/*
 * MinIO Cloud Storage, (C) 2018 MinIO, Inc.
 *
 * 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 iampolicy

import (
	"strings"

	"github.com/minio/minio/pkg/bucket/policy"
	"github.com/minio/minio/pkg/bucket/policy/condition"
)

// Statement - iam policy statement.
type Statement struct {
	SID        policy.ID           `json:"Sid,omitempty"`
	Effect     policy.Effect       `json:"Effect"`
	Actions    ActionSet           `json:"Action"`
	Resources  ResourceSet         `json:"Resource,omitempty"`
	Conditions condition.Functions `json:"Condition,omitempty"`
}

// IsAllowed - checks given policy args is allowed to continue the Rest API.
func (statement Statement) IsAllowed(args Args) bool {
	check := func() bool {
		if !statement.Actions.Match(args.Action) {
			return false
		}

		resource := args.BucketName
		if args.ObjectName != "" {
			if !strings.HasPrefix(args.ObjectName, "/") {
				resource += "/"
			}

			resource += args.ObjectName
		} else {
			resource += "/"
		}

		// For admin statements, resource match can be ignored.
		if !statement.Resources.Match(resource, args.ConditionValues) && !statement.isAdmin() {
			return false
		}

		return statement.Conditions.Evaluate(args.ConditionValues)
	}

	return statement.Effect.IsAllowed(check())
}
func (statement Statement) isAdmin() bool {
	for action := range statement.Actions {
		if AdminAction(action).IsValid() {
			return true
		}
	}
	return false
}

// isValid - checks whether statement is valid or not.
func (statement Statement) isValid() error {
	if !statement.Effect.IsValid() {
		return Errorf("invalid Effect %v", statement.Effect)
	}

	if len(statement.Actions) == 0 {
		return Errorf("Action must not be empty")
	}

	if statement.isAdmin() {
		if err := statement.Actions.ValidateAdmin(); err != nil {
			return err
		}
		for action := range statement.Actions {
			keys := statement.Conditions.Keys()
			keyDiff := keys.Difference(adminActionConditionKeyMap[action])
			if !keyDiff.IsEmpty() {
				return Errorf("unsupported condition keys '%v' used for action '%v'", keyDiff, action)
			}
		}
		return nil
	}

	if !statement.SID.IsValid() {
		return Errorf("invalid SID %v", statement.SID)
	}

	if len(statement.Resources) == 0 {
		return Errorf("Resource must not be empty")
	}

	if err := statement.Resources.Validate(); err != nil {
		return err
	}

	if err := statement.Actions.Validate(); err != nil {
		return err
	}

	for action := range statement.Actions {
		if !statement.Resources.objectResourceExists() && !statement.Resources.bucketResourceExists() {
			return Errorf("unsupported Resource found %v for action %v", statement.Resources, action)
		}

		keys := statement.Conditions.Keys()
		keyDiff := keys.Difference(iamActionConditionKeyMap.Lookup(action))
		if !keyDiff.IsEmpty() {
			return Errorf("unsupported condition keys '%v' used for action '%v'", keyDiff, action)
		}
	}

	return nil
}

// Validate - validates Statement is for given bucket or not.
func (statement Statement) Validate() error {
	return statement.isValid()
}

// NewStatement - creates new statement.
func NewStatement(effect policy.Effect, actionSet ActionSet, resourceSet ResourceSet, conditions condition.Functions) Statement {
	return Statement{
		Effect:     effect,
		Actions:    actionSet,
		Resources:  resourceSet,
		Conditions: conditions,
	}
}