package peer

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"

	"omnisocketgo/cmd/internal/latencylog"
	"omnisocketgo/cmd/internal/protocol"
)

const textInboxFileName = "messages.log"

type textInboxRecord struct {
	MessageType protocol.MessageType `json:"message_type"`
	MessageID   uint64               `json:"message_id"`
	From        string               `json:"from"`
	To          string               `json:"to"`
	Body        string               `json:"body"`
}

// PersistMessage 将收到的业务消息写入本地磁盘，并记录处理完成节点。
func (c *Client) PersistMessage(msg protocol.Message, inboxDir string) (string, error) {
	if !latencylog.IsBusinessMessage(msg) {
		return "", fmt.Errorf("peer: cannot persist message type %s", msg.Type)
	}
	if inboxDir == "" {
		return "", fmt.Errorf("peer: inbox directory is required")
	}

	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventBPersistBegin, msg)

	if err := os.MkdirAll(inboxDir, 0o755); err != nil {
		return "", fmt.Errorf("peer: create inbox dir %s: %w", inboxDir, err)
	}

	path, err := persistMessageToDisk(msg, inboxDir)
	if err != nil {
		return "", err
	}

	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventBPersistEnd, msg)

	return path, nil
}

// persistMessageToDisk 根据消息类型将消息内容写入磁盘，文本消息追加到文本日志文件，文件消息写成独立文件。
func persistMessageToDisk(msg protocol.Message, inboxDir string) (string, error) {
	switch msg.Type {
	case protocol.MessageTypeText:
		return persistTextMessage(msg, inboxDir)
	case protocol.MessageTypeFile:
		return persistFileMessage(msg, inboxDir)
	default:
		return "", fmt.Errorf("peer: cannot persist unsupported message type %s", msg.Type)
	}
}

// registerPeer 验证 peer ID 的合法性和唯一性，并将其与连接关联起来。
func persistTextMessage(msg protocol.Message, inboxDir string) (string, error) {
	record := textInboxRecord{
		MessageType: msg.Type,
		MessageID:   msg.ID,
		From:        msg.From,
		To:          msg.To,
		Body:        string(msg.Body),
	}

	line, err := json.Marshal(record)
	if err != nil {
		return "", fmt.Errorf("peer: encode text inbox record: %w", err)
	}

	path := filepath.Join(inboxDir, textInboxFileName)
	file, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
	if err != nil {
		return "", fmt.Errorf("peer: open text inbox %s: %w", path, err)
	}
	defer file.Close()

	if _, err := file.Write(append(line, '\n')); err != nil {
		return "", fmt.Errorf("peer: append text inbox %s: %w", path, err)
	}

	return path, nil
}

// persistFileMessage 将文件消息的内容写成独立文件，文件名包含发送方、消息 ID 和原始文件名，保证唯一性和可读性。
func persistFileMessage(msg protocol.Message, inboxDir string) (string, error) {
	fileName := filepath.Base(msg.FileName)
	path := filepath.Join(inboxDir, fmt.Sprintf("%s-%d-%s", msg.From, msg.ID, fileName))

	if err := os.WriteFile(path, msg.Body, 0o644); err != nil {
		return "", fmt.Errorf("peer: write received file %s: %w", path, err)
	}

	return path, nil
}