/*
 * 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 cl

import (
	"fmt"
	"go/ast"
	"go/constant"
	"go/token"
	"go/types"
	"log"
	"os"
	"sort"
	"strings"

	llssa "github.com/goplus/llgo/ssa"
	"golang.org/x/tools/go/ssa"
)

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

type dbgFlags = int

const (
	DbgFlagInstruction dbgFlags = 1 << iota
	DbgFlagGoSSA

	DbgFlagAll = DbgFlagInstruction | DbgFlagGoSSA
)

var (
	debugInstr bool
	debugGoSSA bool
)

// SetDebug sets debug flags.
func SetDebug(dbgFlags dbgFlags) {
	debugInstr = (dbgFlags & DbgFlagInstruction) != 0
	debugGoSSA = (dbgFlags & DbgFlagGoSSA) != 0
}

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

const (
	fnNormal = iota
	fnHasVArg
	fnIgnore
)

func funcKind(vfn ssa.Value) int {
	if fn, ok := vfn.(*ssa.Function); ok && fn.Signature.Recv() == nil {
		params := fn.Signature.Params()
		n := params.Len()
		if n == 0 {
			if fn.Name() == "init" && ignorePkgInit(fn.Pkg.Pkg.Path()) {
				return fnIgnore
			}
		} else {
			last := params.At(n - 1)
			if last.Name() == llssa.NameValist {
				return fnHasVArg
			}
		}
	}
	return fnNormal
}

func ignorePkgInit(pkgPath string) bool {
	switch pkgPath {
	case "unsafe", "syscall", "runtime/cgo":
		return true
	}
	return false
}

func ignoreName(name string) bool {
	/* TODO(xsw): confirm this is not needed more
	if name == "unsafe.init" {
		return true
	}
	*/
	if strings.HasPrefix(name, "internal/") || strings.HasPrefix(name, "crypto/") ||
		strings.HasPrefix(name, "arena.") || strings.HasPrefix(name, "maps.") ||
		strings.HasPrefix(name, "time.") || strings.HasPrefix(name, "syscall.") ||
		strings.HasPrefix(name, "os.") || strings.HasPrefix(name, "plugin.") ||
		strings.HasPrefix(name, "reflect.") || strings.HasPrefix(name, "errors.") {
		return true // TODO(xsw)
	}
	return inPkg(name, "runtime") || inPkg(name, "sync")
}

func inPkg(name, pkg string) bool {
	if len(name) > len(pkg) && strings.HasPrefix(name, pkg) {
		c := name[len(pkg)]
		return c == '.' || c == '/'
	}
	return false
}

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

type none = struct{}

type instrAndValue interface {
	ssa.Instruction
	ssa.Value
}

type context struct {
	prog   llssa.Program
	pkg    llssa.Package
	fn     llssa.Function
	fset   *token.FileSet
	goProg *ssa.Program
	goTyps *types.Package
	goPkg  *ssa.Package
	link   map[string]string           // pkgPath.nameInPkg => linkname
	loaded map[*types.Package]none     // loaded packages
	bvals  map[ssa.Value]llssa.Expr    // block values
	vargs  map[*ssa.Alloc][]llssa.Expr // varargs
	inits  []func()
}

func (p *context) compileType(pkg llssa.Package, t *ssa.Type) {
	tn := t.Object().(*types.TypeName)
	tnName := tn.Name()
	typ := tn.Type()
	name := llssa.FullName(tn.Pkg(), tnName)
	if ignoreName(name) {
		return
	}
	if debugInstr {
		log.Println("==> NewType", name, typ)
	}
	p.compileMethods(pkg, typ)
	p.compileMethods(pkg, types.NewPointer(typ))
}

func (p *context) compileMethods(pkg llssa.Package, typ types.Type) {
	prog := p.goProg
	mthds := prog.MethodSets.MethodSet(typ)
	for i, n := 0, mthds.Len(); i < n; i++ {
		mthd := mthds.At(i)
		if ssaMthd := prog.MethodValue(mthd); ssaMthd != nil {
			p.compileFunc(pkg, mthd.Obj().Pkg(), ssaMthd)
		}
	}
}

// Global variable.
func (p *context) compileGlobal(pkg llssa.Package, gbl *ssa.Global) {
	typ := gbl.Type()
	name := llssa.FullName(gbl.Pkg.Pkg, gbl.Name())
	if ignoreName(name) || checkCgo(gbl.Name()) {
		return
	}
	if debugInstr {
		log.Println("==> NewVar", name, typ)
	}
	g := pkg.NewVar(name, typ)
	g.Init(p.prog.Null(g.Type))
}

func (p *context) compileFunc(pkg llssa.Package, pkgTypes *types.Package, f *ssa.Function) {
	sig := f.Signature
	name, ok := p.funcName(pkgTypes, f, true)
	if !ok { // ignored
		return
	}
	if debugInstr {
		log.Println("==> NewFunc", name, "type:", sig.Recv(), sig)
	}
	fn := pkg.NewFunc(name, sig)
	p.inits = append(p.inits, func() {
		p.fn = fn
		defer func() {
			p.fn = nil
		}()
		nblk := len(f.Blocks)
		if nblk == 0 { // external function
			return
		}
		if debugGoSSA {
			f.WriteTo(os.Stderr)
		}
		if debugInstr {
			log.Println("==> FuncBody", name)
		}
		fn.MakeBlocks(nblk)
		b := fn.NewBuilder()
		for i, block := range f.Blocks {
			p.compileBlock(b, block, i == 0 && name == "main")
		}
	})
}

func (p *context) compileBlock(b llssa.Builder, block *ssa.BasicBlock, doInit bool) llssa.BasicBlock {
	ret := p.fn.Block(block.Index)
	b.SetBlock(ret)
	p.bvals = make(map[ssa.Value]llssa.Expr)
	if doInit {
		fn := p.pkg.FuncOf("main.init")
		b.Call(fn.Expr)
	}
	for _, instr := range block.Instrs {
		p.compileInstr(b, instr)
	}
	return ret
}

func isAny(t types.Type) bool {
	if t, ok := t.(*types.Interface); ok {
		return t.Empty()
	}
	return false
}

func intVal(v ssa.Value) int64 {
	if c, ok := v.(*ssa.Const); ok {
		if iv, exact := constant.Int64Val(c.Value); exact {
			return iv
		}
	}
	panic("intVal: ssa.Value is not a const int")
}

func (p *context) isVArgs(vx ssa.Value) (ret []llssa.Expr, ok bool) {
	if va, vok := vx.(*ssa.Alloc); vok {
		ret, ok = p.vargs[va] // varargs: this is a varargs index
	}
	return
}

func (p *context) checkVArgs(v *ssa.Alloc, t types.Type) bool {
	if v.Comment == "varargs" { // this is a varargs allocation
		if t, ok := t.(*types.Pointer); ok {
			if arr, ok := t.Elem().(*types.Array); ok {
				if isAny(arr.Elem()) {
					p.vargs[v] = make([]llssa.Expr, arr.Len())
					return true
				}
			}
		}
	}
	return false
}

func (p *context) compileInstrAndValue(b llssa.Builder, iv instrAndValue) (ret llssa.Expr) {
	if v, ok := p.bvals[iv]; ok {
		return v
	}
	switch v := iv.(type) {
	case *ssa.Call:
		call := v.Call
		cv := call.Value
		kind := funcKind(cv)
		if kind == fnIgnore {
			return
		}
		if debugGoSSA {
			log.Println(">>> Call", cv, call.Args)
		}
		if builtin, ok := cv.(*ssa.Builtin); ok {
			fn := builtin.Name()
			if fn == "ssa:wrapnilchk" { // TODO(xsw): check nil ptr
				arg := call.Args[0]
				ret = p.compileValue(b, arg)
				// log.Println("wrapnilchk:", ret.TypeOf())
			} else {
				args := p.compileValues(b, call.Args, kind)
				ret = b.BuiltinCall(fn, args...)
			}
		} else {
			fn := p.compileValue(b, cv)
			args := p.compileValues(b, call.Args, kind)
			ret = b.Call(fn, args...)
		}
	case *ssa.BinOp:
		x := p.compileValue(b, v.X)
		y := p.compileValue(b, v.Y)
		ret = b.BinOp(v.Op, x, y)
	case *ssa.UnOp:
		x := p.compileValue(b, v.X)
		ret = b.UnOp(v.Op, x)
	case *ssa.ChangeType:
		t := v.Type()
		x := p.compileValue(b, v.X)
		ret = b.ChangeType(p.prog.Type(t), x)
	case *ssa.FieldAddr:
		x := p.compileValue(b, v.X)
		ret = b.FieldAddr(x, v.Field)
	case *ssa.IndexAddr:
		vx := v.X
		if _, ok := p.isVArgs(vx); ok { // varargs: this is a varargs index
			return
		}
		x := p.compileValue(b, vx)
		idx := p.compileValue(b, v.Index)
		ret = b.IndexAddr(x, idx)
	case *ssa.Slice:
		vx := v.X
		if _, ok := p.isVArgs(vx); ok { // varargs: this is a varargs slice
			return
		}
		panic("todo")
	case *ssa.Alloc:
		t := v.Type()
		if p.checkVArgs(v, t) { // varargs: this is a varargs allocation
			return
		}
		ret = b.Alloc(p.prog.Type(t), v.Heap)
	case *ssa.MakeInterface:
		t := v.Type()
		if isAny(t) { // varargs: don't need to convert an expr to any
			return
		}
		panic("todo")
	case *ssa.TypeAssert:
		x := p.compileValue(b, v.X)
		ret = b.TypeAssert(x, p.prog.Type(v.AssertedType), v.CommaOk)
	default:
		panic(fmt.Sprintf("compileInstrAndValue: unknown instr - %T\n", iv))
	}
	p.bvals[iv] = ret
	return ret
}

func (p *context) compileInstr(b llssa.Builder, instr ssa.Instruction) {
	if iv, ok := instr.(instrAndValue); ok {
		p.compileInstrAndValue(b, iv)
		return
	}
	switch v := instr.(type) {
	case *ssa.Store:
		va := v.Addr
		if va, ok := va.(*ssa.IndexAddr); ok {
			if args, ok := p.isVArgs(va.X); ok { // varargs: this is a varargs store
				idx := intVal(va.Index)
				val := v.Val
				if vi, ok := val.(*ssa.MakeInterface); ok {
					val = vi.X
				}
				args[idx] = p.compileValue(b, val)
				return
			}
		}
		ptr := p.compileValue(b, va)
		val := p.compileValue(b, v.Val)
		b.Store(ptr, val)
	case *ssa.Jump:
		fn := p.fn
		succs := v.Block().Succs
		jmpb := fn.Block(succs[0].Index)
		b.Jump(jmpb)
	case *ssa.Return:
		var results []llssa.Expr
		if n := len(v.Results); n > 0 {
			results = make([]llssa.Expr, n)
			for i, r := range v.Results {
				results[i] = p.compileValue(b, r)
			}
		}
		b.Return(results...)
	case *ssa.If:
		fn := p.fn
		cond := p.compileValue(b, v.Cond)
		succs := v.Block().Succs
		thenb := fn.Block(succs[0].Index)
		elseb := fn.Block(succs[1].Index)
		b.If(cond, thenb, elseb)
	default:
		panic(fmt.Sprintf("compileInstr: unknown instr - %T\n", instr))
	}
}

func (p *context) compileValue(b llssa.Builder, v ssa.Value) llssa.Expr {
	if iv, ok := v.(instrAndValue); ok {
		return p.compileInstrAndValue(b, iv)
	}
	switch v := v.(type) {
	case *ssa.Parameter:
		fn := v.Parent()
		for idx, param := range fn.Params {
			if param == v {
				return p.fn.Param(idx)
			}
		}
	case *ssa.Function:
		fn := p.funcOf(v)
		return fn.Expr
	case *ssa.Global:
		g := p.varOf(v)
		return g.Expr
	case *ssa.Const:
		t := v.Type()
		return b.Const(v.Value, p.prog.Type(t))
	}
	panic(fmt.Sprintf("compileValue: unknown value - %T\n", v))
}

func (p *context) compileVArg(ret []llssa.Expr, b llssa.Builder, v ssa.Value) []llssa.Expr {
	_ = b
	switch v := v.(type) {
	case *ssa.Slice: // varargs: this is a varargs slice
		if args, ok := p.isVArgs(v.X); ok {
			return append(ret, args...)
		}
	case *ssa.Const:
		if v.Value == nil {
			return ret
		}
	}
	panic(fmt.Sprintf("compileVArg: unknown value - %T\n", v))
}

func (p *context) compileValues(b llssa.Builder, vals []ssa.Value, hasVArg int) []llssa.Expr {
	n := len(vals) - hasVArg
	ret := make([]llssa.Expr, n)
	for i := 0; i < n; i++ {
		ret[i] = p.compileValue(b, vals[i])
	}
	if hasVArg > 0 {
		ret = p.compileVArg(ret, b, vals[n])
	}
	return ret
}

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

// NewPackage compiles a Go package to LLVM IR package.
func NewPackage(prog llssa.Program, pkg *ssa.Package, files []*ast.File) (ret llssa.Package, err error) {
	type namedMember struct {
		name string
		val  ssa.Member
	}

	members := make([]*namedMember, 0, len(pkg.Members))
	for name, v := range pkg.Members {
		members = append(members, &namedMember{name, v})
	}
	sort.Slice(members, func(i, j int) bool {
		return members[i].name < members[j].name
	})

	pkgProg := pkg.Prog
	pkgTypes := pkg.Pkg
	pkgName, pkgPath := pkgTypes.Name(), llssa.PathOf(pkgTypes)
	ret = prog.NewPackage(pkgName, pkgPath)

	ctx := &context{
		prog:   prog,
		pkg:    ret,
		fset:   pkgProg.Fset,
		goProg: pkgProg,
		goTyps: pkgTypes,
		goPkg:  pkg,
		link:   make(map[string]string),
		loaded: make(map[*types.Package]none),
		vargs:  make(map[*ssa.Alloc][]llssa.Expr),
	}
	ctx.initFiles(pkgPath, files)
	for _, m := range members {
		member := m.val
		switch member := member.(type) {
		case *ssa.Function:
			if member.TypeParams() != nil {
				// Do not try to build generic (non-instantiated) functions.
				continue
			}
			ctx.compileFunc(ret, member.Pkg.Pkg, member)
		case *ssa.Type:
			ctx.compileType(ret, member)
		case *ssa.Global:
			ctx.compileGlobal(ret, member)
		}
	}
	for _, ini := range ctx.inits {
		ini()
	}
	return
}

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