/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you 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 main

import (
	"errors"
	"fmt"

	"encoding/asn1"
	"encoding/base64"
	"strings"

	"github.com/hyperledger/fabric/core/chaincode/shim"
	"github.com/hyperledger/fabric/core/crypto"
	"github.com/op/go-logging"
)

var myLogger = logging.MustGetLogger("rbac_chaincode")

// RBACMetadata metadata structure for RBAC information
type RBACMetadata struct {
	Cert  []byte
	Sigma []byte
}

// RBACChaincode RBAC chaincode structure
type RBACChaincode struct {
}

// Init method will be called during deployment
func (t *RBACChaincode) Init(stub shim.ChaincodeStubInterface, function string, args []string) ([]byte, error) {

	// Init the crypto layer
	if err := crypto.Init(); err != nil {
		panic(fmt.Errorf("Failed initializing the crypto layer [%s]", err))
	}

	myLogger.Info("Init")
	// if len(args) != 0 {
	// 	return nil, errors.New("Incorrect number of arguments. Expecting 0")
	// }

	myLogger.Debug("Creating RBAC Table...")

	// Create RBAC table
	err := stub.CreateTable("RBAC", []*shim.ColumnDefinition{
		&shim.ColumnDefinition{Name: "ID", Type: shim.ColumnDefinition_BYTES, Key: true},
		&shim.ColumnDefinition{Name: "Roles", Type: shim.ColumnDefinition_STRING, Key: false},
	})
	if err != nil {
		return nil, errors.New("Failed creating RBAC table.")
	}

	myLogger.Debug("Assign 'admin' role...")

	// Give to the deployer the role 'admin'
	deployer, err := stub.GetCallerMetadata()
	if err != nil {
		return nil, errors.New("Failed getting metadata.")
	}
	if len(deployer) == 0 {
		return nil, errors.New("Invalid admin certificate. Empty.")
	}

	myLogger.Debug("Add admin [% x][%s]", deployer, "admin")
	ok, err := stub.InsertRow("RBAC", shim.Row{
		Columns: []*shim.Column{
			&shim.Column{Value: &shim.Column_Bytes{Bytes: deployer}},
			&shim.Column{Value: &shim.Column_String_{String_: "admin"}},
		},
	})
	if !ok && err == nil {
		return nil, fmt.Errorf("Failed initiliazing RBAC entries.")
	}
	if err != nil {
		return nil, fmt.Errorf("Failed initiliazing RBAC entries [%s]", err)
	}

	myLogger.Debug("Done.")

	return nil, nil
}

// Invoke Run callback representing the invocation of a chaincode
func (t *RBACChaincode) Invoke(stub shim.ChaincodeStubInterface, function string, args []string) ([]byte, error) {
	// Handle different functions
	switch function {
	case "addRole":
		return t.addRole(stub, args)
	case "write":
		return t.write(stub, args)
	}

	return nil, fmt.Errorf("Received unknown function invocation [%s]", function)
}

// Query callback representing the query of a chaincode
func (t *RBACChaincode) Query(stub shim.ChaincodeStubInterface, function string, args []string) ([]byte, error) {
	// Handle different functions
	switch function {
	case "read":
		return t.read(stub, args)
	}

	return nil, fmt.Errorf("Received unknown function invocation [%s]", function)
}

func (t *RBACChaincode) addRole(stub shim.ChaincodeStubInterface, args []string) ([]byte, error) {
	if len(args) != 2 {
		return nil, errors.New("Incorrect number of arguments. Expecting 2")
	}
	id, err := base64.StdEncoding.DecodeString(args[0])
	if err != nil {
		return nil, fmt.Errorf("Failed decoding tcert:  %s", err)
	}
	//id := []byte(args[0])
	role := args[1]

	myLogger.Debug("Add role [% x][%s]", id, role)

	// Verify that the invoker has the 'admin' role
	ok, _, err := t.hasInvokerRole(stub, "admin")
	if err != nil {
		return nil, fmt.Errorf("Failed checking role [%s]", err)
	}
	if !ok {
		return nil, errors.New("The invoker does not have the required roles.")
	}

	// Add role to id
	myLogger.Debug("Permission granted to the invoker")

	// Retrieve id's row
	var columns []shim.Column
	idCol := shim.Column{Value: &shim.Column_Bytes{Bytes: id}}
	columns = append(columns, idCol)
	row, err := stub.GetRow("RBAC", columns)
	if err != nil {
		return nil, fmt.Errorf("Failed retriving associated row [%s]", err)
	}
	if len(row.Columns) == 0 {
		// Insert row
		ok, err = stub.InsertRow("RBAC", shim.Row{
			Columns: []*shim.Column{
				&shim.Column{Value: &shim.Column_Bytes{Bytes: id}},
				&shim.Column{Value: &shim.Column_String_{String_: role}},
			},
		})
		if err != nil {
			return nil, fmt.Errorf("Failed inserting row [%s]", err)
		}
		if !ok {
			return nil, errors.New("Failed inserting row.")
		}

	} else {
		// Update row
		ok, err = stub.ReplaceRow("RBAC", shim.Row{
			Columns: []*shim.Column{
				&shim.Column{Value: &shim.Column_Bytes{Bytes: id}},
				&shim.Column{Value: &shim.Column_String_{String_: row.Columns[1].GetString_() + " " + role}},
			},
		})
		if err != nil {
			return nil, fmt.Errorf("Failed replacing row [%s]", err)
		}
		if !ok {
			return nil, errors.New("Failed replacing row.")
		}
	}

	return nil, err
}

func (t *RBACChaincode) read(stub shim.ChaincodeStubInterface, args []string) ([]byte, error) {
	if len(args) != 0 {
		return nil, errors.New("Incorrect number of arguments. Expecting 0")
	}
	myLogger.Debug("Read...")

	// Verify that the invoker has the 'reader' role
	ok, _, err := t.hasInvokerRole(stub, "reader")
	if err != nil {
		return nil, fmt.Errorf("Failed checking role [%s]", err)
	}
	if !ok {
		return nil, fmt.Errorf("The invoker does not have the required roles")
	}

	res, err := stub.GetState("state")
	if err != nil {
		return nil, fmt.Errorf("Failed getting state [%s]", err)
	}

	myLogger.Debug("State [%s]", string(res))

	return res, nil
}

func (t *RBACChaincode) write(stub shim.ChaincodeStubInterface, args []string) ([]byte, error) {
	if len(args) != 1 {
		return nil, errors.New("Incorrect number of arguments. Expecting 1")
	}

	value := args[0]

	myLogger.Debug("Write [%s]", value)

	// Verify that the invoker has the 'writer' role
	ok, _, err := t.hasInvokerRole(stub, "writer")
	if err != nil {
		return nil, fmt.Errorf("Failed checking role [%s]", err)
	}
	if !ok {
		return nil, errors.New("The invoker does not have the required roles.")
	}

	return nil, stub.PutState("state", []byte(value))
}

func (t *RBACChaincode) hasInvokerRole(stub shim.ChaincodeStubInterface, role string) (bool, []byte, error) {
	// In order to enforce access control, we require that the
	// metadata contains the following items:
	// 1. a certificate Cert
	// 2. a signature Sigma under the signing key corresponding
	// to the verification key inside Cert of :
	// (a) Cert;
	// (b) The payload of the transaction (namely, function name and args) and
	// (c) the transaction binding.

	// Verify Sigma=Sign(certificate.sk, Cert||tx.Payload||tx.Binding) against Cert.vk

	// Unmarshall metadata
	metadata, err := stub.GetCallerMetadata()
	rbacMetadata := new(RBACMetadata)
	_, err = asn1.Unmarshal(metadata, rbacMetadata)
	if err != nil {
		return false, nil, fmt.Errorf("Failed unmarshalling metadata [%s]", err)
	}

	// Verify signature
	payload, err := stub.GetPayload()
	if err != nil {
		return false, nil, errors.New("Failed getting payload")
	}
	binding, err := stub.GetBinding()
	if err != nil {
		return false, nil, errors.New("Failed getting binding")
	}

	myLogger.Debug("passed certificate [% x]", rbacMetadata.Cert)
	myLogger.Debug("passed sigma [% x]", rbacMetadata.Sigma)
	myLogger.Debug("passed payload [% x]", payload)
	myLogger.Debug("passed binding [% x]", binding)

	ok, err := stub.VerifySignature(
		rbacMetadata.Cert,
		rbacMetadata.Sigma,
		append(rbacMetadata.Cert, append(payload, binding...)...),
	)
	if err != nil {
		return false, nil, fmt.Errorf("Failed verifying signature [%s]", err)
	}
	if !ok {
		return false, nil, fmt.Errorf("Signature is not valid!")
	}

	myLogger.Debug("Signature verified. Check for role...")

	myLogger.Debug("ID [% x]", rbacMetadata.Cert)

	// Check role
	var columns []shim.Column
	idCol := shim.Column{Value: &shim.Column_Bytes{Bytes: rbacMetadata.Cert}}
	columns = append(columns, idCol)
	row, err := stub.GetRow("RBAC", columns)
	if err != nil {
		return false, nil, fmt.Errorf("Failed retrieveing RBAC row [%s]", err)
	}
	if len(row.GetColumns()) == 0 {
		return false, nil, fmt.Errorf("Failed retrieveing RBAC row [%s]", err)
	}

	myLogger.Debug("#Columns: [%d]", len(row.Columns))
	roles := row.Columns[1].GetString_()

	result := strings.Split(roles, " ")
	for i := range result {
		if result[i] == role {
			myLogger.Debug("Role found.")
			return true, rbacMetadata.Cert, nil
		}
	}

	myLogger.Debug("Role not found.")

	return false, nil, nil
}

func main() {
	err := shim.Start(new(RBACChaincode))
	if err != nil {
		fmt.Printf("Error starting AssetManagementChaincode: %s", err)
	}
}