/*
 * Copyright (c) 2018 - present.  Boling Consulting Solutions (bcsw.net)
 * Copyright 2020-present Open Networking Foundation

 * 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 meframe

import (
	"errors"
	"fmt"
	"github.com/google/gopacket"
	. "github.com/opencord/omci-lib-go/v2"
	me "github.com/opencord/omci-lib-go/v2/generated"
)

func GetRequestFrame(m *me.ManagedEntity, opt options) (gopacket.SerializableLayer, error) {
	// Given mask sent in (could be default of 0xFFFF) get what is allowable.
	// This will be all allowed if 0xFFFF is passed in, or a subset if a fixed
	// number of items.
	maxMask, err := checkAttributeMask(m, opt.attributeMask)
	if err != nil {
		return nil, err
	}
	// Now scan attributes and reduce mask to only those requested
	var mask uint16
	mask, err = calculateAttributeMask(m, maxMask)
	if err != nil {
		return nil, err
	}
	if mask == 0 {
		// TODO: Is a Get request with no attributes valid?
		return nil, errors.New("no attributes requested for GetRequest")
	}
	meLayer := &GetRequest{
		MeBasePacket: MeBasePacket{
			EntityClass:    m.GetClassID(),
			EntityInstance: m.GetEntityID(),
			Extended:       opt.frameFormat == ExtendedIdent,
		},
		AttributeMask: mask,
	}
	return meLayer, nil
}

func GetResponseFrame(m *me.ManagedEntity, opt options) (gopacket.SerializableLayer, error) {
	mask, err := checkAttributeMask(m, opt.attributeMask)
	if err != nil {
		return nil, err
	}
	mask, err = calculateAttributeMask(m, mask)
	if err != nil {
		return nil, err
	}
	meLayer := &GetResponse{
		MeBasePacket: MeBasePacket{
			EntityClass:    m.GetClassID(),
			EntityInstance: m.GetEntityID(),
			Extended:       opt.frameFormat == ExtendedIdent,
		},
		Result:        opt.result,
		AttributeMask: 0,
		Attributes:    make(me.AttributeValueMap),
	}
	if meLayer.Result == me.AttributeFailure {
		meLayer.UnsupportedAttributeMask = opt.unsupportedMask
		meLayer.FailedAttributeMask = opt.attrExecutionMask
	}
	// Encode whatever we can
	if meLayer.Result == me.Success || meLayer.Result == me.AttributeFailure {
		// Encode results
		// Get payload space available
		maxPayload := maxPacketAvailable(m, opt)
		payloadAvailable := int(maxPayload) - 2 - 4 // Less attribute mask and attribute error encoding
		meDefinition := m.GetManagedEntityDefinition()
		attrDefs := meDefinition.GetAttributeDefinitions()
		attrMap := m.GetAttributeValueMap()

		if mask != 0 {
			// Iterate down the attributes (Attribute 0 is the ManagedEntity ID)
			var attrIndex uint
			for attrIndex = 1; attrIndex <= 16; attrIndex++ {
				// Is this attribute requested
				if mask&(1<<(16-attrIndex)) != 0 {
					// Get definitions since we need the name
					attrDef, ok := attrDefs[attrIndex]
					if !ok {
						msg := fmt.Sprintf("Unexpected error, index %v not valued for ME %v",
							attrIndex, meDefinition.GetName())
						return nil, errors.New(msg)
					}
					var attrValue interface{}
					attrValue, ok = attrMap[attrDef.Name]
					if !ok {
						msg := fmt.Sprintf("Unexpected error, attribute %v not provided in ME %v: %v",
							attrDef.GetName(), meDefinition.GetName(), m)
						return nil, errors.New(msg)
					}
					// Is space available?
					if attrDef.Size <= payloadAvailable {
						// Mark bit handled
						mask &= ^attrDef.Mask
						meLayer.AttributeMask |= attrDef.Mask
						meLayer.Attributes[attrDef.Name] = attrValue
						payloadAvailable -= attrDef.Size

					} else if opt.failIfTruncated {
						// TODO: Should we set truncate?
						msg := fmt.Sprintf("out-of-space. Cannot fit attribute %v into GetResponse message",
							attrDef.GetName())
						return nil, me.NewMessageTruncatedError(msg)
					} else {
						// Add to existing 'failed' mask and update result
						meLayer.FailedAttributeMask |= attrDef.Mask
						meLayer.Result = me.AttributeFailure
					}
				}
			}
		}
	}
	return meLayer, nil
}