// Package adapter defines the cross-platform IM channel adaptation contract for
// Cyrene v2. It declares the normalized message model, the per-platform adapter
// interface, the capability declaration, and the strongly typed identity (actor)
// metadata that the channel layer uses for owner detection and group-chat
// isolation.
//
// The contract is intentionally platform-neutral: concrete adapters (qq-obv11,
// weixin-ilink, telegram, webhook) are implemented behind this interface in
// milestone M6, not here. The design authority is DevDocs/design/08-渠道接入.md
// (sections 0-2) and DevDocs/design/02-会话与上下文模型.md (section 3).
package adapter

import (
	"errors"
	"fmt"
	"time"
)

// ChannelType classifies where a message originated or is destined.
type ChannelType string

const (
	// ChannelDirect is a one-to-one private conversation.
	ChannelDirect ChannelType = "direct"
	// ChannelGroup is a group / room conversation.
	ChannelGroup ChannelType = "group"
)

// Valid reports whether ct is one of the known channel kinds.
func (ct ChannelType) Valid() bool {
	switch ct {
	case ChannelDirect, ChannelGroup:
		return true
	default:
		return false
	}
}

// ContentType classifies the primary payload of a message.
type ContentType string

const (
	// ContentText is a plain-text chat message.
	ContentText ContentType = "text"
	// ContentImage is an image attachment.
	ContentImage ContentType = "image"
	// ContentVoice is a voice/audio clip.
	ContentVoice ContentType = "voice"
	// ContentFile is an arbitrary file attachment.
	ContentFile ContentType = "file"
	// ContentAction is a non-chat action signal (typing, join/leave, recall).
	ContentAction ContentType = "action"
)

// Valid reports whether ct is one of the known content kinds.
func (ct ContentType) Valid() bool {
	switch ct {
	case ContentText, ContentImage, ContentVoice, ContentFile, ContentAction:
		return true
	default:
		return false
	}
}

// MediaKind classifies an individual media attachment. It is broader than
// ContentType so attachments can also carry video or other payloads.
type MediaKind string

const (
	// MediaImage is an image file.
	MediaImage MediaKind = "image"
	// MediaVoice is an audio/voice file.
	MediaVoice MediaKind = "voice"
	// MediaVideo is a video file.
	MediaVideo MediaKind = "video"
	// MediaFile is an arbitrary file.
	MediaFile MediaKind = "file"
)

// Media is a single attachment carried by a UnifiedMessage. URL and Data are
// mutually exclusive representations: prefer URL for remote media to
// keep payloads out of memory.
type Media struct {
	// Kind classifies the attachment.
	Kind MediaKind
	// URL is the remote location of the media when not inlined.
	URL string
	// Name is the original file name, when known.
	Name string
	// Size is the media size in bytes.
	Size int64
	// MIMEType is the media content type, when known.
	MIMEType string
	// Data carries inlined bytes for small, locally produced payloads.
	Data []byte
}

// Mention is a reference to a user inside a message body.
type Mention struct {
	UserID   string
	UserName string
}

// UnifiedMessage is the normalized, platform-neutral representation of an IM
// event or inbound message. Every channel adapter converts its native payload
// into UnifiedMessage so the runtime can reason about them uniformly.
//
// SenderID/SenderName are kept per design/08 section 0; Sender carries the
// strongly typed identity metadata (Role, group flags) used for owner detection
// and group isolation. The strategy engine (M6) decides access from Sender, not
// from the free-text SenderName.
type UnifiedMessage struct {
	Platform    string
	ChannelID   string
	ChannelType ChannelType
	SenderID    string
	SenderName  string
	Sender      Actor
	// SelfID 是**她自己在该平台的账号 id**（OneBot 的 self_id、KOOK 的 bot_id…），
	// 只从平台元数据取，绝不从正文推断。空串 = 平台没给 / 适配器尚未接线：此时
	// 「是否指向她」的判定必须 fail-closed（见 AddressedToMe），判据缺失不等于命中。
	SelfID      string
	Content     string
	ContentType ContentType
	Media       []Media
	Mentions    []Mention
	// MentionAll 报告本条是否 **@全体**（OneBot 的 at 段 qq="all"；design/26 §2.4 要求
	// 以结构化标志留痕的 mention_all）。它是 AddressedToMe 的子集信号：true ⇒ 该字段也 true。
	// 单独留一列是为了让「@全体」与「直接点名她」在数据上可分辨（审计 / 降噪各取所需）。
	MentionAll bool
	// AddressedToMe 报告本条消息在结构上**是否指向她本人**（design/18 §2 触发① 的判据，
	// 主人 2026-10-13 裁决「甲 = 要」）。语义与推导见 AddressedToSelf：
	// 群聊 = 点名她或 @全体；私聊 = 恒 true；平台未给 SelfID = false（fail-closed）。
	// 判据**全部来自平台元数据**，绝不匹配正文里的 "@<数字>"（项目红线）。
	AddressedToMe bool
	ReplyToID     string
	ReplyToText   string
	GroupID       string
	GroupName     string
	ThreadID      string
	MessageID     string
	Timestamp     time.Time
	// RawData is the opaque native payload the message was converted from.
	RawData []byte
}

// UnifiedResponse is the normalized outbound payload for SendMessage. It may
// carry several messages so an adapter can burst a reply.
type UnifiedResponse struct {
	// Messages are the reply messages to deliver.
	Messages []UnifiedMessage
	// ReplyTo is an optional context identifier the messages reply to.
	ReplyTo string
	// Hint is an optional human hint surfaced by the runtime.
	Hint string
}

// Validate reports whether the message is well-formed for downstream handling.
// It checks the enum fields and requires a group id on group messages.
func (m UnifiedMessage) Validate() error {
	if !m.ChannelType.Valid() {
		return fmt.Errorf("adapter: invalid channel type %q", m.ChannelType)
	}
	if !m.ContentType.Valid() {
		return fmt.Errorf("adapter: invalid content type %q", m.ContentType)
	}
	if m.ChannelType == ChannelGroup && m.GroupID == "" {
		return errors.New("adapter: group message missing group id")
	}
	return nil
}

// IsGroup reports whether the message belongs to a group conversation.
func (m UnifiedMessage) IsGroup() bool { return m.ChannelType == ChannelGroup }

// MentionedSelf 报告 mentions 里是否**点名**了 selfID：结构化 id 的精确比对，
// 绝不做正文匹配。selfID 为空（平台没给她的账号 id，或适配器未接线）或 mentions
// 为空时一律 false —— 判据缺失就 fail-closed，绝不猜。它是各适配器接线的唯一出处：
// 适配器只需把平台给出的 SelfID 与 Mentions 交给它。
func MentionedSelf(selfID string, mentions []Mention) bool {
	if selfID == "" {
		return false
	}
	for _, m := range mentions {
		if m.UserID == selfID {
			return true
		}
	}
	return false
}

// AddressedToSelf 依据本条消息的**结构化平台元数据**推导 AddressedToMe
// （design/18 §2 触发①；主人 2026-10-13 裁决「甲 = 要」）：
//
//   - 私聊：恒 true —— 对端就是发送者，本条天然是对她说的；
//   - 群聊：点名了她（Mentions 含 SelfID）**或** @全体（MentionAll）；
//   - SelfID 为空：一律 false —— 判据缺失 ⇒ fail-closed，绝不退回正文文本匹配。
//
// 适配器在填好 SelfID / ChannelType / Mentions / MentionAll 之后调用它回写
// AddressedToMe；推导的**唯一出处**在这里，避免每个适配器各写一份判据而互相漂移。
// 它只用于**真消息**（走 toUnified 的那条路径），系统事件包装不适用。
func (m UnifiedMessage) AddressedToSelf() bool {
	if m.ChannelType == ChannelDirect {
		return true
	}
	return m.MentionAll || MentionedSelf(m.SelfID, m.Mentions)
}