// 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 bind generates Ethereum contract Go bindings.
package bind

import (
	"bytes"
	"fmt"
	"sort"
	"strings"

	"github.com/ethereum/go-ethereum/accounts/abi"
	"golang.org/x/tools/imports"
)

// Bind generates a Go wrapper around a contract ABI. This wrapper isn't meant
// to be used as is in client code, but rather as an intermediate struct which
// enforces compile time type safety and naming convention opposed to having to
// manually maintain hard coded strings that break on runtime.
func Bind(abijson string, bytecode string, pkg string, kind string) (string, error) {
	// Parse the actual ABI to generate the binding for
	abi, err := abi.JSON(strings.NewReader(abijson))
	if err != nil {
		return "", err
	}
	// Generate the contract type, fields and methods
	code := new(bytes.Buffer)
	kind = strings.ToUpper(kind[:1]) + kind[1:]

	fmt.Fprintf(code, "%s\n", bindContract(kind, strings.TrimSpace(abijson)))
	fmt.Fprintf(code, "%s\n", bindConstructor(kind, strings.TrimSpace(bytecode), abi.Constructor))

	methods := make([]string, 0, len(abi.Methods))
	for name, _ := range abi.Methods {
		methods = append(methods, name)
	}
	sort.Strings(methods)

	for _, method := range methods {
		fmt.Fprintf(code, "%s\n", bindMethod(kind, abi.Methods[method]))
	}
	// Format the code with goimports and return
	buffer := new(bytes.Buffer)

	fmt.Fprintf(buffer, "// This file is an automatically generated Go binding based on the contract ABI\n")
	fmt.Fprintf(buffer, "// defined in %sABI. Do not modify as any change will likely be lost!\n\n", kind)
	fmt.Fprintf(buffer, "package %s\n\n", pkg)
	fmt.Fprintf(buffer, "%s\n\n", string(code.Bytes()))

	blob, err := imports.Process("", buffer.Bytes(), nil)
	if err != nil {
		return "", fmt.Errorf("%v\n%s", err, code)
	}
	return string(blob), nil
}

// bindContract generates the basic wrapper code for interacting with an Ethereum
// contract via the abi package. All contract methods will call into the generic
// ones generated here.
func bindContract(kind string, abijson string) string {
	code := ""

	// Generate the hard coded ABI used for Ethereum interaction
	code += fmt.Sprintf("// Ethereum ABI used to generate the binding from.\nconst %sABI = `%s`\n\n", kind, abijson)

	// Generate the high level contract wrapper types
	code += fmt.Sprintf("// %s is an auto generated Go binding around an Ethereum contract.\n", kind)
	code += fmt.Sprintf("type %s struct {\n", kind)
	code += fmt.Sprintf("  %sCaller     // Read-only binding to the contract\n", kind)
	code += fmt.Sprintf("  %sTransactor // Write-only binding to the contract\n", kind)
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// %sCaller is an auto generated read-only Go binding around an Ethereum contract.\n", kind)
	code += fmt.Sprintf("type %sCaller struct {\n", kind)
	code += fmt.Sprintf("  contract *bind.BoundContract // Generic contract wrapper for the low level calls\n")
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// %sTransactor is an auto generated write-only Go binding around an Ethereum contract.\n", kind)
	code += fmt.Sprintf("type %sTransactor struct {\n", kind)
	code += fmt.Sprintf("  contract *bind.BoundContract // Generic contract wrapper for the low level calls\n")
	code += fmt.Sprintf("}\n\n")

	// Generate the high level contract session wrapper types
	code += fmt.Sprintf("// %sSession is an auto generated Go binding around an Ethereum contract,\n// with pre-set call and transact options.\n", kind)
	code += fmt.Sprintf("type %sSession struct {\n", kind)
	code += fmt.Sprintf("  Contract     *%s               // Generic contract binding to set the session for\n", kind)
	code += fmt.Sprintf("  CallOpts     bind.CallOpts     // Call options to use throughout this session\n")
	code += fmt.Sprintf("  TransactOpts bind.TransactOpts // Transaction auth options to use throughout this session\n")
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// %sCallerSession is an auto generated read-only Go binding around an Ethereum contract,\n// with pre-set call options.\n", kind)
	code += fmt.Sprintf("type %sCallerSession struct {\n", kind)
	code += fmt.Sprintf("  Contract *%sCaller     // Generic contract caller binding to set the session for\n", kind)
	code += fmt.Sprintf("  CallOpts bind.CallOpts // Call options to use throughout this session\n")
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// %sTransactorSession is an auto generated write-only Go binding around an Ethereum contract,\n// with pre-set transact options.\n", kind)
	code += fmt.Sprintf("type %sTransactorSession struct {\n", kind)
	code += fmt.Sprintf("  Contract     *%sTransactor     // Generic contract transactor binding to set the session for\n", kind)
	code += fmt.Sprintf("  TransactOpts bind.TransactOpts // Transaction auth options to use throughout this session\n")
	code += fmt.Sprintf("}\n\n")

	// Generate the constructor to create a bound contract
	code += fmt.Sprintf("// New%s creates a new instance of %s, bound to a specific deployed contract.\n", kind, kind)
	code += fmt.Sprintf("func New%s(address common.Address, backend bind.ContractBackend) (*%s, error) {\n", kind, kind)
	code += fmt.Sprintf("  contract, err := bind%s(address, backend.(bind.ContractCaller), backend.(bind.ContractTransactor))\n", kind)
	code += fmt.Sprintf("  if err != nil {\n")
	code += fmt.Sprintf("    return nil, err\n")
	code += fmt.Sprintf("  }\n")
	code += fmt.Sprintf("  return &%s{%sCaller: %sCaller{contract: contract}, %sTransactor: %sTransactor{contract: contract}}, nil\n", kind, kind, kind, kind, kind)
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// New%sCaller creates a new read-only instance of %s, bound to a specific deployed contract.\n", kind, kind)
	code += fmt.Sprintf("func New%sCaller(address common.Address, caller bind.ContractCaller) (*%sCaller, error) {\n", kind, kind)
	code += fmt.Sprintf("  contract, err := bind%s(address, caller, nil)\n", kind)
	code += fmt.Sprintf("  if err != nil {\n")
	code += fmt.Sprintf("    return nil, err\n")
	code += fmt.Sprintf("  }\n")
	code += fmt.Sprintf("  return &%sCaller{contract: contract}, nil\n", kind)
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// New%sTransactor creates a new write-only instance of %s, bound to a specific deployed contract.\n", kind, kind)
	code += fmt.Sprintf("func New%sTransactor(address common.Address, transactor bind.ContractTransactor) (*%sTransactor, error) {\n", kind, kind)
	code += fmt.Sprintf("  contract, err := bind%s(address, nil, transactor)\n", kind)
	code += fmt.Sprintf("  if err != nil {\n")
	code += fmt.Sprintf("    return nil, err\n")
	code += fmt.Sprintf("  }\n")
	code += fmt.Sprintf("  return &%sTransactor{contract: contract}, nil\n", kind)
	code += fmt.Sprintf("}\n\n")

	code += fmt.Sprintf("// bind%s binds a generic wrapper to an already deployed contract.\n", kind)
	code += fmt.Sprintf("func bind%s(address common.Address, caller bind.ContractCaller, transactor bind.ContractTransactor) (*bind.BoundContract, error) {\n", kind)
	code += fmt.Sprintf("  parsed, err := abi.JSON(strings.NewReader(%sABI))\n", kind)
	code += fmt.Sprintf("  if err != nil {\n")
	code += fmt.Sprintf("    return nil, err\n")
	code += fmt.Sprintf("  }\n")
	code += fmt.Sprintf("  return bind.NewBoundContract(address, parsed, caller, transactor), nil\n")
	code += fmt.Sprintf("}")

	return code
}

// bindConstructor
func bindConstructor(kind string, bytecode string, constructor abi.Method) string {
	// If no byte code was supplied, we cannot deploy
	if bytecode == "" {
		return ""
	}
	// Otherwise store the bytecode into a global constant
	code := fmt.Sprintf("// Ethereum VM bytecode used for deploying new contracts.\nconst %sBin = `%s`\n\n", kind, bytecode)

	// Generate the argument list for the constructor
	args := make([]string, 0, len(constructor.Inputs))
	for i, arg := range constructor.Inputs {
		param := arg.Name
		if param == "" {
			param = fmt.Sprintf("arg%d", i)
		}
		args = append(args, fmt.Sprintf("%s %s", param, bindType(arg.Type)))
	}
	arglist := ""
	if len(args) > 0 {
		arglist = "," + strings.Join(args, ",")
	}
	// Generate the cal parameter list for the dpeloyer
	params := make([]string, len(args))
	for i, param := range args {
		params[i] = strings.Split(param, " ")[0]
	}
	paramlist := ""
	if len(params) > 0 {
		paramlist = "," + strings.Join(params, ",")
	}
	// And generate the global deployment function
	code += fmt.Sprintf("// Deploy%s deploys a new contract, binding an instance of %s to it.\n", kind, kind)
	code += fmt.Sprintf("func Deploy%s(auth *bind.TransactOpts, backend bind.ContractBackend %s) (common.Address, *types.Transaction, *%s, error) {\n", kind, arglist, kind)
	code += fmt.Sprintf("  parsed, err := abi.JSON(strings.NewReader(%sABI))\n", kind)
	code += fmt.Sprintf("  if err != nil {\n")
	code += fmt.Sprintf("    return common.Address{}, nil, nil, err\n")
	code += fmt.Sprintf("  }\n")
	code += fmt.Sprintf("  address, tx, contract, err := bind.DeployContract(auth, parsed, common.FromHex(%sBin), backend %s)\n", kind, paramlist)
	code += fmt.Sprintf("  if err != nil {\n")
	code += fmt.Sprintf("    return common.Address{}, nil, nil, err\n")
	code += fmt.Sprintf("  }\n")
	code += fmt.Sprintf("  return address, tx, &%s{%sCaller: %sCaller{contract: contract}, %sTransactor: %sTransactor{contract: contract}}, nil\n", kind, kind, kind, kind, kind)
	code += fmt.Sprintf("}\n\n")

	return code
}

// bindMethod
func bindMethod(kind string, method abi.Method) string {
	var (
		name     = strings.ToUpper(method.Name[:1]) + method.Name[1:]
		prologue = new(bytes.Buffer)
	)
	// Generate the argument and return list for the function
	args := make([]string, 0, len(method.Inputs))
	for i, arg := range method.Inputs {
		param := arg.Name
		if param == "" {
			param = fmt.Sprintf("arg%d", i)
		}
		args = append(args, fmt.Sprintf("%s %s", param, bindType(arg.Type)))
	}
	returns, _ := bindReturn(prologue, name, method.Outputs)

	// Generate the docs to help with coding against the binding
	callTypeDoc := "free data retrieval call"
	if !method.Const {
		callTypeDoc = "paid mutator transaction"
	}
	docs := fmt.Sprintf("// %s is a %s binding the contract method 0x%x.\n", name, callTypeDoc, method.Id())
	docs += fmt.Sprintf("// \n")
	docs += fmt.Sprintf("// Solidity: %s", strings.TrimPrefix(method.String(), "function "))

	// Generate the passthrough argument list for sessions
	params := make([]string, len(args))
	for i, param := range args {
		params[i] = strings.Split(param, " ")[0]
	}
	sessargs := ""
	if len(params) > 0 {
		sessargs = "," + strings.Join(params, ",")
	}
	// Generate the method itself for both the read/write version and the combo too
	code := fmt.Sprintf("%s\n", prologue)
	if method.Const {
		// Create the main call implementation
		callargs := append([]string{"opts *bind.CallOpts"}, args...)

		code += fmt.Sprintf("%s\n", docs)
		code += fmt.Sprintf("func (_%s *%sCaller) %s(%s) (%s) {\n", kind, kind, name, strings.Join(callargs, ","), strings.Join(returns, ","))
		code += fmt.Sprintf("  %s\n", bindCallBody(kind, method.Name, callargs, returns))
		code += fmt.Sprintf("}\n\n")

		// Create the wrapping session call implementation
		code += fmt.Sprintf("%s\n", docs)
		code += fmt.Sprintf("func (_%s *%sSession) %s(%s) (%s) {\n", kind, kind, name, strings.Join(args, ","), strings.Join(returns, ","))
		code += fmt.Sprintf("  return _%s.Contract.%s(&_%s.CallOpts %s)\n", kind, name, kind, sessargs)
		code += fmt.Sprintf("}\n\n")

		code += fmt.Sprintf("%s\n", docs)
		code += fmt.Sprintf("func (_%s *%sCallerSession) %s(%s) (%s) {\n", kind, kind, name, strings.Join(args, ","), strings.Join(returns, ","))
		code += fmt.Sprintf("  return _%s.Contract.%s(&_%s.CallOpts %s)\n", kind, name, kind, sessargs)
		code += fmt.Sprintf("}\n\n")
	} else {
		// Create the main transaction implementation
		txargs := append([]string{"opts *bind.TransactOpts"}, args...)

		code += fmt.Sprintf("%s\n", docs)
		code += fmt.Sprintf("func (_%s *%sTransactor) %s(%s) (*types.Transaction, error) {\n", kind, kind, name, strings.Join(txargs, ","))
		code += fmt.Sprintf("  %s\n", bindTransactionBody(kind, method.Name, txargs))
		code += fmt.Sprintf("}\n\n")

		// Create the wrapping session call implementation
		code += fmt.Sprintf("%s\n", docs)
		code += fmt.Sprintf("func (_%s *%sSession) %s(%s) (*types.Transaction, error) {\n", kind, kind, name, strings.Join(args, ","))
		code += fmt.Sprintf("  return _%s.Contract.%s(&_%s.TransactOpts %s)\n", kind, name, kind, sessargs)
		code += fmt.Sprintf("}\n\n")

		code += fmt.Sprintf("%s\n", docs)
		code += fmt.Sprintf("func (_%s *%sTransactorSession) %s(%s) (*types.Transaction, error) {\n", kind, kind, name, strings.Join(args, ","))
		code += fmt.Sprintf("  return _%s.Contract.%s(&_%s.TransactOpts %s)\n", kind, name, kind, sessargs)
		code += fmt.Sprintf("}\n\n")
	}
	return code
}

// bindType converts a Solidity type to a Go one. Since there is no clear mapping
// from all Solidity types to Go ones (e.g. uint17), those that cannot be exactly
// mapped will use an upscaled type (e.g. *big.Int).
func bindType(kind abi.Type) string {
	stringKind := kind.String()

	switch {
	case stringKind == "address":
		return "common.Address"

	case stringKind == "hash":
		return "common.Hash"

	case strings.HasPrefix(stringKind, "bytes"):
		if stringKind == "bytes" {
			return "[]byte"
		}
		return fmt.Sprintf("[%s]byte", stringKind[5:])

	case strings.HasPrefix(stringKind, "int"):
		switch stringKind[:3] {
		case "8", "16", "32", "64":
			return stringKind
		}
		return "*big.Int"

	case strings.HasPrefix(stringKind, "uint"):
		switch stringKind[:4] {
		case "8", "16", "32", "64":
			return stringKind
		}
		return "*big.Int"

	default:
		return stringKind
	}
}

// bindReturn creates the list of return parameters for a method invocation. If
// all the fields of the return type are named, and there is more than one value
// being returned, the returns are wrapped in a result struct.
func bindReturn(prologue *bytes.Buffer, method string, outputs []abi.Argument) ([]string, string) {
	// Generate the anonymous return list for when a struct is not needed/possible
	var (
		returns   = make([]string, 0, len(outputs)+1)
		anonymous = false
	)
	for _, ret := range outputs {
		returns = append(returns, bindType(ret.Type))
		if ret.Name == "" {
			anonymous = true
		}
	}
	if anonymous || len(returns) < 2 {
		returns = append(returns, "error")
		return returns, ""
	}
	// If the returns are named and numerous, wrap in a result struct
	wrapper, impl := bindReturnStruct(method, outputs)
	prologue.WriteString(impl + "\n")
	return []string{"*" + wrapper, "error"}, wrapper
}

// bindReturnStruct creates a Go structure with the specified fields to be used
// as the return type from a method call.
func bindReturnStruct(method string, returns []abi.Argument) (string, string) {
	fields := make([]string, 0, len(returns))
	for _, ret := range returns {
		fields = append(fields, fmt.Sprintf("%s %s", strings.ToUpper(ret.Name[:1])+ret.Name[1:], bindType(ret.Type)))
	}
	kind := fmt.Sprintf("%sResult", method)
	docs := fmt.Sprintf("// %s is the result of the %s invocation.", kind, method)

	return kind, fmt.Sprintf("%s\ntype %s struct {\n%s\n}", docs, kind, strings.Join(fields, "\n"))
}

// bindCallBody creates the Go code to declare a batch of return values, invoke
// an Ethereum method call with the requested parameters, parse the binary output
// into the return values and return them.
func bindCallBody(kind string, method string, params []string, returns []string) string {
	body := ""

	// Allocate memory for each of the return values
	rets := make([]string, 0, len(returns)-1)
	if len(returns) > 1 {
		body += "var ("
		for i, kind := range returns[:len(returns)-1] { // Omit the final error
			name := fmt.Sprintf("ret%d", i)

			rets = append(rets, name)
			body += fmt.Sprintf("%s = new(%s)\n", name, kind)
		}
		body += ")\n"
	}
	// Assemble a single collector variable for the result ABI initialization
	result := strings.Join(rets, ",")
	if len(returns) > 2 {
		result = "[]interface{}{" + result + "}"
	}
	// Extract the parameter list into a flat variable name list
	inputs := make([]string, len(params)-1) // Omit the call options
	for i, param := range params[1:] {
		inputs[i] = strings.Split(param, " ")[0]
	}
	input := ""
	if len(inputs) > 0 {
		input = "," + strings.Join(inputs, ",")
	}
	// Request executing the contract call and return the results with the errors
	body += fmt.Sprintf("err := _%s.contract.Call(opts, %s, \"%s\" %s)\n", kind, result, method, input)

	outs := make([]string, 0, len(returns))
	for _, ret := range rets { // Handle th final error separately
		outs = append(outs, "*"+ret)
	}
	outs = append(outs, "err")

	body += fmt.Sprintf("return %s", strings.Join(outs, ","))

	return body
}

// bindTransactionBody creates the Go code to invoke an Ethereum transaction call
// with the requested parameters, and return the assembled transaction object.
func bindTransactionBody(kind string, method string, params []string) string {
	// Extract the parameter list into a flat variable name list
	inputs := make([]string, len(params)-1) // Omit the auth options
	for i, param := range params[1:] {
		inputs[i] = strings.Split(param, " ")[0]
	}
	input := ""
	if len(inputs) > 0 {
		input = "," + strings.Join(inputs, ",")
	}
	// Request executing the contract call and return the results with the errors
	return fmt.Sprintf("return _%s.contract.Transact(opts, \"%s\" %s)", kind, method, input)
}