// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package abi

import (
	"fmt"
	"reflect"
)

// indirect recursively dereferences the value until it either gets the value
// or finds a big.Int
func indirect(v reflect.Value) reflect.Value {
	if v.Kind() == reflect.Ptr && v.Elem().Type() != derefbigT {
		return indirect(v.Elem())
	}
	return v
}

// reflectIntKind returns the reflect using the given size and
// unsignedness.
func reflectIntKindAndType(unsigned bool, size int) (reflect.Kind, reflect.Type) {
	switch size {
	case 8:
		if unsigned {
			return reflect.Uint8, uint8T
		}
		return reflect.Int8, int8T
	case 16:
		if unsigned {
			return reflect.Uint16, uint16T
		}
		return reflect.Int16, int16T
	case 32:
		if unsigned {
			return reflect.Uint32, uint32T
		}
		return reflect.Int32, int32T
	case 64:
		if unsigned {
			return reflect.Uint64, uint64T
		}
		return reflect.Int64, int64T
	}
	return reflect.Ptr, bigT
}

// mustArrayToBytesSlice creates a new byte slice with the exact same size as value
// and copies the bytes in value to the new slice.
func mustArrayToByteSlice(value reflect.Value) reflect.Value {
	slice := reflect.MakeSlice(reflect.TypeOf([]byte{}), value.Len(), value.Len())
	reflect.Copy(slice, value)
	return slice
}

// set attempts to assign src to dst by either setting, copying or otherwise.
//
// set is a bit more lenient when it comes to assignment and doesn't force an as
// strict ruleset as bare `reflect` does.
func set(dst, src reflect.Value, output Argument) error {
	dstType := dst.Type()
	srcType := src.Type()
	switch {
	case dstType.AssignableTo(srcType):
		dst.Set(src)
	case dstType.Kind() == reflect.Interface:
		dst.Set(src)
	case dstType.Kind() == reflect.Ptr:
		return set(dst.Elem(), src, output)
	default:
		return fmt.Errorf("abi: cannot unmarshal %v in to %v", src.Type(), dst.Type())
	}
	return nil
}

// requireAssignable assures that `dest` is a pointer and it's not an interface.
func requireAssignable(dst, src reflect.Value) error {
	if dst.Kind() != reflect.Ptr && dst.Kind() != reflect.Interface {
		return fmt.Errorf("abi: cannot unmarshal %v into %v", src.Type(), dst.Type())
	}
	return nil
}

// requireUnpackKind verifies preconditions for unpacking `args` into `kind`
func requireUnpackKind(v reflect.Value, t reflect.Type, k reflect.Kind,
	args Arguments) error {

	switch k {
	case reflect.Struct:
	case reflect.Slice, reflect.Array:
		if minLen := args.LengthNonIndexed(); v.Len() < minLen {
			return fmt.Errorf("abi: insufficient number of elements in the list/array for unpack, want %d, got %d",
				minLen, v.Len())
		}
	default:
		return fmt.Errorf("abi: cannot unmarshal tuple into %v", t)
	}
	return nil
}

// requireUniqueStructFieldNames makes sure field names don't collide
func requireUniqueStructFieldNames(args Arguments) error {
	exists := make(map[string]bool)
	for _, arg := range args {
		field := capitalise(arg.Name)
		if field == "" {
			return fmt.Errorf("abi: purely underscored output cannot unpack to struct")
		}
		if exists[field] {
			return fmt.Errorf("abi: multiple outputs mapping to the same struct field '%s'", field)
		}
		exists[field] = true
	}
	return nil
}
