// 本文件解析任务类 C2S 请求体。
// C# QuestManager 会在 body 长度大于 2 时去掉前 2 字节 wire-type echo，再交给 QuestService。
package quest

import (
	"encoding/binary"
	"fmt"

	"longheng.io/server/internal/modules/dnf/dnfenum"
)

const (
	CurrentFinishQuestRequestBodySize    = 10
	CurrentFinishQuestObservedTailMarker = ^uint16(0)

	// CurrentSetTriggerRequestBodySize is the scalar op33 shape:
	// echo | quest | add/remove | reserved-or-answer.
	CurrentSetTriggerRequestBodySize = 6
	// CurrentMaskedSetTriggerRequestBodySize is the current-client packed
	// objective shape used by multi-lane tasks such as the Hell Party
	// challenges: echo | quest | lane mask | add/remove | reserved.
	CurrentMaskedSetTriggerRequestBodySize = 7
)

// QuestIDRequest 描述只携带 questId 的任务请求。
type QuestIDRequest struct {
	QuestID uint16
}

// SetTriggerRequest 描述任务触发进度请求。
type SetTriggerRequest struct {
	QuestID         uint16
	TriggerType     byte
	TriggerArgument byte
	IsIncrement     bool
}

// FinishQuestRequest 描述完成任务请求。
type FinishQuestRequest struct {
	QuestID           uint16
	RewardSelectIndex uint16
	HasRewardSelect   bool
	Multiplier        uint16
	Reserved          uint16
}

// DecodeQuestIDRequest 解析接取/放弃任务请求。
func DecodeQuestIDRequest(body []byte) (QuestIDRequest, error) {
	qBody := stripEcho(body)
	if len(qBody) < 2 {
		return QuestIDRequest{}, fmt.Errorf("body too short after echo strip: got %d want >= 2", len(qBody))
	}
	return QuestIDRequest{QuestID: binary.LittleEndian.Uint16(qBody)}, nil
}

// DecodeSetTriggerRequest parses both proven current-client op33 forms. The
// seven-byte form is not a transport trailer: its 0x10/0x20/0x40 mask selects
// one 9-bit lane of the packed quest trigger. Older six-byte masked clones are
// retained only as a compatibility input for an already-supported profile.
func DecodeSetTriggerRequest(body []byte) (SetTriggerRequest, error) {
	if len(body) != CurrentSetTriggerRequestBodySize && len(body) != CurrentMaskedSetTriggerRequestBodySize {
		return SetTriggerRequest{}, fmt.Errorf("set quest trigger body size: got %d want %d or %d", len(body), CurrentSetTriggerRequestBodySize, CurrentMaskedSetTriggerRequestBodySize)
	}
	if echo := binary.LittleEndian.Uint16(body[:2]); echo != uint16(dnfenum.CmdPacketSetQuestTrigger) {
		return SetTriggerRequest{}, fmt.Errorf("set quest trigger echo: got %d want %d", echo, dnfenum.CmdPacketSetQuestTrigger)
	}
	request := SetTriggerRequest{QuestID: binary.LittleEndian.Uint16(body[2:4])}
	if request.QuestID == 0 {
		return SetTriggerRequest{}, fmt.Errorf("set quest trigger has zero quest ID")
	}

	if len(body) == CurrentMaskedSetTriggerRequestBodySize {
		switch body[4] {
		case 0x10, 0x20, 0x40:
			request.TriggerType = body[4]
		default:
			return SetTriggerRequest{}, fmt.Errorf("set quest trigger mask: got %#x want 0x10, 0x20, or 0x40", body[4])
		}
		if body[5] > 1 {
			return SetTriggerRequest{}, fmt.Errorf("set quest trigger add/remove: got %d want boolean", body[5])
		}
		if body[6] != 0 {
			return SetTriggerRequest{}, fmt.Errorf("set quest trigger masked reserved: got %#x want 0", body[6])
		}
		request.IsIncrement = body[5] != 0
		return request, nil
	}

	// Retain the established local six-byte clone unchanged. Its last two
	// bytes are trigger type and trigger argument; several existing quest
	// families (notably seeking) still use type 1 through that compatibility
	// route. The current masked Hell Party form above is unambiguous because it
	// is seven bytes.
	request.TriggerType = body[4]
	request.TriggerArgument = body[5]
	request.IsIncrement = body[5] != 0
	return request, nil
}

// DecodeFinishQuestRequest 解析完成任务请求。
func DecodeFinishQuestRequest(body []byte) (FinishQuestRequest, error) {
	if len(body) != CurrentFinishQuestRequestBodySize {
		return FinishQuestRequest{}, fmt.Errorf("current EXE finish-quest body size: got %d want %d", len(body), CurrentFinishQuestRequestBodySize)
	}
	if echo := binary.LittleEndian.Uint16(body[0:2]); echo != uint16(dnfenum.CmdPacketFinishQuest) {
		return FinishQuestRequest{}, fmt.Errorf("current EXE finish-quest echo: got %d want %d", echo, dnfenum.CmdPacketFinishQuest)
	}
	req := FinishQuestRequest{
		QuestID:           binary.LittleEndian.Uint16(body[2:4]),
		RewardSelectIndex: binary.LittleEndian.Uint16(body[4:6]),
		Multiplier:        binary.LittleEndian.Uint16(body[6:8]),
		Reserved:          binary.LittleEndian.Uint16(body[8:10]),
	}
	req.HasRewardSelect = req.RewardSelectIndex != ^uint16(0)
	return req, nil
}

func stripEcho(body []byte) []byte {
	if body == nil || len(body) <= 2 {
		return body
	}
	return body[2:]
}

func (r QuestIDRequest) String() string {
	return fmt.Sprintf("quest=%d", r.QuestID)
}

func (r SetTriggerRequest) String() string {
	return fmt.Sprintf("quest=%d triggerType=%d argument=%d increment=%t", r.QuestID, r.TriggerType, r.TriggerArgument, r.IsIncrement)
}

func (r FinishQuestRequest) String() string {
	return fmt.Sprintf("quest=%d rewardSelect=%d hasReward=%t multiplier=%d reserved=%d", r.QuestID, r.RewardSelectIndex, r.HasRewardSelect, r.Multiplier, r.Reserved)
}