/*
 * 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 (
	"bytes"
	"fmt"
	"go/constant"
	"go/token"
	"go/types"
	"log"

	"github.com/goplus/llvm"
)

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

type Expr struct {
	impl llvm.Value
	Type
}

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

func llvmValues(vals []Expr) []llvm.Value {
	ret := make([]llvm.Value, len(vals))
	for i, v := range vals {
		ret[i] = v.impl
	}
	return ret
}

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

func (p Program) Null(t Type) Expr {
	return Expr{llvm.ConstNull(t.ll), t}
}

func (p Program) BoolVal(v bool) Expr {
	t := p.Bool()
	var bv uint64
	if v {
		bv = 1
	}
	ret := llvm.ConstInt(t.ll, bv, v)
	return Expr{ret, t}
}

func (p Program) IntVal(v uint64, t Type) Expr {
	ret := llvm.ConstInt(t.ll, v, false)
	return Expr{ret, t}
}

func (p Program) Val(v interface{}) Expr {
	switch v := v.(type) {
	case int:
		return p.IntVal(uint64(v), p.Int())
	case bool:
		return p.BoolVal(v)
	case float64:
		t := p.Float64()
		ret := llvm.ConstFloat(t.ll, v)
		return Expr{ret, t}
	}
	panic("todo")
}

func (b Builder) Const(v constant.Value, typ Type) Expr {
	switch t := typ.t.(type) {
	case *types.Basic:
		kind := t.Kind()
		switch {
		case kind == types.Bool:
			return b.prog.BoolVal(constant.BoolVal(v))
		case kind >= types.Int && kind <= types.Uintptr:
			if v, exact := constant.Uint64Val(v); exact {
				return b.prog.IntVal(v, typ)
			}
		}
	}
	panic("todo")
}

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

const (
	mathOpBase = token.ADD
	mathOpLast = token.REM
)

var mathOpToLLVM = []llvm.Opcode{
	int(token.ADD-mathOpBase)<<2 | vkSigned:   llvm.Add,
	int(token.ADD-mathOpBase)<<2 | vkUnsigned: llvm.Add,
	int(token.ADD-mathOpBase)<<2 | vkFloat:    llvm.FAdd,

	int(token.SUB-mathOpBase)<<2 | vkSigned:   llvm.Sub,
	int(token.SUB-mathOpBase)<<2 | vkUnsigned: llvm.Sub,
	int(token.SUB-mathOpBase)<<2 | vkFloat:    llvm.FSub,

	int(token.MUL-mathOpBase)<<2 | vkSigned:   llvm.Mul,
	int(token.MUL-mathOpBase)<<2 | vkUnsigned: llvm.Mul,
	int(token.MUL-mathOpBase)<<2 | vkFloat:    llvm.FMul,

	int(token.QUO-mathOpBase)<<2 | vkSigned:   llvm.SDiv,
	int(token.QUO-mathOpBase)<<2 | vkUnsigned: llvm.UDiv,
	int(token.QUO-mathOpBase)<<2 | vkFloat:    llvm.FDiv,

	int(token.REM-mathOpBase)<<2 | vkSigned:   llvm.SRem,
	int(token.REM-mathOpBase)<<2 | vkUnsigned: llvm.URem,
	int(token.REM-mathOpBase)<<2 | vkFloat:    llvm.FRem,
}

func mathOpIdx(op token.Token, x valueKind) int {
	return int(op-mathOpBase)<<2 | x
}

// ADD SUB MUL QUO REM          + - * / %
func isMathOp(op token.Token) bool {
	return op >= mathOpBase && op <= mathOpLast
}

const (
	logicOpBase = token.AND
	logicOpLast = token.AND_NOT
)

var logicOpToLLVM = []llvm.Opcode{
	token.AND - logicOpBase: llvm.And,
	token.OR - logicOpBase:  llvm.Or,
	token.XOR - logicOpBase: llvm.Xor,
	token.SHL - logicOpBase: llvm.Shl,
	token.SHR - logicOpBase: llvm.AShr, // Arithmetic Shift Right
}

// AND OR XOR SHL SHR AND_NOT   & | ^ << >> &^
func isLogicOp(op token.Token) bool {
	return op >= logicOpBase && op <= logicOpLast
}

const (
	predOpBase = token.EQL
	predOpLast = token.GEQ
)

var intPredOpToLLVM = []llvm.IntPredicate{
	token.EQL - predOpBase: llvm.IntEQ,
	token.NEQ - predOpBase: llvm.IntNE,
	token.LSS - predOpBase: llvm.IntSLT,
	token.LEQ - predOpBase: llvm.IntSLE,
	token.GTR - predOpBase: llvm.IntSGT,
	token.GEQ - predOpBase: llvm.IntSGE,
}

var uintPredOpToLLVM = []llvm.IntPredicate{
	token.EQL - predOpBase: llvm.IntEQ,
	token.NEQ - predOpBase: llvm.IntNE,
	token.LSS - predOpBase: llvm.IntULT,
	token.LEQ - predOpBase: llvm.IntULE,
	token.GTR - predOpBase: llvm.IntUGT,
	token.GEQ - predOpBase: llvm.IntUGE,
}

var floatPredOpToLLVM = []llvm.FloatPredicate{
	token.EQL - predOpBase: llvm.FloatOEQ,
	token.NEQ - predOpBase: llvm.FloatONE,
	token.LSS - predOpBase: llvm.FloatOLT,
	token.LEQ - predOpBase: llvm.FloatOLE,
	token.GTR - predOpBase: llvm.FloatOGT,
	token.GEQ - predOpBase: llvm.FloatOGE,
}

// EQL NEQ LSS LEQ GTR GEQ      == != < <= < >=
func isPredOp(op token.Token) bool {
	return op >= predOpBase && op <= predOpLast
}

// The BinOp instruction yields the result of binary operation (x op y).
// op can be:
// ADD SUB MUL QUO REM          + - * / %
// AND OR XOR SHL SHR AND_NOT   & | ^ << >> &^
// EQL NEQ LSS LEQ GTR GEQ      == != < <= < >=
func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
	if debugInstr {
		log.Printf("BinOp %d, %v, %v\n", op, x.impl, y.impl)
	}
	switch {
	case isMathOp(op): // op: + - * / %
		kind := x.kind
		switch kind {
		case vkString, vkComplex:
			panic("todo")
		}
		idx := mathOpIdx(op, kind)
		if llop := mathOpToLLVM[idx]; llop != 0 {
			return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
		}
	case isLogicOp(op): // op: & | ^ << >> &^
		if op == token.AND_NOT {
			panic("todo")
		}
		kind := x.kind
		llop := logicOpToLLVM[op-logicOpBase]
		if op == token.SHR && kind == vkUnsigned {
			llop = llvm.LShr // Logical Shift Right
		}
		return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
	case isPredOp(op): // op: == != < <= < >=
		tret := b.prog.Bool()
		kind := x.kind
		switch kind {
		case vkSigned:
			pred := intPredOpToLLVM[op-predOpBase]
			return Expr{llvm.CreateICmp(b.impl, pred, x.impl, y.impl), tret}
		case vkUnsigned:
			pred := uintPredOpToLLVM[op-predOpBase]
			return Expr{llvm.CreateICmp(b.impl, pred, x.impl, y.impl), tret}
		case vkFloat:
			pred := floatPredOpToLLVM[op-predOpBase]
			return Expr{llvm.CreateFCmp(b.impl, pred, x.impl, y.impl), tret}
		case vkString, vkComplex, vkBool:
			panic("todo")
		}
	}
	panic("todo")
}

// The UnOp instruction yields the result of (op x).
// ARROW is channel receive.
// MUL is pointer indirection (load).
// XOR is bitwise complement.
// SUB is negation.
// NOT is logical negation.
func (b Builder) UnOp(op token.Token, x Expr) Expr {
	switch op {
	case token.MUL:
		return b.Load(x)
	}
	if debugInstr {
		log.Printf("UnOp %v, %v\n", op, x.impl)
	}
	panic("todo")
}

// Load returns the value at the pointer ptr.
func (b Builder) Load(ptr Expr) Expr {
	if debugInstr {
		log.Printf("Load %v\n", ptr.impl.Name())
	}
	telem := b.prog.Elem(ptr.Type)
	return Expr{llvm.CreateLoad(b.impl, telem.ll, ptr.impl), telem}
}

// Store stores val at the pointer ptr.
func (b Builder) Store(ptr, val Expr) Builder {
	if debugInstr {
		log.Printf("Store %v, %v\n", ptr.impl.Name(), val.impl)
	}
	b.impl.CreateStore(val.impl, ptr.impl)
	return b
}

// The IndexAddr instruction yields the address of the element at
// index `idx` of collection `x`.  `idx` is an integer expression.
//
// The elements of maps and strings are not addressable; use Lookup (map),
// Index (string), or MapUpdate instead.
//
// Dynamically, this instruction panics if `x` evaluates to a nil *array
// pointer.
//
// Example printed form:
//
//	t2 = &t0[t1]
func (b Builder) IndexAddr(x, idx Expr) Expr {
	if debugInstr {
		log.Printf("IndexAddr %v, %v\n", x.impl, idx.impl)
	}
	prog := b.prog
	telem := prog.Index(x.Type)
	pt := prog.Pointer(telem)
	indices := []llvm.Value{idx.impl}
	return Expr{llvm.CreateInBoundsGEP(b.impl, telem.ll, x.impl, indices), pt}
}

// The Alloc instruction reserves space for a variable of the given type,
// zero-initializes it, and yields its address.
//
// If heap is false, Alloc zero-initializes the same local variable in
// the call frame and returns its address; in this case the Alloc must
// be present in Function.Locals. We call this a "local" alloc.
//
// If heap is true, Alloc allocates a new zero-initialized variable
// each time the instruction is executed. We call this a "new" alloc.
//
// When Alloc is applied to a channel, map or slice type, it returns
// the address of an uninitialized (nil) reference of that kind; store
// the result of MakeSlice, MakeMap or MakeChan in that location to
// instantiate these types.
//
// Example printed form:
//
//	t0 = local int
//	t1 = new int
func (b Builder) Alloc(t Type, heap bool) (ret Expr) {
	if debugInstr {
		log.Printf("Alloc %v, %v\n", t.ll, heap)
	}
	telem := b.prog.Elem(t)
	if heap {
		ret.impl = llvm.CreateAlloca(b.impl, telem.ll)
	} else {
		panic("todo")
	}
	// TODO: zero-initialize
	ret.Type = t
	return
}

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

// The Call instruction represents a function or method call.
//
// The Call instruction yields the function result if there is exactly
// one.  Otherwise it returns a tuple, the components of which are
// accessed via Extract.
//
// Example printed form:
//
//	t2 = println(t0, t1)
//	t4 = t3()
//	t7 = invoke t5.Println(...t6)
func (b Builder) Call(fn Expr, args ...Expr) (ret Expr) {
	if debugInstr {
		var b bytes.Buffer
		fmt.Fprint(&b, "Call @", fn.impl.Name())
		for _, arg := range args {
			fmt.Fprint(&b, ", ", arg.impl)
		}
		log.Println(b.String())
	}
	switch t := fn.t.(type) {
	case *types.Signature:
		ret.Type = b.prog.retType(t)
	default:
		panic("todo")
	}
	ret.impl = llvm.CreateCall(b.impl, fn.ll, fn.impl, llvmValues(args))
	return
}

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