// argCanBeChecked reports whether the specified argument is statically present;
// it may be beyond the list of arguments or in a terminal slice... argument, which
// means we can't see it.
func (f *File) argCanBeChecked(call *ast.CallExpr, formatArg int, isStar bool, state *formatState) bool {
	argNum := state.argNums[formatArg]
	if argNum < 0 {
		// Shouldn't happen, so catch it with prejudice.
		panic("negative arg num")
	}
	if argNum == 0 {
		f.Badf(call.Pos(), `index value [0] for %s("%s"); indexes start at 1`, state.name, state.format)
		return false
	}
	if argNum < len(call.Args)-1 {
		return true // Always OK.
	}
	if call.Ellipsis.IsValid() {
		return false // We just can't tell; there could be many more arguments.
	}
	if argNum < len(call.Args) {
		return true
	}
	// There are bad indexes in the format or there are fewer arguments than the format needs.
	// This is the argument number relative to the format: Printf("%s", "hi") will give 1 for the "hi".
	arg := argNum - state.firstArg + 1 // People think of arguments as 1-indexed.
	f.Badf(call.Pos(), `missing argument for %s("%s"): format reads arg %d, have only %d args`, state.name, state.format, arg, len(call.Args)-state.firstArg)
	return false
}

// okPrintfArg compares the formatState to the arguments actually present,
// reporting any discrepancies it can discern. If the final argument is ellipsissed,
// there's little it can do for that.
func (f *File) okPrintfArg(call *ast.CallExpr, state *formatState) (ok bool) {
	var v printVerb
	found := false
	// Linear scan is fast enough for a small list.
	for _, v = range printVerbs {
		if v.verb == state.verb {
			found = true
			break
		}
	}
	if !found {
		f.Badf(call.Pos(), "unrecognized printf verb %q", state.verb)
		return false
	}
	for _, flag := range state.flags {
		if !strings.ContainsRune(v.flags, rune(flag)) {
			f.Badf(call.Pos(), "unrecognized printf flag for verb %q: %q", state.verb, flag)
			return false
		}
	}
	// Verb is good. If len(state.argNums)>trueArgs, we have something like %.*s and all
	// but the final arg must be an integer.
	trueArgs := 1
	if state.verb == '%' {
		trueArgs = 0
	}
	nargs := len(state.argNums)
	for i := 0; i < nargs-trueArgs; i++ {
		argNum := state.argNums[i]
		if !f.argCanBeChecked(call, i, true, state) {
			return
		}
		arg := call.Args[argNum]
		if !f.matchArgType(argInt, nil, arg) {
			f.Badf(call.Pos(), "arg %s for * in printf format not of type int", f.gofmt(arg))
			return false
		}
	}
	if state.verb == '%' {
		return true
	}
	argNum := state.argNums[len(state.argNums)-1]
	if !f.argCanBeChecked(call, len(state.argNums)-1, false, state) {
		return false
	}
	arg := call.Args[argNum]
	if !f.matchArgType(v.typ, nil, arg) {
		typeString := ""
		if typ := f.pkg.types[arg].Type; typ != nil {
			typeString = typ.String()
		}
		f.Badf(call.Pos(), "arg %s for printf verb %%%c of wrong type: %s", f.gofmt(arg), state.verb, typeString)
		return false
	}
	if v.typ&argString != 0 && v.verb != 'T' && !bytes.Contains(state.flags, []byte{'#'}) && f.recursiveStringer(arg) {
		f.Badf(call.Pos(), "arg %s for printf causes recursive call to String method", f.gofmt(arg))
		return false
	}
	return true
}

// argCanBeChecked reports whether the specified argument is statically present;
// it may be beyond the list of arguments or in a terminal slice... argument, which
// means we can't see it.
func (f *File) argCanBeChecked(call *ast.CallExpr, formatArg int, isStar bool, state *formatState) bool {
	argNum := state.argNums[formatArg]
	if argNum < 0 {
		// Shouldn't happen, so catch it with prejudice.
		panic("negative arg num")
	}
	if argNum < len(call.Args)-1 {
		return true // Always OK.
	}
	if call.Ellipsis.IsValid() {
		return false // We just can't tell; there could be many more arguments.
	}
	if argNum < len(call.Args) {
		return true
	}
	// There are bad indexes in the format or there are fewer arguments than the format needs.
	verb := fmt.Sprintf("verb %%%c", state.verb)
	if isStar {
		verb = "indirect *"
	}
	// This is the argument number relative to the format: Printf("%s", "hi") will give 1 for the "hi".
	arg := argNum - state.firstArg + 1 // People think of arguments as 1-indexed.
	f.Badf(call.Pos(), "missing argument for %s %s: need %d, have %d", state.name, verb, arg, len(call.Args)-state.firstArg)
	return false
}

// conversion typechecks the type conversion conv to type typ. iota is the current
// value of iota or -1 if iota doesn't have a value in the current context. The result
// of the conversion is returned via x. If the conversion has type errors, the returned
// x is marked as invalid (x.mode == invalid).
//
func (check *checker) conversion(x *operand, conv *ast.CallExpr, typ Type, iota int) {
	// all conversions have one argument
	if len(conv.Args) != 1 {
		check.invalidOp(conv.Pos(), "%s conversion requires exactly one argument", conv)
		goto Error
	}

	// evaluate argument
	check.expr(x, conv.Args[0], nil, iota)
	if x.mode == invalid {
		goto Error
	}

	if x.mode == constant && isConstType(typ) {
		// constant conversion
		// TODO(gri) implement this
	} else {
		// non-constant conversion
		if !x.isConvertible(typ) {
			check.invalidOp(conv.Pos(), "cannot convert %s to %s", x, typ)
			goto Error
		}
		x.mode = value
	}

	x.expr = conv
	x.typ = typ
	return

Error:
	x.mode = invalid
}

// conversion typechecks the type conversion conv to type typ. iota is the current
// value of iota or -1 if iota doesn't have a value in the current context. The result
// of the conversion is returned via x. If the conversion has type errors, the returned
// x is marked as invalid (x.mode == invalid).
//
func (check *checker) conversion(x *operand, conv *ast.CallExpr, typ Type, iota int) {
	// all conversions have one argument
	if len(conv.Args) != 1 {
		check.invalidOp(conv.Pos(), "%s conversion requires exactly one argument", conv)
		goto Error
	}

	// evaluate argument
	check.expr(x, conv.Args[0], nil, iota)
	if x.mode == invalid {
		goto Error
	}

	if x.mode == constant && isConstType(typ) {
		// constant conversion
		typ := typ.Underlying().(*Basic)
		// For now just implement string(x) where x is an integer,
		// as a temporary work-around for issue 4982, which is a
		// common issue.
		if typ.kind == String {
			switch {
			case x.isInteger():
				codepoint := int64(-1)
				if i, ok := exact.Int64Val(x.val); ok {
					codepoint = i
				}
				// If codepoint < 0 the absolute value is too large (or unknown) for
				// conversion. This is the same as converting any other out-of-range
				// value - let string(codepoint) do the work.
				x.val = exact.MakeString(string(codepoint))
			case isString(x.typ):
				// nothing to do
			default:
				goto ErrorMsg
			}
		}
		// TODO(gri) verify the remaining conversions.
	} else {
		// non-constant conversion
		if !x.isConvertible(check.ctxt, typ) {
			goto ErrorMsg
		}
		x.mode = value
	}

	// the conversion argument types are final; for now we just use x.typ
	// TODO(gri) Fix this. For untyped constants, the type should be typ.
	check.updateExprType(x.expr, x.typ, true)

	check.conversions[conv] = true // for cap/len checking
	x.expr = conv
	x.typ = typ
	return

ErrorMsg:
	check.invalidOp(conv.Pos(), "cannot convert %s to %s", x, typ)
Error:
	x.mode = invalid
	x.expr = conv
}

// checkPrintf checks a call to a formatted print routine such as Printf.
// call.Args[formatIndex] is (well, should be) the format argument.
func (f *File) checkPrintf(call *ast.CallExpr, name string, formatIndex int) {
	if formatIndex >= len(call.Args) {
		f.Bad(call.Pos(), "too few arguments in call to", name)
		return
	}
	lit := f.pkg.types[call.Args[formatIndex]].Value
	if lit == nil {
		if *verbose {
			f.Warn(call.Pos(), "can't check non-constant format in call to", name)
		}
		return
	}
	if lit.Kind() != exact.String {
		f.Badf(call.Pos(), "constant %v not a string in call to %s", lit, name)
		return
	}
	format := exact.StringVal(lit)
	firstArg := formatIndex + 1 // Arguments are immediately after format string.
	if !strings.Contains(format, "%") {
		if len(call.Args) > firstArg {
			f.Badf(call.Pos(), "no formatting directive in %s call", name)
		}
		return
	}
	// Hard part: check formats against args.
	argNum := firstArg
	indexed := false
	for i, w := 0, 0; i < len(format); i += w {
		w = 1
		if format[i] == '%' {
			state := f.parsePrintfVerb(call, name, format[i:], firstArg, argNum)
			if state == nil {
				return
			}
			w = len(state.format)
			if state.indexed {
				indexed = true
			}
			if !f.okPrintfArg(call, state) { // One error per format is enough.
				return
			}
			if len(state.argNums) > 0 {
				// Continue with the next sequential argument.
				argNum = state.argNums[len(state.argNums)-1] + 1
			}
		}
	}
	// Dotdotdot is hard.
	if call.Ellipsis.IsValid() && argNum >= len(call.Args)-1 {
		return
	}
	// If the arguments were direct indexed, we assume the programmer knows what's up.
	// Otherwise, there should be no leftover arguments.
	if !indexed && argNum != len(call.Args) {
		expect := argNum - firstArg
		numArgs := len(call.Args) - firstArg
		f.Badf(call.Pos(), "wrong number of args for format in %s call: %d needed but %d args", name, expect, numArgs)
	}
}

func (f *File) checkUnsafePointer(x *ast.CallExpr) {
	if !vet("unsafeptr") {
		return
	}
	if len(x.Args) != 1 {
		return
	}
	if f.hasBasicType(x.Fun, types.UnsafePointer) && f.hasBasicType(x.Args[0], types.Uintptr) && !f.isSafeUintptr(x.Args[0]) {
		f.Badf(x.Pos(), "possible misuse of unsafe.Pointer")
	}
}

// checkPrintf checks a call to a formatted print routine such as Printf.
// call.Args[formatIndex] is (well, should be) the format argument.
func (f *File) checkPrintf(call *ast.CallExpr, name string, formatIndex int) {
	if formatIndex >= len(call.Args) {
		return
	}
	lit := f.literal(call.Args[formatIndex])
	if lit == nil {
		if *verbose {
			f.Warn(call.Pos(), "can't check non-literal format in call to", name)
		}
		return
	}
	if lit.Kind != token.STRING {
		f.Badf(call.Pos(), "literal %v not a string in call to", lit.Value, name)
	}
	format, err := strconv.Unquote(lit.Value)
	if err != nil {
		// Shouldn't happen if parser returned no errors, but be safe.
		f.Badf(call.Pos(), "invalid quoted string literal")
	}
	firstArg := formatIndex + 1 // Arguments are immediately after format string.
	if !strings.Contains(format, "%") {
		if len(call.Args) > firstArg {
			f.Badf(call.Pos(), "no formatting directive in %s call", name)
		}
		return
	}
	// Hard part: check formats against args.
	argNum := firstArg
	for i, w := 0, 0; i < len(format); i += w {
		w = 1
		if format[i] == '%' {
			verb, flags, nbytes, nargs := f.parsePrintfVerb(call, format[i:])
			w = nbytes
			if verb == '%' { // "%%" does nothing interesting.
				continue
			}
			// If we've run out of args, print after loop will pick that up.
			if argNum+nargs <= len(call.Args) {
				f.checkPrintfArg(call, verb, flags, argNum, nargs)
			}
			argNum += nargs
		}
	}
	// TODO: Dotdotdot is hard.
	if call.Ellipsis.IsValid() && argNum != len(call.Args) {
		return
	}
	if argNum != len(call.Args) {
		expect := argNum - firstArg
		numArgs := len(call.Args) - firstArg
		f.Badf(call.Pos(), "wrong number of args for format in %s call: %d needed but %d args", name, expect, numArgs)
	}
}

func (vis *getUsedMethodsVisitor) checkEditME(callExpr *ast.CallExpr, mId *ast.Ident) {
	m, ok := vis.identMap.GetSymbol(mId).(*st.FunctionSymbol)
	if !ok {
		panic("couldn't find method selector in method expression")
	}
	if id, ok := callExpr.Args[0].(*ast.Ident); ok {
		if vis.identMap.GetSymbol(id) == vis.varS {
			callExpr.Fun = &ast.SelectorExpr{id, mId}
			callExpr.Args = callExpr.Args[1:]
			vis.result[m] = true
		}
	}
}

// checkPrint checks a call to an unformatted print routine such as Println.
// call.Args[firstArg] is the first argument to be printed.
func (f *File) checkPrint(call *ast.CallExpr, name string, firstArg int) {
	isLn := strings.HasSuffix(name, "ln")
	isF := strings.HasPrefix(name, "F")
	args := call.Args
	// check for Println(os.Stderr, ...)
	if firstArg == 0 && !isF && len(args) > 0 {
		if sel, ok := args[0].(*ast.SelectorExpr); ok {
			if x, ok := sel.X.(*ast.Ident); ok {
				if x.Name == "os" && strings.HasPrefix(sel.Sel.Name, "Std") {
					f.Badf(call.Pos(), "first argument to %s is %s.%s", name, x.Name, sel.Sel.Name)
				}
			}
		}
	}
	if len(args) <= firstArg {
		// If we have a call to a method called Error that satisfies the Error interface,
		// then it's ok. Otherwise it's something like (*T).Error from the testing package
		// and we need to check it.
		if name == "Error" && f.isErrorMethodCall(call) {
			return
		}
		// If it's an Error call now, it's probably for printing errors.
		if !isLn {
			// Check the signature to be sure: there are niladic functions called "error".
			if firstArg != 0 || f.numArgsInSignature(call) != firstArg {
				f.Badf(call.Pos(), "no args in %s call", name)
			}
		}
		return
	}
	arg := args[firstArg]
	if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
		if strings.Contains(lit.Value, "%") {
			f.Badf(call.Pos(), "possible formatting directive in %s call", name)
		}
	}
	if isLn {
		// The last item, if a string, should not have a newline.
		arg = args[len(call.Args)-1]
		if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
			if strings.HasSuffix(lit.Value, `\n"`) {
				f.Badf(call.Pos(), "%s call ends with newline", name)
			}
		}
	}
	for _, arg := range args {
		if f.recursiveStringer(arg) {
			f.Badf(call.Pos(), "arg %s for print causes recursive call to String method", f.gofmt(arg))
		}
	}
}

func (f *File) checkPrintfArg(call *ast.CallExpr, verb rune, flags []byte, argNum, nargs int) {
	// Linear scan is fast enough for a small list.
	for _, v := range printVerbs {
		if v.verb == verb {
			for _, flag := range flags {
				if !strings.ContainsRune(v.flags, rune(flag)) {
					f.Badf(call.Pos(), "unrecognized printf flag for verb %q: %q", verb, flag)
					return
				}
			}
			// Verb is good. If nargs>1, we have something like %.*s and all but the final
			// arg must be integer.
			for i := 0; i < nargs-1; i++ {
				if !f.matchArgType(argInt, call.Args[argNum+i]) {
					f.Badf(call.Pos(), "arg %s for * in printf format not of type int", f.gofmt(call.Args[argNum+i]))
				}
			}
			for _, v := range printVerbs {
				if v.verb == verb {
					arg := call.Args[argNum+nargs-1]
					if !f.matchArgType(v.typ, arg) {
						typeString := ""
						if typ := f.pkg.types[arg]; typ != nil {
							typeString = typ.String()
						}
						f.Badf(call.Pos(), "arg %s for printf verb %%%c of wrong type: %s", f.gofmt(arg), verb, typeString)
					}
					break
				}
			}
			return
		}
	}
	f.Badf(call.Pos(), "unrecognized printf verb %q", verb)
}

func (f *File) checkPrintfVerb(call *ast.CallExpr, verb rune, flags []byte) {
	// Linear scan is fast enough for a small list.
	for _, v := range printVerbs {
		if v.verb == verb {
			for _, flag := range flags {
				if !strings.ContainsRune(v.flags, rune(flag)) {
					f.Badf(call.Pos(), "unrecognized printf flag for verb %q: %q", verb, flag)
				}
			}
			return
		}
	}
	f.Badf(call.Pos(), "unrecognized printf verb %q", verb)
}

// c may be nil.
func insertContext(f *ast.File, call *ast.CallExpr, c *ast.Ident) {
	if c == nil {
		// c is unknown, so use a plain "c".
		c = ast.NewIdent("c")
	}

	call.Args = append([]ast.Expr{c}, call.Args...)
}

// ctx may be nil.
func insertContext(f *ast.File, call *ast.CallExpr, ctx *ast.Ident) {
	if ctx == nil {
		// context is unknown, so use a plain "ctx".
		ctx = ast.NewIdent("ctx")
	}

	call.Args = append([]ast.Expr{ctx}, call.Args...)
}

// parsePrintfVerb looks the formatting directive that begins the format string
// and returns a formatState that encodes what the directive wants, without looking
// at the actual arguments present in the call. The result is nil if there is an error.
func (f *File) parsePrintfVerb(call *ast.CallExpr, name, format string, firstArg, argNum int) *formatState {
	state := &formatState{
		format:   format,
		name:     name,
		flags:    make([]byte, 0, 5),
		argNum:   argNum,
		argNums:  make([]int, 0, 1),
		nbytes:   1, // There's guaranteed to be a percent sign.
		indexed:  false,
		firstArg: firstArg,
		file:     f,
		call:     call,
	}
	// There may be flags.
	state.parseFlags()
	indexPending := false
	// There may be an index.
	if !state.parseIndex() {
		return nil
	}
	// There may be a width.
	if !state.parseNum() {
		return nil
	}
	// There may be a precision.
	if !state.parsePrecision() {
		return nil
	}
	// Now a verb, possibly prefixed by an index (which we may already have).
	if !indexPending && !state.parseIndex() {
		return nil
	}
	if state.nbytes == len(state.format) {
		f.Badf(call.Pos(), "missing verb at end of format string in %s call", name)
		return nil
	}
	verb, w := utf8.DecodeRuneInString(state.format[state.nbytes:])
	state.verb = verb
	state.nbytes += w
	if verb != '%' {
		state.argNums = append(state.argNums, state.argNum)
	}
	state.format = state.format[:state.nbytes]
	return state
}

// checkPrintf checks a call to a formatted print routine such as Printf.
// The skip argument records how many arguments to ignore; that is,
// call.Args[skip] is (well, should be) the format argument.
func (f *File) checkPrintf(call *ast.CallExpr, name string, skip int) {
	if len(call.Args) <= skip {
		return
	}
	lit := f.literal(call.Args[skip])
	if lit == nil {
		if *verbose {
			f.Warn(call.Pos(), "can't check non-literal format in call to", name)
		}
		return
	}
	if lit.Kind != token.STRING {
		f.Badf(call.Pos(), "literal %v not a string in call to", lit.Value, name)
	}
	format, err := strconv.Unquote(lit.Value)
	if err != nil {
		f.Badf(call.Pos(), "invalid quoted string literal")
	}
	if !strings.Contains(format, "%") {
		if len(call.Args) > skip+1 {
			f.Badf(call.Pos(), "no formatting directive in %s call", name)
		}
		return
	}
	// Hard part: check formats against args.
	// Trivial but useful test: count.
	numArgs := 0
	for i, w := 0, 0; i < len(format); i += w {
		w = 1
		if format[i] == '%' {
			nbytes, nargs := f.parsePrintfVerb(call, format[i:])
			w = nbytes
			numArgs += nargs
		}
	}
	expect := len(call.Args) - (skip + 1)
	// Don't be too strict on dotdotdot.
	if call.Ellipsis.IsValid() && numArgs >= expect {
		return
	}
	if numArgs != expect {
		f.Badf(call.Pos(), "wrong number of args in %s call: %d needed but %d args", name, numArgs, expect)
	}
}

func changeFuncNameAndAddWriter(callExpr *ast.CallExpr, newFuncName string) {
	// Hacky; we should really create a proper AST. Fine for now, though, and faster, anyway.
	callExpr.Fun.(*ast.Ident).Name = newFuncName

	// Prepend w to the arg list.
	newArgList := make([]ast.Expr, 0, 1+len(callExpr.Args))
	newArgList = append(newArgList, writerArg)
	newArgList = append(newArgList, callExpr.Args...)
	callExpr.Args = newArgList
}

// ctx may be nil.
func insertContext(f *ast.File, call *ast.CallExpr, ctx *ast.Ident) {
	if ctx == nil {
		// context is unknown, so use a plain "ctx".
		ctx = ast.NewIdent("ctx")
	} else {
		// Create a fresh *ast.Ident so we drop the position information.
		ctx = ast.NewIdent(ctx.Name)
	}

	call.Args = append([]ast.Expr{ctx}, call.Args...)
}

// checkPrint checks a call to an unformatted print routine such as Println.
// The skip argument records how many arguments to ignore; that is,
// call.Args[skip] is the first argument to be printed.
func (f *File) checkPrint(call *ast.CallExpr, name string, skip int) {
	isLn := strings.HasSuffix(name, "ln")
	args := call.Args
	if len(args) <= skip {
		if *verbose && !isLn {
			f.Badf(call.Pos(), "no args in %s call", name)
		}
		return
	}
	arg := args[skip]
	if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
		if strings.Contains(lit.Value, "%") {
			f.Badf(call.Pos(), "possible formatting directive in %s call", name)
		}
	}
	if isLn {
		// The last item, if a string, should not have a newline.
		arg = args[len(call.Args)-1]
		if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
			if strings.HasSuffix(lit.Value, `\n"`) {
				f.Badf(call.Pos(), "%s call ends with newline", name)
			}
		}
	}
}

func NewFunctionCall(fs *token.FileSet, n *ast.CallExpr) (*FunctionCall, error) {
	parts := make([]string, 0)
	ast.Inspect(n.Fun, func(n ast.Node) bool {
		if n == nil {
			return true
		}
		switch obj := n.(type) {
		case *ast.SelectorExpr:
			// do nothing, just avoid the default case
			break
		case *ast.Ident:
			parts = append(parts, obj.Name)
		default:
			return false
		}
		return true
	})
	if len(parts) == 0 {
		return nil, ErrNotSupported
	}
	args := make([]string, len(n.Args))
	for i, arg := range n.Args {
		ast.Inspect(arg, func(n ast.Node) bool {
			switch t := n.(type) {
			case *ast.Ident:
				args[i] = t.Name
			case *ast.BasicLit:
				args[i] = t.Value
			}
			return true
		})
	}
	return &FunctionCall{
		Line: fs.Position(n.Pos()).Line,
		Expr: strings.Join(parts, "."),
		Name: parts[len(parts)-1],
		Args: args,
	}, nil
}