCast(b.impl, ximpl, tu.ll)
	default:
		panic("todo")
	}
	data := llvm.CreateIntToPtr(b.impl, u, prog.tyVoidPtr())
	return Expr{b.unsafeEface(tabi.impl, data), tinter}
}

func (b Builder) valFromData(typ Type, data llvm.Value) Expr {
	prog := b.Prog
	kind, real, lvl := abi.KindOf(typ.raw.Type, 0, prog.is32Bits)
	switch kind {
	case abi.Indirect:
		impl := b.impl
		tll := typ.ll
		tptr := llvm.PointerType(tll, 0)
		ptr := llvm.CreatePointerCast(impl, data, tptr)
		return Expr{llvm.CreateLoad(impl, tll, ptr), typ}
	}
	t := typ
	if lvl > 0 {
		t = prog.rawType(real)
	}
	switch kind {
	case abi.Pointer:
		return b.buildVal(typ, data, lvl)
	case abi.Integer:
		x := castUintptr(b, data, prog.Uintptr())
		return b.buildVal(typ, castInt(b, x, t), lvl)
	case abi.BitCast:
		x := castUintptr(b, data, prog.Uintptr())
		if int(prog.SizeOf(t)) != prog.PointerSize() {
			x = castInt(b, x, prog.Int32())
		}
		return b.buildVal(typ, llvm.CreateBitCast(b.impl, x, t.ll), lvl)
	}
	panic("todo")
}

func extractVal(b llvm.Builder, val llvm.Value, lvl int) llvm.Value {
	for lvl > 0 {
		// TODO(xsw): check array support
		val = llvm.CreateExtractValue(b, val, 0)
		lvl--
	}
	return val
}

func (b Builder) buildVal(typ Type, val llvm.Value, lvl int) Expr {
	if lvl == 0 {
		return Expr{val, typ}
	}
	switch t := typ.raw.Type.Underlying().(type) {
	case *types.Struct:
		telem := b.Prog.rawType(t.Field(0).Type())
		elem := b.buildVal(telem, val, lvl-1)
		return Expr{aggregateValue(b.impl, typ.ll, elem.impl), typ}
	}
	panic("todo")
}

// The TypeAssert instruction tests whether interface value X has type
// AssertedType.
//
// If !CommaOk, on success it returns v, the result of the conversion
// (defined below); on failure it panics.
//
// If CommaOk: on success it returns a pair (v, true) where v is the
// result of the conversion; on failure it returns (z, false) where z
// is AssertedType's zero value.  The components of the pair must be
// accessed using the Extract instruction.
//
// If Underlying: tests whether interface value X has the underlying
// type AssertedType.
//
// If AssertedType is a concrete type, TypeAssert checks whether the
// dynamic type in interface X is equal to it, and if so, the result
// of the conversion is a copy of the value in the interface.
//
// If AssertedType is an interface, TypeAssert checks whether the
// dynamic type of the interface is assignable to it, and if so, the
// result of the conversion is a copy of the interface value X.
// If AssertedType is a superinterface of X.Type(), the operation will
// fail iff the operand is nil.  (Contrast with ChangeInterface, which
// performs no nil-check.)
//
// Type() reflects the actual type of the result, possibly a
// 2-types.Tuple; AssertedType is the asserted type.
//
// Depending on the TypeAssert's purpose, Pos may return:
//   - the ast.CallExpr.Lparen of an explicit T(e) conversion;
//   - the ast.TypeAssertExpr.Lparen of an explicit e.(T) operation;
//   - the ast.CaseClause.Case of a case of a type-switch statement;
//   - the Ident(m).NamePos of an interface method value i.m
//     (for which TypeAssert may be used to effect the nil check).
//
// Example printed form:
//
//	t1 = typeassert t0.(int)
//	t3 = typeassert,ok t2.(T)
func (b Builder) TypeAssert(x Expr, assertedTyp Type, commaOk bool) Expr {
	if debugInstr {
		log.Printf("TypeAssert %v, %v, %v\n", x.impl, assertedTyp.raw.Type, commaOk)
	}
	tx := b.faceAbiType(x)
	tabi := b.abiType(assertedTyp.raw.Type)
	eq := b.BinOp(token.EQL, tx, tabi)
	if commaOk {
		prog := b.Prog
		t := prog.Tuple(assertedTyp, prog.Bool())
		val := b.valFromData(assertedTyp, b.faceData(x.impl))
		zero := prog.Zero(assertedTyp)
		valTrue := aggregateValue(b.impl, t.ll, val.impl, prog.BoolVal(true).impl)
		valFalse := aggregateValue(b.impl, t.ll, zero.impl, prog.BoolVal(false).impl)
		return Expr{llvm.CreateSelect(b.impl, eq.impl, valTrue, valFalse), t}
	}
	blks := b.Func.MakeBlocks(2)
	b.If(eq, blks[0], blks[1])
	b.SetBlockEx(blks[1], AtEnd, false)
	b.Panic(b.Str("type assertion failed"))
	b.SetBlockEx(blks[0], AtEnd, false)
	b.blk.last = blks[0].last
	return b.valFromData(assertedTyp, b.faceData(x.impl))
}

/*
func (b Builder) TypeAssert(x Expr, assertedTyp Type, commaOk bool) (ret Expr) {
	if debugInstr {
		log.Printf("TypeAssert %v, %v, %v\n", x.impl, assertedTyp.raw.Type, commaOk)
	}
	// TODO(xsw)
	// if x.kind != vkEface {
	//	 panic("todo: non empty interface")
	// }
	switch assertedTyp.kind {
	case vkSigned, vkUnsigned, vkFloat, vkBool:
		pkg := b.Pkg
		fnName := "I2Int"
		if commaOk {
			fnName = "CheckI2Int"
		}
		fn := pkg.rtFunc(fnName)
		var kind types.BasicKind
		var typ Expr
		switch t := assertedTyp.raw.Type.(type) {
		case *types.Basic:
			kind = t.Kind()
			typ = b.abiBasic(t)
		default:
			panic("todo")
		}
		ret = b.InlineCall(fn, x, typ)
		if kind != types.Uintptr {
			conv := func(v llvm.Value) llvm.Value {
				switch kind {
				case types.Float32:
					v = castInt(b, v, b.Prog.Int32())
					v = llvm.CreateBitCast(b.impl, v, assertedTyp.ll)
				case types.Float64:
					v = llvm.CreateBitCast(b.impl, v, assertedTyp.ll)
				default:
					v = castInt(b, v, assertedTyp)
				}
				return v
			}
			if !commaOk {
				ret.Type = assertedTyp
				ret.impl = conv(ret.impl)
			} else {
				ret.Type = b.Prog.toTuple(
					types.NewTuple(
						types.NewVar(token.NoPos, nil, "", assertedTyp.RawType()),
						ret.Type.RawType().(*types.Tuple).At(1),
					),
				)
				val0 := conv(llvm.CreateExtractValue(b.impl, ret.impl, 0))
				val1 := llvm.CreateExtractValue(b.impl, ret.impl, 1)
				ret.impl = llvm.ConstStruct([]llvm.Value{val0, val1}, false)
			}
		}
		return
	case vkString:
		pkg := b.Pkg
		fnName := "I2String"
		if commaOk {
			fnName = "CheckI2String"
		}
		return b.InlineCall(pkg.rtFunc(fnName), x)
	}
	panic("todo")
}
*/

// -----------------------------------------------------------------------------

// InterfaceData returns the data pointer of an interface.
func (b Builder) InterfaceData(x Expr) Expr {
	if debugInstr {
		log.Printf("InterfaceData %v\n", x.impl)
	}
	return Expr{b.faceData(x.impl), b.Prog.VoidPtr()}
}

func (b Builder) faceData(x llvm.Value) llvm.Value {
	return llvm.CreateExtractValue(b.impl, x, 1)
}

func (b Builder) faceAbiType(x Expr) Expr {
	if x.kind == vkIface {
		panic("todo")
	}
	typ := llvm.CreateExtractValue(b.impl, x.impl, 0)
	return Expr{typ, b.Prog.AbiTypePtr()}
}

// -----------------------------------------------------------------------------